1. When placing roots in the soil, plants integrate information about soil nutrients, plant neighbours and beneficial/detrimental soil organisms. While the fine-scale spatial heterogeneity in soil nutrients and plant neighbours have been described previously, virtually nothing is known about the spatial structure in soil biotic quality (measured here as a soil Biota-Induced plant Growth Response, or BIGR), or its correlation with nutrients or neighbours. Such correlations could imply trade-offs in root placement decisions.
2. Theory would predict that soil BIGR is (1) negatively related to soil fertility and (2) associated with plant community structure, such that plants influence soil biota (and vice versa) through plant-soil feedbacks. We would also expect that since plants have species-specific impacts on soil organisms, spatially homogeneous plant communities should also homogenize soil BIGR.
3. Here, we test these hypotheses in a semiarid grassland by (1) characterizing the spatial structure of soil BIGR at a scale experienced by an individual plant and (2) correlating it to soil abiotic properties and plant community structure. We do so in two types of plant communities: (1) low-diversity patches dominated by an invasive grass (Bromus inermis Leyss.) and (2) patches covered mostly by native vegetation, with the expectation that dominance by Bromus would homogenize soil BIGR.
4. Soil BIGR was spatially heterogeneous, but not autocorrelated. This was true in both vegetation types (Bromus-invaded vs. native patches). Conversely, soil abiotic properties and plant community structure were frequently spatially autocorrelated at similar scales. Also, contrary to many studies, we found a positive correlation between soil BIGR and soil fertility. Soil BIGR was also associated with plant community structure.
5. Synthesis. The positive correlation between soil BIGR and some soil nutrient levels suggests that plants don't necessarily trade-off between foraging for nutrients vs. biotic interactions: nutritional cues could rather indicate the presence of beneficial soil biota. Moreover, the spatial structure in plant communities, coupled with their correlation with soil BIGR, jointly suggest that plant-soil feedbacks operate at local scales in the field: this has been identified in modelling studies as an important driver of plant coexistence.

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1. What drives the evolution of increased growth and fecundity in plants introduced to a novel range is not well understood.

2. We investigate between-range differences in performance for Verbascum thapsus, a weedy invader known to grow larger in its introduced than native range. Specifically, we question whether adaptation to herbivory or climate best explains increased performance of introduced populations.

3. We grew 14 native and 22 introduced populations of V. thapsus in two common garden locations: near Prague, Czech Republic (native range) and in Colorado, USA (introduced range). By removing herbivores from half of the plants within each garden we tested the prediction of the Evolution of Increased Competitive Ability (EICA) hypothesis: increased performance is driven by an evolutionary shift of resources away from defence against herbivory towards growth and reproduction. We then investigated whether genetically based clines in performance are expressed along climate gradients within both the native and introduced ranges.

4. On average, seeds produce larger rosettes when collected from the introduced versus native range. While this evolution of increased growth in introduced populations in part matches the prediction of EICA, climate, not herbivory, best explains this between-range difference. Specifically, seeds collected from the native range produce smaller rosettes as the climate of origin becomes cooler and drier, while there is no cline in performance in rosettes grown from seed collected from the introduced range, which are large regardless of climate of origin. Thus, a climate-based cline within the native range best explains lower average performance of native compared to introduced populations.

SYNTHESIS: The breakdown in a potentially adaptive cline emphasizes the need to more closely investigate the evolutionary processes that shape geographic structuring (or its absence) within the introduced range. In addition, EICA is not universally applicable to all invasion scenarios, and our findings underscore the importance of testing underlying assumptions alongside the predictions of this hypothesis.

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1.Secondary forests are increasingly dominant in human-modified tropical landscapes, but the drivers of forest recovery remain poorly understood. Soil conditions influence plant community composition, and are expected to change over a gradient of succession. However, the role of soil conditions as an environmental filter driving community assembly during forest succession has rarely been explicitly assessed.

2.We evaluated the role of stand basal area and soil conditions on community assembly and its consequences for community functional properties along a chronosequence of Atlantic forest regeneration following sugar cane cultivation. Specifically, we tested whether community functional properties are related to stand basal area, soil fertility and soil moisture. Our expectations were that edaphic environmental filters play an increasingly important role along secondary succession by increasing functional trait convergence towards more conservative attributes.

3.We sampled soil and woody vegetation features across 15 second-growth (3-30 years) and 11 old-growth forest plots (300 m² each). We recorded tree functional traits related to resource-use strategies (specific leaf area, SLA; leaf dry matter content, LDMC; leaf area, LA; leaf thickness, LT; and leaf succulence, LS) and calculated community functional properties using the community-weighted mean (CWM) of each trait and the functional dispersion (FDis) of each trait separately and all traits together.

4.With exception of LA, all leaf traits were strongly associated with stand basal area; LDMC and SLA increased, while LT and LS decreased with forest development. Such changes in LDMC, LT and LS were also related to the decrease in soil nutrient availability and pH along succession, while soil moisture was weakly related to community functional properties. Considering all traits, as well as leaf thickness and succulence separately, FDis strongly decreased with increasing basal area and decreasing soil fertility along forest succession, presenting the lowest values in old-growth forests.

5.Synthesis. Our findings suggest that tropical forest regeneration may be a deterministic process shaped by soil conditions. Soil fertility operates as a key filter causing functional convergence towards more conservative resource-use strategies, such as leaves with higher leaf dry mass content.

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1.Despite strong climate change in the tropics, little is known about the responses of tropical plants to changing environments. Moreover, while variation in responses to climate change across plant functional groups may help to predict future vegetation dynamics, tropical multi-species studies are missing.

2.To study plant responses to changes in temperature, we compared the survival, growth and reproduction of 101 herbaceous species originating from the savanna and the submontane vegetation zones in two experimental gardens representing the climate of both zones at Kilimanjaro, Tanzania. Additionally, we tested whether plant functional groups, such as annuals and perennials, shade-tolerant and shade-intolerant species, grasses and forbs, and natives and exotics differ in their responses to transplantation.

3.We show that the submontane species in the lower Kilimanjaro area clearly prefer the cooler submontane temperature in terms of survival, growth and reproduction, while savanna plants can grow equally well under both, the submontane and the savanna temperature regimes. This suggests that tropical submontane plants will likely face severe challenges with future climate warming and that the upper distributional limit of savanna plants may be due to biotic interactions rather than to climate. Moreover, we found different responses of grasses and forbs, and natives and exotics to transplantation irrespective of their origin, underlining the importance of considering plant functional groups in climate change research.

4.Synthesis: We demonstrate different responses of tropical submontane and savanna plants to experimental temperature variation. Together with the observed differences between important functional plant groups, this leads us to suggest that strong future changes in vegetation composition on African tropical mountains are likely.

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1.The ‘habitat-specific species pool hypothesis’ proposes that differences between habitats in the sizes of their species pools are the main drivers of diversity responses to habitat heterogeneity. Empirical tests of this hypothesis are not trivial since species might be missing from ecologically suitable habitats due to limited dispersal, while others may occur in unsuitable habitats by means of source-sink dynamics and mass effect.

2.We tested the habitat-specific species pool hypothesis in a local, environmentally heterogeneous community of annual plants using a novel ‘ecological selection’ experiment. Mixtures of seeds representing the whole community were sown in each habitat, and the emerging species were exposed to six generations of selection by environmental filtering and competition while being blocked from dispersal. A comparison of the total number of species that were able to survive in each habitat (i.e., to pass the selection test) with data on species richness in the natural community allowed us to test the degree to which observed differences in species richness between habitats could be explained by differences in the sizes of the respective species pools.

3.Results supported the species pool hypothesis, showing that differences in the sizes of the habitat-specific species pools were important in determining diversity responses to habitat heterogeneity. Moreover, species richness showed a unimodal response to local-scale gradients in habitat productivity, and this response could be attributed to underlying differences in species-pool sizes. Both results were robust to properties of the data and the method of analysis.

4.Synthesis. Our results provide a strong experimental evidence that differences in the sizes of habitat-specific species pools might be important in shaping the diversity of local communities. Future theoretical and empirical studies in community ecology should explore the potential sources and implications of such differences.

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1.Overyielding in mixed-species forests has been demonstrated in a vast body of literature, and the focus of functional biodiversity research is now shifting towards a mechanistic understanding of these observations.

2.We explored diversity-productivity relationships (DPRs) at two sites of a large-scale tree diversity experiment, with harsh (Ged) and benign (Zed) environmental conditions for plantation establishment. Additive partitioning methodologies were adopted to detect phenomenological patterns in the productivity data, and the trait structure of mixed communities was used to advance insights into compositional effects.

3.After six years of plantation development, biomass productivity was significantly higher in mixtures compared to the monocultures of component species. We observed that processes operated through direct tree-tree interactions, since the diversity signal disappeared where trees in mixed stands were surrounded by conspecific neighbours only. This result is particularly relevant for mixed-species planation systems, as trees are commonly planted in monospecific patches to simplify management.

Partitioning unveiled strong selection effects at both plantation sites. However, at the harsh Ged-site this was caused by competitive dominance of species with fast young growth whereas at the benign Zed-site, species with slow young growth improved their performances but not at the expense of others (i.e., trait-dependent complementarity). Species tolerance to shading is an influential trait for predicting biodiversity effects, with community-weighted means in shade tolerance mediating dominance effects (Ged) and functional diversity in shade tolerance mediating (trait-dependent) complementarity effects (Zed).

4.Synthesis. This study highlights that biodiversity effects in young tree plantations could be explained by the functional composition of mixed communities, with a key role for species levels of shade tolerance. As contrasting results between plantation sites were observed, future research should target the context-dependency of DPRs.

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1.Host manipulation refers to the expression of a host phenotype that is partly under the genetic control of a parasite. This phenomenon can enhance parasite transmission rates and is responsible for biological marvels such as ‘Zombie-ants’ and the ‘fatal attraction’ of Toxoplasma-infected rodents to their feline predators. Such host manipulation has evolved in all major phylogenetic lineages of parasites and is assumed to enhance the fitness of the parasite.

2.However, the capacity to manipulate is not ubiquitous; that is, many clades of parasites comprise manipulating and non-manipulating species. This pattern leads to the prediction of costs that select against the evolution of manipulation, but this has been difficult to show empirically.

3.In the present study, we used a tripartitate system consisting of chili (Capsicum annuum) plants infected with Pepper golden mosaic virus and colonized by non-vector whiteflies (Trialeurodes vaporariorum), to study the effects on viral load when a non-vector herbivore feeds on the infected plants.

4.We observed that virus-infected plants emitted odours that attracted adult whiteflies, contained three times more amino acids in the phloem than mock-inoculated controls and supported higher whitefly reproduction as compared to controls. However, viral load decreased almost 100-fold in whitefly-carrying plants, which was associated with a depletion of phloem amino acids.

5.Synthesis. We show that a plant virus can suffer from a reduced within-host reproduction rate when virus-induced alterations of the plant cause a ‘fatal attraction’ of a non-vector insect that exploits the altered plant phenotype at its own benefits. The resulting fitness costs might represent a force that can select against the evolution of host manipulation by parasites.

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1.Predictions of upslope range shifts for tree species with warming are based on assumptions of moisture stress at lower elevation limits and low temperature stress at high elevation limits. However, recent studies have shown that warming can reduce tree seedling establishment across the entire gradient from subalpine forest to alpine via moisture limitation. Warming effects also vary with species, potentially resulting in community shifts in high elevation forests.

2.We examined the growth and physiology underlying effects of warming on seedling demographic patterns. We evaluated dry mass (DM), root length, allocation above- and belowground, and relative growth rate (RGR) of whole seedlings, and their ability to avoid or endure water stress via water-use efficiency and resisting turgor loss, for Pinus flexilis, Picea engelmannii and Pinus contorta seeded below, at, and above treeline in experimentally warmed, watered, and control plots in the Rocky Mountains, USA. We expected that growth and allocation responses to warming would relate to moisture status and that variation in drought tolerance traits would explain species differences in survival rates.

3.Across treatments and elevations, seedlings of all species had weak turgor-loss resistance, and growth was marginal with negative RGR in the first growth phase (-0.01 to -0.04 g/g/d). Growth was correlated with soil moisture, particularly in the relatively small-seeded P. contorta and P. engelmannii. P. flexilis, known to have the highest survivorship, attained the greatest DM and longest root but was also the slowest growing and most water-use-efficient. This was likely due to its greater reliance on seed reserves. Seedlings developed 15% less total DM, 25% less root DM, and 11% shorter roots in heated compared to unheated plots. Higher temperatures slightly increased DM, root length and RGR where soils were wettest, but more strongly decreased these variables under drier conditions.

4.Synthesis: The surprising heat-inhibition of tree seedling establishment at the cold edge of forests appears to have a physiological basis: newly germinated seedlings have poor moisture stress tolerance, which appears related to marginal initial growth and heavy reliance on seed reserves. Variation in these attributes among tree species at treeline helps explain their different climate responses.

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1.In a unique phenomenon restricted to the ever wet forests of Southeast Asia, hundreds of species from dozens of plant families reproduce synchronously at irregular, multi-year intervals. The proximate environmental cues that synchronize these general flowering events have not been evaluated systematically because there have been no long-term, high temporal-resolution, species-level records from the region.

2.We present 13 years of weekly flowering records for five Shorea species as well as daily temperature and rainfall records from the Pasoh Forest Reserve, Peninsular Malaysia. We constructed models to evaluate hypothesized relationships between flowering and cool temperature, drought, and additive and synergistic effects of cool temperature and drought for each species. Model parameters include periods of time for floral cue accumulation and flower development and temperature and/or rainfall thresholds required for floral initiation. Parameters estimated using flowering observations from 2001–2011 were used to forecast flowering for 2011–2014.

3.We show that drought and cool temperatures acting synergistically best explain the timing of flowering events for all Shorea species in the section Mutica and forecast the largest general flowering event accurately. Periods estimated for signal accumulation ranged from 54 to 90 days among species. Periods estimated for flowers to develop ranged between 43 to 96 days and closely followed the interspecific sequence of flowering in the Shorea species. Drought and temperature thresholds also varied among species, with S. maxwelliana requiring the most severe drought and S. leprosula the lowest temperatures.

4.Synthesis. Our results indicate that cool temperatures and low rainfall occurring on seasonal time scales of about two to three months rather than brief cold snaps or brief droughts best explain general flowering in Shorea species at the Pasoh Forest Reserve. Low rainfall is equally likely in winter (December–February) and summer (July–August) and cool temperatures are most likely in winter at Pasoh, which explains why general flowering events are restricted to spring and fall, with more frequent and stronger flowering in spring. In addition, species-specific sensitivity to environmental cues suggests that future climate change will have differential impacts on the frequency of reproduction, with potential consequences for regeneration of these dominant species of lowland tropical forests.

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1.Functional diversity (FD) metrics are widely used to assess invasion ecosystem impacts, but we have limited theory to predict how FD should respond to invasion. A key challenge to effectively using FD metrics is the complexity of conceptualizing alterations to multi-dimensional trait space, making it difficult to select a priori the most appropriate metric for specific ecological questions.

2.Here, we provide expectations on how invasion should change four commonly used FD metrics—functional richness (FRic), evenness (FEve), divergence (FDiv), and dispersion (FDis)—and then test these expectations in a lab decomposition experiment. We simulate invasion of a forest by understory plants by adding leaf litter from 18 natives and nonnatives to a representative canopy tree litter mixture to test changes in FD and decomposition.

3.All four metrics changed predictably with invasion. Species that were more functionally unique or when added at greater proportions had larger impacts on FD. Overall, FRic, FEve, and FDiv were poor choices for understanding impacts of nonnative species. FDis was the only metric that both changed predictably with addition of understory litter and correlated intuitively with changes in carbon mineralization. Furthermore, ranking species based upon how much they changed FDis of the litter mixture provided a fair assessment of which species had the largest impact on decomposition. As such, functional dispersion may be a key tool for predicting a priori which nonnatives will have the greatest impact on ecosystem processes.

4.Synthesis: We highlight the need to assess the suitability of each FD metric for the specific ecological question at hand. Our work reveals the pitfalls of considering multiple metrics or randomly choosing a single metric without suitability assessments. At the same time, it suggests a framework for metric assessment that should help lead to selection of a metric or metrics that provide robust a priori insights into how invasion by nonnative species can impact ecosystem processes.

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1. Flowering plants exhibit striking interspecific and intraspecific variation in flower number, which strongly influences the reproductive success of animal-pollinated plants. However, the reproductive consequences of producing a single flower are poorly understood.

2. Here, we test if plants producing a single flower have a reproductive disadvantage compared to plants producing multiple flowers by combining field investigation of five deceptive orchids and a survey of published literature. Pollen limitation was estimated by comparing fruit production between hand pollination and open pollination. Flowering frequency was monitored over years to assess the potential advantage of producing a single flower.

3. Both single- and multiple-flowered species suffered strong pollen limitation. However, single-flowered species had significantly lower fruit set and produced fewer seeds per individual, though they had a significantly higher pollen removal than species with multiple flowers. A phylogenetically independent contrast (PIC) of 28 species representing four out of the five subfamilies of Orchidaceae revealed that fruit set was significantly positively associated with flower number. Both pollen removal and fruit set had a positive relationship with flower number within the multiple-flowered species.

4. Synthesis Current data and PIC support the hypothesis that producing a single flower has reproductive disadvantages. Single-flowered species may compensate for low female success through high flowering frequency over years. This study provides insight into costs and benefits of producing a single flower in deceptive orchids.

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1. Contemporary global change, including the widespread mortality of foundation tree species, is altering ecosystems and plant communities at unprecedented rates. Plant-soil interactions drive myriad community dynamics, and we hypothesized such interactions may be an important driver of succession following the loss of foundation tree species.

2. We examined whether plant-soil biota interactions, in the context of a putatively important light gradient associated with foundation tree decline, mediate the expansion of Rhododendron maximum in southeastern US forests where Tsuga canadensis (eastern hemlock), a dominant foundation tree species, is in decline. Using an 11-month, controlled inoculation experiment paired with Illumina sequencing, we tested the following hypotheses: (1) Relative to conspecific (R. maximum-conditioned) soils, R. maximum seedlings have higher performance in soils conditioned by T. canadensis and lower performance in interspace soils (conditioned by neither T. canadensis nor R. maximum) due to variation in soil fungal biota, and (2) seedling performance is greater in high light versus low light environments (matching environments under infested versus uninfested T. canadensis crowns, respectively).

3. In partial support of the first hypothesis, we found that R. maximum seedling performance was highest in T. canadensis-conditioned and R. maximum-conditioned soils and lowest in interspace soils. Mechanistically, soils conditioned by T. canadensis and R. maximum had more ericoid and ectomycorrhizal fungi, less saprotrophic fungi, and were less species-rich than interspace soils, and variation in these community traits predicted substantial variation in R. maximum seedling biomass. However, in support of our second hypothesis, soil effects on plant performance were evident in high light only; in low light, soil inoculation did not affect plant performance and plants performed worse on average.

4. Synthesis. Our findings suggest interactions with soil biota act synergistically with altered abiotic environments to mediate species responses to widespread foundation tree mortality, providing evidence for a novel mechanism of plant response to large-scale disturbance. Examining plant-soil interactions in the context of relevant abiotic gradients can therefore enhance our understanding, predictions, and management of community development processes following forest disturbance.

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1. Establishing a horizontally transmitted mutualism is a critical step for many organisms, particularly when an individual can engage with only one partner over its lifetime. Ant foundresses shed their wings before they start to lay eggs, which makes host choice particularly critical for plant-ants that exclusively colonize myrmecophytes.
2. Volatile organic compounds (VOCs) can indicate the identity and physiological condition of an individual and frequently serve as signals or cues that facilitate partner choice. Thus, we hypothesised that obligate plant-ants use VOCs to determine the quality of potential host plants.
3. Indeed, winged females of the plant-ant, Pseudomyrmex ferrugineus, used plant odours to identify high-quality acacia hosts among different species and among individuals of the same species. The VOC blend of a branch was related to reward production and, interestingly, the least attractive blend contained the highest number of compounds.
4. Whereas only seven different VOCs could be detected in the blend of the high-reward host species, the low-reward host emitted 13 different compounds, among which (S)-(-)-limonene and β-linalool were the dominant ones. Complementing the odour of the high-reward host with (S)-(-)-limonene, β-linalool or α-terpinene reduced its attractiveness. Strikingly, these compounds inhibited bacterial pathogens of the host plant.
5. Synthesis. Plant-ants can use host plant odours that contain resistance-related VOCs to judge on host quality, likely because of negative crosstalk between direct resistance to disease and investment in ant-mediated defence. VOCs can serve as cues that provide reliable information for partner choice, particularly when their emission results from a physiological process that causally relates to the quality of an individual as a mutualist.

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1. This account presents information on all aspects of the biology of S. tinctoria L. that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation.

2. Serratula tinctoria is a gynodioecious perennial forb of open or semi-shaded habitats including grassland, heath, mire, open woodland and scrub and their ecotones. It is found throughout most of England and Wales but it is very rare in Scotland and absent from Ireland. Serratula tinctoria is found in Europe as far north as southern Sweden and Norway. It is absent from much of the Boreal biogeographical zone, including most of Fennoscandia and northern Poland, Russia and the Baltic States, and from the lowland Mediterranean zone.

3. Serratula tinctoria occurs on soils overlying a wide variety superficial deposits and sedimentary, metamorphic and igneous rocks, including ultramafic rocks. The pH range of these soils is wide, ranging from acidic to moderately alkaline but with nutrient status classed as oligotrophic, or more rarely mesotrophic. In mire or fen habitats, it occurs in topogenous or soligenous situations with a similar soil-water pH range. It is able to tolerate a wide spectrum of soil water table conditions, ranging from very dry to flooded.

4. Serratula tinctoria is pollinated by various insects of the orders Hymenoptera, Diptera and Lepidoptera, particularly bumblebees, hoverflies and butterflies. It produces phytoecdysteroids, which mimic a hormone that regulates insect development.

5. The seed has a feathery pappus for wind dispersal and establishment is primarily from seed. However, it has strong dispersal limitation with slow migration rates into restored grasslands of 1 m year ⁻¹. The species has a short-term persistent seed bank. Seedling recruitment is enhanced by disturbance that creates bare ground, increasing light flux and lower cover of bryophytes and litter, and reduced by higher nutrient availability and lack of management.

6. Formerly the source of a yellow dye, S. tinctoria has declined in Britain since at least the late 19th Century primarily due to a combination of drainage, ploughing and agricultural improvement and, conversely, lack of management by cutting and grazing in its grassland, heath and mire habitats. There is evidence that the decline slowed or stabilised between the late-1980s and the mid-2000s, in part due to the positive impact of conservation via statutory protection on designated sites and wider measures delivered through agri-environment schemes.

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1.Vertical differentiation in root placement is one of the potential mechanisms of plant niche differentiation. It can be due to the remarkable plasticity of roots in response to nutrients and neighbours, but most data on it come from pot or garden experiments. The roles of vertical differentiation and of plasticity in it in the field are thus not well known.

2.We examined species-specific root vertical distribution in a montane grassland using quantitative Real-Time PCR. We asked whether individual species differ in their rooting depths, whether such differences are associated with aboveground functional traits (such as height or specific leaf area), and whether they respond to the presence of a competitor. This response was assessed by comparison of species-specific vertical profiles between control plots and plots where the dominant species, Festuca rubra, had been removed.

3.Vertical profiles of individual species varied considerably, from species with most root biomass concentrated in the uppermost (<2 cm) soil layer, through species with uniform vertical distribution, to a species with roots predominantly below 8 cm (Nardus stricta). Species at the fast end of the plant economy spectrum were more likely to place their roots in the uppermost layers. Grassland species thus exploit different parts of the belowground resources in spite of their short stature, minor differences in height aboveground and shallow soil.

4.While belowground and aboveground biomasses of most species were higher in the removal plots, species rooting patterns did not change in response to the removal. The interspecific differences in vertical profiles were thus due to species’ innate differences, not to plastic responses to the presence of the dominant species.

