Lake Taihu, the third largest freshwater lake of China, provides drinking water supply for 5 million people. Over the last 30 years the lake has suffered from serious cyanobacterial blooms that deteriorate drinking water quality and in some cases have led to serious water supply crises. In order for local government to respond quickly to the onset of a cyanobacterial bloom, it is crucial to forecast the probability, areas and intensity of the bloom. In this paper, an attempt to forecast the cyanobacterial bloom in Lake Taihu is documented. The forecast is based on a short-term cyanobacterial bloom forecasting numerical model which containing a three-dimensional, coupled hydrodynamic-algal biomass model and a probability of bloom occurrence forecasting model. The former model was based on solving the governing equations of the cyanobacterial bloom dynamics in shallow lakes. Unstructured mesh division was used to fit the irregular coastal boundaries where harmful blooms often happened. The finite volume method discretised the governing equations and the conservation laws were preserved. To drive the model, the initial algae chlorophyll-a concentrations were obtained from 18 automatic monitoring buoys and boat survey measurements. Combining calculation and prediction of the hydrological and meteorologic scenarios over the ensuing three days, the dynamic distributions of the algae concentration scenarios in Lake Taihu were simulated. Blooming probabilities were then predicted by a forecast model which included the weight of algal biomass, wind velocity and weather condition. The model was applied to predict the occurrences of the algae blooms of the next three days in Lake Taihu during April to September in 2009-2010. Independent evaluation from remote sensing images and boat survey data showed that the accuracy of this bloom forecasts was more than 80%. Copyright © 2013 John Wiley & Sons, Ltd.

Water relations are essential in plant-plant interactions, particularly in Mediterranean coastal sand dunes due to marked drought periods and the possibility of groundwater salinization. In this study, seasonal water use dynamics were explored in the interaction between a native-invasive species, Retama monosperma, and the endangered Thymus carnosus, in southwestern Spain. The following variables were measured: xylem water isotopic composition to determine water sources, predawn and midday stem water potential, and free leaf proline content as stress indicator. Groundwater electrical conductivity and stable isotopes were also analysed to assess water table salinity. In late summer and spring, the warmest seasons, Thymus beneath Retama displayed significantly lower water potential and higher leaf proline content than isolated Thymus, whereas Retama showed the highest proline content in autumn and winter. Water sources showed different patterns depending on the Thymus situation: isolated ones always matched the brackish groundwater, as well as Retama plants, whereas Thymus beneath Retama switched among rainfall, soil and water table, showing a seasonal change in the water-harvesting strategy. Overall, competition for water sources between both species was discovered, which led to a shift in water use and water uptake strategies of understorey Thymus. The results also demonstrate the importance and potential use of species interaction studies in the development of threatened species management strategies. Copyright © 2013 John Wiley & Sons, Ltd.

Groynes help to protect river banks and support water levels for navigation. Since recently, groyne fields are considered as surrogate habitat for various species and may, in terms of ecology, partially replace flood plains that were lost in the course of river training in the last centuries. In order to maintain and improve the hydraulic function and ecological value of groyne fields, the German Federal Institutes of Hydrology (BfG) and of Waterways Engineering and Research (BAW) studied innovative groyne types and regular groynes on the River Elbe, Germany. In a 10-year field campaign groyne field hydraulics and morphology were monitored using ADCP and echo-sounding techniques. The data is used to assess groyne field heterogeneity and morphodynamics over the 10-year period as well as flow patterns at different flow stages. The results indicate a high morphological activity in the groyne fields associated with flood discharges. Significant sedimentation in the bank regions was observed while sedimentation in deeper areas of the groyne fields was less pronounced. The sedimentation patterns and rates in the groyne fields are, to some extent, found to be influenced by different groyne types and associated flow patterns. Copyright © 2013 John Wiley & Sons, Ltd.

We present our personal view of some of the exciting research avenues in ecohydrology, which are related to quantifying the effects of hydrologic variability and anthropogenic disturbance on ecohydrological processes. Using several examples, we discuss how concepts and tools inspired from information theory, statistical mechanics and nonequilibrium thermodynamics may help us advance in some of the challenges posed by the need to sustainably manage our soil and water resources, while preserving ecosystem services. Copyright © 2013 John Wiley & Sons, Ltd.

Internal water storage and water exchanges that sustain hydration are critical for the physiological function of Sphagnum mosses that have recolonized cutover peatlands characterized by low soil water pressures. The relative importance of water gains and losses for spontaneously regenerated Sphagnum moss cushions was addressed through investigation of the sensitivity of moss moisture dynamics to a range of environmental variables. Precipitation waters are poorly retained within the cushions, which indicated that rain event water can only be relied upon by the mosses for a short period of time. The relationship between water table depth and moisture content within moss cushions was strong when the water table was within 30 cm of the surface of the cutover peat but weakened as conditions became drier, as reflected by weakened upward hydraulic gradients in the unsaturated zone below the moss cushions. Calculation of a water budget between 19-May and 16-August, 2006 for relatively wet and dry cushions, respectively, identified a water deficit of 28 and 44 mm. It is hypothesized that additional (small) sources of water during deficit conditions may be critical for maintaining physiological processes. Rewetting of the peatland by blocking drainage ditches created conditions more favourable for Sphagnum survival through increasing the moisture content and soil-water pressures within the remnant peat deposit; although restoration efforts should aim to constrain the water table position to within the upper 30 cm. Copyright © 2013 John Wiley & Sons, Ltd.

Transpiration-driven nutrient accumulation has been identified as a potential mechanism governing the creation and maintenance of wetland vegetation patterning. This process may contribute to the formation of nutrient-rich tree islands within the expansive oligotrophic marshes of the Everglades (Florida, USA). This study presents hydrogeochemical data indicating that tree root water uptake is a primary driver of groundwater ion accumulation across one of these islands. Sap flow, soil moisture, water level, water chemistry, and rainfall were measured to identify the relationships between climate, transpiration and groundwater uptake by phreatophytes, and to examine the effect this uptake has on groundwater chemistry and mineral formation in three woody plant communities of differing elevations. During the dry season, trees relied more on groundwater for transpiration, which led to a depressed water table and the advective movement of groundwater and dissolved ions, including phosphorus, from the surrounding marsh toward the center of the island. Ion exclusion during root water uptake led to elevated concentrations of all major dissolved ions in the tree island groundwater compared to the adjacent marsh. Groundwater was predominately supersaturated with respect to aragonite and calcite in the lower elevation woody communities, indicating the potential for soil formation. Elevated groundwater phosphorous concentrations detected in the highest elevation woody community were associated with the leaching of inorganic sediments (i.e., hydroxyapatite) in the vadose zone. Understanding the complex feedback mechanisms regulating plant/groundwater/surface-water interactions, nutrient dynamics, and potential soil formation is necessary to manage and restore patterned wetlands such as the Everglades. Copyright © 2013 John Wiley & Sons, Ltd.

Concern over forest dieback due to environmental change and the long residence times of standing dead trees necessitate understanding the impact of forest health on the redistribution of precipitation by forest canopies. Stemflow, represents a critical point source input of water and nutrients to forest ecosystems. We investigate the variation in water storage capacity, stemflow volume, and stemflow funneling ratios from two co-occurring dominant canopy species, Fagus grandifolia Ehrh. [American beech] and Liriodendron tulipifera L. [yellow poplar], across three different mortality classes: live, stressed (girdled), and standing dead. Over 25 rainfall events, interspecific differences in stemflow volume distributions were significant over all (U = 45881, p < 0.0001), leaf-off (U = 11285, p < 0.0001), and leaf-on (U = 11582, p < 0.0001) events. Stemflow funneling ratios were greater in F. grandifolia (26.0 ± 1.2) compared with L. tulipifera (4.9 ± 0.4). Minimum precipitation threshold amounts required to initiate stemflow were lower for F. grandifolia compared to L. tulipifera, and lower for live and stressed compared with dead. Mean stemflow volume from both species was 1.5 ± 0.2 L stem^-1 event^-1 from dead stems, 89.2 ± 7.7 L stem^-1 event^-1 from stressed stems and 91.3 ± 8.9 L stem^-1 event^-1 from live stems. The results of this study improve our understanding of the influence of mortality on rainfall partitioning and stemflow fluxes and may give insight into how mortality generating factors such as pest defoliation and climate change may alter stemflow relationships in forested ecosystems. Copyright © 2013 John Wiley & Sons, Ltd.

Setting instream flows to protect aquatic resources is required by state law, but this task is not straightforward for an intermittent river that is naturally dry six or more months of every year. The Santa Maria River, 200 km northwest of the Los Angeles metropolitan area, lies within the northern range of the federally endangered southern California steelhead (Oncorhynchus mykiss) and is a logical candidate for instream flow protection: the watershed historically supported the anadromous life history of this species, but fish must navigate the lowermost 39 km of the commonly dry mainstem river to move between the ocean and freshwater habitats in the upper watershed. Mainstem flows are partly controlled by Twitchell Dam, constructed across one of the Santa Maria River's two main tributaries in 1962. The dam is operated to maximize groundwater recharge through the bed of the mainstem Santa Maria River, thus minimizing discharge to the Pacific Ocean and so reducing already limited steelhead passage opportunities. Conventional criteria for determining suitable instream flows for steelhead passage are ill-suited to intermittent, Mediterranean-type rivers because they ignore the dynamic channel morphology and critical importance of headwater flows in providing cues that once presaged passage-adequate mainstem discharges but no longer do so. Hydrologic analysis of pre-dam flows, coupled with established criteria for successful O. mykiss migration, provide an objective basis for evaluating alternative dam-management scenarios for enhancing steelhead passage, although their implementation would redirect some water that for the past half-century has exclusively supported irrigated agriculture and municipal water supplies. Copyright © 2013 John Wiley & Sons, Ltd.

The Vietnam War played a decisive role in the pre-1990s deforestation of the lower Mekong Basin, which in turn, likely influenced regional broad-scale hydrology. This note presents and discusses new analyses that strengthen this thesis. While concurrent overestimation of discharge and underestimation of rainfall, a couple of years after bombing climaxed in the early 1970s, could theoretically explain the sharp rise in water yield previously attributed to bomb-induced deforestation, new observations suggest that bombing has durably modified the landscape: by 2002, degraded forests still largely overlapped with areas heavily bombed 30 years earlier. This corroborates observed long-term hydrological changes and suggests that warfare-induced deforestation has more profound and durable hydrological effects than previously thought. Copyright © 2013 John Wiley & Sons, Ltd.

Previous research has developed a method to assess the impact of check-dams on riparian vegetation and related river bed sediment size with vegetation coverage and development. Based on this knowledge this paper aims to investigate the effects on riparian species diversity induced by 32 check-dams in 4 torrent headwaters of Southern Italy. Species richness and composition of riparian vegetation in the active channel were surveyed upstream and downstream of each check-dam and in intermediate (less disturbed) sites. Furthermore, links between hydromorphological processes and vegetation diversity were analysed.