5.Synthesis. The findings imply that vertical root differentiation in the field is strong and can contribute to niche differentiation. However, the role of root plasticity in natural systems may be considerably weaker than in artificial systems with few species and strong nutrient gradients. This absence of the plastic response in the field is likely to be due to a fairly homogeneous distribution of nutrients in the soil and to the predominantly symmetric nature of belowground competition.

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1.Plant species that arrive first in the system can affect assembly (priority effects). However, effects of order of arrival of different plant functional groups on root development has not yet been investigated under field conditions.

2.We measured standing and fine root length density in the first and third year of a grassland field experiment. We wanted to know if manipulating plant functional groups order of arrival would affect root development, and if these priority effects are modulated by soil type.

3.Sowing legumes first created a priority effect that was found in the first and third year, with a lower standing root length density in this treatment, even though the plant composition was different in each of the studied years. Fine root length density was not affected by order of arrival, but changed according to the soil type.

4.Synthesis: We found strong evidence that sowing legumes first created a priority effect belowground that was found in the first and third year of this field experiment, even though the functional group dominance was different in each of the studied years.

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1. Climate warming is predicted to alter ecological boundaries in high-latitude ecosystems including the elevational or latitudinal extent of tall shrubs in Arctic and alpine tundra. Over 60 studies from 128 locations around the tundra biome have investigated shrub expansion in tundra ecosystems; however, only six studies test whether shrublines are actually advancing up hill-slopes or northward into tundra where tall shrubs are currently absent.
2. We test the hypothesis that willow shrublines have expanded to higher elevations in relation to climate across a 50 x 50 km area in the Kluane Region of the southwest Yukon Territory, Canada by surveying of 379 shrubs at 14 sites and sampling of 297 of the surveyed shrubs at 10 sites. We compared growth and recruitment to climate variables to test the climate sensitivity of shrub increase using annual radial growth analysis, age distributions and repeat field surveys to estimate the current rate of shrubline advance.
3. We found consistent and increasing rates of recruitment of alpine willows, with estimates of faster advancing shrublines on shallower hill-slopes. Mortality was extremely low across the elevation gradient. Aspect, elevation and species identity did not explain variation in recruitment patterns, suggesting a regional factor, such as climate, as the driver of the observed shrubline advance.
4. Annual radial growth of willows was best explained by variation in summer temperatures, and recruitment pulses by winter temperatures. Measured recruitment rates are ˜20 ± 5 individuals per hectare per decade (mean ± SE) and measured rates of increased shrub cover of ˜5 ± 1% per decade (mean ± SE) measured at the Pika Camp site between field surveys in 2009 and 2013. Our results suggest that shrubline will continue to advance over the next 50 years, if growing conditions remain suitable. However, if future conditions differ between summer and winter seasons, this could lead to contrasting trajectories for recruitment versus growth, and influence the vegetation change observed on the landscape.
5. Synthesis. Our findings in the context of a review of the existing literature indicate that elevational and latitudinal shrublines, like treelines, are advancing in response to climate warming; however, the trajectories of change will depend on the climate drivers controlling recruitment versus growth.

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1. Partial mycoheterotrophy (PMH) is a nutritional mode in which plants utilize organic matter, i.e. carbon, both from photosynthesis and a fungal source. The latter reverses the direction of plant-to-fungus carbon flow as usually assumed in mycorrhizal mutualisms. Based on significant enrichment in the heavy isotope ¹³C, a growing number of PMH orchid species have been identified. These PMH orchids are mostly associated with fungi simultaneously forming ectomycorrhizas with forest trees. In contrast, the much more common orchids that associate with rhizoctonia fungi, which are decomposers, have stable isotope profiles most often characterized by high ¹⁵N enrichment and high nitrogen concentrations but either an insignificant ¹³C enrichment or depletion relative to autotrophic plants. Using hydrogen stable isotope abundances recent investigations showed PMH in rhizoctonia-associated orchids growing under light-limited conditions. Hydrogen isotope abundances can be used as substitute for carbon isotope abundances in cases where autotrophic and heterotrophic carbon sources are insufficiently distinctive to indicate PMH.
2. To determine whether rhizoctonia-associated orchids growing in habitats with high irradiance feature PMH as a nutritional mode, we sampled 13 orchid species growing in montane meadows, four forest orchid species and 34 autotrophic reference species. We analysed δ²H, δ¹³C, δ¹⁵N and δ¹⁸O and determined nitrogen concentrations. Orchid mycorrhizal fungi were identified by DNA sequencing.
3. As expected, we found high enrichments in ²H, ¹³C, ¹⁵N and nitrogen concentrations in the ectomycorrhiza-associated forest orchids, and the rhizoctonia-associated Neottia cordata from a forest site was identified as PMH. Most orchids inhabiting sunny meadows lacked ¹³C enrichment or were even significantly depleted in ¹³C relative to autotrophic references. However, we infer PMH for the majority of these meadow orchids due to both significant ²H and ¹⁵N enrichment and high nitrogen concentrations. Pseudorchis albida was the sole autotrophic orchid in this study as it exhibited neither enrichment in any isotope nor a distinctive leaf nitrogen concentration.
4. Synthesis. Our findings demonstrate that partial mycoheterotrophy is a trophic continuum between the extreme endpoints of autotrophy and full mycoheterotrophy, ranging from marginal to pronounced. In rhizoctonia-associated orchids, partial mycoheterotrophy plays a far greater role than previously assumed, even in full light conditions.

In our study we investigate the nutritional mode of meadow orchids using stable isotope natural abundances. We find that partial mycoheterotrophy plays a far greater role in rhizoctonia-associated orchids growing in full light conditions than previously assumed. We demonstrate that partial mycoheterotrophy is a trophic continuum between the extreme endpoints of autotrophy and full mycoheterotrophy, ranging from marginal to pronounced.

1. In northern Idaho (USA), more than 100 vascular plant species are disjunct >160 km from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within this interior forest disjunction, including Tsuga mertensiana, survived the last glacial period in a north-Idaho refugium or whether these species colonized the region via long-distance dispersal during the Holocene.
2. Sediment cores were extracted from three mid- to high-elevation lakes within T. mertensiana-dominated forests in the Northern Rocky Mountains of Idaho. Pollen and macrofossils were used to reconstruct forest composition, determine the timing of T. mertensiana establishment, examine the hypothesis that the region was a glacial refugium, and contrast how climate, competition and/or dispersal limitation have influenced its modern distribution.
3. The modern distribution of T. mertensiana was analysed by constructing a range map and modelling the potential species distribution. The presence of outlier populations surrounding the Idaho disjunction along with broad areas of unoccupied suitable habitat indicates that the range of T. mertensiana is currently expanding. To assess the accuracy of T. mertensiana pollen at detecting its range limit, a network of pollen surface samples was used to analyse the probability of detecting T. mertensiana pollen as a function of distance from its geographical range limit. Consistent T. mertensiana pollen occurrence at ≥1% abundance is likely only within 42 km of its range limit.
4. Tsuga mertensiana first appears in the pollen and macrofossil record at the highest-elevation site at c. 4,100 cal year bp, then at the next highest-elevation site at c. 1,600 cal year bp, and last at the mid-elevation site at 800 cal year bp. Tsuga mertensiana pollen occurs continuously at ≥1% at all three sites by c. 300 cal year bp suggesting regional presence. The timing of arrival suggests that T. mertensiana is a recent component of the forests of Idaho, having arrived during the Holocene via long-distance dispersal from coastal populations over 160 km away.
5. Synthesis. Comparison with palaeoclimate reconstructions from the broader region suggests that climate was a greater limiting factor than dispersal in the Holocene establishment in the interior, indicating little difficulty overcoming a large dispersal barrier. However, T. mertensiana remained at low abundances for millennia until Little Ice Age climates promoted its recent increase in abundance. Unoccupied areas of suitable habitat suggest that competition, rather than climate or dispersal, is a limiting range infilling in the interior mesic forests today.

We examined palaeoecological records to address the establishment of Tsuga mertensiana in an interior disjunction >160 km separated from its main coastal distribution. Lack of any fossil evidence >4,000 years ago suggests surprising long-distance dispersal. The timing of first detection coincides with climate changes consistent with a warmer climate limiting its interior distribution. T. mertensiana remained at low abundances for millennia until Little Ice Age climates promoted its recent increase in abundance. Unoccupied areas of suitable habitat suggest that competition, rather than climate or dispersal, is limiting range infilling in the interior mesic forests today.

1. Plant invasions are affected by many factors that must be favourable in order for invasions to occur. Factors can be grouped into three major categories: propagule pressure, biotic factors and abiotic characteristics; all may be moderated by human activity. However, studies examining all factors simultaneously are rare, and most are limited to a single factor. This hampers our understanding of the mechanisms driving invasions.
2. In recent decades, an alien walnut (Juglans regia) has become invasive in Central Europe due to an increase in the populations of native dispersers, rooks (Corvus frugilegus) and political changes that have resulted in the abandonment of farmland. Here, we test whether increased propagule pressure resulting from the presence of seed-bearing walnuts in abandoned fields interacts with native forest seed-dispersing animals (biotic factors), landscape structure and management, and passive secondary dispersal by gravity (abiotic factors) to facilitate the further invasion of walnuts into forests.
3. Seed-dispersing animals were observed visiting walnuts growing in abandoned fields and in human settlements. Walnuts and seed dispersers were surveyed in 102 forest patches. Forest characteristics were examined, and field experiments examining passive dispersal were conducted.
4. Walnut seeds were carried into forests by native birds, jays (Garrulus glandarius). Jays harvested seeds from both wild walnuts growing in abandoned fields and walnuts planted in human settlements. The density of walnuts in forest patches was correlated with jay density. Forest occupancy by walnuts and walnut densities were correlated with the cover of abandoned fields and human settlements containing seed-bearing walnuts. Secondary seed dispersal also affected forest colonization. Walnut seeds hidden by native rooks in sloping, arable fields may be transported passively to forest edges.
5. Synthesis. Our results show that this invasion is a multifaceted process in which human-related alterations to propagule pressure and biotic and abiotic factors have led to the spread of alien walnuts from human settlements and abandoned fields into forest ecosystems. Thus, politically related land use changes can create an invasion debt that causes unexpected linkages among the invasive plant, native dispersers, land management and topography that together can cause cascading changes in ecosystems.

Juglans regia invasion into Central European forests is the complex interaction between humans planting trees, land abandonment and bird dispersal. J. regia have long been planted in human settlements. Native Corvus frugilegus spread seeds into abandoned agricultural fields. Next Garrulus glandarius transport seeds both from human settlements and from abandoned fields into forests. In addition, seeds hidden by C. frugilegus in sloping agricultural fields can be passively transported to forest edges.

1. Reductions in community evenness can lead to local extinctions as dominant species exclude subordinate species; however, herbivores can prevent competitive exclusion by consuming otherwise dominant plant species, thus increasing evenness. While these predictions logically result from chronic, gradual reductions in evenness, rapid, temporary pulses of dominance may also reduce species richness. Short pulses of dominance can occur as biotic or abiotic conditions temporarily favour one or a few species, manifested as increased temporal variability (the inverse of temporal stability) in community evenness. Here, we tested whether consumers help maintain plant diversity by reducing the temporal variability in community evenness.
2. We tested our hypothesis by reducing herbivore abundance in a detailed study of a developing, tallgrass prairie restoration. To assess the broader implications of the importance of herbivory on community evenness as well as potential mechanisms, we paired this study with a global herbivore reduction experiment.
3. We found that herbivores maintained plant richness in a tallgrass prairie restoration by limiting temporary pulses in dominance by a single species. Dominance by an annual species in a single year was negatively associated with species richness, suggesting that short pulses of dominance may be sufficient to exclude subordinate species.
4. The generality of this site-level relationship was supported by the global experiment in which inter-annual variability in evenness declined in the presence of vertebrate herbivores over timeframes ranging in length from 2 to 5 years, preventing declines in species richness. Furthermore, inter-annual variability of community evenness was also negatively associated with pre-treatment species richness.
5. Synthesis. A loss or reduction of herbivores can destabilize plant communities by allowing brief periods of dominance by one or a few species, potentially triggering a feedback cycle of dominance and extinction. Such cycles may not occur immediately following the loss of herbivores, being delayed until conditions allow temporary periods of dominance by a subset of plant species.

A loss or reduction of herbivores can destabilize plant communities by allowing brief periods of dominance by one or a few species, potentially triggering a feedback cycle of dominance and extinction. Such cycles may not occur immediately following the loss of herbivores, being delayed until conditions allow temporary periods of dominance by a subset of plant species.

1. Lianas are structural parasites of trees and reduce individual host tree growth, survival and fecundity. Thus, liana infestation is expected to affect tree population growth rates, with potentially different effects in different species depending on the frequency of liana infestation and the impact of liana infestation on population growth rates. Previous studies have documented the myriad negative effects of lianas on trees and variation in liana infestation among tree species; however, no study has quantified the impact of liana infestation on individual tree species population growth rates. Lianas are increasing in abundance in multiple Neotropical sites, which may have profound consequences for tree species composition if lianas differentially affect host tree species population growth.
2. Here, we use long-term data to evaluate the effects of liana infestation on the reproduction, growth, survival and ultimately population growth rates of dozens of tree species from Barro Colorado Island, Panama. We then test whether liana infestation affects tree species differentially with respect to two axes of life-history variation: adult stature and position along the fast–slow axis, a measure of shade tolerance.
3. Liana infestation decreased tree growth, survival and reproduction, with the strongest effects on survival in fast-growing, light-demanding species and on reproduction in large-statured species. In combination, these effects reduced tree population growth rates such that liana-infested populations declined by an average of 1.4% annually relative to conspecific liana-free populations. The reduction in population growth rates was greatest among fast-growing species and smaller in slow-growing species.
4. Synthesis. Our results demonstrate that liana infestation has strong negative effects on tree population growth rates, which vary systematically among tree species with tree life history. The finding that liana infestation is more harmful to fast-growing tree species appears to be at odds with the general expectations in the literature. We propose that this is likely due to survivorship bias, as infestation greatly decreases survival in fast-growing species such that the observable sample is biased towards those that survived and liana-free. In combination with data on how tree species vary in liana infestation rates, these results provide a basis for predicting the impacts of changes in liana abundance on tree species composition.

Lianas are structural parasites of trees that are increasing across the Neotropics. Here we show that liana infestation has strong negative effects on tree population growth rates, and that these effects vary systematically among tree species with tree life history, with especially light demanding tree species being more severely affected. Our results provide evidence that lianas are capable of impacting tree species composition.

1. We studied the effects of fuel type, fuel load and their associated flammability attributes on growth and survival of Callitris intratropica saplings. Callitris intratropica is a fire-sensitive conifer that is widespread across northern Australia, but its range is contracting because of frequent and intense fires.
2. A small-scale field experiment was used to compare the effect of three fuel types (grass, eucalypt litter and C. intratropica litter), and a mix of grass and eucalypt litter by varying fuel loads within their naturally occurring bounds, and measuring multiple flammability attributes.
3. Fuel type had the strongest influence on flammability attributes and hence sapling survival. Grass burnt rapidly, producing high temperatures, while duration of flaming was longer for eucalypt litter. Grass–eucalypt litter mixtures had flammability attributes more like grass, while C. intratropica litter was difficult to burn. Fuel load had a secondary effect, with strong interactions between fuel type and load.
4. Differences in sapling survival could be attributed to temperatures at 5 cm height; there was no additional effect of fuel type or canopy temperature. Sapling size variables were also important, and strongly correlated with bark thickness, so we could not identify the protective mechanism.
5. Synthesis. Mortality of Callitris intratropica saplings was consistent with damage to the lower stem, because of the direct relationship with temperatures at 5 cm height. Our results demonstrate the existence of a grass–fire cycle in C. intratropica stands, whereby hot fires damage the stands and allow grass to invade, increasing the stand ignitability and combustibility and promoting further fires. Interrupting this cycle by reducing grass fuel loads and hence the frequency of hot fires should therefore be a management priority to safeguard C. intratropica populations. Our findings also highlight that, under a common climate, vegetation type can shape fire regimes, because fuel type strongly influences flammability attributes, which in turn act as a powerful filter of plant populations.

Mortality of Callitris intratropica saplings was consistent with damage to the lower stem, because of the direct relationship with temperatures at 5 cm height. Our results demonstrate the existence of a grass-fire cycle in C. intratropica stands, whereby hot fires damage the stands and allow grass to invade, increasing the stand ignitability and combustibility and promoting further fires. Interrupting this cycle by reducing grass fuel loads and hence the frequency of hot fires should therefore be a management priority to safeguard C. intratropica populations. Our findings also highlight that, under a common climate, vegetation type can shape fire regimes, because fuel type strongly influences flammability attributes, which in turn act as a powerful filter of plant populations.

1. More frequent drought episodes are expected to cause higher mortality in isohydric tree species such as pines, because individuals close their stomata early during drought in order to maintain constant needle water potentials. It has been suggested that trees delay the ensuing carbon starvation by actively storing carbon at the expense of growth (“bet hedging”). Because such a strategy is only adaptive in drought-prone regions, we hypothesise that the degree of carbon “bet hedging” should differ between ecotypes.
2. We repeatedly measured the allocation of biomass, starch and soluble sugars to needles, stem and roots in seedlings of nine populations of Pinus sylvestris and Pinus nigra along a gradient from Central Europe to the Mediterranean. During two consecutive growing seasons, seedlings grown from seed were exposed to factorial combinations of 4 months of drought (D1, D2) and ambient/elevated CO₂ (aCO₂/eCO₂).
3. Drought-stressed pine seedlings did neither increase starch concentrations, nor change biomass production or experience lower mortality under eCO₂ compared to aCO₂. By the end of D2, seedlings from drier origin had accumulated more starch but at the same time also more biomass than seedlings from wetter origin.
4. Surprisingly, seedlings acclimatised to dry conditions after D1 so that mortality dropped to zero and drought effects on needle starch (P. sylvestris) and overall starch (P. nigra), respectively, disappeared after D2.
5. Synthesis. The absence of a trade-off between carbon storage (starch) and growth (biomass), and the patterns of mortality observed in seedlings growing under combined drought and eCO₂ do not support the theory of carbon “bet hedging” in isohydric Pinus sylvestris and Pinus nigra. Results suggest that reduced growth and acclimatisation minimised seedling mortality in the second year. Acclimatisation might thus enable pine seedlings to resist a moderate increase in summer drought frequency expected in the future.

The absence of a trade-off between carbon storage (starch) and growth (biomass), and the patterns of mortality observed in seedlings growing under combined drought and elevated CO₂ do not support the theory of carbon “bet hedging” in isohydric P. sylvestris and P. nigra. Reduced growth and acclimatisation minimised mortality in the second year, enabling pine seedlings to resist a moderate increase in summer drought frequency expected in the future.

1. Potential variability in nutrient limitation among tree size classes, functional groups and species calls for an integrated community- and ecosystem-level perspective of lowland tropical rainforest nutrient limitation. In particular, canopy trees determine ecosystem nutrient conditions, but competitive success for nutrients and light during the sapling bottleneck determines canopy composition.
2. We conducted an in situ multi-nutrient sapling fertilization experiment at La Selva Biological Station, Costa Rica, to determine how functional group identity, species identity and light availability can impact nutrient limitation of stem growth in three functional groups and nine species.
3. Despite high soil fertility, we found nutrient-light limitation in two functional groups and four species. Unexpectedly, the nitrogen-fixing (“N₂ fixers”) and shade-tolerant functional groups were significantly nutrient limited, while the light-demanding functional group was not.
4. This was partially explained by species-level variation in nutrient limitation within these functional groups, with only some species conforming to the prediction of stronger nutrient limitation in light demanders compared to shade-tolerants.
5. Most surprisingly, we found strong nutrient limitation at low-light levels in the N₂ fixers (which were shade-tolerant), but not in the shade-tolerant non-fixers. We hypothesize that the N₂ fixers were actually nitrogen limited at low-light levels because of their nitrogen-rich leaves and the high carbon cost of their symbionts.
6. This finding suggests a highly shade-tolerant, N₂ fixation strategy, in addition to the perception that N₂ fixation is mostly advantageous in high-light environments during early and gap succession. The shade-tolerant, N₂ fixation strategy may be part of a sapling and canopy tree feedback, where the canopy N₂ fixers enrich the soil N, enhancing growth of their shade-tolerant saplings relative to non-fixing competitors, enabling further canopy domination by shade-tolerant N₂ fixers, as seen at La Selva.
7. Synthesis. The pervasiveness of functional group- and species-specific nutrient and light co-limitation in our saplings indicates that these interactions likely play an important role in the dynamics of lowland tropical rainforest nutrient limitation, potentially via other such sapling and canopy tree feedbacks as the one hypothesized.

This study revealed functional group- and species-specific interactions between light availability and nutrient limitation of lowland tropical rain forest sapling growth. Two out of three functional groups and four out of nine species responded to fertilization, confirming the importance of nutrients in addition to light availability for sapling growth and emphasizing the significance of sapling nutrient and light co-limitation in lowland tropical rain forest nutrient dynamics.

1. Mammalian herbivores can strongly influence nitrogen (N) cycling and herbivore urine could be a central component of the N cycle in grazed ecosystems. Despite its potential role for ecosystem productivity and functioning, the fate of N derived from urine has rarely been investigated in grazed ecosystems.
2. This study explored the fate of ¹⁵N-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer for more than 50 years. We followed the fate of the ¹⁵N applied to the plant canopy, at 2 weeks and 1 year after tracer addition, in the different ecosystem N pools.
3. ¹⁵N-urea was rapidly incorporated in cryptogams and in above-ground parts of vascular plants, while the soil microbial pool and plant roots sequestered only a marginal proportion. Furthermore, the litter layer constituted a large sink for the ¹⁵N-urea, at least in the short term, indicating a high biological activity in the litter layer and high immobilization in the first phases of organic matter decomposition.
4. Mosses and lichens still constituted the largest sink for the ¹⁵N-urea 1 year after tracer addition at both levels of grazing intensity demonstrating their large ability to capture and retain N from urine. Despite large fundamental differences in their traits, deciduous and evergreen shrubs were just as efficient as graminoids in taking up the ¹⁵N-urea. The total recovery of ¹⁵N-urea was lower in the intensively grazed sites, suggesting that reindeer reduce ecosystem N retention.
5. Synthesis. The rapid incorporation of the applied ¹⁵N-urea indicates that arctic plants can take advantage of a pulse of incoming N from urine. In addition, δ¹⁵N values of all taxa in the heavily grazed sites converged towards the δ¹⁵N values for urine, bringing further evidence that urine is an important N source for plants in grazed tundra ecosystems.

Herbivore urine could be a central component of the nitrogen cycle in grazed ecosystems. This study explored the fate of ¹⁵N-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer. We demonstrated a rapid incorporation of the applied ¹⁵N-urea by all plants indicating that urine is an important N source for plants in grazed tundra ecosystems.

1. Density dependence is of fundamental importance for population and range dynamics. Density-dependent reproduction of plants arises from competitive and facilitative plant–plant interactions that can be pollination independent or pollination mediated. In small and sparse populations, conspecific density dependence often turns from negative to positive and causes Allee effects. Reproduction may also increase with heterospecific density (community-level Allee effect), but the underlying mechanisms are poorly understood and the consequences for community dynamics can be complex. Allee effects have crucial consequences for the conservation of declining species, but also the dynamics of range edge populations. In invasive species, Allee effects may slow or stop range expansion.
2. Observational studies in natural plant communities cannot distinguish whether reproduction is limited by pollination-mediated interactions among plants or by other neighbourhood effects (e.g. competition for abiotic resources). Even experimental pollen supply cannot distinguish whether variation in reproduction is caused by direct density effects or by plant traits correlated with density. Finally, it is unknown over which spatial scales pollination-mediated interactions occur.
3. To circumvent these problems, we introduce a comprehensive experimental and analytical framework which simultaneously (1) manipulates pollen availability and quality by hand pollination and pollinator exclusion, (2) manipulates neighbourhoods by transplanting target plants, and (3) analyses the effects of con- and heterospecific neighbourhoods on reproduction with spatially explicit trait-based neighbourhood models.
4. Applying this framework to Senecio inaequidens, one of Europe's fastest plant invaders, we found that the seed set was strongly pollen limited. Reproduction had increased by pollinator-mediated facilitation by both con- and heterospecific neighbours which may lead to (community-level) Allee effects. Pollination-independent interactions, such as amelioration of abiotic conditions through neighbours, contributed to additional positive neighbour effects. However, these pollination-independent interactions were weaker than the pollination-mediated interactions and they occurred over smaller spatial scales. Finally, the strength and direction of neighbourhood effects depended on neighbour traits and thus changed with the trait composition of the neighbourhood.
5. Synthesis. By manipulating both pollen availability and target plant locations within neighbourhoods, we can comprehensively analyse spatially explicit density dependence of plant reproduction. This experimental approach enhances our ability to understand the dynamics of sparse populations and of species geographical ranges.

Density-dependent reproduction of plants arises from competitive and facilitative plant–plant interactions that can be pollination independent or pollination mediated. We introduce a comprehensive experimental and analytical framework which simultaneously manipulates both pollen availability and target plant locations within neighbourhoods. Pollination-independent and pollination-mediated effects of con- and heterospecific neighbourhoods on reproduction of the invasive Senecio inaequidens are analysed with spatially explicit trait-based neighbourhood models.

1. Abiotic factors, biotic interactions and dispersal ability determine the spatial distribution of species. Theory predicts that abiotic constraints set range limits under harsh climatic conditions and biotic interactions set range limits under benign climatic conditions, whereas dispersal ability should limit both ends of the distribution. However, empirical studies exploring how these three components jointly affect species across environmental gradients are scarce.
2. Here, we present a study that jointly examines these factors to investigate the constraints of the recruitment of Swiss stone pine (Pinus cembra) at and beyond its upper and lower elevational range limits in the Swiss Alps. We investigated the natural recruitment of pines and additionally conducted seed transplant experiments to test how much abiotic factors (mean summer and winter temperatures, soil moisture), biotic interactions (understorey vegetation cover, canopy cover, seed predation) and/or seed deposition by the spotted nutcracker (Nucifraga caryocatactes) affect pine establishment.
3. We found significant effects of biotic interactions and seed deposition by spotted nutcrackers on the recruitment of Swiss stone pine at both the upper and lower elevational range, but could not detect significant effects of abiotic factors. Importantly, dispersal limitation rather than temperature and soil moisture restricted the recruitment of pines at the upper elevational range.
4. Synthesis. Our study highlights the importance of biotic interactions and dispersal ability in setting the upper range limits of species that have been regarded as mainly controlled by climate. This suggests that potential range shifts of plants in response to climate warming may strongly depend on seed dispersal and biotic interactions and not only on climatic factors.

In our study we show that biotic interactions and seed deposition, rather than abiotic factors, limit the recruitment of an alpine plant not only at lower elevational ranges but also at and beyond the tree line. These findings reveal that biotic interactions and seed dispersal might be more important for the dynamics of plant range expansions than previously assumed.

1. Herbivore grazing has major effects on soil nutrient dynamics in a variety of grassland ecosystems. Previous studies have examined how large herbivores as a group affect nutrient cycling, but little information is available on how assemblages of different herbivore species may influence nutrient cycling, and whether herbivore assemblage effects are influenced by plant community characteristics (e.g. composition, diversity) of the grazed grassland.
2. We conducted a 5-year, replicated grazing experiment to test the effects of different large herbivore assemblages (cattle grazing, sheep grazing, combined cattle and sheep grazing, no grazing) under moderate grazing intensity on soil nitrogen (N) mineralization rate in two types of grassland communities (high forbs/high diversity and low forbs/low diversity) in meadow steppe habitat of northeast China. Moreover, we examined two distinctly different pathways that herbivores could influence soil N availability: directly through urine and dung deposition and indirectly by shifting grassland species composition (i.e. the grass: forb ratio), thereby the quality of plant litter available to soil decomposers.
3. We found that grazer effects on soil N availability (indexed with anion and cation adsorption strips) depended on herbivore assemblage, and the herbivore assemblage effects varied in the two types of grasslands. In one type of grassland characterized by low diversity, grazing by each of the herbivore assemblages enhanced soil N availability compared to the ungrazed plots, and mixed species (cattle and sheep) grazing had a greater effect than single species grazing. In high diversity grassland, single species herbivore grazing significantly increased soil N availability, but mixed grazing had no effect.
4. Mixed linear modelling revealed that soil N availability was facilitated primarily by excreta additions to the soil and secondarily by the abundance of grasses.
5. Synthesis. Grazers increased soil N availability directly by adding readily accessible N in urine and dung to the soil. Herbivores indirectly influenced soil N availability by altering the plant composition (grass: forb cover). Both mechanisms contributed to the variation in how different herbivore assemblages affected soil N availability in the two grassland types.

Grazers increased soil N availability directly by adding readily accessible N in urine and dung to the soil. Herbivores indirectly influenced soil N availability by altering the plant composition (grass: forb cover). Both mechanisms contributed to the variation in how different herbivore assemblages affected soil N availability in the two grassland types.

1. The loss of marine foundation species, in particular kelps at temperate latitudes, has been linked to climatic drivers and co-occurring human perturbations. Ocean temperature and nutrients typically covary over local and regional scales and play a crucial role on kelp dynamics. Examining their independent and interactive effects on kelp physiological performance is essential to understand and predict patterns of kelp distribution, particularly under scenarios of global change.
2. Crossed combinations of ocean temperatures and availability of nutrients were experimentally tested on juveniles of the ‘golden kelp’, Laminaria ochroleuca, from the northwestern Iberian Peninsula. Eco-physiological responses included: survival, growth and total N content. Results were embedded into a Species Distribution Model (SDM), which relates presence records and climatic and non-climatic data to forecast distribution patterns of L. ochroleuca under different climate change scenarios.
3. Temperatures above 24.6°C were lethal irrespective of nutrients. Optimal growth of juvenile sporophytes occurred between 12 and 18°C and no nutrient limitation. The SDM, where ocean temperature was the main predictor of kelp distribution in line with temperature thresholds given by eco-physiological responses, suggests a future expansion towards northern latitudes and a retreat from the southern limit/boundary of the current distribution.
4. Synthesis. Range-shifting of the golden kelp can have severe ecological impacts at regional and local scales. The expansion or retraction of the species along the European coast seems to be modulated mainly by temperature, but nutrient availability would be a key to maintain optimal physiological performance. Our work highlights that the combination of empirical and modelling approaches is accessible to researchers and crucial to building more robust predictions of ecological and biogeographic responses of habitat-forming species to forecasted environmental change.

Range-shifting of the golden kelp can have severe ecological impacts at regional and local scales. The expansion or retraction of the species along the European coast seems to be modulated mainly by temperature, but nutrient availability would be a key to maintain optimal physiological performance. Our work highlights that the combination of empirical and modelling approaches is accessible to researchers and crucial to building more robust predictions of ecological and biogeographic responses of habitat-forming species to forecasted environmental change.

1. Assessing how species productivity in mixtures is influenced by species shade tolerance (ST) and phylogeny would be helpful to improve our general understanding of the relationship between tree species diversity and productivity in forests.
2. We investigated the effects of differences in ST and phylogenetic distances (PDs) between pairs of species on the productivity of Quercus petraea growing in 18 mixtures in lowland temperate forests. We calculated the mixture effect as the difference in productivity of Q. petraea in mixed vs. pure stands. Our analyses were based on data from seven annual campaigns of the French National Forest Inventory covering 1,573 plots.
3. The mixture effect on Q. petraea productivity increased when the ST of the companion species decreased. Compared to its productivity in pure stands, Q. petraea productivity in mixed coniferous stands varied from −14.6% up to +39.6% as the ST of the companion species inversely varied from highest to lowest. With broadleaved companion species, the mixture effect varied from −10% up to +13.9% with decreasing ST. We found no effect of PD between Q. petraea and the companion species on the mixture effect.
4. Synthesis. Our results confirm that shade tolerance is an important driver of the diversity effect on productivity at species level in temperate forests and that phylogenetic distance is not a relevant proxy for species functional dissimilarity.

The mixture effect on Quercus petraea productivity increased when the shade tolerance of the companion species decreased. Our results confirm that shade tolerance is an important driver of the diversity effect on productivity at species level in temperate forests and that phylogenetic distance is not a relevant proxy for species functional dissimilarity.

1. Polyphenols are one of the most common groups of secondary metabolites in plants and thought to play a key role in enhancing plant fitness by protecting plants against enemies. Although enemy-inflicted mortality at the seed stage can be an important regulator of plant populations and a key determinant of community structure, few studies have assessed community-level patterns of polyphenol content in seeds.
2. We describe the distribution of the main seed polyphenol groups across 196 tree and liana species on Barro Colorado Island (Panama) and community-level patterns in two aspects of their biological activity (protein precipitation and oxidative capacity). Taking advantage of substantial variation in morphological and ecological traits in the studied plant community, we test for correlations and trade-offs between seed polyphenols and nonchemical plant traits hypothesised to make plant species more or less likely to invest in polyphenol production.
3. The majority of species have polyphenols in their seeds. The incidence and concentrations of polyphenols were related to a set of nonchemical plant traits. Polyphenols were most likely to be present (and where present, to be expressed in high concentrations) in species with large seeds, short seed dormancy times, low investment in mechanical seed defences, high wood density, high leaf mass per area, tough leaves and slow growth rates.
4. Synthesis. Our study reveals a potential trade-off between chemical and mechanical seed defences and shows that plant species that invest in physical defences at later life stages (high wood density and tough leaves) tend not to invest in physical defences of seeds but instead produce secondary metabolites likely to act as seed defences. Overall, our results conform to predictions from the resource availability hypothesis, which states that species in resource-limited environments (such as slow-growing shade-tolerant tree species) will invest more in defences than fast-growing pioneer species.

Our study reveals a potential trade-off between chemical and mechanical seed defences. It also shows that plant species that invest in physical defences at later life stages (high wood density and tough leaves) tend not to invest in physical defences of seeds but instead produce secondary metabolites likely to act as seed defences. Photo credit: Steve Paton.

1. When tree-species mixtures are more productive than monocultures, higher light absorption is often suggested as a cause. However, few studies have quantified this effect and even fewer have examined which light-related interactions are most important, such as the effects of species interactions on tree allometric relationships and crown architecture, differences in vertical or horizontal canopy structure, phenology of deciduous species or the mixing effects on tree size and stand density.
2. In this study, measurements of tree sizes and stand structures were combined with a detailed tree-level light model (Maestra) to examine the contribution of each light-related interaction on tree- and stand-level light absorption at 21 sites, each of which contained a triplet of plots including a mixture and monocultures of Fagus sylvatica and Pinus sylvestris (63 plots). These sites were distributed across the current distribution of these species within Europe.
3. Averaged across all sites, the light absorption of mixtures was 14% higher than the mean of the monocultures. At the whole community level, this positive effect of mixing on light absorption increased as canopy volume or site productivity increased, but was unrelated to climate. At the species population or individual tree levels, the mixing effect on light absorption resulted from light-related interactions involving vertical canopy structure, stand density, the presence of a deciduous species (F. sylvatica), as well as the effects of mixing on tree size and allometric relationships between diameter and height, crown diameter and crown length.
4. The mixing effects on light absorption were only correlated with the mixing effects on growth for P. sylvestris, suggesting that the mixing effects on this species were driven by the light-related interactions, whereas mixing effects on F. sylvatica or whole community growth were probably driven by non-light-related interactions.
5. Synthesis. The overall positive effect of mixing on light absorption was the result of a range of light-related interactions. However, the relative importance of these interactions varied between sites and is likely to vary between other species combinations and as stands develop.

The overall positive effect of mixing on light absorption was the result of a range of light-related interactions. However, the relative importance of these interactions varied between sites and is likely to vary between other species combinations and as stands develop.

1. Mixed conifer–hardwood forests can be more productive than pure forests and they are increasingly considered as ecosystems that could provide adaptation strategies in the face of global change. However, the combined effects of tree-to-tree competition, rising atmospheric CO₂ concentrations and climate on such mixtures remain poorly characterized and understood.
2. To fill this research gap, we reconstructed 34-year series (1980–2013) of growth (basal area increment, BAI) and intrinsic water-use efficiency (iWUE) of Scots pine (Pinus sylvestris L.)–European beech (Fagus sylvatica L.) mixed stands at two climatically contrasting sites located in the southwestern Pyrenees. We also gathered data on tree-to-tree competition and climate variables in order to test the hypotheses that (1) radial growth will be greater when exposed to inter- than to intraspecific competition, that is, when species complementarity occurs and (2) enhanced iWUE could be linked to improved stem radial growth.
3. Growth of both species was reduced when intraspecific competition increased. Species complementarity was linked to improved growth of Scots pine at the continental site, while competition overrode any complementarity advantage at the drought-prone Mediterranean site. Beech growth did not show any significant response to pine admixture likely due to shade tolerance and the highly competitive nature of this species. Increasing interspecific competition drove recent iWUE changes, which increased in Scots pine but decreased in European beech. The iWUE enhancement did not involve any growth improvement in Scots pine. However, the positive BAI-iWUE relationship found for beech suggests an enhanced beech growth in drought-prone sites due to improved water use.
4. Synthesis. Complementarity may enhance growth in mixed forests. However, water scarcity can constrict light-related complementarity for shade intolerant species (Scots pine) in drought-prone sites. Basal area increment–intrinsic water-use efficiency relationships were negative for Scots pine and positive for European beech. These contrasting behaviours have got implications for coping with the expected increasing drought events in Scots pine–European beech mixtures located near the ecological limit of the two species. Complementarity effects between tree species should be considered to avoid overestimating the degree of future carbon uptake by mixed conifer–broadleaf forests.

In mixed forests, tree species can complement each other resulting in enhanced stand growth. However, water scarcity can constrict light-related complementarity for shade-intolerant species (such as Scots pine), particularly in dense forests, whereas growth of companion shade-tolerant species (such as European beech) can benefit from increased CO₂ atmospheric level by increasing their water-use efficiency.

1. Dispersal and density dependence are major determinants of spatial structure, population dynamics and coexistence for tropical forest plants. However, because these two processes can jointly influence spatial structure at similar scales, analysing spatial patterns to separate and quantify them is often difficult.
2. Species functional traits can be useful indicators of dispersal and density dependence. However, few methods exist for linking functional traits to quantitative estimates of these processes that can be compared across multiple species.
3. We analysed static spatial patterns of woody plant populations in the 50 ha Forest Dynamics Plot on Barro Colorado Island, Panama with methods that distinguished scale-specific differences in species aggregation. We then tested how these differences related to seven functional traits: growth form, dispersal syndrome, tree canopy layer, adult stature, seed mass, wood density and shade tolerance. Next, we fit analytically tractable spatial moment models to the observed spatial structure of species characterized by similar trait values, which allowed us to estimate relationships of functional traits with the spatial scale of dispersal, and the spatial scale and intensity of negative density dependence.
4. Our results confirm that lianas are more aggregated than trees, and exhibit increased aggregation within canopy gaps. For trees, increased seed mass, wood density and shade tolerance were associated with less intense negative density dependence, while higher canopy layers and increased stature were associated with decreased aggregation and better dispersal. Spatial structure for trees was also strongly determined by dispersal syndrome. Averaged across all spatial scales, zoochory was more effective than wind dispersal, which was more effective than explosive dispersal. However, at intermediate scales, zoochory was associated with more aggregation than wind dispersal, potentially because of differences in short-distance dispersal and the intensity of negative density dependence.
5. Synthesis. We develop new tools for identifying significant associations between functional traits and spatial structure, and for linking these associations to quantitative estimates of dispersal scale and the strength and scale of density dependence. Our results help clarify how these processes influence woody plant species on Barro Colorado, and demonstrate how these tools can be applied to other sites and systems.

The forest of Barro Colorado Island as seen from above, revealing the spatial distribution of canopy trees such as Dipteryx oleifera (purple flowers), among many others. Using new spatial analysis tools, we relate these patterns to differences in species functional traits, and generate quantitative estimates of how individuals disperse and interact with one another and their environments. Orthomosaic image constructed with photogrammetry software from photos taken by Jonathan Dandois on June 29, 2015, using an unmanned aerial vehicle.

1. Plant neighbours can strongly influence the interactions between herbivores and focal plants, for instance by providing food of different quality (consumptive effects) or by changing the behaviour and metabolism of the herbivore and the focal plant without being consumed (non-consumptive effects). Determining the species-specific contributions of consumptive and non-consumptive effects is important to understand the ecophysiological mechanisms which underlie neighbourhood effects.
2. We quantified the impact of nine different grassland plant species on the interaction between Taraxacum officinale and the root-feeding insect Melolontha melolontha. We investigated the contribution of consumptive and non-consumptive effects to the observed patterns, and evaluated the impact of neighbouring plants on the growth and physiology of T. officinale upon M. melolontha attack.
3. Melolontha melolontha growth was strongly affected by the presence of different neighbouring species. The three grass species increased larval growth when growing with T. officinale, with Poa pratensis having a synergistic effect in the mixture compared to both monocultures. The forb Centaurea stoebe reduced larval growth when growing with T. officinale or alone. The other five species had no measurable impact on larval performance. Based on these results, P. pratensis and C. stoebe were selected for further experiments.
4. Diet-mixing experiments showed that P. pratensis increased M. melolontha growth when offered together with T. officinale, while C. stoebe suppressed it. When feeding was restricted to artificial diet, larval growth was not changed by the presence of P. pratensis or C. stoebe. However, when feeding was restricted to T. officinale, larval growth was increased by both heterospecific neighbours. Biomass and primary metabolism of T. officinale under attack by M. melolontha was also altered by the presence of C. stoebe and P. pratensis. Together, these results show that consumptive and non-consumptive effects can explain the positive effect of P. pratensis. In contrast, the negative effect of C. stoebe is likely driven exclusively by intoxication.
5. Synthesis. The performed experiments suggest that different combinations of consumptive and non-consumptive effects are likely to contribute to the diversity of neighbourhood effects in nature. Furthermore, they show that neighbourhood effects are important factors in below-ground plant–insect interactions.

The presence of other plant species can strongly influence the interaction between a focal plant and its herbivore natural enemies. However, the ecophysiological mechanisms remain poorly understood, especially below-ground. We show that different combinations of consumptive and non-consumptive determine the influence of neighbouring plants on below-ground herbivore performance. This result can explain the diversity of neighbour effects in nature.

1. In this study, we compare two community modelling approaches to determine their ability to predict the taxonomic, functional and phylogenetic properties of plant assemblages along a broad elevation gradient and at a fine resolution. The first method is the standard stacking individual species distribution modelling (SSDM) approach, which applies a simple environmental filter to predict species assemblages. The second method couples the SSDM and macroecological modelling (MEM—SSDM-MEM) approaches to impose a limit on the number of species co-occurring at each site. Because the detection of diversity patterns can be influenced by different levels of phylogenetic or functional trees, we also examine whether performing our analyses from broad to more exact structures in the trees influences the performance of the two modelling approaches when calculating diversity indices.
2. We found that coupling the SSDM with the MEM improves the overall predictions for the three diversity facets compared with those of the SSDM alone. The accuracy of the SSDM predictions for the diversity indices varied greatly along the elevation gradient, and when considering broad to more exact structure in the functional and phylogenetic trees, the SSDM-MEM predictions were more stable.
3. SSDM-MEM moderately but significantly improved the prediction of taxonomic diversity, which was mainly driven by the corrected number of predicted species. The performance of both modelling frameworks increased when predicting the functional and phylogenetic diversity indices. In particular, fair predictions of the taxonomic composition by SSDM-MEM led to increasingly accurate predictions of the functional and phylogenetic indices, suggesting that the compositional errors were associated with species that were functionally or phylogenetically close to the correct ones; however, this did not always hold for the SSDM predictions.
4. Synthesis. In this study, we tested the use of a recently published approach that couples species distribution and macroecological models to provide the first predictions of the distribution of multiple facets of plant diversity: taxonomic, functional and phylogenetic. Moderate but significant improvements were obtained; thus, our results open promising avenues for improving our ability to predict the different facets of biodiversity in space and time across broad environmental gradients when functional and phylogenetic information is available.

In this study, we tested the use of a recently published approach that couples species distribution and macroecological models to provide the first predictions of the distribution of multiple facets of plant diversity: taxonomic, functional and phylogenetic. Moderate but significant improvements were obtained; thus, our results open promising avenues for improving our ability to predict the different facets of biodiversity in space and time across broad environmental gradients when functional and phylogenetic information is available.

1. In forest ecosystems, the influence of landscape history on contemporary biodiversity patterns has been shown to provide a convenient framework to explain shifts in plant assemblages. However, very few studies have controlled for present human-induced activities when analysing the effect of forest continuity on community structures. By cutting and removing trees, foresters substantially change stand ecological conditions, with consequences on biodiversity patterns. Disentangling the effect of past and present human activities on biodiversity is thus crucial for ecosystem management and conservation.
2. We explored the response of plant and springtail species richness and composition to forest continuity (ancient vs. recent) in montane forests, while controlling for stand maturity (mature vs. overmature). We established 70 sites in landscapes dominated by unfragmented ancient forests where we surveyed plants and assessed springtails by analysing environmental DNA.
3. Neither plant nor springtail species richness was influenced by forest continuity or by stand maturity. Instead, site-specific characteristics, especially soil properties and canopy openness, were of major importance in shaping above- and below-ground richness.
4. For plant and springtail species composition, the effect of forest continuity was mediated by stand maturity. Thus, both plants and springtails showed a convergence in assemblage patterns with the increasing availability of overmature stand attributes. Moreover, soil and stand-scale factors were evidently more important than landscape-scale factors in shaping above- and below-ground species composition.
5. Synthesis. We clearly demonstrated that biodiversity patterns are more strongly influenced by present human-induced activities than by past human-induced activities. In the Northern Alps where our study sites were located, the colonization credit of most species has been paid off and the transient biodiversity deficit usually related to forest continuity has moved towards equilibrium. These findings emphasize the necessity to better control for local-scale factors when analysing the response of biodiversity to forest continuity; we call for more research into the effects of forest continuity in unfragmented mountain forests.

We clearly demonstrated that biodiversity patterns are more strongly influenced by present human-induced activities than by past human-induced activities. In the Northern Alps where our study sites were located, the colonization credit of most species has been paid off and the transient biodiversity deficit usually related to forest continuity has moved towards equilibrium. These findings emphasize the necessity to better control for local-scale factors when analysing the response of biodiversity to forest continuity; we call for more research into the effects of forest continuity in unfragmented mountain forests.

1. Lianas are a key component of tropical forests, where they compete intensely with trees, reducing tree recruitment, growth and survival. One of the most important potential outcomes of liana competition is the reduction of tree reproduction; however, no previous study has experimentally determined the effects of lianas on tree reproduction beyond a single tree species.
2. We used a large-scale liana removal experiment to quantify the effect of lianas on community-level canopy and understorey tree and palm reproduction. In 2011, we removed lianas from eight 6,400-m² plots (eight plots served as controls) and surveyed understorey tree reproduction in 2012, canopy tree and palm reproduction in 2013, and a second census of all plants in 2016.
3. We found that lianas significantly reduced canopy tree community flowering and fruiting after liana removal. Two years after liana removal, the number of canopy trees with fruits was 173% higher, fruiting individuals had 50% more of their canopy covered by fruits and the number of tree species with fruits was 169% higher than in control plots where lianas were present. Five years after liana removal, the number of canopy trees with fruits was 150% higher, fruiting individuals had 31% more of their canopy covered by fruits and the number of tree species with fruits was 109% higher than in unmanipulated control plots.
4. Liana removal had only a slight positive effect on palms and on understorey tree flower and fruit production, even though understorey light levels had increased 20% following liana cutting.
5. Synthesis. Our findings provide the first experimental demonstration that competition from lianas significantly reduces community-level canopy tree reproduction. Reduced reproduction increases canopy tree seed and dispersal limitations, and may interfere with deterministic mechanisms thought to maintain tropical canopy tree species diversity, as well as reduce food availability to many animal species. Because lianas are increasing in abundance in many neotropical forests, the effects of lianas on tree reproduction will likely increase, and if the effects of lianas on tree reproduction vary with tree species identity, lianas ultimately could have a destabilizing effect on both tree and animal population dynamics.