The identified differences in species diversity seem to be related to the morphological adjustments of the channel after the installation of check-dams. These fluvial morphological adjustments introduced variations to the flood depth and frequency of the riparian areas creating new riparian conditions. Higher species richness and evenness were observed upstream of check-dams, where alien species prevail over native ones in new habitats on the sedimentation wedge behind the dam. Conversely, downstream of check-dams, where the boundary of the inundated area moves down towards the thalweg (due to incision processes after check-dam installation), riparian vegetation tends to assume a terrestrial character, losing some herbaceous species of the riparian environment.

This research confirms that the discontinuity in the fluvial environment caused by check-dams induces morphological adjustments that can be translated in new riparian conditions for the establishment of vegetation, affecting the ecological aspects and species diversity of riparian habitats. Copyright © 2013 John Wiley & Sons, Ltd.

Lakeshore deterioration is a major threat to the ecological integrity of lakes worldwide. In this study, the relationship between littoral benthic invertebrates and the Lakeshore Modification Index (LMI) was examined. The influence of the taxonomic resolution on littoral benthic invertebrate community response to LMI was assessed using the results of the canonical correspondence analysis and the relationship between the taxa richness, Shannon–Wiener diversity index and the LMI. Benthic invertebrates were sampled in summer between 2006 and 2011 in two natural and two artificial Alpine lakes using a littoral microhabitat type sampling scheme. Ordination analyses show a similar explanation power when the lowest available taxonomic level was used in comparison with the family level. Taxa richness and the Shannon–Wiener diversity index indicate that lakeshore modifications impair littoral biological conditions with a loss of richness and diversity independently of lake type and used taxonomic level. For 64 families, a lakeshore modification indicative value between one and nine were set on the basis of distribution among five lakeshore modification classes. A Littoral Fauna Index (LFI) was then derived by summation of the lakeshore modification indicative values recorded at each site. A validation dataset from natural and artificial lakes confirmed the good relationships between LMI and LFI but revealed some differences in the relationships. The results show that the impacts of lakeshore modifications can be assessed using littoral benthic invertebrate assemblages with a family-level-based LFI, which makes this method cost effective and appropriate for routine monitoring. Copyright © 2013 John Wiley & Sons, Ltd.

Hydrological characteristics significantly drive the formation of and variations in wetland vegetation. Given increasing impact from human activities and climate change, the hydrological regime has become exceedingly unstable, thereby heavily affecting the distribution and dynamics of wetland vegetation. The relationship between inundation frequency – an important hydrological factor – and vegetation community distribution in Dongting Lake was analysed to depict how the hydrological regime determines the distribution of wetland vegetation cover. Wide tempo-spatial scales were used to calculate the inundation frequency in the lake and to compare the distribution patterns of the communities. For the implementation of the aforementioned tasks, this study provides remote sensing- and geographical information system-based methods. The responses of individual vegetation communities to inundation frequency differ depending on their specific physiological characteristics. Wood and reed communities are more suitable for regions with low inundation frequency, whereas grass and lake-grass communities are more adaptable to areas of high inundation frequency. The variations in inundation frequency may explain the succession of vegetation communities, which occurs when inundation frequency decreases with increasing wood and reed communities. These results can serve as support for evaluating the impact of hydrological changes on the community structures and distributions of wetland vegetation. Copyright © 2013 John Wiley & Sons, Ltd.

Restoring jurisdictional wetland hydrology does not ensure that the hydrologic conditions of any specific natural forested wetland community are recreated. This is especially problematic for a state like North Carolina, which has roughly two dozen different forested wetland communities. Because forested wetland communities align themselves across edaphic and hydrologic gradients, we suggest exploiting these relationships to guide restoration design and set performance standards. However, methods to compare hydrology between multiple reference sites and restored wetlands are lacking. To address this, we studied three different forested wetlands across 13 reference sites to determine which measures of water table levels, based on correlation with plant community composition, would be useful to distinguish these three communities. We then used the best measures of water table levels to assess two restoration sites and compare them with the reference sites. Our results showed that monthly median water table levels encompassing the start of the growing season had the strongest correlation with plant community composition, whereas roughly five other measures also had strong correlations. On the basis of the best measures, both of the restoration sites had water table levels that generally fell within the natural range of the reference sites. Because there was variation in water table levels across each restoration site, the different measures where useful to identify which areas were least similar to the reference sites and might need further monitoring in the future. On the basis of our results, we recommend using community-specific measures of hydrology to guide and assess forested wetland restoration. Copyright © 2013 John Wiley & Sons, Ltd.

Biotic and abiotic interactions between the riparian zone and the river determine relevant hydrological processes and exert control over riparian and bordering upland vegetation types. Vegetation growth and development are mainly controlled by water availability on semi-arid regions, where a moisture gradient determines the transition between the densely vegetated riparian zone and the semi-arid upland. To reproduce this spatial distribution, a mathematical model named RibAV is presented. Its conceptualization is based on the main ecohydrological modelling approaches and field expertise. The implementation of RibAV that is proposed in this paper allows the simulation of the distribution of three plant functional types [herbaceous riparian vegetation (HRV), woody riparian vegetation (WRV) and terrestrial vegetation (TV)] within the riparian zone. An evapotranspiration index (E_idx) obtained through RibAV is used as a criterion for plant absence/presence prediction. Two permanent river reaches of semi-arid Mediterranean basins, the Terde reach (Mijares River, Spain) and the Lorcha reach (Serpis River, Spain), have been selected as case studies for the calibration and validation of the model, respectively. Several criteria based on the confusion matrix were used to analyse the efficiency of RibAV on the prediction of plant distribution. The satisfactory performance of the model establishing the distribution of the riparian vegetation types and the limit between this zone and the bordering upland are demonstrated in this paper; the strength of the E_idx to classify plant functional types in riparian semi-arid environments is additionally proven. Copyright © 2013 John Wiley & Sons, Ltd.

Measured diurnal curves of dissolved oxygen (DO) concentration have been used to estimate the gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NP) of aquatic communities. Open-system one-station and two-station methods have been employed to estimate the rate of NP, R, and GPP. We conducted field measurements in Minnehaha Creek, MN (44^o56'N, 93^o28'W), to quantify the spatial and temporal variabilities of DO concentrations and, consequently, evaluated the estimates of NP. Dimensionless analysis of DO mass balance revealed the dominance of local photosynthesis over respiration, advection, re-aeration, and dispersion along the studied reach. Two alternative estimation methods of stream metabolism provided similar estimates of NP with 0.65 > k_aT_a > 0.17 within the studied reach where k_a is the re-aeration rate and T_a is the water parcel average travel time. The spatial variability of DO change along the creek revealed an average length scale of 10 m over which DO exhibited significant autocorrelation. The autotrophic–heterotrophic balance, quantified by GPP to R ratio, scaled with local stream geomorphic and hydraulic conditions from diverse geographic areas, providing useful predictive relationships expressed in terms of easily measurable abiotic parameters. Copyright © 2013 John Wiley & Sons, Ltd.

Flowing water bodies often have plants that differ greatly in size and type, which interfere with fluid flow structure. Although there are studies describing vegetation–flow interactions in ideal laboratory conditions, their practical application is sometimes still difficult. This paper presents results of research involving laboratory simulations channel flow and the effects upon its structure as it passes through a combined layer of submerged and emerged vegetation in an open-channel flume. Instantaneous time-average velocity and turbulence at various locations were measured with a 3D acoustic Doppler velocimeter. The experimental results showed that the mean velocity profiles can be divided into three layers: bottom, middle and upper. The velocity profiles show the flow structure was complex variable over time creating mixing velocity layers associated with inflection points and velocity spikes. Turbulence intensity u_rms, v_rms, w_rms was nearly invariant for the flow depth at the bottom layer in most locations within the vegetation area. Maximum turbulence intensity occurred within the middle layer and migrated vertically as frontal width of the plant increased. Maximum turbulence intensity fluctuated at the velocity mixing layer where there is significant momentum exchange. The Manning's vegetation roughness coefficient n_(v) due to vegetation resistance increased with vegetation density as expected. In all, the results show flow structure varies substantially at the stem section and at the canopy top of submerged vegetation. These analytical findings will be useful in understanding river channel hydraulic transport and mixing processes and useful in river engineering applications and modelling. Copyright © 2013 John Wiley & Sons, Ltd.

Global vegetation models are used to estimate water and carbon fluxes in current and future climates. To accurately estimate these fluxes, it is crucial to incorporate tree processes, such as transpiration. Some models accurately predict fluxes in well-watered conditions; however, our ability to predict responses of trees when water availability is limited remains restricted. Including mechanistic responses of trees during drought in models will improve estimates of water and carbon fluxes.

Estimating water fluxes over large spatial scales may be calculated by combining (1) remotely sensed estimates of evapotranspiration with (2) knowledge of whether tree water use for a particular forest type or plant functional type follows universal scaling rules. There is little knowledge of whether universal scaling rules apply to water-limited ecosystems.

This review examines ‘convergence’ in relationships among tree water use, leaf area, and tree size, using Australian broad-leaved evergreen vegetation as a case study. Broad-leaved evergreen is a plant functional type commonly used in global vegetation models. If convergence is observed among leaf area and water use relationships for different species within this plant functional type, this would provide a powerful tool for scaling ecohydrological processes. This work tests the hypothesis that tree water use (Q) converges along a common relationship with leaf area for a continent-wide range of species (n = 21), spanning a 100-fold difference in size across broad-leaved evergreens, including Acacia, Corymbia, and Eucalyptus as well as Callitris.

Remarkably, the slope of the relationship between tree water use and leaf area was similar for the broad-leaved evergreen genus, Eucalyptus, despite different slopes in relationships among diameter at breast height, leaf area, sapwood area, and Q. Realistic modelling of water and carbon fluxes requires an understanding of physiological mechanisms influencing Q, for each plant functional type, and for these mechanisms to be incorporated into vegetation models. Copyright © 2013 John Wiley & Sons, Ltd.

The Loess Plateau of China has long been suffering from severe soil erosion due to deforestation and other human being-related activities. Reforestation has been regarded as an important measure to protect and recover degraded ecosystems. The two typical forest stands, the secondary natural succession Populus davidiana stand (PDS) and the plantation Pinus tabulaeformis stand (PTS), were chosen to analyse their effectiveness in conserving soil and water and understand their impacts on rainfall distribution. On the basis of observations in 1988–2000 (no available data in 1989), compared with croplands, PDS and PTS reduced soil loss by 99·9% and reduced runoff by 92·3% and 84·4%, respectively. The mean annual canopy interception was 14·0% for PDS and 25·3% for PTS, and litter interception was 7·7% for PDS and 11·6% for PTS in 1995–2000. Both forest stands had almost the same stemflow percentage of 3·3%. However, there was no significant difference in runoff and soil loss between the two reforestation types. These results suggest that both the plantation PTS and the natural regeneration PDS are effective in controlling soil erosion, with similar potentials in conserving soil and water in the study region. Copyright © 2013 John Wiley & Sons, Ltd.