Our findings provide the first experimental demonstration that competition from lianas significantly reduces community-level canopy tree reproduction. Reduced reproduction increases canopy tree seed and dispersal limitations, and may interfere with deterministic mechanisms thought to maintain tropical canopy tree species diversity, as well as reduce food availability to many animal species. Because lianas are increasing in abundance in many neotropical forests, the effects of lianas on tree reproduction will likely increase, and if the effects of lianas on tree reproduction vary with tree species identity, lianas ultimately could have a destabilizing effect on both tree and animal population dynamics.

1. Optimal defence allocation theory (ODT) is one of the most prominent theoretical frameworks to explain the allocation of defence compounds within plants. It predicts that the most valuable and vulnerable plant organs have the highest levels of chemical defence. The ODT has been well worked out and experimentally tested for shoot defences, but not for root defences. To assess if ODT principles apply similarly to roots and shoots, we examined glucosinolates in above-ground and below-ground organs of nine plant species belonging to two families.
2. In order to evaluate whether ODT equally applies to shoot and root organs, we designed a conceptual model in which above-ground and below-ground organs were assigned to orders of importance to plant performance. We hypothesized that organs constituting the plant's core structure are better protected than more distal organs.
3. The nine plant species were cultivated, and their roots and shoots were harvested and divided into three orders for glucosinolate analysis. Using a specialist (Delia radicum) and a generalist (Amphimallon solstitiale) root herbivore, we also experimentally tested the hypothesis that the generalist herbivore prefers to feed on fine roots (FRs) with a low glucosinolate concentration, while the specialist prefers taproots (TRs) with a high glucosinolate concentration.
4. We found that both in roots and shoots, the higher ordered core structural organs (TRs and stems) had the highest levels of glucosinolates. Below-ground, TRs and lateral roots were better protected than the more distal, and less costly, FRs in seven out of nine species tested. The specialist root herbivore preferred feeding on the highly defended TRs, which is in line with what has been found for above-ground specialist herbivores. Moreover, the glucosinolate concentration in roots overall was significantly higher than that in shoots.
5. Synthesis. These results support the hypothesis that Optimal defence allocation theory (ODT) generally applies to glucosinolate allocation in above-ground and below-ground organs and may mainly serve to maintain the integrity of the main plant structure. Moreover, it suggests that above-ground and below-ground insect herbivores independently exert similar selection pressures on defence allocation patterns in roots and shoots.

These results support the hypothesis that Optimal defence allocation theory (ODT) generally applies to glucosinolate allocation in above-ground and below-ground organs and may mainly serve to maintain the integrity of the main plant structure. Moreover, it suggests that above-ground and below-ground insect herbivores independently exert similar selection pressures on defence allocation patterns in roots and shoots.

1. How the patterns of niche occupancy vary from species-poor to species-rich communities is a fundamental question in ecology that has a central bearing on the processes that drive patterns of biodiversity. As species richness increases, habitat filtering should constrain the expansion of total niche volume, while limiting similarity should restrict the degree of niche overlap between species. Here, by explicitly incorporating intraspecific trait variability, we investigate the relationship between functional niche occupancy and species richness at the global scale.
2. We assembled 21 datasets worldwide, spanning tropical to temperate biomes and consisting of 313 plant communities representing different growth forms. We quantified three key niche occupancy components (the total functional volume, the functional overlap between species and the average functional volume per species) for each community, related each component to species richness, and compared each component to the null expectations.
3. As species richness increased, communities were more functionally diverse (an increase in total functional volume), and species overlapped more within the community (an increase in functional overlap) but did not more finely divide the functional space (no decline in average functional volume). Null model analyses provided evidence for habitat filtering (smaller total functional volume than expectation), but not for limiting similarity (larger functional overlap and larger average functional volume than expectation) as a process driving the pattern of functional niche occupancy.
4. Synthesis. Habitat filtering is a widespread process driving the pattern of functional niche occupancy across plant communities and coexisting species tend to be more functionally similar rather than more functionally specialized. Our results indicate that including intraspecific trait variability will contribute to a better understanding of the processes driving patterns of functional niche occupancy.

Both the total functional volume and the functional overlap increased with increasing species richness, while the average functional volume did not vary significantly. Habitat filtering is a widespread process driving the pattern of functional niche occupancy across plant communities and coexisting species tend to be more functionally similar rather than more functionally specialized.

1. Changing climate threatens the structure and function of saltmarshes, which are often severely degraded by other human perturbations. Along the Mediterranean coastline, increasing temperature and decreasing rainfall have been hypothesised to trigger habitat shifts from perennial grasses to annual succulents in fragile saltmarsh ecosystems, such as those fringing the North Adriatic coastline.
2. We used manipulative field experiments to investigate the effects of increased temperature, decreased precipitation and increased inundation period associated with rising sea levels on the dominant species in the lower marsh, the perennial grass Spartina spp. and the annual succulent Salicornia veneta.
3. At ambient inundation, the combined effects of increased temperature and decreased precipitation enhanced soil temperature and decreased soil moisture, resulting in an increased number of plants, height and live biomass of S. veneta, as well as greater dead biomass of Spartina spp. compared with current conditions. Increased inundation reduced the soil redox potential, and resulted in losses of both Spartina spp. and S. veneta, but these negative effects were much more pronounced for S. veneta. An inundation tolerance test confirmed that S. veneta is significantly more vulnerable to rapid increases in inundation than Spartina spp.
4. We conclude that at current inundation, the increasing drought conditions in the North Adriatic Sea are favouring the spread of the annual succulent S. veneta. The increasing spread of these succulents could reduce the future capability of the system to respond to projected increasing sea levels, as S. veneta is highly vulnerable to increased inundation.
5. Synthesis. Our results highlight the complex interactions between different components of changing climate. Management strategies for saltmarshes in the Mediterranean and other microtidal locations facing similar changes in climate should focus on maintaining the freshwater and coastal channels free from blockages to ameliorate the effects of episodic drought/heatwave conditions and increasing the sediment supply and preventing coastal squeeze to enhance the resilience of the system to the continuous threat of sea level rise.

Our results highlight the complex interactions between different components of changing climate. Management strategies for saltmarshes in the Mediterranean and other microtidal locations facing similar changes in climate should focus on maintaining the freshwater and coastal channels free from blockages to ameliorate the effects of episodic drought/heatwave conditions and increasing the sediment supply and preventing coastal squeeze to enhance the resilience of the system to the continuous threat of sea level rise.

1. Plants compete for nutrients using a range of strategies. We investigated nutrient foraging within nutrient hot-spots simultaneously available to plant species with diverse root traits. We hypothesized that there would be more root proliferation by thin-root species than by thick-root species, and that root proliferation by thin-root species would limit root proliferation by thick-root species.
2. We conducted a root ingrowth experiment in a temperate forest in eastern USA where root systems of different tree species could interact. Tree species varied in the thickness of their absorptive roots, and were associated with either ectomycorrhizal (EM) or arbuscular mycorrhizal (AM) fungi. Thus, there were thin- and thick-root AM and thin- and thick-root EM plant functional groups. Half the ingrowth cores were amended with organic nutrients (dried green leaves). Relative root length abundance, the proportion of total root length in a given soil volume occupied by a particular plant functional group, was calculated for the original root population and ingrowth roots after 6 months.
3. The shift in relative root length abundance from original to ingrowth roots was positive in thin-root species but negative in thick-root species (p < .001), especially in unamended patches (AM: +6% vs. −7%; EM: +8% vs. −9%). Being thin-rooted may thus allow a species to more rapidly recolonize soil after a disturbance, which may influence competition for nutrients. Moreover, we observed that nutrient additions amplified the shift in root length abundance of thin over thick roots in AM trees (+13% vs. −14%), but not in EM trees (+1% vs −3%). In contrast, phospholipid fatty acid biomarkers suggested that EM fungal hyphae strongly proliferated in nutrient hot-spots whereas AM fungal hyphae exhibited only modest proliferation.
4. We found no evidence that when growing in the shared patch, the proliferation of thin roots inhibited the growth of thick roots.
5. Synthesis. Knowledge of root morphology and mycorrhizal type of co-existing tree species may improve prediction of patch exploitation and nutrient acquisition in heterogeneous soils.

Knowledge of root morphology and mycorrhizal type of co-existing tree species may improve prediction of patch exploitation and nutrient acquisition in heterogeneous soils.

1. A large number of alien plant species have been introduced as ornamental garden plants to Europe, but relatively few have become invasive. Low climatic suitability may be limiting the current invasion potential of many alien ornamental species. However, with ongoing disturbance and climate change, this barrier may be reduced for some species.
2. Here, we tested how colonization ability (a prerequisite for invasion) of frequently planted alien ornamentals depends on disturbance and heating, and on their species characteristics. We sowed seeds of 37 non-naturalized alien herbaceous garden-plant species into native grassland plots with and without disturbance, and with and without infrared-heating lamps. To assess whether their responses differ from those within the regional wild flora, we also sowed 14 native species and 12 naturalized alien species. During 2 years, we assessed the likelihoods of germination, first-year survival, second-year survival and flowering of these 63 study species.
3. The heating treatment, which also reduced soil moisture, decreased all measures of colonization success, but more so for sown native species than for the non-naturalized and naturalized alien ones. The disturbance treatment increased colonization success, and because heating decreased productivity of the undisturbed grassland plots, it also increased invasibility of these plots. Average colonization success of non-naturalized aliens was reduced by heating, but some species were not affected or performed even better with heating, particularly those with an annual life span and a high seed mass. Winter hardiness improved colonization ability of non-naturalized aliens, but this advantage was reduced in the heated plots.
4. Synthesis. Disturbance increased and heating decreased the absolute colonization success of most of the 63 species sown. However, heating had stronger adverse effects on the resident grassland and sown native species than either type of sown alien species. Together, these results suggest that some alien plants may have greater colonization success relative to native plants under a warmer climate.

Disturbance increased and heating decreased the absolute colonization success of most of the 63 species sown. However, heating had stronger adverse effects on the resident grassland and sown native species than either sown non-naturalized or naturalized alien species. Together, these results suggest that some alien plants may have greater colonization success relative to native plants under a warmer climate.

1. The interplay between dispersal and adaptation to local environments ultimately determines the distribution of plant species, but their relative contribution remains little understood. Tropical mistletoes provide the opportunity to dissect these contributions of dispersal and adaptation, because as hemiparasitic plants, they are typically adapted to grow on a handful of species within diverse tropical communities and are non-randomly dispersed by mutualistic frugivorous birds.
2. Here we hypothesized that the primary determinant of the abundance of a tropical mistletoe (Dendropemon caribaeus, Loranthaceae) in Puerto Rico will be the compatibility between the mistletoe and plant species in a community. Alternatively, the mistletoe's abundance could be primarily shaped by other factors such as the availability of potential host plants, or factors that determine how mistletoe seeds are dispersed by avian frugivores. We conducted surveys and experiments to assess the capacity of this mistletoe to grow on trees available in the local community, and measured the monthly phenology and seed dispersal patterns of the mistletoe and other bird-dispersed plants in the community over a period of 4 years. A path model was used to evaluate how the abundance of the mistletoe was shaped by host abundance, fruiting phenology, bird dispersal and compatibilities with host plants.
3. Our analyses show that the compatibility between mistletoe and host tree species, measured by mistletoe survival and growth rate, was the most important factor for mistletoe abundance. The next most important factor was the phenological characteristics of the hosts; this outcome likely arose because frugivory and seed dispersal services for mistletoes and hosts are performed by the same birds.
4. Synthesis. Mistletoes often parasitize only a subset of the suitable plant species that are available in a given community. Our results indicate that such patterns are not only determined by host quality and abundance but also by the phenological patterns of trees that influence the probabilities of mistletoe seeds being deposited on them by shared avian seed dispersers.

Mistletoes often parasitize only a subset of the suitable plant species that are available in a given community. Our results indicate that such patterns are not only determined by host quality and abundance, but also by the phenological patterns of trees that influence the probabilities of mistletoe seeds being deposited on them by shared avian seed dispersers.

1. Ecological memory, often determined by the extent and type of retained biological legacies present following disturbance, may produce persistent landscape patterns. However, after fire, the persistence or switch to an alternative state may depend on the complex interplay of ecological memory (biological legacies) and potential effects of new external factors influencing the post-fire environment. The current study assesses both the strength of ecological memory resulting from biological legacies of pre-burn vegetation types as well as post-fire effects of livestock.
2. Following a severe fire in 1999, we set up a network of long-term exclosures to examine the effects of legacies and cumulative herbivory by cattle on fuel types, amounts, distribution, flammability and microenvironmental conditions in two post-fire communities representing alternative fire-driven states: pyrophobic Nothofagus pumilio subalpine forests and pyrophytic Nothofagus antarctica tall shrublands in northwestern Patagonia, Argentina.
3. Our results show that the retained post-disturbance legacies of tall shrublands and subalpine forests largely determine fuel and flammability traits of the post-fire plant communities 16 years after fire. The importance of biological legacies retained from the unburned plant communities was reflected by the substantially higher amounts of total fine fuel, greater vertical and horizontal fuel continuity and the higher temperatures reached during experimental tissue combustion at post-fire shrubland compared to post-fire forest sites.
4. We show that herbivores may produce antagonistic effects on flammability by decreasing tissue ignitability, total fine fuel and litter depth, and disrupting the vertical and horizontal fine fuel continuity, therefore reducing the probability of fire propagation. However, cattle can increase ratios of dead to live fine fuels, reduce soil moisture, and inhibit tree height growth to canopy size, consequently impeding the development of a closed pyrophobic forest canopy.
5. Synthesis. Our results support the hypothesis that biological legacies, most importantly the dominance by pyrophytic woody plants that resprout vigorously vs. the dominance by pyrophobic obligate seeders, favour fuel and flammability characteristics at the community level which reinforce the mechanisms maintaining pyrophytic shrublands vs. pyrophobic forests. Herbivory by introduced cattle can partially blur sharp pyrophobic/pyrophytic state boundaries by promoting the development of novel post-fire transitional states.

Biological legacies, most importantly the dominance by pyrophytic woody resprouting plants versus the dominance by pyrophobic obligate seeders, favour fuel and flammability characteristics at the community level which reinforce the mechanisms maintaining pyrophytic shrublands versus pyrophobic forests. Herbivory by introduced cattle can partially blur sharp pyrophobic/pyrophytic state boundaries by promoting the development of novel post-fire transitional states.

1. Logging is a major driver of tropical forest degradation, with severe impacts on plant richness and composition. Rarely have these effects been considered in terms of their impact on the functional and phylogenetic diversity of understorey plant communities, despite the direct relevance to community reassembly trajectories. Here, we test the effects of logging on functional traits and evolutionary relatedness, over and above effects that can be explained by changes in species richness alone. We hypothesised that strong environmental filtering will result in more clustered (under-dispersed) functional and phylogenetic structures within communities as logging intensity increases.
2. We surveyed understorey plant communities at 180 locations across a logging intensity gradient from primary to repeatedly logged tropical lowland rain forest in Sabah, Malaysia. For the 691 recorded plant taxa, we generated a phylogeny to assess plot-level phylogenetic relatedness. We quantified 10 plant traits known to respond to disturbance and affect ecosystem functioning, and tested the influence of logging on functional and phylogenetic structure.
3. We found no significant effect of forest canopy loss or road configuration on species richness. By contrast, both functional dispersion and phylogenetic dispersion (net relatedness index) showed strong gradients from clustered towards more randomly assembled communities at higher logging intensity, independent of variation in species richness. Moreover, there was a significant nonlinear shift in the trait dispersion relationship above a logging intensity threshold of c. 65% canopy loss (±17% CL). All functional traits showed significant phylogenetic signals, suggesting broad concordance between functional and phylogenetic dispersion, at least below the logging intensity threshold.
4. Synthesis. We found a strong logging signal in the functional and phylogenetic structure of understorey plant communities, over and above species richness, but this effect was opposite to that predicted. Logging increased, rather than decreased, functional and phylogenetic dispersion in understorey plant communities. This effect was particularly pronounced for functional response traits, which directly link disturbance with plant community reassembly. Our study provides novel insights into the way logging affects understorey plant communities in tropical rain forest and highlights the importance of trait-based approaches to improve our understanding of the broad range of logging-associated impacts.

In tropical lowland rain forests in Borneo, we found significant change in functional and phylogenetic dispersion, including a significant ‘logging-threshold’ effect, along a gradient from primary forest to repeatedly logged forest. Our study provides new insights into the way logging affects understorey plant communities, over and above changes in species richness, and highlights the importance of trait-based approaches to understand logging impacts.

1. Despite recent advances in understanding community assembly processes, appreciating how these processes vary across multiple spatial scales and environmental gradients remains a crucial issue in ecology.
2. This study aimed to disentangle the drivers of diversity and composition of seaweed communities through a gradient of spatial scales based on a hierarchical sampling design consisting of 19 sites distributed in four sectors along the Brittany coastline. Using randomised community matrices and Moran's eigenvector maps (MEMs), we compared (i) the relative importance of deterministic and stochastic processes, (ii) the environmental correlates of community composition, and (iii) the scale of variation in community composition for seaweed communities located at two different tidal heights.
3. Processes shaping community patterns are expected to vary along a gradient of tidal heights. Therefore, we specifically examined the following hypotheses: the contribution of deterministic over stochastic processes as well as the relative importance of environmental filtering over biotic interactions should be enhanced for seaweed communities of the infralittoral fringe compared to subtidal ones, whereas dispersal of propagules in the water column should be more restricted resulting in finer scale variation in community composition for seaweed communities of the infralittoral fringe compared to subtidal communities.
4. Seaweed communities were largely shaped by deterministic processes, although the relative importance of deterministic processes was greater for communities of the infralittoral fringe than for subtidal communities. Sea surface temperature and geophysical variables were correlates of community composition at the two tidal heights; additionally, waves and current were correlated with the composition of the communities of the infralittoral fringe while kelp density was correlated with the composition of subtidal communities. Variation in community composition was observed at a finer scale for infralittoral fringe than for subtidal communities.
5. Synthesis. Our results suggest that the relative importance of deterministic and stochastic processes in structuring seaweed communities varies across tidal heights. Furthermore, the Moran's eigenvector maps framework highlights that the nature of environmental correlates and the spatial scale at which they were good correlates of community composition also vary across tidal heights and may therefore be useful to broaden our understanding of community assembly across vertical gradients.

Our results suggest that the relative importance of deterministic and stochastic processes in structuring seaweed communities varies across tidal heights. Furthermore, the MEMs framework highlights that the nature of environmental correlates and the spatial scale at which they were good correlates of community composition also vary across tidal heights and may therefore be useful to broaden our understanding of community assembly across vertical gradients.

1. Climate is widely assumed to influence physiological and demographic processes in trees, and hence forest composition, biomass and range limits. Growth in trees is an important barometer of climate change impacts on forests as growth is highly correlated with other demographic processes including tree mortality and fecundity.
2. We investigated the main drivers of diameter growth for five common tree species occurring in the Rocky Mountains of the western United States using nonlinear regression methods. We quantified growth at the individual tree level from tree core samples collected across broad environmental gradients. We estimated the effects of both climate variation and biotic interactions on growth processes and tested for evidence that disjunct populations of a species respond differentially to climate.
3. Relationships between tree growth and climate varied by species and location. Growth in all species responded positively to increases in annual moisture up to a threshold level. Modest linear responses to temperature, both positive and negative, were observed at many sites. However, model results also revealed evidence for differentiated responses to local site conditions in all species. In severe environments in particular, growth responses varied nonlinearly with temperature. For example, in northerly cold locations pronounced positive growth responses to increasing temperatures were observed. In warmer southerly climates, growth responses were unimodal, declining markedly above a threshold temperature level.
4. Net effects from biotic interactions on diameter growth were negative for all study species. Evidence for facilitative effects was not detected. For some species, competitive effects more strongly influenced growth performance than climate. Competitive interactions also modified growth responses to climate to some degree.
5. Synthesis. These analyses suggest that climate change will have complex, species-specific effects on tree growth in the Rocky Mountains due to nonlinear responses to climate, differentiated growth processes that vary by location and complex species interactions that impact growth and potentially modify responses to climate. Thus, robust model simulations of future growth responses to climate trends may need to integrate realistic scenarios of neighbourhood effects as well as variability in tree performance attributed to differentiated populations.

These analyses suggest that climate change will have complex, species-specific effects on tree growth in the Rocky Mountains due to nonlinear responses to climate, differentiated growth processes that vary by location and complex species interactions that impact growth and potentially modify responses to climate. Thus, robust model simulations of future growth responses to climate trends may need to integrate realistic scenarios of neighbourhood effects as well as variability in tree performance attributed to differentiated populations.

1. The evolution of increased competitive ability (EICA) hypothesis predicts that release from specialist herbivores enables invasive plants to evolve increased growth. The most powerful tests of EICA hypothesis are provided by approaches that simultaneously assess the effects of specialist herbivory and competitive interactions. However, such approaches are extremely rare, and hence how simultaneous release from root and shoot herbivory influence competitive ability of invasive plants remains little understood.

2. Here, we tested whether invasive-range Brassica nigra plants have evolved increased competitive ability, and whether expression of competitive ability depends on separate and simultaneous effects of specialist root and shoot herbivory. To do this, we grew B. nigra plants from eight invasive-range and eight native-range populations in the presence vs. absence of competition with a community of native plant species, and in the absence vs. presence of separate and simultaneous damage by a specialist root herbivore (Delia radicum) and a specialist shoot herbivore (Plutella xylostella). Brassica nigra performance was assessed by measuring biomass production and flowering of individual B. nigra plants.

3. In partial support of the EICA hypothesis, invasive-range B. nigra had greater flowering than native-range conspecifics in the absence of competition. However, contrary to a prediction of the EICA hypothesis, invasive-range B. nigra produced less above-ground biomass than native-range B. nigra in the absence of shoot herbivory and competition. Moreover, with simultaneous root and shoot herbivory, invasive-range B. nigra suppressed a competing community more strongly than native-range B. nigra did.

4. Synthesis. Our results suggest that invasiveness may be driven by mechanisms other than increased individual size. Simultaneous root and shoot herbivory in the invasive range may enhance suppressive effects of introduced plant species that have not completely escaped herbivore damage in the introduced range.

Brassica nigra plants grown in the absence versus presence of damage by a specialist root herbivore (Delia radicum) and a specialist shoot herbivore (Plutella xylostella).

The multiple-choice preference tests in the field and Y-tube olfactometer assays in laboratory demonstrated that a specialized herbivorous beetle, Agasicles hygrophila, uses the ratio of two common plant volatiles, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (Z)-3-hexenol, to discriminate between its host and non-host plants. DMNT positively encourages the beetle's feeding and oviposition preferences, whereas (Z)-3-hexenol displays repellent effect. This study highlights an important mechanism by which olfactory cues could lead to undesired host range expansion in biocontrol agent, thus representing an important warning of the potential for a host shift and development of invasiveness in a common biocontrol agent, the flea beetle.

1. Global warming may accelerate nitrogen (N) transformations in the soil, with potentially large effects in N-poor high-elevation ecosystems. To gain insight into the partitioning of inorganic and organic N inputs within the plant–soil system and how warming influences these patterns, we applied a ¹⁵N label (¹⁵NH₄Cl or ¹⁵N-glycine) shortly after snowmelt during the sixth year of experimental soil warming (+4 °C) at treeline in the Swiss Alps.
2. Seven weeks after labelling, approximately 60% of the applied label remained in the soil organic layer to 10 cm depth, whereas label recovery summed over all measured plant pools was <10% of the added label. Soil warming led to a weaker Δ¹⁵N signal in plants and no change in the amount of added label recovered in plants. This ¹⁵N dilution resulted from a greater N pool size of some plant species in warmed plots as well as enhanced availability of (unlabelled) N under warming. Temporal dynamics of foliar Δ¹⁵N in dominant dwarf shrub species suggested that these plants primarily take up N early in the season. In a subset of plots labelled with ¹³C-enriched glycine (U-¹³C₂-¹⁵N-glycine), the labelled glycine was mineralized rapidly, with approximately 50% of the applied ¹³C respired as CO₂ during the first 99 h, suggesting that effects of warmer soils on N dynamics in this treeline system are only slightly modulated by the preferences of different plant species for inorganic and organic N forms.
3. Synthesis. Plants growing in warmer soils acquired more unlabelled, soil-derived N in the sixth year of treatment, implying a sustained increase in N mineralization and availability in alpine treeline ecosystems with higher soil temperatures predicted for the future. Wide variation in the ability of plant species and functional groups to compete for early-summer N inputs means that there is a feedback between plant community shifts and N dynamics under environmental change at the treeline.

We applied a ¹⁵N label after snowmelt during the sixth year of soil warming at the Swiss treeline. Plants growing in warmer soils acquired more unlabelled, soil-derived ¹⁵N, implying a sustained increase in N availability in treeline ecosystems with warming. Variation in the ability of plant groups to compete for early-summer N inputs suggests a feedback between plant community shifts and N dynamics under environmental change.

1. The timing of the seasonal activity of organisms is a tractable indicator of climate change. Many studies in North America have investigated the role of temperature on the onset date of phenological transitions in temperate deciduous trees and found that the onset of leafing and flowering in numerous species has occurred earlier in recent years, apparently in response to higher temperatures in winter and spring.
2. Few studies have examined the climatic and biogeographic drivers of phenological responses in water-limited ecosystems or explored interspecific variation in responses of phenological metrics other than the timing of onset, such as the periodicity or duration of phenological activity.
3. This study used phenological observations of four species of Quercus contributed to the USA National Phenology Network database from 2009 to 2014 to investigate how responses to climate (temperature and precipitation) and geographic location (latitude, longitude and elevation) varied among two western North American species (Q. agrifolia and Q. lobata) and two eastern and central North American species (Q. alba and Q. rubra).
4. Within years, in species in the western, water-limited ecosystems, the phenological phases observed here (bud break, flowers or flower buds) tend to occur intermittently throughout the growing season, and each event is of longer duration than the same phenophases of the temperate-zone species, rendering a single onset date an incomplete metric with which to track responsiveness or to compare species. By contrast, the eastern/central U.S. species were phenologically more responsive than the western species to spatial and temporal variation in winter, spring, and fall precipitation and maximum temperature.
5. Synthesis. Within and between regions these congeners exhibited a diversity of responses to seasonal temperature and precipitation. This indicates that for predictive model development it is critical to understand how each underlying driver influences species that are adapted to different climatic regimes. These results underscore the value of studying a range of phenological metrics and species from a variety of ecosystems to better predict phenological responses to short-term variation and to long-term change in climate.

Within and between regions, Quercus congeners exhibited a diversity of responses to seasonal temperature and precipitation. To develop predictive phenology models, it is critical to understand how underlying drivers influence species that are adapted to different climatic regimes. These results underscore the value of studying a range of phenological metrics to understand responses to short-term variation and to long-term change.

1. Trait-based approaches evaluate ecosystem functioning under environmental change by relating traits predicting changes in species densities (response traits) to traits driving ecosystem functioning (effect traits). Stressors can, however, affect ecosystem functioning not only by altering species densities but also by directly changing species effect traits.
2. We first identified the response traits predicting the cell density of 18 marine benthic diatom strains along gradients of two chemical stressors (a pesticide and a metal, atrazine and copper). We then tested if response traits could predict stressor-induced changes in ecosystem functioning, i.e. changes in the effect traits driving the diatoms’ potential contribution to primary production, sediment stabilization and energy content in intertidal systems. Finally, we examined if changes in density and changes in ecosystem functioning were correlated, to assess whether species capable of growing under stressful conditions could maintain their contribution to ecosystem functioning.
3. The relationship between response traits and stressor-induced changes in density and ecosystem functioning was different depending on stressor type: a set of intercorrelated morphological traits predicted changes in both density and ecosystem functioning under metal stress, with large cells being more stress resistant. Changes in density and changes in ecosystem functioning were positively related: diatoms whose density was least affected by the metal were also able to sustain functioning under metal exposure.
4. In contrast, the capacity for mixotrophic growth predicted changes in density, but not changes in ecosystem functioning under pesticide stress. Pesticide effects on density and on ecosystem functioning were negatively related for energy content and sediment stabilization, indicating a limited capacity of pesticide-tolerant diatoms to maintain their contribution to ecosystem functioning.
5. Synthesis. Ecosystem functioning under stress can depend on whether the response traits driving changes in species densities also predict direct stress effects on the species’ contribution to functioning. Based on our results, we expect a disproportionate loss of functioning when traits driving species densities do not allow to maintain ecosystem functioning under stress.

Ecosystem functioning under stress can depend on whether the response traits driving changes in species densities also predict direct stress effects on the species’ contribution to functioning. Based on our results, we expect a disproportionate loss of functioning when traits driving species densities do not allow to maintain ecosystem functioning under stress.

1. The visual landscape of marine and terrestrial systems is changing as a result of anthropogenic factors. Often these shifts involve introduced species that are morphologically dissimilar to native species, creating a unique biogenic structure and habitat for associated species within the landscape. While community-level changes as a result of introduced species have been documented in both terrestrial and marine systems, it is still unclear how long-term shifts in species composition will affect habitat complexity or its potential to influence the biodiversity of species that occur at the base of the food web.
2. We analysed quadrat photos collected at several subtidal sites in the Gulf of Maine over a 30+ year period, and collected individual seaweed species to determine their complexity and the biodiversity of meso-invertebrates associated with each species.
3. By coupling the relationship of 30+ years of shifts in seaweed assemblages, morphological structure of the seaweed assemblage, and their meso-invertebrates, we determined introduced seaweeds have increased by up to 90%, corresponding to a rise in two-dimensional (2D) structure, and a decline in canopy height of subtidal rocky habitats. The highly complex two-dimensional habitat provided by introduced filamentous red seaweeds supports two to three times more meso-invertebrate individuals and species that form the base of the food web than simpler forms of morphological habitat.
4. Synthesis. The present study demonstrates a long-term shift in foundation species towards a dominance of invasive seaweeds that directly reduce canopy height and increase the 2D biogenic structure of the habitat. These introduced seaweeds harbour greater biodiversity of species found at the base of the food web than seaweeds with simpler forms such as the native kelp species. Such shifts in habitat structure will propagate to food webs by influencing the structure of lower trophic-level meso-invertebrates and indirectly upper trophic-level species that feed on these invertebrates and use the seaweed structure as refuge.

The present study demonstrates a long-term shift in foundation species towards a dominance of invasive seaweeds that directly reduce canopy height and increase the 2D biogenic structure of the habitat. These introduced seaweeds harbour greater biodiversity of species found at the base of the food web than seaweeds with simpler forms such as the native kelp species. Such shifts in habitat structure will propagate to food webs by influencing the structure of lower trophic-level meso-invertebrates and indirectly upper trophic-level species that feed on these invertebrates and use the seaweed structure as refuge.

1. It is becoming increasingly clear that plant roots can impact the decomposition of existing soil C in the rhizosphere. Studies under controlled conditions suggest this impact may be plant species dependent, but whether this is the case in natural conditions or what factors underlie this variation is mostly unknown.
2. With a novel field-based isotopic approach combining ¹³C-enriched glucose and 5-bromo-2-deoxyuridine additions, we compared in situ C decomposition of added labile C and native soil C (priming) among eight semi-arid grassland species’ rhizospheres to investigate the factors driving inter-species variation. We examined the influence of several rhizosphere factors related to soil chemistry, microbial activity, microbial community, microbial stoichiometry, plant chemistry and root morphology.
3. Plant species generated distinct microbial and chemical rhizosphere environments, which translated into differences in the direction, magnitude and temporal dynamics of the soil C priming. Soil C decomposition was positively related to soil C/P and soil N/P (via its influence on the bacterial community), which in turn were positively related to plant N/P. Plant C/N was also a significant factor via its negative influence on soil N/P. In contrast, the main direct predictors of labile C decomposition were microbial biomass, microbial C/N and the C-degrading enzymes, which in turn were linked to root morphology and C chemistry.
4. Synthesis. Within this community, plant species’ rhizospheres can vary in their susceptibility to C loss in response to changes in C availability. Soil stoichiometry, driven by plant chemical traits, appeared to be the strongest driver of priming. Our study suggests that shifts in plant communities involving increases in N relative to P have the greatest potential to lead to C loss. We provide evidence of root morphology and C chemistry as drivers of labile C processing in soil, a novel empirical contribution to our understanding of the role of plant traits below-ground. The contrasting regulation of different pools of soil C suggests observations of the regulation of simple C compounds should not be extrapolated to the whole C pool. Our findings provide support for rhizosphere-driven mechanisms by which shifts in plant community composition could have implications on the ecosystem-level C balance.

Within this community, plant species’ rhizospheres can vary in their susceptibility to C loss in response to changes in C availability. Soil stoichiometry, driven by plant chemical traits, appeared to be the strongest driver of priming. Our study suggests that shifts in plant communities involving increases in N relative to P have the greatest potential to lead to C loss. We provide evidence of root morphology and C chemistry as drivers of labile C processing in soil, a novel empirical contribution to our understanding of the role of plant traits below-ground. The contrasting regulation of different pools of soil C suggests that observations of the regulation of simple C compounds should not be extrapolated to the whole C pool. Our findings provide support for rhizosphere-driven mechanisms by which shifts in plant community composition could have implications on the ecosystem-level C balance.

1. Plant community productivity commonly increases with increasing plant diversity, which is explained by complementarity among plant species in resource utilization (complementarity effect), or by selection of particularly productive plant species in diverse plant communities (selection effect). Recent studies have also shown that soil biota can drive the positive plant diversity–productivity relationship by suppressing productivity more in low- than in high-diversity plant communities. However, much remains unknown about whether soil fertility plays a role in determining how soil biota affect plant diversity–productivity relationships.
2. We hypothesized that under high soil fertility conditions, negative soil biota effects dominate, which reduces plant monoculture biomass more than that of high-diversity plant communities. Conversely, under low soil fertility conditions, we hypothesized positive soil biota effects dominate, which facilitates plant resource partitioning and enhances community-level biomass in high-diversity plant communities. Hence, we expected positive plant diversity–community productivity relationships under low and high soil fertility conditions but caused by different mechanisms.
3. We tested these hypotheses using woody seedlings and set up plant assemblages with four species richness levels (one, two, four and eight species), and grew them in sterilized and unsterilized (sterilized soil + living soil inoculum) soils at two nutrient levels (low versus high fertility).
4. We found that at high fertility negative soil biota effects dominated and suppressed plant community biomass more in high-diversity plant communities than in monocultures, resulting in reduced complementarity effects of diverse plant communities and a non-significant plant species richness–community biomass relationship in unsterilized soil. Whereas at low fertility soil biota had net neutral to positive effects on plant community biomass but the beneficial effects did not increase with increasing plant species richness. Instead, soil biota neutrally affected the positive plant species richness–community biomass relationship, presumably due to non-specific effects of beneficial soil biota.
5. Synthesis. Soil biota and soil fertility interactively determine plant species richness–community biomass relationships. Moreover, soil biota modulate the complementary resource use among plant species. These findings suggest that environmental context plays an important role in determining whether and how soil biota generate the biodiversity–productivity relationship. Future studies would benefit from revealing the mechanisms underlying the interactive effects of soil biota, soil fertility, and plant diversity on ecosystem functioning.

Soil biota and soil fertility interactively determine plant species richness–community biomass relationships. Moreover, soil biota modulate the complementary resource use among plant species. These findings suggest that environmental context plays an important role in determining whether and how soil biota generate the biodiversity–productivity relationship. Future studies would benefit from revealing the mechanisms underlying the interactive effects of soil biota, soil fertility, and plant diversity on ecosystem functioning.

1. Impacts of invasive species may change in magnitude and even direction with invasion age. Impacts could increase as the population increases, individuals grow in size and ecological changes accumulate.
2. We used a chronosequence approach to characterize the development of soil impacts over time following the invasion of Cytisus scoparius, a widespread nitrogen-fixing shrub thought to limit reforestation success. In a greenhouse experiment, we evaluated how abundance of ectomycorrhizal fungi, Douglas-fir performance and leaf nitrogen changed across a 3- to 31-year chronosequence of invasion. Each of the chronosequence sites were clearcuts where reforestation efforts were unsuccessful and where C. scoparius invaded. To estimate the contributions of the invasion separately from contributions of the accompanying disturbance, i.e. deforestation, we included soils from both invaded and uninvaded patches in each site of the chronosequence. In a complementary soil conditioning experiment, we examined the separate effects of host absence and invader presence on the mycorrhizal mutualism, leaf nitrogen and seedling growth.
3. Ectomycorrhizal colonization was lower in invaded soil, but this effect did not intensify with time. Despite the suppression of the mutualism, Douglas-fir grew larger in invaded soils. This positive response is likely due to nitrogen fertilization, a conclusion supported by higher concentrations of leaf nitrogen of Douglas-fir grown in invaded soils. While leaf N concentration increased with invasion duration, Douglas-fir survival and growth did not.
4. Synthesis. Our findings suggest that soil impacts of an invader can develop rapidly and can be surprisingly stable over time. In such systems, recently invaded areas may be as difficult to restore as long-invaded areas, especially where ectomycorrhizal fungi are important drivers of reforestation success. More chronosequence studies or long time series are needed to evaluate whether this is a general pattern.

We characterized the development of impacts on ectomycorrhizal fungi, Douglas-fir survival and growth, and leaf nitrogen over time following the invasion of Cytisus scoparius, a nitrogen-fixing shrub thought to limit reforestation. Ectomycorrhizal colonization was lower and Douglas-fir survival was lower in invaded soil, but these effects did not intensify with time. The Douglas-fir seedlings that survived grew larger in invaded soils. This is likely due to nitrogen fertilization, a conclusion supported by higher leaf N of Douglas-fir grown in invaded soils. Both nitrogen and growth increased with the age of the site, but not disproportionately more in invaded patches.

1. Ecosystem functioning relies heavily on below-ground processes, which are largely regulated by plant fine-roots and their functional traits. However, our knowledge of fine-root trait distribution relies to date on local- and regional-scale studies with limited numbers of species, growth forms and environmental variation.
2. We compiled a world-wide fine-root trait dataset, featuring 1115 species from contrasting climatic areas, phylogeny and growth forms to test a series of hypotheses pertaining to the influence of plant functional types, soil and climate variables, and the degree of manipulation of plant growing conditions on species fine-root trait variation. Most particularly, we tested the competing hypotheses that fine-root traits typical of faster return on investment would be most strongly associated with conditions of limiting versus favourable soil resource availability. We accounted for both data source and species phylogenetic relatedness.
3. We demonstrate that: (i) Climate conditions promoting soil fertility relate negatively to fine-root traits favouring fast soil resource acquisition, with a particularly strong positive effect of temperature on fine-root diameter and negative effect on specific root length (SRL), and a negative effect of rainfall on root nitrogen concentration; (ii) Soil bulk density strongly influences species fine-root morphology, by favouring thicker, denser fine-roots; (iii) Fine-roots from herbaceous species are on average finer and have higher SRL than those of woody species, and N₂-fixing capacity positively relates to root nitrogen; and (iv) Plants growing in pots have higher SRL than those grown in the field.
4. Synthesis. This study reveals both the large variation in fine-root traits encountered globally and the relevance of several key plant functional types and soil and climate variables for explaining a substantial part of this variation. Climate, particularly temperature, and plant functional types were the two strongest predictors of fine-root trait variation. High trait variation occurred at local scales, suggesting that wide-ranging below-ground resource economics strategies are viable within most climatic areas and soil conditions.

The long and complex evolution of plant roots, and their occurrence in multiple environmental conditions, have shaped a large diversity of forms and functions among plant species. Here we gathered a worldwide fine-root trait dataset and demonstrated that climate and plant functional types were the two strongest predictors of fine-root trait variation. Particularly, climate conditions promoting soil fertility related negatively to fine-root traits favouring fast soil resource acquisition, with a particularly strong positive effect of temperature on fine-root diameter and negative effect on specific root length, and a negative effect of rainfall on root nitrogen.

1. Global change is threatening ecosystems and biodiversity world-wide, creating a pressing need to understand how climate and disturbance regimes interact and influence the persistence of species. We quantify how three ecosystem drivers – rainfall, fire and herbivory – influence vital rates in the perennial resprouting graminoid, Triodia scariosa, a foundation species of semi-arid Australia.
2. We used an 11-year dataset from a fire and herbivore exclosure experiment, to model flowering, post-fire recruitment and the post-fire survival of seedlings and resprouting plants. Regression modelling quantified the effect of rainfall, inter-fire interval, fire type (wildfire or prescribed fire), grazing by herbivores (native and feral) and an interaction between fire type and herbivory on T. scariosa populations.
3. Rainfall, fire and herbivory had significant effects on post-fire recruitment and the survival of seedlings and resprouting plants, including strong interactions between these drivers. Herbivory following wildfire had a minor effect, but in years of below-average rainfall herbivory following prescribed fire had a large effect, reducing the survival of seedlings and resprouting plants by 20% and over 50% respectively, relative to post-fire survival under average rainfall conditions.
4. Variation in rainfall underpinned significant variation in post-fire resprouting and seedling survival, thus we postulate rainfall primarily drives the dynamics of T. scariosa populations.
5. Synthesis. This study highlights the importance of modelling interactions between key ecosystem drivers when predicting how changes in global climate and disturbance regimes influence plant vital rates. Relatively small changes to disturbance regimes can substantially alter population processes, even in perennial resprouting species. This work suggests that conservation of foundation species, such as T. scariosa, will benefit if fire management decisions are better integrated with inter-annual weather forecasts and herbivore management.

Our study shows the importance of modelling interactions between key ecosystem drivers when predicting how changes in global climate and disturbance regimes influence plant vital rates. Relatively small changes to disturbance regimes substantially altered population processes in a perennial resprouting species. This suggests that conservation of foundation species will benefit if fire management decisions are better integrated with inter-annual weather forecasts and herbivore management. The photo was taken by David Keith at Tarawi Nature Reserve in 2013 and shows part of a herbivore exclosure at 7 years post-fire.

1. During soil development, bacteria and fungi can be differentially affected by changes in soil biogeochemistry. Since the chemistry of parent material affects soil pH, nutrient availability, and indirectly litter quality, we hypothesize that parent material has an important influence on microbial community patterns during long-term soil development.
2. In this paper, we tested for the effect of parent material, as well as, soil and litter properties upon microbial community patterns in three c. 20 000-year-old semi-arid chronosequences developed on sedimentary and volcanic (i.e. Andesitic and Dacitic) soils in the Dry Puna of Bolivia. We evaluated microbial patterns by analysing the terminal restriction fragment length polymorphism from amplified bacterial 16S rRNA genes, and the fungal internal transcribed spacer region, and quantitative real-time polymerase chain reaction.
3. Soil and litter characteristics differed significantly between the Sedimentary and volcanic chronosequences. In particular, soil pH was alkaline in all stages of the Sedimentary chronosequence; whereas it changed from alkaline to near neutral across stages in both volcanic chronosequences. Composition of bacterial communities changed across volcanic chronosequences, and this change was associated with a reduction in soil pH and increases in litter quality, whereas no differences were found in the Sedimentary chronosequence. Fungal community composition, in contrast, did not change across any chronosequence.
4. Relative microbial abundance, expressed as the fungal:bacterial ratio, declined across stages of the Sedimentary chronosequence in association with decreases in TC and TP, whereas in the Andesitic chronosequence decreases in fungal:bacterial ratios were related with increases in litter quality and declines in soil pH.
5. Synthesis. Our results show the importance of parent material in affecting bacterial and fungal communities during soil development. Further, in semi-arid chronosequences, fungal:bacterial ratios tend to decline given that soil pH in young soils is rather alkaline. Our results also are consistent with the general framework that highlights the importance of above-ground (i.e. litter quality) and below-ground (i.e. soil properties) in affecting microbial relative abundance and community composition during soil development.

We tested the effect of parent material, as well as soil and litter properties, upon microbial community patterns in c. 20 000-year-old chronosequences of sedimentary and volcanic origin in the Dry Puna of Bolivia. We show that parent material is paramount in affecting soil pedogenesis and ecosystem dynamics via its effects upon soil pH, soil nutrient availability and litter quality, which in turn affects microbial abundance and composition.

1. Recent global trends of increasing woody plant abundance in grass-dominated ecosystems may substantially enhance soil organic carbon (SOC) storage and could represent a strong carbon (C) sink in the terrestrial environment. However, few studies have quantitatively addressed the influence of spatial heterogeneity of vegetation and soil properties on SOC storage at the landscape scale. In addition, most studies assessing SOC response to woody encroachment consider only surface soils, and have not explicitly assessed the extent to which deeper portions of the soil profile may be sequestering C.
2. We quantified the direction, magnitude and pattern of spatial heterogeneity of SOC in the upper 1·2 m of the profile following woody encroachment via spatially specific intensive soil sampling across a landscape in a subtropical savanna in the Rio Grande Plains, USA, that has undergone woody proliferation during the past century.
3. Increased SOC accumulation following woody encroachment was observed to considerable depth, albeit at reduced magnitudes in deeper portions of the profile. Overall, woody clusters and groves accumulated 12·87 and 18·67 Mg C ha⁻¹ more SOC compared to grasslands to a depth of 1·2 m.
4. Woody encroachment significantly altered the pattern of spatial heterogeneity of SOC to a depth of 5 cm, with marginal effect at 5–15 cm, and no significant impact on soils below 15 cm. Fine root density explained greater variability of SOC in the upper 15 cm, while a combination of fine root density and soil clay content accounted for more of the variation in SOC in soils below 15 cm across this landscape.
5. Synthesis. Substantial soil organic carbon sequestration can occur in deeper portions of the soil profile following woody encroachment. Furthermore, vegetation patterns and soil properties influenced the spatial heterogeneity and uncertainty of soil organic carbon in this landscape, highlighting the need for spatially specific sampling that can characterize this variability and enable scaling and modelling. Given the geographic extent of woody encroachment on a global scale, this undocumented deep soil carbon sequestration suggests this vegetation change may play a more significant role in regional and global carbon sequestration than previously thought.

Woody plant encroachment into grasslands increased soil organic carbon (SOC) storage and influenced the spatial heterogeneity and uncertainty of SOC throughout the soil profile. In addition, much of the SOC accrual following woody encroachment was stored deep in the profile. Given the geographic extent of woody encroachment on a global scale, this undocumented deep soil C sequestration suggests this vegetation change may play a more significant role in regional and global C sequestration than previously thought.