The interactive relationships of ecological and hydrological processes on individual plant growth and development as well as community succession have been a main focus of research in plant ecohydrology. In this paper, we firstly explore the spatial difference of the desert riparian ecosystems as distance to the river in the arid inland Tarim River Basin and then investigate the response of vegetation communities to emergent ecological water conveyances. Results showed that the decreasing groundwater table is the main driving force for vegetation degradation. Herbs exhibit degradation when the groundwater table is 4–6 m below the surface, whereas trees do not exhibit degradation until the groundwater table exceeds 6 m from the soil surface, in the lower reaches of the Tarim River. In addition, the structure of the plant community is controlled by the depth of the groundwater table. The mixed trees/shrubs/herbs structure is distributed in areas where the groundwater table is between 2 and 4 m in depth, the trees/shrubs structure is distributed in areas where the groundwater depth is 4–8 m and the simple structure of degraded Populus euphratica/Tamarix chinensis dominates the areas where the groundwater depth is >8 m. After ecological water conveyance, the Phraginites communis leaf weight, length and width decrease with the increasing distance from the river channel. The length of current-year twigs and average number of leaves of P. euphratica are significantly greater in the upstream section of the lower reach than in the downstream section of the lower reach. We concluded that the ecologically suitable groundwater depth for P. euphratica and T. chinensis is 2–4 m and the critical groundwater depth for drought stress is about 9 m. Copyright © 2013 John Wiley & Sons, Ltd.

Dispersal of fluvial freshwater fish larvae occurs commonly in heavily regulated rivers. Studies increasingly indicate that drifting young fish have an active component to their movement and so are capable of coping with the dynamic hydraulic forces typical of rivers. We investigated hydraulic–drift relationships of the young stages of fish over one breeding season along a gravel shore of the Austrian Danube using stationary drift nets from the first occurrence until the end of the seasonal peak (April–June 2008). Observed densities of families and developmental stages were related to the hydraulic parameters flow velocity (in three spatial directions), turbulent kinetic energy and water depth, derived from a three-dimensional hydrodynamic model of the sampling site. We detected distinct responses of drifting young fish to several hydro-physical factors under conditions (low light level, over-critical currents), which were considered to cause washouts and passive drift. In general, drift densities decreased with water depth and flow velocity. Weak swimmers (e.g. bull head Cottus gobio and early-stage cyprinid larvae) avoided turbulent flows, as their abilities to orientate and hold position may be limited. Early larval as well as early juvenile stages of cyprinids used lateral currents directing to the bank, potentially to drop out of the flow and reach inshore areas. Our study indicates that there are family-specific and stage-specific responses to hydraulic variables and that fish actively disperse, probably to minimize mortality and maximize successful dispersal. Copyright © 2013 John Wiley & Sons, Ltd.

The paper reports the development of an individual-based fish dynamics model, of which the key components are the rules for the movement of individual fish and the definition of the habitat suitability. The distribution of the fish mainly depends on the flow conditions (velocity, depth, substrate) and life cycle of the fish. A major contribution is the refinement of the rules for fish movement, based on laboratory experiments under volitional swimming conditions, which also provided the ranges of preferential velocities and substrate size for the target fish, Spinibarbus hollandi. Moreover, they provided data on the fish trajectories and distribution patterns that allowed for validation of the movement rules. The validated fish dynamics model was applied to investigate the effect of discharge increase during the dry season by means of reservoir operation in the Lijiang River, which was the subject of field investigations in 2007 and 2008. The model results indicated that reservoir operation leads to an increase of fish biomass. According to the fish movement rules, fish cannot always escape from riverbed regions that dry during decreasing discharge events, which causes them to be trapped and die. Reservoir operation decreases the area of dry riverbed and reduces the travel distance for fish to escape from dry regions. Critical advantages of the individual fish model over global models defined on the population level are that they can account for the time that the fish needs to reach a region of suitable habitat and for the spatial pattern of suitable zones and their connectivity. Copyright © 2013 John Wiley & Sons, Ltd.

In mountainous areas, high-head-storage hydropower plants produce peak load energy. The resulting unsteady water release to rivers, called hydropeaking, alters the natural flow regime. Mitigating the adverse impacts of hydropeaking on aquatic ecosystems has become a crucial step in recent water policies.

We developed a novel economic-ecological diagnostic and intervention method to assess hydropeaking mitigation measures for fish habitat improvement. This method was applied to an Alpine river downstream of a complex storage hydropower scheme. The approach comprises (1) a hydropower operation model of flow regime generation and cost estimates for different mitigation measures, (2) a two-dimensional hydrodynamic model to simulate the flow conditions in representative river reaches and (3) a dynamic fish habitat simulation tool to assess the sub-daily changes in habitat conditions of three brown trout (Salmo trutta fario) life stages (adult, spawning and young-of-the-year). Simulations showed that operational measures such as limiting maximum turbine discharge, increasing residual flow and limiting drawdown range incur high costs in relation to their ecological effectiveness. Compensation basins and powerhouse outflow deviation achieved the best cost–benefit ratio. Hydropeaking impact was strongly dependent on river morphology. Monotonous river reaches exhibited low habitat suitability for peak discharge, whereas a braided morphology provided high in-stream structure and thus suitable habitat for unsteady flow conditions.

The interdisciplinary approach to economic and habitat rating informs decision makers regarding the effectiveness of measures implemented to mitigate the environmental impacts associated with fluctuating hydropower operations. Copyright © 2013 John Wiley & Sons, Ltd.

Understanding the links between instream ecology and hydrology has become a critical task in contemporary river research and management. Habitat selection behaviour is a central dimension in applied ecology because it is a primary way that mobile organisms adapt to changing environmental conditions. Here, we analyzed brown trout habitat selection during two consecutive years in rivers presenting contrasting flow conditions to test the following hypotheses: (1) given that adaptation to flow regimes occurs as a response to the interaction between frequency, magnitude and predictability of mortality-causing events, habitat selection would vary across populations subject to different disturbance regimes; (2) because adaptations are directed towards enduring both intra-annual and interannual variations in flow, habitat selection would shift across years as a response to changing flow conditions and (3) such responses to yearly flow fluctuations would depend on the historical long-term hydrologic regime. We found that trout from rivers with highly variable flow and more frequent, longer and stronger extreme flow events were more willing to occupy positions in high-velocity habitats and showed stronger requirements for velocity refuges, whereas trout inhabiting more stable and benign flow environments selected visually-covered habitats to minimize biotic interactions. Results also revealed that trout shifted habitat selection patterns across years differing in flow conditions irrespective of river typology, but this shift was markedly stronger in rivers with higher flow variability and extremity. Overall, observed ecological patterns have strong implications for predicting the consequences of flow alteration for species adapted to particular flow regimes. Copyright © 2013 John Wiley & Sons, Ltd.

Culicoides imicola is the main biological vector in the transmission of the Bluetongue virus in the Mediterranean basin. Its geographical range is constrained by environmental characteristics, and soil moisture has been proposed as an important constraint because of its effect on C. imicola breeding habitat. The few field studies on breeding habitat of C. imicola indicate the favourability of (semi-)moist habitat that is not flooded. Data on C. imicola in Calabria revealed the presence of C. imicola at the eastern Ionian coastal area and the absence at the greater part of the western Tyrrhenian coastal area. A spatially distributed soil moisture model was applied to obtain daily soil moisture estimates for Calabria and to assess the relationship between soil moisture and the particular C. imicola distribution at the study region. The temporal soil moisture pattern was not significantly different between locations of contrasting C. imicola occurrence. The monthly average volumetric soil moisture content, however, was found to differ substantially. Soil moisture conditions of the topsoil at locations of C. imicola presence were consistently wetter. Particularly in August, at the onset of the season of high C. imicola abundance, soil moisture was significantly higher at the presence sites and sustained the larval stages of the C. imicola life cycle. This study provides evidence that soil moisture imposes an important constraint on the geographical distribution of C. imicola. Soil moisture may therefore be considered as a key environmental variable for the delineation of suitable C. imicola habitat. Copyright © 2013 John Wiley & Sons, Ltd.

A conundrum exists in the US Pacific Northwest (PNW) whereby increasingly stringent federal environmental regulations governing the discharge of nutrients from wastewater treatment plants (WWTP) to low order streams may negatively impact salmonid species listed under the US Endangered Species Act (ESA). We examined baseflow, water chemistry, benthic algal biomass, macroinvertebrate diversity, and steelhead in the West Fork Little Bear Creek (WFLBC), Idaho, USA, above and below the city of Troy WWTP to explain why this creek is the most productive juvenile steelhead stream in the Potlatch River drainage. Discharge from the WWTP maintained 6 km of perennial flow during summer. Dissolved oxygen (DO) levels indicate that nitrification depressed DO below the Idaho state standard of 6 mg/L within the first 200 m downstream of the discharge. Because of rapid re-aeration, DO concentrations recovered by 1.3 km. Despite high nitrate (0.12 – 4.3 mg/L) and total phosphorus (0.11 – 0.60 mg/L) concentrations 2.5 km downstream, benthic algal biomass remained below the US Environmental Protection Agency's ‘nuisance algae’ level (i.e., 150 mg/m²) throughout the stream. Family biotic index indicated good water quality conditions above and 2.5 km downstream of the discharge, although fairly poor condictions were found 200 m downstream from the effluent. The WFLBC ecosystem appears to have the capacity to accept and actually benefit from high nutrient loads from a WWTP. This work emphasizes the importance of developing a thorough understanding of the site-specific biochemical functioning of an ecosystem before selecting and applying standard management practices. Copyright © 2013 John Wiley & Sons, Ltd.

In arid ecosystems, evapotranspiration generally exceeds precipitation, preventing deep drainage and groundwater recharge. We propose that vegetation changes associated with the establishment of pastoralist settlements (i.e. livestock stations) can disrupt the ecological and hydrological linkages in arid groundwater-coupled ecosystems of the Monte desert (Argentina), allowing local groundwater recharge and nitrate leaching to the aquifer, affecting groundwater quality. We tested this hypothesis by analysing vegetation, land use indicators, water and nitrate dynamics in three pairs of livestock stations and relatively undisturbed control woodlands. Livestock stations had lower vegetation and dead wood but higher dung covers than control woodlands, indicating soil and vegetation changes associated to land use. Water and nitrate dynamics were also affected by land use. Soil nitrate and water contents sampled down to the water table were higher, and soil chloride and salinity were lower in livestock stations, indicating higher water percolation and N input/transport rates. Higher groundwater nitrate concentrations in livestock stations indicate that these areas behave as foci of N and water export from ecosystems to the phreatic aquifer. Our study supports the idea that vegetation in arid areas prevents downward surface–groundwater interactions, but it also indicates that human modifications of vegetation disrupt this control, reducing soil water consumption and allowing vertical movement of water and solutes to the aquifer, which can modify groundwater quality. Disruptions of ecological processes by livestock activities clearly affect the hydrological links between surface and groundwater. Copyright © 2013 John Wiley & Sons, Ltd.