1. This paper addresses the origin and development of the oldest prehistoric pasture in the timberline ecotone known so far in the Alps and its relation to anthropogenic pressure and natural climate change.
2. Palaeoecological and geochemical techniques were applied on the Crotte Basse mire stratigraphy (2365 m a.s.l, northwestern Italy) to describe changes in vegetation composition, forest biomass, land use and fertilization between c. 6400–1800 cal years bp.
3. Subalpine forests dominated by Pinus cembra occurred at very high-altitude up to c. 5600 cal years bp, when a sharp contraction of woody vegetation took place. This major vegetation shift is matched by increasing charcoal input and markers of pastoral/grazing activities (pollen, dung spores and forms of phosphorus) in the sediment sequence in this small basin.
4. Major phases of landscape change detected in our multiproxy record chronologically match intervals of cumulative probability density of ¹⁴C ages from nearby archaeological sites, suggesting that human activity was the factor leading to massive landscape change from the onset of the Copper Age (c. 5600 cal years bp). The change may have been reinforced by climate variability in the period 5700–5300 cal years bp.
5. Sensitivity of woody species to fires was statistically explored (Appendix S1, Supporting Information), revealing negative reactions of P. cembra and Betula to frequent fire episodes and positive reactions of Alnus viridis and Juniperus. Fire episodes do not affect Larix dynamics.
6. Synthesis. Mt. Fallère provides some of the oldest and consistent evidence so far available in the Alps for major anthropogenic pressure at the upper forest limit. As far back as 5600 cal years bp, high-elevation forest ecosystems were permanently disrupted and the alpine pastures were created. Palaeoecological data enable a clear distinction between a random and sporadic use of the alpine space, typical for Mesolithic and Neolithic societies, and an organized seasonal exploitation of natural resources, starting from the Copper Age onwards. The chronological comparison of independent climate proxies, palaeoecological information and pollen-based temperature reconstructions sheds light on the relationships between climate and humans since prehistoric times.

This extensive and biodiverse cow pasture in the elevational belt of the western Italian Alps was suddenly installed at the Copper Age onset at the expenses of timberline forests. A 5600 years-long history of permanent herding and landscape management is narrated by the palaeoecological archive retrieved from a pond used for livestock watering.

1. Tropical forests play an important role in the global carbon cycle, but the drivers of net forest biomass change (i.e. net carbon sequestration) are poorly understood. Here, we evaluate how abiotic factors (soil conditions and disturbance) and biotic factors (forest structure, diversity and community trait composition) shape three important demographic processes (biomass recruitment, growth and mortality) and how these underlie net biomass change.
2. To test this, we evaluated 9 years of biomass dynamics using 48 1-ha plots in a Bolivian tropical moist forest, and measured for the most abundant species eight functional traits that are important for plant carbon gain and loss. Demographic processes were related to the abiotic and biotic factors using structural equation models.
3. Variation in net biomass change across plots was mostly due to stand-level mortality, but mortality itself could not be predicted at this scale. Contrary to expectations, we found that species richness and trait composition – which is an indicator for the mass-ratio theory – had little effect on the demographic processes. Biomass recruitment (i.e. the biomass growth by recruiting trees) increased with higher resource availability (i.e. water and light) and with high species richness, probably because of increased resource use efficiency. Biomass growth of larger, established trees increased with higher sand content, which may facilitate root growth of larger trees to deeper soil layers.
4. In sum, diversity and mass-ratio are of limited importance for the productivity of this forest. Instead, in this moist tropical forest with a marked dry season, demographic processes are most strongly determined by soil texture, soil water availability and forest structure. Only by simultaneously evaluating multiple abiotic and biotic drivers of demographic processes, better insights can be gained into mechanisms playing a role in the carbon sequestration potential of tropical forests and natural systems in general.

We evaluate how abiotic and biotic factors shape biomass recruitment, growth and mortality, and how these processes underlie net biomass change in a tropical forest. Net biomass change is mainly driven by mortality, but mortality is poorly predicted by abiotic and biotic factors. Productivity is determined by soil texture, soil water availability and forest structure, and not by diversity and mass-ratio.

1. Plant phenotypic diversity is shaped by the interplay of trade-offs and constraints in evolution. Closely integrated groups of traits (i.e. trait dimensions) are used to classify plant phenotypic diversity into plant strategies, but we do not know the degree of interdependence among trait dimensions. To assess how selection has shaped the phenotypic space, we examine whether trait dimensions are independent.
2. We gathered data on saplings of 24 locally coexisting tree species in a temperate forest, and examined the correlation structure of 20 leaf, branch, stem and root traits. These traits fall into three well-established trait dimensions (the leaf economic spectrum, the wood spectrum and Corner's Rules) that characterize vital plant functions: resource acquisition, sap transport, mechanical support and canopy architecture. Using ordinations, network analyses and Mantel tests, we tested whether the sapling phenotype of these tree species is organized along independent trait dimensions.
3. Across species, the sapling phenotype is not structured into clear trait dimensions. The trait relationships defining trait dimensions are either weak or absent and do not dominate the correlation structure of the sapling phenotype as a whole. Instead traits from the three commonly recognized trait dimensions are organized into an integrated trait network. The effect of phylogeny on trait correlations is minimal.
4. Our results indicate that trait dimensions apparent in broad-based interspecific surveys do not hold up among locally coexisting species. Furthermore, architectural traits appear central to the phenotypic network, suggesting a pivotal role for branching architecture in linking resource acquisition, mechanical support and hydraulic functions.
5. Synthesis. Our study indicates that local and global patterns of phenotypic integration differ and calls into question the use of trait dimensions at local scales. We propose that a network approach to assessing plant function more effectively reflects the multiple trade-offs and constraints shaping the phenotype in locally co-occurring species.

Our study finds that globally defined trait dimensions are not independent (or even present) at a local scale. This calls into question the use of trait dimensions for local-scale ecology. We propose that a network approach to assessing plant function more effectively reflects the multiple trade-offs and constraints shaping the phenotype in locally co-occurring species.

1. We investigated the potential of cross-scale interactions to affect the outcome of density reduction in a large-scale silvicultural experiment to better understand options for managing forests under climate change.
2. We measured tree growth and intrinsic water-use efficiency (iWUE) based on stable carbon isotopes (δ¹³C) to investigate impacts of density reduction across a range of progressively finer spatial scales: site, stand, hillslope position and neighbourhood. In particular, we focused on the influence of treatments beyond the boundaries of treated stands to include impacts on downslope and neighbouring stands across sites varying in soil moisture.
3. Trees at the wet site responded with increased growth when compared with trees at the dry site. Additionally, trees in treated stands at the dry site responded with increased iWUE while trees at the wet site showed no difference in iWUE compared to untreated stands.
4. We hypothesized that water is not the primary limiting factor for growth at our sites, but that density reduction released other resources, such as growing space or nutrients to drive the growth response. At progressively finer spatial scales we found that tree responses were not driven by hillslope location (i.e. downslope of treatment) but to changes in local neighbourhood tree density.
5. Synthesis. This study demonstrated that water can be viewed as an agent to investigate cross-scale interactions as it links processes operating at coarse to finer spatial scales and vice versa. Consequently, management prescriptions such as density reductions to increase resistance and resilience of trees to climate change, specifically to drought, need to consider cross-scale interactions as specific magnitude and mechanisms of growth responses can only be predicted when multiple scales are taken into account.

This study demonstrated that water can be viewed as an agent to investigate cross-scale interactions as it links processes operating at coarse to finer spatial scales and vice versa. Consequently, management prescriptions such as density reductions to increase resistance and resilience of trees to climate change, specifically to drought, need to consider cross-scale interactions, as specific magnitude and mechanisms of growth responses can only be predicted when multiple scales are taken into account.

1. The understorey of tropical forests is heterogeneous across time, and plants that inhabit this layer may exhibit adaptations (e.g. trait plasticity) that enable them to exploit this variability to their advantage. We tested the hypothesis that two widespread understorey herbs would perform equally well in a variable as in a constant environment, using a 2-year shade-house experiment.
2. We measured demographic traits (growth and survival), a physiological trait (maximum photosynthetic capacity), and life-history traits (leaf life span and biomass allocation) of Heliconia tortuosa and Calathea crotalifera. We investigated how these traits were affected by light availability at the seedling stage, precipitation, and whether individuals experienced a constant or variable light environment.
3. Whether or not a variable environment was favourable for plants depended upon precipitation and the environment in which individuals started life. At low precipitation, plants in a variable light environment grew more than those in a constant environment, but only when individuals had lived as seedlings in low light. At high precipitation, plants in a constant environment grew more than those in a variable environment, regardless of early conditions. Survival was lower in a variable environment at low precipitation, and more so at high precipitation. Photosynthetic capacity was lower for individuals in a variable environment than in a constant environment when they had lived in high light as seedlings.
4. Calathea grew faster and survived more poorly than Heliconia, independently of the treatments. Calathea grew more at high than low precipitation while Heliconia grew more at low than high precipitation. Leaf life span and biomass allocation did not differ among treatments, although Calathea had a significantly greater proportion of its biomass above-ground vs. that of Heliconia.
5. Synthesis. Environmental variability had a neutral or positive effect on biomass allocation, photosynthetic capacity, and leaf life span for these species. Survival was the only trait that was always lower in a variable environment. The effect of environmental variability was dependent on early life conditions as well as precipitation, suggesting that generalist species may experience high fitness as forest environments become more variable by maintaining high growth at the expense of survival.

Environmental variability had a neutral or positive effect on biomass allocation, photosynthetic capacity and leaf life span for two widespread, understorey herbs. Survival was always lower in a variable environment. The effect of environmental variability depended on earlier conditions and precipitation, suggesting that generalists may experience high fitness as environments become more variable by maintaining high growth but reduced survival.

1. Increased species diversity promotes ecosystem function; however, the dynamics of multi-species grassland systems over time and their role in sustaining higher yields generated by increased diversity are still poorly understood. We investigated the development of species’ relative abundances in grassland mixtures over 3 years to identify drivers of diversity change and their links to yield diversity effects.
2. A continental-scale field experiment was conducted at 31 sites using 11 different four-species mixtures each sown at two seed abundances. The four species consisted of two grasses and two legumes, of which one was fast establishing and the other temporally persistent. We modelled the dynamics of the four-species mixtures, and tested associations with diversity effects on yield.
3. We found that species’ dynamics were primarily driven by differences in the relative growth rates (RGRs) of competing species, and secondarily by density dependence and climate. The temporally persistent grass species typically had the highest RGRs and hence became dominant over time. Density dependence sometimes induced stabilising processes on the dominant species and inhibited shifts to monoculture. Legumes persisted at most sites at low or medium abundances and persistence was improved at sites with higher annual minimum temperature.
4. Significant diversity effects were present at the majority of sites in all years and the strength of diversity effects was improved with higher legume abundance in the previous year. Observed diversity effects, when legumes had declined, may be due to (i) important effects of legumes even at low abundance, (ii) interaction between the two grass species or (iii) a store of N because of previous presence of legumes.
5. Synthesis. Alongside major compositional changes driven by RGR differences, diversity effects were observed at most sites, albeit at reduced strength as legumes declined. This evidence strongly supports the sowing of multi-species mixtures that include legumes over the long-standing practice of sowing grass monocultures. Careful and strategic selection of the identity of the species used in mixtures is suggested to facilitate the maintenance of species diversity and especially persistence of legumes over time, and to preserve the strength of yield increases associated with diversity.

Alongside major compositional changes driven by relative growth rate differences, diversity effects were observed at most sites, albeit at reduced strength as legumes declined. This evidence strongly supports the sowing of multi-species mixtures that include legumes over the long-standing practice of sowing grass monocultures. Careful and strategic selection of the identity of the species used in mixtures is suggested to facilitate the maintenance of species diversity and especially persistence of legumes over time, and to preserve the strength of yield increases associated with diversity.

1. Litter drives a wide variety of important functions in both terrestrial and aquatic ecosystems. However, the role of litter in regulating community dynamics and ecosystem processes has mostly been studied in terms of litter presence or amount. Besides in biogeochemistry, we still do not know how litters from distinct plant species differ in their effects on other ecosystem processes and services including biodiversity support.

2. We briefly synthesize the multiple litter functions and services by using the afterlife legacy of interspecific variation in plant morphological, physical and chemical traits as a unifying tool. We do so by explicit reference to two highly distinct but possibly interacting ‘trait spectra’: the widely known Resource Economic Spectrum, and the Size and Shape Spectrum, a trait-based axis ranging from small and relatively simply shaped distal plant organs to large and more intricately shaped ones.

3. Synthesis. Ecosystem services provided by plant litter are driven by either one of the trait spectra or by both. In this way, the Size and Shape Spectrum-Resource Economic Spectrum concept is a promising tool for understanding and predicting the contributions of different plant species, through the afterlife effects of their litter traits, to various important services in different ecosystems and human contexts.

Ecosystem services provided by plant litter are driven by traits related to both the Size and Shape Spectrum (SSS) and the Resource Economic Spectrum (RES). In this way, the SSS-RES concept is a promising tool for understanding and predicting the contributions of different plant species, through the afterlife effects of their litter traits, to various important services in different ecosystems and human contexts.

1. Understanding species' abilities to cope with changing climate is a key prerequisite for predicting the future fates of species and ecosystems. Despite considerable research on species responses to changing climate, we still lack understanding of the role of specific climatic factors, and their interactions, for species responses. We also lack understanding of the relative importance of plasticity vs. adaptation in determining the observed responses.
2. As a model, we use a dominant clonal grass, Festuca rubra, originating from a natural climatic grid of 12 localities in western Norway that allows factorial combinations of temperature (mean growing season temperatures ranging from 6·5 to 10·5 °C) and precipitation (annual precipitation ranging from 600 to 2700 mm). We grew clones from all populations in four growth chambers representing the four climatic extremes in the climate grid (warm/cold × wet/dry).
3. Genetic differentiation and direction and magnitude of plastic responses vary systematically among populations throughout the climatic grid. Growth-related plant traits are highly plastic and their degree of plasticity depends on their origin. In contrast, the traits reflecting species' foraging strategy are not plastic but vary with the climate of origin. Levels of plasticity of growth-related traits and genetically differentiated foraging traits thus might constrain local populations' ability to cope with novel climates.
4. Synthesis. Shifts in temperature and precipitation, at the scale and direction expected for the region in the next century, are likely to dramatically affect plant performance. This study illustrates how the interplay between genetic differentiation and plasticity in response to both temperature and precipitation will affect the specific responses of species to climate change. Such complex responses will affect how climate-change impacts scale up to the community and ecosystem levels. Future studies thus need to specifically consider regionally relevant climate-change projections, and also explore the role of genetic differentiation and plasticity and how this varies within local floras. Our study also demonstrates that even widespread species with seemingly broad climatic niches may strongly differ in their population performance and plasticity. Climate-change studies should therefore not be limited to rare and restricted species.

Shifts in temperature and precipitation, at the scale and direction expected for the region in the next century, are likely to dramatically affect plant performance. This study illustrates how the interplay between genetic differentiation and plasticity in response to both temperature and precipitation will affect the specific responses of species to climate change. Such complex responses will affect how climate-change impacts scale up to the community and ecosystem levels. Future studies thus need to specifically consider regionally relevant climate-change projections, and also explore the role of genetic differentiation and plasticity and how this varies within local floras. Our study also demonstrates that even widespread species with seemingly broad climatic niches may strongly differ in their population performance and plasticity. Climate-change studies should therefore not be limited to rare and restricted species.

1. The abundance of nitrogen (N)-fixing plants in ecosystems where phosphorus (P) limits plant productivity poses a paradox because N fixation entails a high P cost. One explanation for this paradox is that the N-fixing strategy allows greater root phosphatase activity to enhance P acquisition from organic sources, but evidence to support this contention is limited.
2. We measured root phosphomonoesterase (PME) activity of 10 N-fixing species, including rhizobial legumes and actinorhizal Allocasuarina species, and eight non-N-fixing species across a retrogressive soil chronosequence showing a clear shift from N to P limitation of plant growth and representing a strong natural gradient in P availability.
3. Legumes showed greater root PME activity than non-legumes, with the difference between these two groups increasing markedly as soil P availability declined. By contrast, root PME activity of actinorhizal species was always lower than that of co-occurring legumes and not different from non-N-fixing plants.
4. The difference in root PME activity between legumes and actinorhizal plants was not reflected in a greater or similar reliance on N fixation for N acquisition by actinorhizal species compared to co-occurring legumes.
5. Synthesis. Our results support the idea that N-fixing legumes show high root phosphatase activity, especially at low soil P availability, but suggest that this is a phylogenetically conserved trait rather than one directly linked to their N-fixation capacity.

Our results support the idea that N-fixing legumes show high root phosphatase activity, especially at low soil P availability, but suggest that this is a phylogenetically conserved trait rather than one directly linked to their N-fixation capacity.

1. One of the most palpable effects of warming in Arctic ecosystems is shrub expansion above the tree line. However, previous studies have found that reindeer can influence plant community responses to warming and inhibit shrubification of the tundra.

2. We revisited grazed (ambient) and ungrazed study plots (exclosures), at the southern as well as the northern limits of the Swedish alpine region, to study long-term grazing effects and vegetation changes in response to increasing temperatures between 1995 and 2011, in two vegetation types (shrub heath and mountain birch forest).

3. In the field layer at the shrub heath sites, evergreen dwarf shrubs had increased in cover from 26% to 49% but were unaffected by grazing. Deciduous dwarf and tall shrubs also showed significant, though smaller, increases over time. At the birch forest sites, the increase was similar for evergreen dwarf shrubs (20–48%) but deciduous tall shrubs did not show the same consistent increase over time as in the shrub heath.

4. The cover and height of the shrub layer were significantly greater in exclosures at the shrub heath sites, but no significant treatment effects were found on species richness or diversity.

5. July soil temperatures and growing season thawing degree days (TDD) were higher in exclosures at all but one site, and there was a significant negative correlation between mean shrub layer height and soil TDD at the shrub heath sites.

6. Synthesis. This study shows that shrub expansion is occurring rapidly in the Scandes mountain range, both above and below the tree line. Tall, deciduous shrubs had benefitted significantly from grazing exclosure, both in terms of cover and height, which in turn lowered summer soil temperatures. However, the overriding vegetation shift across our sites was the striking increase in evergreen dwarf shrubs, which were not influenced by grazing. As the effects of an increase in evergreen dwarf shrubs and more recalcitrant plant litter may to some degree counteract some of the effects of an increase in deciduous tall shrubs, herbivore influence on shrub interactions is potentially of great importance for shaping arctic shrub expansion and its associated ecosystem effects.

This study shows that shrub expansion is occurring rapidly in the Scandes mountain range, both above and below the tree line. Although tall, deciduous shrubs had benefitted significantly from grazing exclosure, both in terms of cover and height, which in turn lowered summer soil temperatures, the overriding vegetation shift across our sites was the striking increase in evergreen dwarf shrubs, which were not influenced by grazing. As the effects of an increase in evergreen dwarf shrubs and more recalcitrant plant litter may to some degree counteract some of the effects of an increase in deciduous tall shrubs, herbivore influence on shrub interactions is potentially of great importance for shaping arctic shrub expansion and its associated ecosystem effects.

1. Theory has shown that sterilizing diseases with frequency-dependent transmission (characteristics shared by many sexually transmitted diseases) can drive host populations to extinction.
2. Anther-smut disease (caused by Microbotryum sp.) has become a model plant pathogen system for studying the dynamics of vector- and sexually transmitted diseases: infected individuals are sterilized, producing spores instead of pollen, and the disease is spread between reproductive individuals by insect pollinators. We investigated anther-smut disease in a heavily infected population of Dianthus pavonius (alpine carnation) over an 8-year period to determine disease impacts on host population dynamics.
3. Over the 8 years, disease prevalence remained consistently high (>40%), while the host population numbers declined by over 50%.
4. The observed rate of vector transmission to reproductive, adult hosts was inadequate to explain the high disease prevalence. Additional density-dependent aerial transmission to highly susceptible juveniles, indicated from experimental field and greenhouse studies, is likely to play a key role in maintaining the high disease prevalence.
5. Epidemiological models that accounted for the mixed transmission mode predicted an eventual decline in disease.
6. Synthesis. Our results demonstrate that high prevalence of a sterilizing disease does not necessarily drive host populations towards extinction and also highlights the importance of demographic studies for establishing the presence of alternative transmission modes.

We studied the transmission dynamics of vector-borne sterilizing disease in a heavily diseased natural plant population for 8 years. Our results demonstrate that high disease prevalence does not necessarily drive host populations towards extinction and also highlights the importance of demographic studies for establishing the presence of alternative transmission modes.

1. Species distribution shifts in response to climate change require that recruitment increase beyond current range boundaries. For trees with long life spans, the importance of climate-sensitive seedling establishment to the pace of range shifts has not been demonstrated quantitatively.
2. Using spatially explicit, stochastic population models combined with data from long-term forest surveys, we explored whether the climate-sensitivity of recruitment observed in climate manipulation experiments was sufficient to alter populations and elevation ranges of two widely distributed, high-elevation North American conifers.
3. Empirically observed, warming-driven declines in recruitment led to rapid modelled population declines at the low-elevation, ‘warm edge’ of subalpine forest and slow emergence of populations beyond the high-elevation, ‘cool edge’. Because population declines in the forest occurred much faster than population emergence in the alpine, we observed range contraction for both species. For Engelmann spruce, this contraction was permanent over the modelled time horizon, even in the presence of increased moisture. For limber pine, lower sensitivity to warming may facilitate persistence at low elevations – especially in the presence of increased moisture – and rapid establishment above tree line, and, ultimately, expansion into the alpine.
4. Synthesis. Assuming 21st century warming and no additional moisture, population dynamics in high-elevation forests led to transient range contractions for limber pine and potentially permanent range contractions for Engelmann spruce. Thus, limitations to seedling recruitment with warming can constrain the pace of subalpine tree range shifts.

Using stochastic demographic models combined with long-term forest survey data, we found that climate-driven changes to recruitment altered populations and elevation ranges of two widely distributed North American conifers. Rapid population declines at low elevations and slow emergence of populations beyond tree line led to transient range contractions for limber pine and potentially permanent range contractions for Engelmann spruce.

1. In forests of eastern North America, white-tailed deer (Odocoileus virginianus) can directly affect, via herbivory, the presence, abundance and reproductive success of many plant species. In addition, deer indirectly influence understorey communities by altering environmental conditions.
2. To examine how deer indirectly influence understorey plants via environmental modification, we sampled vegetation and environmental variables in- and outside deer exclosures (10–20 years old) located in temperate forests in northern Wisconsin and the Upper Peninsula of Michigan, USA. We assessed how excluding deer affected understorey community composition and structure, the soil and light environment, and relationships between direct and indirect effects, using non-metric multidimensional scaling (NMDS), mixed linear models and nonparametric multiplicative regression (NPMR).
3. Excluding deer altered sapling communities and several aspects of the understorey environment. Excluding deer from plots with lower overstory basal area increased sapling abundance, decreasing the amount of light available to groundlayer plants. Exclusion also reduced soil compaction and the thickness of the soil E horizon.
4. The composition of understorey communities covaried in apparent response to the environmental factors affected by exclusion. In several common species and groups, E horizon thickness, compaction, openness, and/or total (sapling and overstory) basal area were significant predictors of plant frequency.
5. Complementary analyses revealed that deer exclusion also altered the frequency distributions of several species and groups across environmental space.
6. Synthesis. Deer alter many facets of the understorey environment, such as light availability, soil compaction and thickness of the soil E horizon, which, in turn, appear to mediate variation in plant communities. Those environmental modifications likely compound direct impacts of herbivory as drivers of understorey community change. Our results provide evidence that deer effects on the environment have important implications for forest composition. Thus, we suggest a re-examination of the common assumption that understorey community shifts stem primarily from tissue removal.

Deer alter many facets of the understorey environment, such as light availability, soil compaction and thickness of the soil E horizon, which, in turn, appear to mediate variation in plant communities (e.g. data shown above for a, graminoids and b, Liliaceae). Those environmental modifications likely compound direct impacts of herbivory as drivers of understorey community change. Our results provide evidence that deer effects on the environment have important implications for forest composition.

1. Many short-lived species complete their life cycles during brief seasonal windows of favourable environmental conditions. Such species may persist in the face of climate warming by migration to track their seasonal climate niche in space and/or by phenological shifts to track favourable conditions in time within the year. To describe the seasonal climate niche of the short-lived annual Mollugo verticillata in California, we used data from herbarium specimens and historic climate records to estimate environmental conditions at the location, month and year of each collection.
2. We used these data in a MaxEnt framework to construct a seasonal species distribution model (SDM) of the species’ climate niche within the total climate space available across all seasons and locations in California. The model provides fine-scale spatial and temporal predictions of habitat suitability, predicting both where and when the species should be observed.
3. We compared the predictions of the model to those from a conventional SDM based on mean annual climate data. Both models showed that M. verticillata is limited to warm environments within California. However, the seasonal SDM also predicted phenology by mapping climate suitability across the state for each month of the year. Mollugo verticillata is limited to warm months, and its seasonal climate niche shifts in space across California in the course of the year.
4. We used the seasonal SDM to map the predicted future species distribution for each month of the year under three warming scenarios. The species is predicted to expand its range and occur earlier in the year in most locations; in the warmest locations, seasonal suitability is predicted to decline in the warmest months, which may result in bimodal phenology with a mid-summer gap.
5. Synthesis. We developed a novel species distribution model using herbarium records and monthly weather data, which predicts not only where a short-lived species should be found but also when during the year it is predicted to occur in those areas. This model can be used to predict how climate change will affect the species distribution in space as well as seasonal phenology across the landscape.

We developed a novel species distribution model using herbarium records and monthly weather data, which predicts not only where a short-lived species should be found but also when during the year it is predicted to occur in those areas. This model can be used to predict how climate change will affect the species distribution in space as well as seasonal phenology across the landscape.

1. As global climate changes and the world population increases, agriculture faces an enormous challenge to increase food production in an equitable and sustainable manner. Principles and concepts derived directly from plant ecological research can help meet this challenge.
2. This series of 10 mini-reviews considers some of the key ways that plant ecologists can help inform and contribute to meeting this challenge.
3. The papers are grouped into three main themes of plant ecology, namely plant community diversity and structure, plant population dynamics and plant interactions, and plant–soil (below-ground) interactions.
4. Synthesis. We identify a number of important knowledge gaps in areas where plant ecological research can contribute towards improving yield, nutrition, ecosystem services and environmental resilience of agricultural systems. However, the adoption of plant ecological principles in sustainable agriculture will require practical approaches to their implementation along with improved understanding of social and economic barriers.

We identify a number of important knowledge gaps in areas where plant ecological research can contribute towards improving yield, nutrition, ecosystem services and environmental resilience of agricultural systems. However, the adoption of plant ecological principles in sustainable agriculture will require practical approaches to their implementation along with improved understanding of social and economic barriers.

1. Plant ecological knowledge accumulated over the past 150 years has enormous implications for agriculture, but most of these implications have not been appreciated by ecologists or agronomists. Here, I present several of the most salient examples.
2. Agriculturalists refer to ‘improvements’, but plant ecologists know that ‘trade-offs’ represent a better conceptual framework for agricultural production. There is much evidence for trade-offs between yield and resource use efficiency, and between individual fitness and population yield. I argue that there is also a ‘limiting trade-off’ between short-term yield and sustainability, and it is important to take this into consideration if we are serious about increasing sustainability.
3. At the local level, agricultural sustainability is about maintaining or improving soil fertility, but this is not a priority in most agricultural systems world-wide. Increased biomass density (both living and dead) in the field is the key to increasing sustainability while maintaining high yields, and I present a vision of ‘High Biomass Cropping Systems’.
4. Classical and current research in plant community ecology tells us that rotation of crops with different nutritional needs, pests, diseases and weeds can make a major contribution to sustainability. The very limited crop rotations practised in most modern plant production systems are a clear indication that farming practices are usually based on short-term economic and regulatory factors, without much if any consideration for sustainability.
5. Synthesis. The modern scientific method tells us how we should test hypotheses, but it says nothing about how hypotheses are generated. We need to address the agricultural research agenda if it is to serve the interests of farmers, consumers and society as a whole, rather than narrow but powerful economic interests.

Plant Ecology provides the scientific knowledge needed to develop sustainable agricultural systems, but this knowledge is not widely appreciated or applied. Examples include trade-offs, the ecological processes that determine soil fertility, and the effects of temporal plant diversity. The lack of sustainability of most agricultural systems is primarily due to economic, social and political factors, not a lack of scientific knowledge.

1. Recent studies have revealed many potential benefits of increasing plant diversity in natural ecosystems, as well as in agroecosystems and production forests. Plant diversity potentially provides a partial to complete substitute for many costly agricultural inputs, such as fertilizers, pesticides, imported pollinators and irrigation. Diversification strategies include enhancing crop genetic diversity, mixed plantings, rotating crops, agroforestry and diversifying landscapes surrounding croplands.
2. Here we briefly review studies considering how increasing plant diversity influences the production of crops, forage, and wood, yield stability, and several regulating and supporting agroecosystem services. We also discuss challenges and recommendations for diversifying agroecosystems.
3. There is consistently strong evidence that strategically increasing plant diversity increases crop and forage yield, wood production, yield stability, pollinators, weed suppression and pest suppression, whereas effects of diversification on soil nutrients and carbon remain poorly understood.
4. Synthesis. The benefits of diversifying agroecosystems are expected to be greatest where the aims are to sustainably intensify production while reducing conventional inputs or to optimize both yields and ecosystem services. Over the next few decades, as monoculture yields continue to decelerate or decline for many crops, and as demand for ecosystem services continues to rise, diversification could become an essential tool for sustaining production and ecosystem services in croplands, rangelands and production forests.

The benefits of diversifying agroecosystems are expected to be greatest where the aims are to sustainably intensify production while reducing conventional inputs or to optimize both yields and ecosystem services. Over the next few decades, as monoculture yields continue to decelerate or decline for many crops, and as demand for ecosystem services continues to rise, diversification could become an essential tool for sustaining production and ecosystem services in croplands, rangelands and production forests.

1. Focusing on food production, in this paper we define resilience in the food security context as maintaining production of sufficient and nutritious food in the face of chronic and acute environmental perturbations. In agri-food systems, resilience is manifest over multiple spatial scales: field, farm, regional and global. Metrics comprise production and nutritional diversity as well as socio-economic stability of food supply.
2. Approaches to enhancing resilience show a progression from more ecologically based methods at small scales to more socially based interventions at larger scales. At the field scale, approaches include the use of mixtures of crop varieties, livestock breeds and forage species, polycultures and boosting ecosystem functions. Stress-tolerant crops, or with greater plasticity, provide technological solutions.
3. At the farm scale, resilience may be conferred by diversifying crops and livestock and by farmers implementing adaptive approaches in response to perturbations. Biodiverse landscapes may enhance resilience, but the evidence is weak. At regional to global scales, resilient food systems will be achieved by coordination and implementation of resilience approaches among farms, advice to farmers and targeted research.
4. Synthesis. Threats to food production are predicted to increase under climate change and land degradation. Holistic responses are needed that integrate across spatial scales. Ecological knowledge is critical, but should be implemented alongside agronomic solutions and socio-economic transformations.

We define resilience in the food security context as maintaining production of sufficient and nutritious food in the face of chronic and acute environmental perturbations. In agri-food systems, approaches to enhancing resilience show a progression from more ecologically based methods at small scales to more socially based interventions at larger scales. Holistic responses are needed that integrate across spatial scales.

1. Food security faces challenges that must be addressed from multiple perspectives. Ecology and agronomy contribute to that endeavour, allowing improvement in management practices. However, not only management affects food provision but also crop traits modulate key ecosystem services (ESs), including sustained yields.
2. Here we highlight that understanding how crop traits evolved under domestication, affecting ESs delivery, should help to breed future crops. We address the effects of crop evolution (from initial domestication to current times) on crop traits and key ESs: crop yield and its stability over time, soil carbon sequestration, soil nitrogen retention and water provision.
3. Synthesis. There is evidence that crop domestication affects the delivery of ESs. However, most of these evolutionary effects are understudied. Accordingly, we identify research gaps and necessary actions, including (i) assessing whether performance in polyculture is lower for modern crop mixtures than for mixtures of wild progenitors, and breeding for more efficient crop polycultures; and (ii) investigating how crop evolution impacted on plant effects on soil carbon sequestration and nitrogen retention, and how such effects contribute to yield stability. The provision of cropland ESs, and thus food security, will benefit from exploring those avenues from an ecological perspective.

There is evidence that crop domestication affects the delivery of ESs. However, most of these evolutionary effects are understudied. Accordingly, we identify research gaps and necessary actions, including (1) assessing whether performance in polyculture is lower for modern crop mixtures than for mixtures of wild progenitors, and breeding for more efficient crop polycultures; and (2) investigating how crop evolution affected plant effects on soil carbon sequestration and nitrogen retention, and how such effects contribute to yield stability. The provision of cropland ESs, and thus food security, will benefit from exploring those avenues from an ecological perspective.

1. We briefly review current understanding of wild pollinators and pollination services on farmlands.
2. We consider how concepts in plant ecology – community assembly and functional trait diversity - may be applied to create diverse, wild pollinator communities across scales in agroecosystems.
3. We also make recommendations for best practices to enhance pollination services and create more sustainable food production systems under changing environmental conditions, including creating greater landscape connectivity, embracing pollinator dynamics, and providing incentives and other motivations to support these practices.
4. Synthesis. We highlight the opportunity for agricultural lands to serve a dual role for both food production and pollinator conservation, and conclude by posing unanswered questions and top priorities for future studies.

We discuss how concepts in community assembly and functional trait diversity may be applied to agroecosystems in order to enhance pollination services. We provide predictions for best practices expected under changing environmental conditions. We conclude that agricultural lands may serve a dual role for both food production and pollinator conservation.

1. Sustainable cropping systems are needed for future food security. One aspect of sustainable cropping is to manage for desirable grain quality of crops including seed size, protein, oil and metabolite composition.
2. Plant ecology theory on niche relationships and interspecific competition predicts that subordinate species mixtures (i.e. weed species) will affect dominant (i.e. crop) species offspring quality. Beyond individual weed species effects on crop quality, we hypothesise that the integrated effect of weed mixtures will be influenced by taxonomic, functional trait and phylogenetic diversity.
3. Reviewing Glycine max (soybean)–weed systems, we show a complex relationship between the weed community and G. max seed protein, oil, mean seed mass and physiological markers (relative water content, trigonelline leaf content, fluorescence, foliar Cu, Fe and Zn). Increased levels of weed competition led to increased seed protein, at the expense of seed oil.
4. Synthesis. We propose that research on interspecific relationships between crops and weeds consider weed species diversity, weed functional traits associated with the Leaf-Height-Seed strategy and phylogenetic relationships to identify weed mixtures (either sown or manipulated through herbicide control) best suited to minimise their detrimental effects on yield while maximising crop quality as part of sustainable cropping systems.

One aspect of sustainable cropping is to manage for desirable grain quality of crops including seed size, protein, oil and metabolite composition. We propose that ecological research on interspecific relationships between crops and weeds consider weed species diversity, weed functional traits and phylogenetic relationships to identify weed mixtures (either sown or manipulated through herbicide control) best suited to minimise their detrimental effects on yield while maximising crop quality as part of sustainable cropping systems.

1. Climate change poses an unprecedented challenge to agriculture. While growers have always struggled with year-to-year variation in climate – early rains or unusually hot summers – climate change provides a major directional shift in mean climate.
2. Across the globe, growing regions are warming and plants are shifting in both time and space. Current and future shifts pose a major challenge to researchers and growers alike, yet they also highlight a major avenue to adapt crops to climate change – by understanding and exploiting phenological diversity.
3. Using winegrapes (Vitis vinifera subsp. vinifera) as a case study, we review the phenological diversity present within one crop and its underlying environmental and genetic drivers. In winegrapes, harvest dates are strongly tied to temperature, but this sensitivity varies greatly, with different cultivars (or ‘varieties’) of grapes ripening much more or less for the same amount of warming.
4. Synthesis. This phenological diversity provides a mechanism to help growers adapt winegrapes to shifting climates – by planting different varieties that will grow well under current and future climate regimes. More generally, understanding phenological diversity – including its environmental vs. genetic components – offers a major avenue to use ecological knowledge to advance adaptation for winegrapes, and many other crops, to climate change.

Phenological diversity provides a mechanism to help growers adapt winegrapes to shifting climates – by planting different varieties that will grow well under current and future climate regimes. More generally, understanding phenological diversity – including its environmental versus genetic components – offers a major avenue to use ecological knowledge to advance adaptation for winegrapes, and many other crops, to climate change.

1. Healthy soils that contain an active microbiome and food web are critical to sustainably produce food for a growing global human population. Many studies have focussed on the role of microbial species diversity and the presence of key functional groups as important controls on the many functions that a sustainable food system relies on.
2. Here, we synthesise recent ecological empirical evidence and theory to propose that the interactions between organisms in the soil food web are the critical determinant of soil function.
3. We propose the Rhizosphere Interactions for Sustainable Agriculture Model, in which crop roots recruit small, modular, highly connected soil rhizosphere networks from large, static, relatively unconnected and diverse bulk soil networks. We argue that conventional agricultural management disrupts the connections between rhizosphere and bulk soil networks.
4. Synthesis. We identify future research directions for optimising ecological connections between roots and rhizosphere microbial and faunal networks, and between rhizosphere networks and bulk soil networks in agricultural production systems. Knowledge on these connections can be applied in agricultural systems to sustainability produce food for a growing global population.

We identify future research directions for optimising ecological connections between roots and rhizosphere microbial and faunal networks, and between rhizosphere networks and bulk soil networks in agricultural production systems. Knowledge on these connections can be applied in agricultural systems to sustainability produce food for a growing global population.

1. The 20th century saw dramatic increases in agricultural productivity, largely through the development and application of pesticides, fertilisers rich in nitrogen and phosphorus, and advances in plant breeding and genetic technologies. In the last 15 years, however, many key crop yields have plateaued. Climate change, an ever-increasing human population, depletion of global rock-phosphorus and growing energy prices make current fertiliser production unsustainable and represent sizeable challenges to global food security.
2. Many important crops form symbioses with arbuscular mycorrhizal fungi (AMF), and this has motivated the development of novel approaches in crop breeding and agricultural practices to support and promote AMF in agroecosystems.
3. Arbuscular mycorrhizal fungal symbiosis can be high beneficial in crops and wider agroecosystems in many ways, including improved soil structure and resistance to pests. However, AMF colonisation does not necessarily translate directly into enhanced plant performance or crop yield, while land management practices that would encourage mycorrhiza–crop associations, such as low-till or minimal chemical input often incur yield-reducing trade-offs.
4. Synthesis. We draw on ecological knowledge of AMF to inform their role in agroecosystems, providing a balanced look at mycorrhiza–crop symbioses in terms of plant ecophysiology and the wider role of AMF in agroecosystems and ask the question: are AMF our sustainable saviours?

In this mini-review, we draw on ecological and physiological knowledge of arbuscular mycorrhizal fungi to inform their role in agroecosystems, providing a balanced look at mycorrhiza–crop symbioses in terms of plant ecophysiology and the wider role of mycorrhizas in agroecosystems, asking the question: are mycorrhizal fungi our sustainable saviours?

1. Intraspecific competition among crop plants is undesirable. Less competitive crops are predicted to increase yield and decrease the need for added resources.
2. Wild plants demonstrate the ability to recognize kin and potentially help their relatives by reducing their competitive behaviours, a form of altruism. Altruism can also evolve through multilevel selection. Are these processes relevant to sustainable agriculture?
3. Crops do grow predictably with kin. However, their evolution is more strongly dictated by artificial selection (crop breeding), which incorporates individual and group selection, making multilevel selection more relevant than kin selection in favouring altruism. While current crop breeding protocols attempt to target the reduction of competitive traits, early mass selection may have the opposite effect.
4. We predict that kin recognition itself is not relevant to crops, because of the consistently high relatedness within crop stands. Nonetheless, crops have shown cultivar and kin recognition. We argue that these responses cannot be assumed to demonstrate altruism, as current breeding practices offer little opportunity for kin selection.
5. Synthesis. There is the opportunity to favour altruism through artificial breeding. Here we suggest how crop breeding protocols could be changed to favour cooperation by increasing group selection during early breeding.

There is the opportunity to favour altruism through artificial breeding. Here we suggest how crop breeding protocols could be changed to favour cooperation by increasing group selection during early breeding.

1. Tall-shrub expansion into low-statured communities, a hallmark of recent vegetative change across tundra ecosystems, involves three major genera: Alnus, Betula and Salix. Which genus expands most into tundra landscapes will determine ecosystem properties.
2. We show that Alnus and Salix shrubs segregate thermal space (elevation × insolation) and colonize tundra landscapes differently in response to climate warming, thereby replacing different tundra types.
3. Vegetative change estimated from repeat photography should account for hill-slope. Methodologically, slope determines surface area estimated from orthophotos as projected pixel area times secant of pixel slope. Ecologically, the change in thermally responsive vegetative area is sensitive to terrain steepness, scaling as the cosecant of hill-slope, so that studies should expect more shrub expansion in areas of shallow slopes than steep slopes.
4. Repeat aerial photography in Alaska's Chugach Mountains from 1972 to 2012 orthorectified on a high-resolution lidar digital elevation model indicated tall Salix was rare in 1972 and colonized warmer slopes by 2012. Tall Alnus colonized steeper, cooler slopes both by 2012 and by 1972. Salix and forest colonized similar thermal space. Colonization probability for both shrub genera was maximized at intermediate elevations.
5. Alnus colonization adjacent to dwarf-shrub tundra was twenty times as likely as Salix colonization. Salix colonization adjacent to low-shrub/herbaceous tundra was three times as likely as Alnus colonization. Replacement of dwarf-shrub tundra by Alnus and of low-shrub/herbaceous communities by Salix will affect herbivores and soil properties.
6. Good agreement between observations of plant functional type and multinomial predictions in a thermal space defined by elevation and insolation suggested that these two variables were sufficient for forecast modelling. Spatially explicit, climate-driven generalized linear multinomial and random forest classification models in available thermal space forecast surface areas of forest, Alnus, Salix and tundra over a range of warming, modelled as upward shifted isotherms, including expected IPCC scenarios. Both modelling approaches indicated that shrubs may respond nonlinearly to warming.
7. Synthesis. The provision of taxon-specific coefficients for climate-driven, spatially explicit models using high-resolution digital elevation models is necessary for accurately forecasting vegetative change due to climate warming in montane and arctic regions.

The provision of taxon-specific coefficients for climate-driven, spatially explicit models using high-resolution digital elevation models is necessary for accurately forecasting vegetative change due to climate warming in montane and arctic regions.

1. Climate warming is faster in the Arctic than the global average. Nutrient availability in the tundra soil is expected to increase by climate warming through (i) accelerated nutrient mobilization in the surface soil layers, and (ii) increased thawing depths during the growing season which increases accessibility of nutrients in the deeper soil layers. Both processes may initiate shifts in tundra vegetation composition. It is important to understand the effects of these two processes on tundra plant functional types.
2. We manipulated soil thawing depth and nutrient availability at a Northeast-Siberian tundra site to investigate their effects on above- and below-ground responses of four plant functional types (grasses, sedges, deciduous shrubs and evergreen shrubs). Seasonal thawing was accelerated with heating cables at c. 15 cm depth without warming the surface soil, whereas nutrient availability was increased in the surface soil by adding slow-release NPK fertilizer at c. 5 cm depth. A combination of these two treatments was also included. This is the first field experiment specifically investigating the effects of accelerated thawing in tundra ecosystems.
3. Deep soil heating increased the above-ground biomass of sedges, the deepest rooted plant functional type in our study, but did not affect biomass of the other plant functional types. In contrast, fertilization increased above-ground biomass of the two dwarf shrub functional types, both of which had very shallow root systems. Grasses showed the strongest response to fertilization, both above- and below-ground. Grasses were deep-rooted, and they showed the highest plasticity in terms of vertical root distribution, as grass root distribution shifted to deep and surface soil in response to deep soil heating and surface soil fertilization respectively.
4. Synthesis. Our results indicate that increased thawing depth can only benefit deep-rooted sedges, while the shallow-rooted dwarf shrubs, as well as flexible-rooted grasses, take advantage of increased nutrient availability in the upper soil layers. Our results suggest that grasses have the highest root plasticity, which enables them to be more competitive in rapidly changing environments. We conclude that root vertical distribution strategies are important for vegetation responses to climate-induced increases in soil nutrient availability in Arctic tundra, and that future shifts in vegetation composition will depend on the balance between changes in thawing depth and nutrient availability in the surface soil.

Our results indicate that increased thawing depth can only benefit deep-rooted sedges, while the shallow-rooted dwarf shrubs as well as flexible-rooted grasses take advantage of increased nutrient availability in the upper soil layers. Our results suggest that grasses have the highest root plasticity, which enables them to be more competitive in rapidly changing environments. We conclude that root vertical distribution strategies are important for vegetation responses to climate-induced increases in soil nutrient availability in Arctic tundra, and that future shifts in vegetation composition will depend on the balance between changes in thawing depth and nutrient availability in the surface soil.

1. Drought induces changes in the nitrogen (N) and phosphorus (P) cycle but most plant species have limited flexibility to take up nutrients under such variable or unbalanced N and P availability. Both the degree of flexibility in plant N:P ratio and of root symbiosis with arbuscular mycorrhizal fungi might control plant resistance to drought-induced changes in nutrient availability, but this has not been directly tested.
2. Here, we examined the role of plant N:P stoichiometric status and mycorrhizal symbiosis in the drought-resistance of dominant and subordinate species in a semi-natural grassland.
3. We reduced water availability using rainout shelters (control vs. drought) and measured how plant biomass responded for the dominant and subordinate species. We then selected a dominant (Paspalum dilatatum) and a subordinate species (Cynodon dactylon), for which we investigated the N:P stoichiometric status, mycorrhizal root colonization and water-use efficiency.
4. The biomass of all dominant plant species, but not subordinate species, decreased under drought. Drought increased soil available nitrogen, and thus increased soil N:P ratio, due to decreasing plant N uptake. The dominant P. dilatatum showed a high degree of plant N:P homeostasis and a considerable reduction in biomass under drought. At the opposite, the more flexible subordinate species C. dactylon increased its N uptake and water-use efficiency, apparently due to stronger symbiosis with mycorrhizae, and maintained its biomass.
5. Synthesis. We conclude that the maintenance of N:P homeostasis in dominant species, possibly because of a large root nutrient foraging capacity, becomes inefficient when water stress limits N mobility in the soil. By contrast, we demonstrate that higher stoichiometric N:P flexibility coupled with stronger mutualistic association with mycorrhizae allow subordinate species to better withstand drought perturbations. Using a stoichiometric approach in a field experiment, our study provides for the first time clear and novel understandings of the mechanisms involved in drought-resistance within the plant-mycorrhizae-soil system.

Using a stoichiometric approach in a field experiment, our study provides for the first time clear and novel understandings of the mechanisms involved in drought-resistance within the plant-mycorrhizae-soil system. Specifically, we demonstrate that higher stoichiometric N:P flexibility coupled with stronger mutualistic association with mycorrhizae allow subordinate species to better withstand drought perturbations compared to homeostatic and low mycorrhized dominant species.