Permafrost degradation and changes in water balance in a thermokarst lake in the middle part of the Lena River basin in eastern Siberia were investigated. We analysed the role of permafrost thawing in the water balance of a growing thermokarst lake. Long-term observations during the last two decades (1992–2008) at our thermokarst monitoring site, Yukechi, showed significant modifications of the landforms. Observations included ground temperature, thawing depth, soil moisture content in the active layer, surface subsidence rate, and ecological changes in the surrounding environment. We also used data obtained at the Yakutsk weather station to estimate the potential evaporation. During the observation period, the water surface area increased steadily from 195 m² in 1993 to 3135 m² in 2008, and the lake water increased from 33·7 m³ in 1993 to 3503 m³ in 2008. Water balance estimations showed that ground ice melt made up to one third of the total water input into the lake. The rapid development of growing thermokarst lakes indicates an ecological risk on the edges of cryogenic landscapes. Finally, we found that climate change and anthropogenic impacts have led to enhanced activity of cryogenic processes in the region. In particular, cultivated fields underlying ice-rich permafrost face enhanced degradation by cryogenic and hydrological processes because of recent climate change in the region. Copyright © 2013 John Wiley & Sons, Ltd.

To inform management actions to recover the endangered Rio Grande silvery minnow (Hybognathus amarus, RGSM), we (1) calculated the terminal settling velocities of newly expelled and water-hardened RGSM eggs for the observed range of suspended sediment concentrations and water temperatures in the Rio Grande, New Mexico, USA, and (2) reviewed RGSM reproductive ecology in the context of egg biology, the species' life history, and the historic and contemporary hydrology and geomorphology of the Rio Grande. Results show that in a naturally functioning riverine environment, the location and timing of spawning, the ontogenic stage of egg development, and habitat-specific differences in sediment and temperature that influence egg-settling rates interact to (1) prevent egg suffocation, (2) promote egg entrainment in clear, warm, productive floodplain habitats, and (3) limit downstream population displacement. Our research suggests that the RGSM is primarily a demersal, floodplain spawning species that evolved eggs that are secondarily buoyant in high-sediment environments rather than a main channel, pelagic broadcast-spawning species with an evolved long-distance, downstream drift phase, as previously reported. The current high magnitude of egg drift is hypothesized to be an artefact of contemporary river management and channelization, leading to reduced lateral connectivity, floodplain abandonment, and habitat degradation. Conservation actions implemented to restore historic channel form and reconnect low-velocity backwater and floodplain habitats are recommended. In the absence of a documented upstream migration of adult fish, removal of barriers to a presumed upstream movement is unlikely to provide immediate benefits to RGSM. Copyright © 2013 John Wiley & Sons, Ltd.

This work explains the effect of microtopography on the spatio-temporal gradient of topsoil moisture in a first-order stream in a forested mountainous area of northern Spain. This gradient was also related with the availability of suitable microsites for a forest riparian sedge (Carex remota).

Topsoil moisture, presence of C. remota and height and distance from the stream edges were measured in 385 points along 35 transects perpendicular to the stream. Soil moisture measurements were repeated in three different dates.

Topsoil moisture showed a sigmoid trend that defined the limits of a wet riparian zone at 1·25 m of distance from and 0·55 m in elevation above stream banks. Our riparian zone was narrower than other studies because of the steep slopes (25%) of the mountainous area studied. Elevation above stream banks was more influential than distance in defining the limits of the riparian zone.

In the riparian zone, values of soil moisture were high and constant even at the end of a dry period due to the continuous water flow. In the adjacent upland forest, soil moisture varied according to rainfall. These high and constant soil moisture values defined the suitable microsites for C. remota. Copyright © 2013 John Wiley & Sons, Ltd.

In this study, we have investigated the effects of some hydrological and physicochemical parameters such as water quality, velocity, water depth, river width, water pH, water temperature, ammonia-N, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and dissolved oxygen (DO) on diversity of aquatic macroinvertebrates in forest streams of Gunung Tebu (GT), Malaysia. The results of canonical correspondence analysis identified three groups of the aquatic macroinvertebrates according to their relationships with hydrological and physicochemical parameters. The stream velocity, water quality (i.e. DO, BOD and ammonia-N) in addition to canopy cover, total habitat score and substrate quality were the determinant factors controlling the diversity pattern of the aquatic macroinvertebrates in GT streams. Alteration in the hydrological and physicochemical parameters showed to influence the ecological diversity of the aquatic macroinvertebrates in GT streams. The predators were found to be highly associated with the elevated concentrations of BOD and COD. Shredders were positively correlated with pH, stream velocity, DO and habitat quality indicators (total habitat score, embeddedness, epifaunal and canopy cover). However, the collector-gatherers correlated negatively with all of these parameters. It was concluded that stream velocity, substrate structure and water quality were strong attributes for variation in aquatic macroinvertebrate assemblage structure in tropical forest streams of GT. Copyright © 2013 John Wiley & Sons, Ltd.

Changes in species composition and abundance driven by land use change may alter canopy and litter characteristics of forests, and thereby modify rainfall redistribution and hydrological processes. To elucidate the interacting effects between tree species traits, forest structure and annual rainfall patterns on hydrological processes, three types of forest assemblages were selected in a semiarid forest of pine–oak in central northwest Mexico. Forest assemblages included monospecific and mixed patches of Quercus potosina and Pinus cembroides. Total precipitation, throughfall, stemflow and runoff were measured from June 2006 to July 2009. Additionally, tree and litter characteristics were measured. Forest traits played an important role differentiating volumes of each fraction among the three forest patches. Throughfall was 15% greater in Q. potosina than in the other forest patches (P < 0.01) and only occurred with rainfall events larger than 1.4 mm for all patch types, whereas Q. potosina stemflow was >20% larger compared with the other two forest patch types (P < 0.01) and occurred following rain events of at least 4.6 mm. Runoff exhibited divergences among forest patches (P > 0.05) that were related to both the litter decomposition stage and the capacity of litter bed to store water. Thus, Q. potosina litter layer exhibited the largest water holding capacity (62%) and P. cembroides (46%) the least. Hence, surface runoff for Q. potosina was seven times lower than that in P. cembroides patches. This study revealed tree trait effects on water fluxes that might have consequences on the dynamics and productivity of semiarid forests. Copyright © 2013 John Wiley & Sons, Ltd.

This study quantifies for the first time the influence of flow regulation on the river thermal behaviour of an ungauged basin located in central-eastern Argentina. A 30-day data set of continuous summer hourly data was assembled for eight water temperature gauging sites deployed along the main channel upstream and downstream from the impoundment. Analysis methods include descriptive statistics of daily temperature data, classification of diurnal regimes by relative differences in the ‘shape’ and the ‘magnitude’ of the thermographs (RSMC), and quantification of the climatic sensitivity of water temperature regimes using a sensitivity index. Results revealed that temporal fluctuations in water temperatures were linked to meteorological drivers; however, spatial variability in the shape and the magnitude of the thermographs revealed the effects of the dam in regulating river thermal behaviour downstream. Water temperatures immediately below the dam were reduced notably; diurnal cycles were reduced in magnitude, delayed in timing, and revealed overall climatic insensitivity and high temporal stability in regime shape. Dam effects persisted along the 15-km stretch monitored, although declined in the downstream direction. These findings provide new scientific understanding about the river water quality and inform river management about potential shifts in summer water temperature with great implications for the diversity and lifecycles of Neotropical river fauna. The use of the RSMC and sensitivity index approaches in water temperature assessment is novel and has wider applicability for quantifying river thermal regimes and their sensitivity to drivers of change over a range of temporal and spatial scales. Copyright © 2013 John Wiley & Sons, Ltd.

Forest disturbance can greatly alter flow regimes and consequently the structures and functions of ecosystems. However, the impacts of forest disturbance on flow regimes have rarely been investigated in large watersheds. In this study, we used a large severely disturbed watershed, the Baker Creek watershed located in the central interior of British Columbia, Canada, to examine how forest disturbance altered the flow regimes and to discuss the possible ecological implications of these alterations. Equivalent clear-cut area, an indicator combining all types of forest disturbances and accounting for hydrological recovery, was adopted to represent the cumulative forest disturbance levels over time at a watershed scale. Flow duration curves and time series cross-correlation analysis were used to detect the statistical significance of relationships between flow regimes (magnitude, duration, timing, frequency and variability of high flows and low flows) and forest disturbance (clear-cut area). The results showed that the magnitude of high flows was significantly increased and the timing of high flows was significantly advanced by forest disturbance. After forest disturbance, the occurrence of high flows with greater return periods became more frequent with increased variations. In addition, forest disturbance significantly increased the magnitude of low flows but with reduced variability. On average, high flows and low flows in the disturbed period were 31·4% and 16·0% greater than those in the reference period, respectively. Possible ecological implications of these hydrological alterations caused by forest disturbance were also discussed. Copyright © 2013 John Wiley & Sons, Ltd.

Physical heterogeneity is a major topic in river sciences because it is known to be a key factor for ecological integrity. In this paper, we investigated the hydraulic enviroment in an alpine gravel-bed stream with an unaltered hydrological regime. The study was based on the hypothesis that spatial and temporal variability are correlated to the morphological template of a stream. Numerical hydrodynamic modelling was conducted at five morphologically contrasting study sites for different discharges chosen from discharge duration curves. On the basis of the resulting hydraulic variables, namely flow velocity and water depth, and of a recently proposed hydromorphological index of diversity, the differences in spatial and temporal variability were analysed by descriptive statistics. Spatial diversity was higher at morphologically natural sites than at sites that were partially or fully regulated by resectioning and bank protection. Conversely, temporal variability in the hydraulic environment was higher at regulated sites where hydraulic variables were subject to fluctuations with each small discharge modification, which is not the case for more impaired sites. Unless higher discharges with bed reshaping activity occur, natural streams are characterized not only by high spatial variability but also by a sustained persistence of aquatic habitats. Therefore, river engineering projects aimed at enhancing habitat heterogeneity should not only focus on a higher spatial variability of the physical environment but also aim for greater persistence of aquatic habitats. Copyright © 2013 John Wiley & Sons, Ltd.

This work investigated the multi-decadal changes in field saturated hydraulic conductivity, K_fs, beneath severely degraded pasture, natural forest and two mature planted Pinus roxburghii stands between two sets of measurements made in 1986 and 2011 at the same locations in the Middle Mountains of Central Nepal. Multiple measurements of K_fs were made at the four sites, both at the surface and at depths of 0·05–0·15, 0·15–0·25 and 0·25–0·50 m. The K_fs results were subsequently combined with rainfall intensities associated with different time intervals to infer multi-decadal changes in dominant hillslope stormflow pathways.

The widely assumed hydrological benefits of reforesting degraded land through the enhancement of near-surface permeability due to such factors as the incorporation of a greater amount of organic matter, formation of macropores, as well as root development were not observed in this study. Continued heavy use of the natural and planted forests of the Middle Mountains, particularly the removal of understory vegetation and leaf litter, and cattle grazing, are considered to be the chief causal factors of the presently observed deterioration in forest hydrological functioning. This situation is typical not only of the Middle Mountain Zone across the Himalaya but is also observed in other densely populated parts of South and South-East Asia.

The key conclusion of this work is that simply planting trees in degraded landscapes is not sufficient in itself to restore watershed hydrological functioning. Attention also needs to be given to on-going management of the reforested areas to balance product usage with watershed functions. Copyright © 2013 John Wiley & Sons, Ltd.

Whereas the beneficial effects of urban vegetation have long been recognized, growing conditions in urban environments, especially for street trees, are typically harsh and limited by low water availability. Supplemental irrigation may be used to preserve aesthetic quality and ability to provide ecosystem services of urban vegetation but requires careful management of available economic and water resources to reduce urban water footprint. To this purpose, decision makers need quantitative tools, requiring few, physically based parameters and accounting for the uncertainties and future scenarios of the hydroclimatic forcing. Focusing on in-row and isolated trees, a minimalist description of street tree water balance is proposed here, including rainfed and irrigated conditions, and explicitly accounting for tree water requirements, growing conditions (in terms of soil properties and extension of bare soil, permeable and impervious pavements surrounding the tree) and rainfall unpredictability. The proposed model allows the quantification of tree cooling capacity, water stress occurrence and irrigation requirements, as a function of soil, plant and climate characteristics, thus providing indications regarding the tree ability to provide ecosystem services and management costs. In particular, an analysis of different planting designs suggests that a balanced design consisting in bare soil and permeable pavement with size equal to the lateral canopy extension is optimal for water conservation, tree cooling capacity and health. The proposed model provides useful indications towards the definition of site-specific guidelines for species selection and planting design, for sustainable urban vegetation. Copyright © 2013 John Wiley & Sons, Ltd.

Continuous observation over the last decade has revealed evidence of abrupt land surface moistening as well as rapid soil warming within the active layer and upper part of permafrost within the central Lena River basin in eastern Siberia. The present study examined the relationship between permafrost degradation and ecohydrological change in this region. Increases in the depth of the active layer recorded since the winter of 2004 resulting from increases in moisture saturation within the soil have resulted in thawing the upper permafrost causing thermokarst subsidence, which has negatively impacted the growth of boreal (larch) forests in the region. According to multi-year sap flow measurements taken between 2006 and 2009, transpiration from larch trees (Larix cajanderi Mayr.) was significantly reduced as a result of the region's concave micro-topography, which, in conjunction with the deepening and moistening of the active layer, created perennially waterlogged conditions that left mature trees withered and dead. Several trees with reduced amounts of foliage showed a remarkable reduction in seasonal average canopy stomatal conductance during the 2009 growing season. The reduction ratio of canopy stomatal conductance within emergent trees of heights greater than 15 m between 2006 and 2009 had a significant positive correlation with the increase in thickness of the active layer over that same period. These findings indicated that wetting trends in a permafrost region caused by arctic climate change may lead to unexpected ecohydrological responses with respect to permafrost degradation in eastern Siberia. Copyright © 2013 John Wiley & Sons, Ltd.

A series of seven stream barbs were installed in two consecutive channel bends of Sawmill Creek (Ottawa, Canada), a semi-alluvial stream with bed and banks composed of consolidated clay. Stream barbs (also known as submerged groynes) are low-profile linear rock structures that project out from the bank (in an upstream direction) to redirect flow and prevent erosion of the bank. As well as providing bank protection, barbs promote vegetated stream banks, create scour hole resting pools for fish habitat and can increase aquatic species diversity. Flow conditions (discharge and water levels), water velocity distribution using acoustic Doppler velocimeters and an acoustic Doppler current profiler, and bathymetry using a Total Station have been measured over a period of 5 years, both before (2 years) and after (2 years) the construction of the barbs, providing valuable data for understanding stream barb performance in a semi-alluvial channel. Pre-barb velocity measurements indicate that the flow field in the first bend is dominated by strong secondary circulation and high cross-stream bed stresses that comprise a substantial proportion of the total near-bed Reynolds stress. Post-barb results indicate that velocity magnitude along the outer bank was reduced. Scour occurred in the channel centre near barb tips, but in general, little to no bathymetry changes were measured between seasonal surveys, suggesting that the barbs had limited impact on bed topography and/or that semi-alluvial channel bends are resistant to change. Recommendations for future design and implementation of stream barbs are also included. Copyright © 2013 John Wiley & Sons, Ltd.

Seasonally, snow-covered forests are a critical source of water in the Western United States and are subject to major disturbances, including fire, harvest, disease and insect-caused mortality, that have relatively unknown effects on water availability. In this study, we investigated changes in winter season snow accumulation and ablation in a forest following the Las Conchas fire in the Jemez Mountains of New Mexico. We investigated two competing sets of processes that should determine the peak annual snowpack prior to snowmelt: (1) reduced interception by forest canopy results in greater new snow accumulation and (2) increased winter season ablation of the snowpack results in reduced peak snowpack volumes. These processes were evaluated with approximately 800 spatially distributed manual observations of new snow, 1500 manual observations of peak snowpack, and light detection and ranging-derived snow depth, vegetation and terrain datasets collected prior to the fire. A single snowfall event yielded significantly larger snow depths in the post-burn area versus the unburned area (p < 0.001), with 25% to 45% interception in the unburned area and near zero in the post-burn area. Conversely, the peak snowpack depths were significantly larger in the unburned area compared with the post-burn area (mean of 55 and 47 cm, respectively), despite nearly identical peak snowpacks prior to the fire (72 and 72 cm, respectively). The lack of strong vegetation controls led to less variability at peak snowpack in the post-burn area and a shift towards topographically controlled variability, caused by differences in elevation and aspect, occurring at larger spatial scales. The unburned area had roughly 10% more water available for melt than the post-burn area, with winter season ablation reducing snowpacks by nearly 50% prior to melt in the post-burn area. The relative importance of shortwave radiation to the snowpack energy balance and sublimation suggests that the 10% reductions in peak snow water storage found in these north-facing areas could be a conservative estimate for winter season ablation following fire. Further work is necessary to assess the role that topography plays in altering water partitioning following forest disturbance and the potential implications for ecological health and downstream water resources. Copyright © 2013 John Wiley & Sons, Ltd.

Woody plant encroachment on water-limited lands can induce a shift from biotic (plant)-controlled resource retention to abiotic (physical)-driven losses of critical soil resources. The biotic-to-abiotic shift occurs where encroachment propagates connectivity of runoff processes and amplified cross-scale erosion that, in-turn, promote ecohydrologic resilience of the post-encroachment community. We investigated these relationships for woodland-encroached sagebrush steppe in the Great Basin, USA, and evaluated wildfire as a mechanism to reverse the post-encroachment soil erosion feedback. We measured vegetation, soil properties, and runoff/erosion from experimental plots on burned and unburned areas of a late-succession woodland 1 and 2 years post-fire. Our findings suggest that the biotic-to-abiotic shift and amplified cross-scale erosion occur where encroachment-induced bare ground exceeds 50–60% and bare gaps between plant bases frequently extend beyond 1 m. The trigger for amplified cross-scale erosion is formation of concentrated flow within the degraded intercanopy between trees. Burning in this study decreased ecohydrologic resilience of the late-succession woodland through herbaceous recruitment 2 years post-fire. Increased intercanopy herbaceous productivity decreased connectivity of bare ground, improved infiltration, and reduced erosion, but the study site remained vulnerable to runoff and erosion from high-intensity rainfall. We conclude that burning can reduce woodland ecohydrologic resilience and that woodland encroachment-induced structural and functional ecohydrologic attributes may persist during high-intensity storms for an undetermined period post-fire. We cannot conclude whether wildfire reverses the woodland-induced soil erosion feedback on sagebrush rangelands. However, our results suggest that wildfire may provide a restoration pathway for sagebrush steppe by reducing woodland ecohydrologic resilience over time. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

The interactions between atmospheric, hydrological, and ecological processes at various spatial and temporal scales are not fully represented in most ecohydrological models. This first of a two-part paper documents a fully integrated catchment-scale ecohydrological model consisting of a three-dimensional physically based hydrological model and a land surface model. This first part also presents a first application to test the model over an energy-limited catchment (8.4 km²) of the Sleepers River watershed in Vermont.

The physically based hydrological model (CATchment HYdrology, CATHY) describes three-dimensional subsurface flow in variably saturated porous media and surface routing on hillslopes and in stream channels, whereas the land surface model (LSM), an augmented version of Noah LSM with multiple parameterization schemes (NoahMP), accounts for energy, water, and carbon flux exchanges between various land surface elements and the atmosphere. CATHY and NoahMP are coupled through exchanges of water fluxes and states. In the energy-limited catchment of the Sleepers River watershed, where snowmelt runoff generation is the dominant hydrologic flux, the coupled CATHY/NoahMP model at both 90 and 30-m surface grid resolutions, with minimal calibration, performs well in simulating the observed snow accumulation, and melt and subsequent snowmelt discharge. The Nash–Sutcliffe model efficiency of daily discharge is above 0.82 for both resolutions. The simulation at 90-m resolution shows a marginal improvement over that at 30-m resolution because of more elaborate calibration of model parameters. The coupled CATHY/NoahMP also shows a capability of simulating surface-inundated area and distributed surface water height, although the accuracy of these simulations needs further evaluation. The CATHY/NoahMP model is thus also a potentially useful research tool for predicting flash flood and lake dynamics under climatic change. Copyright © 2013 John Wiley & Sons, Ltd.