Editor's Choice

1. The mass-ratio and niche complementarity mechanisms drive the influence of litter trait diversity on decomposition. However, the implications of these mechanisms remain poorly understood, as few studies have evaluated their importance relative to environmental conditions and soil decomposers when assessing different processes during decomposition (e.g. C dynamics and N transformations).
2. We measured litter C and N losses during decomposition in 10 litter mixtures and calculated community-weighted means (CWM) and dissimilarity (Rao's Q) of 13 litter traits as metrics of the mass-ratio and niche complementarity mechanisms respectively. The 10 litter mixtures were incubated along a regional gradient (10 sites) in southern France over a year, where local environmental conditions (climate and soil parameters), and soil decomposers (microbes, nematodes, and macrofauna) were considered as drivers of decomposition.
3. Sites and litter mixtures represented a wide range of environmental conditions, decomposers, and litter diversity. Litter mixture was the major factor affecting litter C and N loss. N was immobilized during the early decomposition stages (up to c. 40% mass loss), especially in mixtures of low N concentrations. Litter CWM traits were the key drivers of litter C and N loss, but litter trait dissimilarity emerged as a major driver of litter N loss. Macrofauna played a significant role on C and N loss, but environmental conditions exerted a minor influence.
4. Our results highlight that distinct aspects of trait diversity in mixed species litter can play a more important role than environmental conditions and decomposers, which can affect the cycling of litter C and N at regional scales. Rather than opposing mass-ratio and niche complementarity mechanisms, our study shows that both can play a critical role simultaneously in litter decomposition.
5. Synthesis. Our study emphasizes that, in the current context of global biodiversity decline, the mass-ratio and niche complementarity mechanisms should be considered to assess litter decomposition dynamics under global change. As litter diversity mechanisms distinctly affected the cycling of C and N, we recommend taking into account such element-specific effects to improve the prediction of the impacts of biodiversity change on biogeochemical cycles.

Our study emphasizes that, in the current context of global biodiversity decline, the mass-ratio and niche complementarity mechanisms should be considered to assess litter decomposition dynamics under global change. As litter diversity mechanisms distinctly affected the cycling of C and N, we recommend taking into account such element-specific effects to improve the prediction of the impacts of biodiversity change on biogeochemical cycles.

1. Flooding events are predicted to increase over the coming decades, calling for a better understanding of plant responses to submergence. Specific root-associated microbes alter plant hormonal balance, affecting plant growth and stress tolerance. We hypothesized that the presence of such microbes may modulate plant responses to submergence.
2. We tested whether root-associated bacteria producing the enzyme ACC (1-aminocyclopropane-1-carboxylate) deaminase affect submergence responses in Rumex palustris, a flood-tolerant riparian plant. Ethylene is a key plant hormone regulating flood-associated acclimations, and ACC deaminase activity of bacteria may decrease ethylene levels in the plant. Rumex palustris plants were inoculated with Pseudomonas putida UW4 or an isogenic mutant lacking ACC deaminase, and subsequently exposed to complete submergence.
3. Submergence triggered ethylene-mediated responses, including an increase in leaf elongation and shoot fresh weight. Flood responses, including post-submergence ethylene production, were reduced in plants inoculated with ACC deaminase-producing wild type bacteria, as compared to plants inoculated with the ACC deaminase-negative mutant.
4. Synthesis. We demonstrate that root-associated bacteria can alter plant response to environmental stress by altering plant hormonal balance. Plant–microbe interactions may thus be an overseen driver of plant life-history strategies that should be taken into account when assessing plant ecological adaptations such as abiotic stress resistance.

We demonstrate that root-associated bacteria can alter plant response to environmental stress by altering plant hormonal balance. Plant–microbe interactions may thus be an overseen driver of plant life-history strategies that should be taken into account when assessing plant ecological adaptations such as abiotic stress resistance.

1. Trees commonly reproduce via masting cycles, which involves synchronized inter-annual variability in fruit crop size. A few individuals in a population will commonly produce much more fruit than others. If these trees produce fruit more frequently, as indicated by a lower inter-annual variability in fruit production, they may dominate fruit production over time.
2. By measuring fruit production of 1635 individuals of 10 temperate tree species across 4 years in northern lower Michigan, we estimated the inter-annual variability and synchrony in each species. We compared fruit production estimates with measurements of tree size, soil nutrient availability and neighbourhood crowding to investigate the source of inter-individual variation in number of fruit produced.
3. We found that trees’ fruit production increased with tree size. The trees that accounted for the largest proportion of total fruit production had lower inter-annual variability and higher synchrony in fruit production. These ‘super-producer’ trees tended to have high nutrient availability and few neighbouring trees, but there were no effects of nutrient availability or neighbourhood crowding on fruit production in the population as a whole.
4. Synthesis. Masting is a population-level phenomenon, and is typically studied at this level. However, when we apply individual tree observations of fruit production to this phenomenon, it reveals super-producers which produce fruit more consistently than the rest of the population. By reducing inter-annual variability in fruit production, but increasing synchrony and making large numbers of fruit, super-producers may be able to reap the benefits of masting while governing population fruit production over time.

Masting is a population-level phenomenon, and is typically studied at this level. However, when we apply individual tree observations of fruit production to this phenomenon, it reveals super-producers which produce fruit more consistently than the rest of the population. By reducing inter-annual variability in fruit production, but increasing synchrony and making large numbers of fruit, super-producers may be able to reap the benefits of masting while governing population fruit production over time.

1. Determining how changes in abiotic conditions influence community interactions is a fundamental challenge in ecology. Meeting this challenge is increasingly imperative in the Anthropocene where climate change and exotic species introductions alter abiotic context and biotic composition to reshuffle natural systems.
2. We created plant assemblages consisting of monocultures or equal abundance of the native community dominant bluebunch wheatgrass (Pseudoroegneria spicata) and the exotic spotted knapweed (Centaurea stoebe), a co-occurring invasive forb that has overtaken grasslands across the western United States. We subjected these composition treatments to drought (20% of average precipitation vs. average) and herbivory on C. stoebe by its biocontrol agent Cyphocleonus achates to explore how reduced precipitation might influence the effects of competition and biocontrol herbivory on C. stoebe's abundance.
3. At the end of 7 years, C. stoebe dominated mixed-species plots under normal precipitation conditions, with biomass 50% greater than that of the native P. spicata. However, under drought stress, P. spicata's biomass was >200% greater than C. stoebe's. Interestingly, both species were impervious to drought in monoculture, indicating the importance of the drought by competition interaction. The biocontrol herbivore reduced C. stoebe abundance and indirectly increased P. spicata biomass in mixed-species drought plots, but these effects were only marginally significant and relatively weak. Overall, C. stoebe abundance was primarily driven by the drought by competition interaction, with negatively additive but weak effects of the drought by herbivory interaction.
4. The response of the exotic to the treatments was driven by rapid changes in population density linked to its fast life-history strategy, while the native's response was driven by changes in per capita plant biomass linked to its slower life-history strategy. Individual plant performance metrics did not predict overall population responses for the invader, indicating the importance of longer term population measures.
5. Synthesis. These results demonstrate that reduced precipitation inputs linked to climate change can dramatically shift the balance of plant competition, even toggling the advantage from exotic to native dominance. They also illustrate the importance of biotic interactions in predicting species responses to abiotic change.

The superinvader spotted knapweed loses to native dominant under drought. This study demonstrates that reduced precipitation inputs linked to climate change can dramatically shift the balance of plant competition, toggling the advantage from exotic to native dominance. Results also illustrate the importance of biotic interactions for predicting species responses to abiotic change, a finding with significant ramifications for assisted migration.

1. Differences between species in their response to environmental fluctuations cause asynchronized growth series, suggesting that species diversity may help communities buffer the effects of environmental fluctuations. However, within-species variability of responses may impact the stabilizing effect of growth asynchrony.
2. We used tree ring data to investigate the diversity–stability relationship and its underlying mechanisms within the temperate and boreal mixed woods of Eastern Canada. We worked at the individual tree level to take into account the intraspecific variability of responses to environmental fluctuations.
3. We found that species diversity stabilized growth in forest ecosystems. The asynchrony of species’ response to climatic fluctuations and to insect outbreaks explained this effect. We also found that the intraspecific variability of responses to environmental fluctuations was high, making the stabilizing effect of diversity highly variable.
4. Synthesis. Our results are consistent with previous studies suggesting that the asynchrony of species’ response to environmental fluctuations drives the stabilizing effect of diversity. The intraspecific variability of these responses modulates the stabilizing effect of species diversity. Interactions between individuals, variation in tree size and spatial heterogeneity of environmental conditions could play a critical role in the stabilizing effect of diversity.

Species diversity may help tree communities buffer the effects of environmental fluctuations. This stabilizing effect stems from the asynchrony of species growth due to species differences in their response to environmental fluctuations. However, within-species variability of responses may modulate the stabilizing effect of diversity. Mechanisms at the origin of this variability, therefore, play a crucial role in the diversity–stability relationship.

1. To understand the eco-evolutionary significance of plant viruses in nature, we must (i) quantify the effects of infection on plant fitness and (ii) recognize that native plants are increasingly exposed to crop-associated viruses. Studies of perennials are particularly needed: most of our knowledge of plant-virus interactions is from annuals, yet long-lived species dominate landscapes. Here we used aster models for life-history analysis and longitudinal measures of plant virus status to evaluate multi-year consequences of crop virus infection in a native perennial.
2. We used Barley yellow dwarf virus acquired from wheat to inoculate seedlings of Panicum virgatum L. (switchgrass), a North American prairie grass. We grew inoculated and mock-inoculated individuals of two ecotypes for 3 years in the field. We measured plant size, infection status and fitness components. Aster modelling provided integrated multi-year measures of fitness.
3. Crop virus inoculation reduced multi-year native plant fitness by 30% over 2 years despite generally asymptomatic infection and evidence of resistance. This reduction was greater than predicted from individual fitness components or most size measures. Ecotypes differed in response, with the lowland ecotype experiencing higher apparent recovery from infection. Virus treatment in the upland ecotype delayed flowering phenology and reduced seed filling.
4. Synthesis. Our use of field experimentation, surveys of plant infection status and aster modelling demonstrates a rigorous and broadly applicable approach for quantifying the effects of viruses and other microbes on multi-year plant fitness. We found that a crop virus had negative multi-year effects on native plant fitness even after infection was no longer detected. Viruses may have substantial effects on native vegetation with domestication of landscapes and agricultural expansion.

Field experimentation, surveys of plant infection status and aster modelling provide a rigorous and broadly applicable approach for quantifying the effects of microbes on multi-year plant fitness. We found that a crop virus had negative multi-year effects on native plant fitness even after infection was no longer detected. Viruses may have substantial effects on native vegetation with agricultural expansion.

1. There is increasing evidence that species diversity enhances the temporal stability (TS) of community productivity in different ecosystems, although its effect at the population and tree levels seems to be negative or neutral. Asynchrony in species responses to environmental conditions was found to be one of the main drivers of this stabilizing process. However, the effect of species mixing on the stability of productivity, and the relative importance of the associated mechanisms, remain poorly understood in forest communities.
2. We investigated the way mixing species influenced the TS of productivity in Pinus sylvestris L. and Fagus sylvatica L. forests, and attempted to determine the main drivers among overyielding, asynchrony between species annual growth responses to environmental conditions, and temporal shifts in species interactions. We used a network of 93 experimental plots distributed across Europe to compare the TS of basal area growth over a 15-year period (1999–2013) in mixed and monospecific forest stands at different organizational levels, namely the community, population and individual tree levels.
3. Mixed stands showed a higher TS of basal area growth than monospecific stands at the community level, but not at the population or individual tree levels. The TS at the community level was related to asynchrony between species growth in mixtures, but not to overyielding nor to asynchrony between species growth in monospecific stands. Temporal shifts in species interactions were also related to asynchrony and to the mixing effect on the TS.
4. Synthesis. Our findings confirm that species mixing can stabilize productivity at the community level, whereas there is a neutral or negative effect on stability at the population and individual tree levels. The contrasting findings regarding the relationships between the temporal stability and asynchrony in species growth in mixed and monospecific stands suggest that the main driver in the stabilizing process may be the temporal niche complementarity between species rather than differences in species’ intrinsic responses to environmental conditions.

Our findings confirm that species mixing can stabilize productivity at the community level but not at the population and tree levels. The different relationships between the mixing effect on the temporal stability and species asynchrony in mixed and monospecific stands suggests that temporal niche complementarity between species may be the main driver rather than differences in species’ intrinsic responses to environmental conditions.

1. Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated annual plant Mercurialis annua that varies geographically in its sexual system to investigate this interaction.
2. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions.
3. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites).
4. As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions.
5. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both sexual systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions.
6. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different sexual systems.

Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different sexual systems.

1. The environmental filtering hypothesis predicts that the abiotic environment selects species with similar trait values within communities. Testing this hypothesis along multiple – and interacting – gradients of climate and soil variables constitutes a great opportunity to better understand and predict the responses of plant communities to ongoing environmental changes.
2. Based on two key plant traits, maximum plant height and specific leaf area (SLA), we assessed the filtering effects of climate (mean annual temperature and precipitation, precipitation seasonality), soil characteristics (soil pH, sand content and total phosphorus) and all potential interactions on the functional structure and diversity of 124 dryland communities spread over the globe. The functional structure and diversity of dryland communities were quantified using the mean, variance, skewness and kurtosis of plant trait distributions.
3. The models accurately explained the observed variations in functional trait diversity across the 124 communities studied. All models included interactions among factors, i.e. climate–climate (9% of explanatory power), climate–soil (24% of explanatory power) and soil–soil interactions (5% of explanatory power). Precipitation seasonality was the main driver of maximum plant height, and interacted with mean annual temperature and precipitation. Soil pH mediated the filtering effects of climate and sand content on SLA. Our results also revealed that communities characterized by a low variance can also exhibit low kurtosis values, indicating that functionally contrasting species can co-occur even in communities with narrow ranges of trait values.
4. Synthesis. We identified the particular set of conditions under which the environmental filtering hypothesis operates in drylands world-wide. Our findings also indicate that species with functionally contrasting strategies can still co-occur locally, even under prevailing environmental filtering. Interactions between sources of environmental stress should be therefore included in global trait-based studies, as this will help to further anticipate where the effects of environmental filtering will impact plant trait diversity under climate change.

We identified the particular set of conditions under which the environmental filtering hypothesis operates in drylands world-wide. Our findings also indicate that species with functionally contrasting strategies can still co-occur locally, even under prevailing environmental filtering. Interactions between sources of environmental stress should be therefore included in global trait-based studies, as this will help to further anticipate where the effects of environmental filtering will impact plant trait diversity under climate change.

1. The identification of traits that influence the responses of the species to environmental variation provides a mechanistic perspective on the assembly processes of ecological communities. While much research linking functional ecology with assembly processes has been conducted with animals and plants, the development of predictive or even conceptual frameworks for fungal functional community ecology remains poorly explored. Particularly, little is known about the contribution of traits to the occurrences of fungal species under different environmental conditions.
2. Wood-inhabiting fungi are known to strongly respond to habitat disturbance, and thus provide an interesting case study for investigating to what extent variation in occurrence patterns of fungi can be related to traits. We apply a trait-based joint species distribution model to a data set consisting of fruit-body occurrence data on 321 wood-inhabiting fungal species collected in 22 460 dead wood units from managed and natural forest sites.
3. Our results show that environmental filtering plays a big role on shaping wood-inhabiting fungal communities, as different environments held different communities in terms of species and trait compositions. Most importantly, forest management selected against species with large and long-lived fruit-bodies as well as late decayers, and promoted the occurrences of species with small fruit-bodies and early decayers. A strong phylogenetic signal in the data suggested the existence of also some other functionally important traits than the ones we considered.
4. We found that those species groups that were more prevalent in natural conditions had more associations to other species than species groups that were tolerant to or benefitted from forest management. Therefore, the changes that forest management causes on wood-inhabiting fungal communities influence ecosystem functioning through simplification of interactive associations among the fungal species.
5. Synthesis. Our results show that functional traits are linked to the responses of wood-inhabiting fungi to variation in their environment, and thus environmental changes alter ecosystem functions via promoting or reducing species with different fruit-body types. However, further research is needed to identify other functional traits and to provide conclusive evidence for the adaptive nature of the links from traits to occurrence patterns found here.

Our results show that functional traits are linked to the responses of wood-inhabiting fungi to variation in their environment, and thus environmental changes alter ecosystem functions via promoting or reducing species with different fruit-body types. However, further research is needed to identify further functional traits and to provide conclusive evidence for the adaptive nature of the links from traits to occurrence patterns found here.

We aimed to overcome sampling bias to derive a best estimate for the proportion of seed plants with desiccation-sensitive seeds, based on current data. Model results suggest that this figure is likely to be approximately 8% of seed plants globally. Alongside our estimates of the global incidence of this seed trait, we provide data on taxa and habitats where the trait may be most prevalent. Our findings can be used to support conservation planning, particularly with respect to providing decision support for in and ex situ conservation techniques.

1. Allometric scaling of net primary production (NPP) with plant biomass (B) is important to ecological carbon dynamics and energetics. Metabolic theory predicts a nonlinear power law for NPP scaling, based on fractal vascular systems, resulting in a linear model when using log NPP/log B axes that are standard in allometry. Alternatively, two other hypotheses predict nonlinear models for log-transformed data, with potential tipping points. Size-based competition may cause a quadratic curve as larger plants limit NPP by smaller plants. More inclusively, the plant adaptive strategies hypothesis predicts a sigmoidal curve to represent those same competitive effects, plus stress and ruderal adaptations that maintain relatively low NPP in habitats that are abiotically limiting or disturbed.
2. We evaluated all three hypotheses for terrestrial vascular plants, using information theoretic model selection based on the Akaike Information Criterion (AICc). Published data (N = 709) were organised in subsets according to reported organisational level and plant growth form. Alternative curves were compared for a general model (using all data) and per subset. Potential tipping points were estimated using segmented regression.
3. The plant adaptive strategies hypothesis was supported in general (AICc weight = 1·00) and via internal consistency for five of six subsets (86% of data). Competition was supported as affecting NPP at greater B, where quadratic and sigmoidal models often coincided. Only non-woody assemblages most plausibly fit a power law model, perhaps related to sparse data at lowest B.
4. Synthesis. Adaptive strategies and corresponding environmental conditions appear to constrain terrestrial net primary production scaling relative to metabolic theory's ideal. Moreover, tipping points in general nonlinear net primary production scaling (at c. 38 and 360 g m⁻² B) indicate thresholds for rapid changes in net primary production given changing B that occurs via changing climate, human appropriation and land use.

Adaptive strategies and corresponding environmental conditions appear to constrain terrestrial NPP scaling relative to metabolic theory's ideal. Moreover, tipping points in general nonlinear NPP scaling (at c. 38 and 360 g m⁻² B) indicate thresholds for rapid changes in NPP given changing B that occurs via changing climate, human appropriation and land use.

1. Although it is widely believed that non-native invasive species threaten the functional integrity of forest ecosystems, their impact on important ecosystem processes such as nitrogen (N) cycling is not well understood.
2. To examine how invasive species alter ecosystem N dynamics, we established monocultures of five phylogenetic pairs of native and non-native invasive understory woody species common to Eastern U.S. forests.
3. After 3 years, we found invaders increased N cycling by enhancing the flow of N to the soil through greater litter N production and litter N content, and increased the uptake of available soil N, via greater fine root production and specific root length.
4. Synthesis. Our results highlight the importance of linking above- and below-ground processes to better understand invader impacts on ecosystem nutrient processes. The rapid shifts in soil N processes as a result of invader dominance observed in our study suggest that invaders may be an important driver of forest ecosystem functioning.

Experimental evidence of how invaders alter ecosystem processes such as soil nitrogen (N) cycling is rare, particularly for woody invaders. Here, we present a 3-year monoculture study that examined above- and below-ground plant traits and soil properties to test how forest woody invaders alter soil N cycling. Our results suggest that invaders promote soil N cycling through greater litter input and faster soil N uptake than co-occurring native species, which may significantly impact the dynamics of a key limiting nutrient in forest ecosystems.

1. Global environmental change not only includes changes in mean environmental conditions but also in temporal environmental fluctuations. Because it is frequently suggested that common species, and particularly invasive alien species, are phenotypically highly plastic, they might benefit more from these fluctuations than rare native and rare alien species. Experimental tests, however, are still lacking.
2. Here, we tested whether alien plant species take more advantage of increases in resource levels and fluctuations therein than native species, and whether common species do so more than rare species. Therefore, we grew seven common alien, seven rare alien, nine common native and six rare native herbaceous plants, in one treatment with constantly low nutrient availability and five treatments with high nutrient availability that differed in temporal availability of nutrients (constant, increasing, decreasing, single large pulse, multiple smaller pulses).
3. We found that all species produced more biomass and longer roots, and had a lower root mass fraction under high nutrient conditions than under low nutrient conditions, irrespective of their origin and commonness. Among the high nutrient treatments, the temporal pattern of nutrient supply also influenced biomass production, root allocation and root thickness, but the magnitude and/or directions of these responses varied among the groups of species. Particularly, we found that alien plant species, irrespective of whether they are common or rare, produced more biomass, and had a higher root mass fraction when nutrients were supplied as a single pulse in the middle of the growth period instead of supplied at a constant rate, whereas the reverse was true for the native species.
4. Synthesis. Our study suggests that species origin does not drive differences in plant biomass production, root morphology and allocation in response to changes in mean environmental nutrient availability. However in our study, alien plant species, in contrast to native plant species, benefited from a large nutrient pulse. This suggests that increased fluctuations in nutrient availability might promote alien plant invasions.

Although the fluctuating-resource-availability hypothesis has been a key hypothesis in invasion biology, few experimental studies have explicitly tested it by using fluctuating nutrient levels. Our multi-species experiment corroborate it, and in addition provide evidence that both common and rare naturalized alien plant species could benefit from a large nutrient pulse.

1. This account presents comprehensive information on the biology of Phragmites australis (Cav.) Trin. ex Steud. (P. communis Trin.; common reed) that is relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors and to the abiotic environment, plant structure and physiology, phenology, floral and seed characters, herbivores and diseases, as well as history including invasive spread in other regions, and conservation.
2. Phragmites australis is a cosmopolitan species native to the British flora and widespread in lowland habitats throughout, from the Shetland archipelago to southern England. It is widespread throughout Ireland and is native in the Channel Islands. Native populations occur naturally in temperate zones and on every continent except Antarctica. Some populations in Australia and North America have been introduced from elsewhere and have become naturalized, and in North America, some of these are known to be invasive where they compete with native local populations of P. australis. Typical habitats in Britain range from shallow still water along waterbody edges to marshlands, saltmarshes and drier habitat on slopes up to 470 m above sea level. Additional habitats outside Britain are springs in arid areas, riverine lowlands (−5 m above sea level) and groundwater seepage points up to 3600 m above sea level. Although it occurs on a wide range of substrates and can tolerate pH from 2·5 to 9·8, in Britain it prefers pH >4·5 and elsewhere it thrives in mildly acidic to mildly basic conditions (pH 5·5–7·5). The species plays a pivotal role in the successional transition from open water to woodland.
3. Phragmites australis is a tall, helophytic, wind-pollinated grass with annual shoots up to 5 m above-ground level from an extensive system of rhizomes and stolons. A single silky inflorescence develops at the end of each fertile stem and produces 500–2000 seeds. The plant is highly variable genetically and morphologically.
4. Expansion of established populations is mainly through clonal growth of the horizontal rhizome system and ground-surface stolons, while new populations can establish from rhizomes, stem fragments and seeds. Shoots generally emerge in spring, with timing determined primarily by physiology that is mediated by external conditions (e.g. local climate including frost).
5. Many populations in the British Isles have experienced some decline over the past two decades and there is concern that there might be further losses along the east coast as sea level rises. There have recently also been localized expansions, especially in highly modified habitats, where P. australis reedbeds have been planted as wildlife habitat, rehabilitated mineral and gravel beds, and bioremediation filter beds for industrial and transport infrastructure. Native populations outside Britain also demonstrate both types of trend: they are declining in many parts of Western Europe and North America, yet also colonize many disturbed, ruderal habitats (e.g. the edges of agricultural fields and motorways) throughout its native and non-native range and can form ‘weedy’ monodominant populations (e.g. in Australia and China).

Phragmites australis is a cosmopolitan species native to the British flora and widespread in lowland habitats. Native populations occur on every continent except Antarctica, from desert oases, river lowlands (−5 m a.s.l.) and up to groundwater seepage points at 3600 m above sea level, but are declining in Europe and North America. Infraspecific taxa within P. australis form a species complex with overlapping native and non-native ranges.