The use of diurnal water-table fluctuation methods to calculate evapotranspiration (ET) and groundwater flow is of increasing interest in ecohydrological studies. Most studies of this type, however, have been located in riparian wetlands of semi-arid regions where groundwater levels are consistently below topographic surface elevations and precipitation events are infrequent. Current methodologies preclude application to a wider variety of wetland systems. In this study, we extended a method for estimating sub-daily ET and groundwater flow rates from water-level fluctuations to fit highly dynamic, non-riparian wetland scenarios. Modifications included (1) varying the specific yield to account for periodic flooded conditions and (2) relating empirically derived ET to estimated potential ET for days when precipitation events masked the diurnal signal. To demonstrate the utility of this method, we estimated ET and groundwater fluxes over two growing seasons (2006–2007) in 15 wetlands within a ridge-and-swale wetland complex of the Laurentian Great Lakes under flooded and non-flooded conditions. Mean daily ET rates for the sites ranged from 4.0 mm d⁻¹ to 6.6 mm d⁻¹. Shallow groundwater discharge rates resulting from evaporative demand ranged from 2.5 mm d⁻¹ to 4.3 mm d⁻¹. This study helps to expand our understanding of the evapotranspirative demand of plants under various hydrologic and climate conditions. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

A pot culture experiment with four levels of soil water content (waterlogged condition, 90%, 75% and 60% of field capacity) and five levels of sodium chloride (NaCl) concentration (0, 60, 120, 180 and 240 mM) was conducted to examine the physiological responses of salt meadows Phragmites australis to soil water content and NaCl salinity in the Yellow River Delta, China. Results indicated that (i) the combined effects of soil water and NaCl salinity had significant influences on the light-saturated photosynthetic rate (P_{n max}, F = 7·19, P < 0·01), intercellular CO₂ concentration (C_i, F = 24·92, P < 0·01) and stomatal conductance (g_s, F = 18·16, P < 0·01) at light saturation of this species. The light-saturated photosynthetic rate (P_{n max}) was the largest at 90% of field capacity with 60 mM NaCl salinity treatment (13·10 µmol CO₂ m⁻² s⁻¹, SD ± 0·46) and decreased with the increase of NaCl salinity and water deficit. Under severe water and salinity stress, P_{n max} decreased with C_i rising substantially, which means the non-stomatal limitations of P. australis occur; (ii) stress resistance in the salt meadow P. australis was closely related to the retention of a relatively higher water status and a higher content of potassium (K⁺) in leaves; and (iii) both content of sodium (Na⁺) and proline were significant increased by water stress and NaCl salinity stress, and the leaf proline content was positively correlated with the leaf Na⁺ content (r = 0·837, n = 60). Copyright © 2012 John Wiley & Sons, Ltd.

Due to its high spatial and temporal variability, preferential flow is difficult to measure and quantify. Earthworms create macropores that provide common pathways for preferential flow. Therefore in this article, we link earthworm abundance to macropore numbers and hydrological effectiveness, with the future aim to use species distribution models of earthworms for the spatial parameterization of preferential flow.

Earthworms are generally categorized into three ecological types with varying burrowing behaviour, resulting in a different impact on soil hydrological processes. Therefore, we studied the relationships between the abundance of the earthworm ecological types and macropores of different size classes and in different soil depths. The abundance and biomass of earthworms were well correlated to different sizes of macropores in different soil depths. This is mainly the case for the larger, vertically oriented macropores (>6 mm diameter), which are generally connected to the soil surface and hydrologically most effective. The correlation of total earthworm biomass and macropores ranges from 0·72 to 0·89 for different soil depths.

Although there is quite some variation in infiltration patterns, infiltration from macropores into the matrix is profile-specific, as it varies strongly between profiles, but not within one profile. Macropore coating seems to have a larger effect on this macropore–matrix interaction than the soil physical properties of the matrix. Although the amount of macropores and their effectiveness are clearly related to the earthworm distribution, the variation in infiltration from macropores to soil matrix should be further studied. Copyright © 2013 John Wiley & Sons, Ltd.

River red gum (Eucalyptus camaldulensis Denhn.) trees along the lower River Murray, Australia, have suffered severe dieback as a result of river regulation and drought. As an environmental flow initiative, the height of the lower River Murray in South Australia was raised during a period of increased flow in the spring and summer of 2005–2006. This was performed by increasing the level of the rivers in channel weirs. This increased the level of anabranch creeks on the Chowilla floodplain and through horizontal recharge freshened the adjacent groundwater, providing water to riparian river red gums. Groundwater depth rose concurrently with the rise in creek level, likely recharging the saline floodplain water table with fresh creek water. Multistate Markov modelling showed that along four creeks, most healthy trees responded positively to the rise in water level and remained healthy 1 year after the surcharge. Healthy trees were three times more likely to respond than stressed trees and thirty times more likely to respond than defoliated trees. Stressed trees were ten times more likely to respond than defoliated trees. Forty eight percent of trees that had no leaves at the start of the study responded to the surcharge by producing new growth. This study demonstrates how existing regulatory infrastructure can be used to manipulate water levels and that the hydrological connection between surface water and groundwater can be used to provide water to riparian trees. Copyright © 2013 John Wiley & Sons, Ltd.

Knowledge of the relationship between soil water dynamics and tree water use is critical to understanding forest response to environmental change in water-limited ecosystems. However, the dynamics in soil water availability for tree transpiration (T_t) cannot be easily deduced from conventional measurements of soil water content (SWC), notably because T_t is influenced by soil water potential (Ψ_s) that, in turn, depends on soil characteristics. Using tree sap flow and water potential and deriving depth-dependent soil water retention curves, we quantified the ‘transpirable soil water content’ (tSWC) and its seasonal and inter-annual variations in a semi-arid Pinus halepensis forest. The results indicated that tSWC varied in time and with soil depth. Over one growing season T_t was 57% of rain and 72% of the infiltrated SWC. In early winter, T_t was exclusively supported by soil moisture at the top 10 cm (tSWC = 11 mm), whereas in spring (tSWC > 18 mm) and throughout the dry season, source water for T_t shifted to 20–40 cm, where the maximum fine root density occurs. Simulation with the soil–plant–atmosphere water and energy transport model MuSICA supported the idea that consistent tSWC at the 20–40 cm soil layer critically depended on limited water infiltration below 40 cm, because of high water retention below this depth. Quantifying tSWC is critical to the precise estimation of the onset and termination of the growing season (when tSWC > 0) in this semi-arid ecosystem. Copyright © 2012 John Wiley & Sons, Ltd.

Macroinvertebrates' response to hydromorphological alterations and regulated flows along lowland rivers is still poorly known despite ecohydrology's fundamental role in river science. Along the Oglio River (Northern Italy), several water abstractions and dams break it into segments with varying hydraulic and morphological properties. Three types of a priori different environments were identified (dammed, downstream and free flowing sections), and macroinvertebrate communities were sampled from each zone. This study aimed (i) to investigate patterns of macroinvertebrate communities along a regulated lowland river by testing the a priori zones; (ii) to find macroinvertebrate taxa that served as indicators of the various hydrological conditions and (iii) to verify hydromorphological control over ecological macroinvertebrate traits resulting in different trait values in each identified zone. Macroinvertebrate community was characterized in a total of 63 stations by means of two quantitative approaches, each exploring a surface of 0.5 m². The lowest richness values were found in dammed sites that tended toward lentic conditions. Ecnomidae (dammed zones), Limoniidae (downstream zones) and Heptageniidae (free flowing section) were identified as the best indicators of varying hydrological conditions. As suggested by the results of 4th Corner Method, environmental constraints define communities with different ecological traits. These results highlight hydromorphological control over macroinvertebrate community structure and reflect how regulated flows affect the Oglio River in terms of biodiversity, indicator taxa and ecological traits. The authors wish to stress the importance of considering the ecological effects of dams and impoundments on river systems in upstream areas as well as downstream. Copyright © 2012 John Wiley & Sons, Ltd.

We run a comparative study of the results of flume experiments and several dynamic models reproducing the effects of streamflow variability on biofilm (i.e. periphyton) temporal dynamics. During the experiment, two contrasting flow regimes, characterised by a constant and a time-varying discharge temporal sequence, and four different light conditions (from 90% to 27% transmission of incident light) were performed to test the effects of availability and temporal variability of light and streamflows on biofilm growth. Several model formulations, describing growth and loss dynamics, have been explored in order to assess the relevant processes that controlled biofilm temporal pattern. Model identification criteria were used to identify the most suitable model, in which the growth rate is found to be dependent on density-limitation dynamics coupled with a saturating light effect, while the loss rate is linearly proportional to the discharge conditions experienced in the flumes. This model formulation proved able to reproduce remarkably well the observed biofilm dynamics. In order to analyse the stationary behaviour of the best-performing model reproducing biofilm biomass dynamics, we also run a long-term simulation, where no significant biomass differences between the constant and stochastic flow regimes were detected. Copyright © 2012 John Wiley & Sons, Ltd.

Partitioning of evapotranspiration (ET) into soil evaporation and vegetation transpiration (T) is important for predicting the response of ecosystem water/energy budgets to climatic change. In this study, a new two-source model of water and energy fluxes was developed and used to partition ET for a temperate–grassland ecosystem in central Japan, throughout a growing season. The Newton–Raphson iteration scheme was employed to solve the equations governing the energy balance at the canopy and the ground surface separately. Measured energy fluxes, including latent heat flux from the eddy covariance and energy balance method, and leaf temperature were compared with model predictions. Agreement between them demonstrates good performance by the model. Sensitivity analysis suggests this model is relatively insensitive to uncertainties/errors in assigned model parameters and measured input variables. Estimated T/ET was mainly controlled by shortwave radiation through changing leaf stomatal resistance at a diurnal timescale. Also, leaf area index is the primary controlling factor at a seasonal timescale and regulates both permittivity and canopy resistance. Soil moisture at the study site was a minor factor with the moderately humid conditions. Our results emphasize that water flow paths (i.e. transpiration and evaporation) from temperate grasslands to the atmosphere are strongly controlled by the physiological responses of plants to solar radiation on a diurnal timescale and vegetation growth on a seasonal timescale. Copyright © 2012 John Wiley & Sons, Ltd.

The dynamics of riparian vegetation in a reach of the Lijiang River, China, are investigated. A new process-based model is developed based on cellular automata, which simulates the key processes in the life cycle of the ten most occurring plant species: germination, normal growth, response to floods and droughts, destruction by high velocities, consumption of resources, colonization and competition. The parameterization of these processes is based on controlled experiments on plants sampled in the study area. A traditional statistical model is also developed, which relates the vegetation state to four flow-related variables. Both models are assessed based on data from 12 field surveys in the period from 2009 to 2011, during the dry season, the wet season and at the end of the growing season. Both models predict satisfactorily the spatial distribution of the vegetation cover at the end of the growing season. Although the statistical model is by definition limited to the steady state conditions at the end of the growing season, the process-based model also satisfactorily simulates the temporal dynamics of the vegetation during the dry season and the wet season. Contrary to the statistical model, the process-based model also satisfactorily simulates the vegetation cover outside the area used for the model parameterization. Thus, process-based models are more robust under flow regimes with spatial heterogeneity and important temporal variations. Field observations and process-based model predictions indicate that the regime of dry season and wet season floods is the main regulator of the vegetation cover in the study area. Copyright © 2012 John Wiley & Sons, Ltd.

Mangroves are expanding into warm temperate-zone salt marsh communities in several locations globally. Although scientists have discovered that expansion might have modest effects on ecosystem functioning, water use characteristics have not been assessed relative to this transition. We measured early growing season sapflow (J_s) and leaf transpiration (T_r) in Avicennia germinans at a latitudinal limit along the northern Gulf of Mexico (Louisiana, United States) under both flooded and drained states and used these data to scale vegetation water use responses in comparison with Spartina alterniflora. We discovered strong convergence when using either J_s or T_r for determining individual tree water use, indicating tight connection between transpiration and xylem water movement in small Avicennia trees. When T_r data were combined with leaf area indices for the region with the use of three separate approaches, we determined that Avicennia stands use approximately 1·0–1·3 mm d^–1 less water than Spartina marsh. Differences were only significant with the use of two of the three approaches, but are suggestive of net conservation of water as Avicennia expands into Spartina marshes at this location. Average J_s for Avicennia trees was not influenced by flooding, but maximum J_s was greater when sites were flooded. Avicennia and Spartina closest to open water (shoreline) used more water than interior locations of the same assemblages by an average of 1·3 mm d⁻¹. Lower water use by Avicennia may indicate a greater overall resilience to drought relative to Spartina, such that aperiodic drought may interact with warmer winter temperatures to facilitate expansion of Avicennia in some years. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Woody encroachment is of great socio-economic and ecological importance in semiarid savannas because it is presumed to alter the water balance in such ecosystems. We compared two encroachers, Ashe juniper (Juniperus ashei) and honey mesquite (Prosopis glandulosa), with the less invasive live oak (Quercus fusiformis) to ascertain whether soil depth or species-specific water use strategy is most important in determining transpirational losses on shallow soils underlain by fractured limestone bedrock on the Edwards Plateau. Sap fluxes, leaf water potentials, soil moisture and meteorological information were monitored during spring 2009 at three sites with differing soil depths and were used in a non-spatial soil–vegetation–atmosphere water transfer model to predict different rooting depths. Sap flux responses and soil water stress were compared using multivariate statistical analysis. At two relatively deep-soil savanna sites, we found that dominant tree species had similar water use behaviour. However, at the shallow-soil forest containing Ashe juniper and live oak, juniper transpiration was much higher early in the season than oak transpiration, indicating that juniper benefited more from early spring rainfall than oaks. The model predicts that maximum rooting depths for the woody vegetation were mostly constrained by site soil depths. This study provides new evidence that these species perform similarly on shallow soils and that their water use is restricted by soil depth. The only species-specific strategy found important in determining transpirational losses was juniper's ability to withstand low soil water potentials in very shallow soils. Copyright © 2012 John Wiley & Sons, Ltd.

The ecological effectiveness and success of river restoration strongly depend on the resources invested in planning. Unfortunately, this trend of restoration engineering is frequently compromised by the application of qualitative assessment and resource intensive adaptive management processes. Habitat simulation models are effective tools for selecting ecologically effective restoration measures as part of the Environmental Benefits Analysis. Through the support from a mesohabitat simulation model, we identified three habitat metrics: (1) Habitat Quantity Deficiency; (2) Alteration of Habitat Structure; and (3) Habitat Stress Days Alteration to quantify and visualize differences between restoration options in Restoration Alternatives Assessment diagram. This concept of quantifying habitat models is supported by an example of application in the Wekepeke Brook in Massachusetts, in which the habitat metrics were used to define quantitative benchmarks, goals and targets to guide the restoration process from the design to the evaluation phase. The three habitat metrics are a cost effective alternative for evaluating the ecological benefits of a planned action. The methodology contributes to a high potential for designing and monitoring restoration projects. Copyright © 2012 John Wiley & Sons, Ltd.

Previous studies have noted the importance of vegetation in controlling run-off in terrestrial landscapes. Here, we hypothesize that ecologic succession from mowed grassland to old field to forest will impact run-off characteristics due to changing vegetation characteristics that affect soil surface processes. We test this idea by measuring depression storage and leaf litter water retention rates in 13 sites across this successional gradient. Sites of similar slope and soil type were also evaluated against one another to isolate the effect of vegetation diversity and management on depression storage. Results showed that average ideal depression storage increased with greater vegetation diversity and structure. Effective depression storage of unmanaged systems was significantly higher than mowed systems, implying that management activities retard the natural development of microtopography. Results of leaf litter water retention varied among land covers but contributed less than depression storage for water capture. These results demonstrate the tight linkages between vegetation succession and run-off. Understanding these characteristics is necessary for developing effective hydrologic models. Copyright © 2012 John Wiley & Sons, Ltd.

Fire is a major disturbance that causes rangeland change. In this study, we compared the turbulent fluxes of carbon dioxide and sensible and latent heat, measured over burned and unburned sites of a sagebrush-dominated mountain in southern Idaho during the late summer of 2006. The outcome of the investigation shows that fire altered the horizontal components of turbulence intensity (i_u and i_v) as well as the partitioning of radiant energy between latent and sensible heat fluxes. Average daytime Bowen ratios (β) at the burned and unburned sites were 2.03 and 1.87. On the basis of Bowen ratios determined from eddy covariance measurements of sensible and latent heat fluxes, the sensible heat fluxes were relatively more significant at the burned site than at the unburned site most of the time, and the converse was true of the latent heat fluxes. The exception to this was for the few days following heavy rainfall, when near-surface soil moisture increased the evapotranspiration at the burned site more than at the unburned site until the shallow moisture supply was depleted. By means of ratios of CO₂/(H + LE), fluxes, carbon sequestration was found to be more significant at the unburned site, declining at both sites as summer progressed but declining more rapidly at the burned site than at the unburned site. Copyright © 2012 John Wiley & Sons, Ltd.

In sap flow studies, there is no method complying with high efficiency and versatility of sap flow measurements. To improve that, we propose combining two methods: (1) thermal dissipation probe (TDP) known to be efficient and cost effective and (2) heat field deformation (HFD) known to be versatile. For that purpose, we used a step-wise TDP sap flux density (J_p) optimization method consisting of (1) natural temperature gradient (NTG) correction applying the cyclic heat dissipation (CHD) method, (2) night flow ΔT_max correction using HFD data as reference and (3) radial-azimuthal correction using HFD as reference. We applied this optimization method on Quercus ilex (Q.i.) and Quercus pyrenaica (Q.p.) trees in a Spanish semi-arid open woodland during dry season. The NTG correction resulted in substantial reduction of J_p as compared with standard TDP. The subsequent ΔT_max night flow correction resulted in the increase of NTG-corrected J_p and good agreement with the outermost 2 cm of HFD measurements for both species. The final radial-azimuthal adjustment of TDP J_p resulted not only, in a good agreement with HFD J_p, but also provided novel ecohydrological insights such as: (1) evidence of continuous night flow in all Q.p. trees and some Q.i. trees, (2) exponential reduction of J_p with sapwood depth for both species, (3) significantly larger J_p in the outermost 1 cm of sapwood for Q.p. than for Q.i. and (4) high azimuthal J_p variability for both species. The presented study offers efficient and versatile method of tree sap flow measurements that contributed to a better understanding of water-related dynamics of Q.i. and Q.p. under water-stress conditions. Copyright © 2013 John Wiley & Sons, Ltd.

Sources of water use by 10 alluvial trees in various hydrogeological and ecological situations at the Pfyn forest (Wallis canton, Switzerland) were assessed by analysing ¹⁸O and ²H isotopes of precipitation, soil water at different depths, surface water, groundwater and xylem sap. The soil water line in a δ¹⁸O versus δ²H diagram shows evidence of kinetic fractionation related to evaporation. The tree water line is close to the soil trend; however, an additional enrichment may occur and could be related to xylem–phloem communication under water stress. At sites where the water table was at least 2 m below the ground surface, isotopic temporal variability of soils and trees was strongly linked with seasonal variation of soil water content. When soil water content was low and water table shallow, trees used both soil water and groundwater. When soil water content was high, this source was usually the dominant source for transpiration. In addition, some ecological strategies, reproduction or growth competition, could explain shifts in the utilization of different water sources, for example, from soil water to a mix of soil water and groundwater. At one site where soil water and groundwater were abundant throughout the year (next to the river course), neighbouring trees permanently used distinct water sources. This is consistent with a strategy of competition limitation, which would favour bank colonization. These results provide insight into the ecohydrological functioning of this system and will aid future management responses to both local and climate changes. Copyright © 2012 John Wiley & Sons, Ltd.

Quantifying regional evapotranspiration (ET) and environmental constraints are particularly important for understanding water and carbon cycles of terrestrial ecosystems. However, a large uncertainty in the regional estimation of ET still remains for the terrestrial ecosystems in China. This study used ET measurements of 34 eddy covariance sites within China and adjacent regions to examine the performance of the revised Remote Sensing-Penman Monteith (RS-PM) model over various ecosystem types including forests, grasslands, wetlands and croplands. No significant systematic error was found in the revised RS-PM model predictions, which explained 61% of the ET variations at all of the validation sites. Regional patterns of ET at a spatial resolution of 10 × 10 km were quantified using a meteorology dataset from 753 meteorological stations, Modern Era Retrospective-analysis for Research and Applications (MERRA) reanalysis products and satellite data such as the Advanced Very High Resolution Radiometer (AVHRR) leaf area index. ET decreased from the southeast of China toward the northwest. Relatively high ET values were found in the southern China such as Yunnan, Hainan, Fujian and Guangdong Provinces, whereas low ET values occurred in northwestern China such as in the Xinjiang autonomous region. On average, the annual ET presented an increasing trend during the 1982–2009, with relatively low ET in 1985, 1993, 1997, 2000 and 2009. We found that the mean annual ET was higher than world average, ranging spatially between 484 and 521 mm yr⁻¹, with a mean value of 500 mm yr⁻¹, which accounted for approximately 5·6–8·3% of the world's total land-surface ET. Copyright © 2012 John Wiley & Sons, Ltd.

This paper intends to show how the radio frequency-electromagnetic (RF-EM) method can be successfully used in coastal wetlands, onshore and in shallow water. It characterizes and reveals geological and hydrogeological singularities that are often hidden by recent sediments and allows target sampling and consequent detection of ecological particularities. RF-EM methods have traditionally been used to detect the presence of groundwater or the existence of subsurface contamination plumes. The great majority of such studies have been conducted on land and to a lesser extent on freshwater lakes but rarely in coastal waters. Previous research in Portugal has shown that despite the attenuation effect of salt water, very valuable information can be obtained with the use of electromagnetic methods, wherever resistivity contrasts exist. In the current case study, RF-EM surveys were carried out in the Estuary of the Guadiana River, in order to understand the importance of geological structures on the formation of the wetland and the influence of groundwater discharge on the existing ecosystem. Structures detected on land were also identified in the tidal channels. Freshwater fault springs were localized; their biota is characterized and the nutrients analysed. The results showed a clear increase in nitrate and silica concentration near the submarine springs, with impact on the planktonic communities, which is most evident in chlorophyll a. This is especially relevant during the end of summer and autumn when a potential limitation of these nutrients exists that can increase the occurrence of toxic blooms in the salt marshes and lower estuary. Copyright © 2012 John Wiley & Sons, Ltd.

We estimated the minimum ecological influx in the lower Tarim River via the wetted perimeter method using the curvature technique. Calculations were based on river geomorphology data during the fifth and sixth ecological water conveyances. Results showed that the minimum ecological influx of the three control sections of the river (Yinsu, Alagan, and Yiganbjima) were 2.85, 3.76, and 1.76 m³/s, which accounted for 9.7%, 14%, and 6.9% of the multi-year average annual discharges, respectively. Except for the dry season, annual ecological water demand of the river was 0.79 × 10⁸ m³, excluding evaporation and leakage. Multiple methods were used to prove the rationality of the results. It is by using the Tennant method that the percentage of minimum ecological influx accounting for multi-year average flux varied from 6.9% to 14% (average 10.2%), which is considered normal for the maintenance of river habitat. It is by using the R2Cross method that the minimum ecological influx of the lower Tarim River was 2.935 m³/s. These calculation results mirror the actual situation and serve as the base of water-source distribution in lower Tarim River. Further research is required to validate and adjust the results according to long-term hydrographic observations. Copyright © 2012 John Wiley & Sons, Ltd.

This study simulates the impacts of reforestation on hydroclimatology of Niger River Basin (NRB) under enhanced greenhouse gases (GHGs). A regional climate model (RegCM3) was used to dynamically downscale hydroclimatological variables of NRB for present-day (PRS), and for future climate scenarios (with and without reforestation). The data were further analysed to detect changes in water balance components and the moisture recycling ratios. Under A1B scenario, warmer climate was projected over the entire basin in all seasons, a drier climate during the rainy season, and a wetter climate during the dry season. Reforestation along NRB (GBR) reduces the GHG warming over the basin both seasons, but increases it north-east of the basin in July–September (JAS). Both reforestation scenarios could enhance rainfall over the reforested area. With reforestation over Sahel (GSR), seasonal evapotranspiration increases between 3·6% and 14·4%; but with GBR, evapotranspiration reduces between −12·4% and −4·3%. The GSR option offsets the projected annual GHG effects on moisture recycling over the basin. Evaporation coefficient decreased by about 5% under elevated CO₂ while runoff coefficient increased. Reforestation reduces the projected warming and drying over the reforested zones because of its influence on the monsoon flow (reduction in speed). Hence, with reforestation in summer, the onset of monsoon delays in bringing in the cool moist air over the area located downwind of the reforested zone; this increases the temperature and reduces rainfall amount over the area. Copyright © 2012 John Wiley & Sons, Ltd.

Seasonal snowpack in forested lands is the primary source of fresh water in western North America, where mountain pine beetle (MPB) infestation has resulted in rapid and extensive tree die-off. Forests significantly influence the amount and spatial distribution of peak seasonal snowpack, but the impacts of large-scale tree mortality on the processes controlling peak snowpack are not well understood. We evaluate the effects of widespread tree mortality on winter snow accumulation and peak seasonal snowpack across multiple spatial scales and several levels of MPB impact in the Central Rocky Mountains. Observations for winters 2010 and 2011 include continuous snow depths in 20 plots, distributed snow surveys at peak accumulation and climate observations above and below canopy including precipitation, temperature, humidity, wind and shortwave radiation. Stable water isotopes were observed for fresh snowfall and for snowpack. Plot-scale snowfall observations showed 20% lower interception (p < 0.05) in grey-phase stands (needles lost) than in unimpacted stands. However, distributed snow surveys found no differences in peak seasonal snow water equivalent between unimpacted and grey-phase stands. Water isotopes of snowpack from MPB-killed stands indicated kinetic fractionation; enriched values demonstrated higher winter snowpack sublimation in MPB-killed forest. Following MPB infestation, reduced canopy sublimation of intercepted snow appeared to be compensated by increased snowpack sublimation, consistent with observations of higher snowpack insolation. Consequently, the effects of widespread tree mortality on peak seasonal snowpack, which is crucial for downstream water resources, will be influenced by compensation for lower interception by higher snowpack sublimation. Copyright © 2012 John Wiley & Sons, Ltd.

Using brackish and saline water is one of the most effective ways to solve the problem of water resource shortage. To rationally exploit and make use of brackish and saline water resources, the effects of drip irrigation underneath a plastic film with different salinities of irrigation water on soil salt content and cotton growth were studied at the Aksu National Field Research Station of Agro-ecosystem in Xinjiang from 2008 to 2009. The results showed that the soil salt increases before the first irrigation of the growing period, then generally decreases during the irrigation period, and increases after the final irrigation of the growing period and before winter irrigation. In extremely arid areas, the leaching effect of rainfall is weakened. When cotton is irrigated with saline water of salinity greater than 2·24 g l⁻¹, the salt is accumulated at the main cotton root zone. The effect of salinity of irrigation water on cotton growth is a gradual process and is highlighted during the boll-opening period. Leaf area index, root area index, root length density, and root weight density all decrease with an increase of salinity of irrigation water and soil salt content in the root zone. The root weight density and root length density of treatments with brackish or saline water are far less than those of treatment with fresh water. After sowing, with the increase of time, the leaf area index changes from small to large, reaches its peak at the flowering-bolling stage, and then reverts from large to small; however, root area index, average cotton root length density, and root weight density of the 0- to 50-cm soil layer continuously increase throughout the entire process. During the boll-opening period, the vitality of the cotton root remains strong. Copyright © 2012 John Wiley & Sons, Ltd.

The flow regime of a river is the main driver of the processes that make up a floodplain ecosystem. Changes in a flow regime will therefore result in changes in the floodplain. The Mana floodplains in the middle Zambezi river basin have been impacted by the construction of the Kariba dam as indicated by the decline in the population of mature, Faidherbia albida (F. albida) trees and the absence young trees. However, the relationship between the effects of the river impoundment, some 50 years ago, and the current ecological state of the floodplain is not well understood. Hence, this study is aimed at describing the historic (pre-Kariba and post-Kariba dam) and the current terrestrial ecological state of the Mana floodplains. Data was gathered through review of literature, archival records and hydrological records. Furthermore, vegetation plots were set up to measure diameter at breast height (dbh) of F. albida trees and hence describe the current F. albida stand structure. Results from this study show that the Kariba dam altered the peak mean monthly flows by about 60%. The frequency distribution of the dbh sizes of the current F. albida trees depicted an even-aged stand structure (mean dbh of 103 cm). There was no evidence of growth of young F. albida trees as there were no trees with smaller (less than 40 cm) dbh sizes. The dry season densities of elephants, (Loxodonta africana) on the Mana floodplains have been increasing since the 1990s, and these also seem to have impacted on the F. albida stand structure. This perhaps partially has to do with the increased length of the dry season as a result of the changed river flows. Therefore, the influence of the altered flow regime and the impact of wildlife have acted interdependently in influencing the noted detectable changes to the ecology of the Mana floodplains. Copyright © 2012 John Wiley & Sons, Ltd.

Woody plants are encroaching into grasslands and savannas of the karst Edwards Plateau, but their impacts on climate and hydrology are unclear because of high variability in soil depth and uncertainties about the contribution of water in fractured limestone to the water available to trees. Water use is controlled by available energy (AE) and its partitioning between latent (λE) and sensible (H) heat fluxes. We hypothesized that the partitioning of AE depends on soil depth, with greater depth leading to more λE and less H. We compared energy fluxes of a deep soil savanna with ~50% woody cover dominated by Ashe juniper (Juniperus ashei) and a shallow soil woodland dominated by live oak (Quercus virginiana) and juniper over a 5-year period, which included periods of unusually high rainfall and severe drought. Although AE was 7% higher in the woodland, λE was about 2% higher at the savanna over the 5-year study. Site differences in evapotranspiration were maximal during dry periods between rainfall events, suggesting greater storage of water at the savanna site. During periods of high rainfall, the impact of water storage limitations was minimal, and site differences in evapotranspiration were controlled mainly by AE and its partitioning into H. Both sites were characterized by rapid reductions in λE and reciprocal increases in H during drying cycles following rainfall, indicating that neither of these ecosystems had access to easily utilized sources of deep water. Copyright © 2012 John Wiley & Sons, Ltd.

The Land-surface Processes and eXchanges Dynamic Global Vegetation Model (LPX-DGVM, one of several developments of the Lund–Potsdam–Jena (LPJ) model) is evaluated in terms of its interception component and used to simulate trends in 20th century global relative throughfall from natural vegetation. Mean global annual runoff is estimated to have been reduced by 163 ± 19 km³ year⁻¹ between 1901 and 2006 as a result of biophysical changes controlling throughfall generation. Widespread decreases in relative throughfall of up to −1% are evident between the periods 1901–1953 and 1954–2006, while changes of up to −15% are shown in parts of North America and East Asia. Areas of simulated decrease in relative throughfall often lie in close proximity to areas of increase, reflecting the effects of vegetation shifts.

It is shown that simulated global absolute throughfall has generally increased (because of increasing precipitation) during the studied period, but the curtailing of runoff caused by decreased relative throughfall (as a result of increased fractional plant coverage and possible vegetation shifts) has caused a slight exacerbation of water stress in some regions (including parts of East Asia, North America and the tropics) and increased water supplies in others (for example, other parts of the tropics and northern Russia). This study offers an initial insight into an often overlooked product of climate-induced vegetation changes and attempts to quantify how these responses may contribute to influencing the global freshwater budget and global water resources. Copyright © 2012 John Wiley & Sons, Ltd.

Spatial patterns of ecosystem productivity arise from the terrain-modulated wetting and drying of the landscape. Using a daily relative greenness (rG) index, we explore the relations between spatial variability of plant productivity and landscape morphology, and how these relations change over time. The rG index is defined as a measure of local vegetation greenness relative to the site's mean greenness, calculated from remotely sensed normalized difference vegetation index. We analyse two semiarid grasslands with pronounced topography, one located in southeastern Arizona, with a mean annual precipitation of 350 mm, and the other in central New Mexico, with a mean annual precipitation of 250 mm. Our results indicate that (1) rG is spatially more uniform after wet conditions (higher biomass) than after dry conditions (lower biomass); (2) differences in the relative frequency distribution of rG among different landscape morphologies (ridges, unchanneled valleys and channels) indicate higher productivity in channels, similar coefficient of variation in all process domains, and higher skewness in the ridges; (3) relatively high correlations between the binned average rG with respect to upstream area, curvature, and annual insolation in more than 80% of the terrain indicate a clear dependence between ecosystem productivity and topography; (4) rG is more sensitive to changes in topographic indices at the wetter Arizona study site. Such improved understanding of vegetation-topography dependence is critical for ecosystem management, testing ecohydrologic models, and offers ideas for the downscaling of coarse-scale satellite-derived vegetation indices.

Copyright © 2012 John Wiley & Sons, Ltd.

Periphytic algae are a rich food resource that sustains the upper trophic levels of stream ecosystems. These algae are susceptible to loss through hydraulic shear and abrasion by mobile sediments, but there are few documented linkages between periphyton biomass and sediment transport regimes. In this study, we use both a large set of field observations and an in situ experiment to document the relationship between periphyton biomass and sand transport rate. The in situ experimental design investigates the response of diatom-dominated periphyton biomass to abrasion from fine and coarse sand in transport over low-lying and higher protruding host rocks. Our results showed that periphyton biomass decreased with increasing transport rates in a threshold-type response (transport rates > 0·04–1·8 g m⁻¹ s⁻¹) quantified using classification and regression trees. The in situ experiment revealed that low-lying rocks lost more biomass for a given transport rate than the higher, protruding ones. Saltating coarse sand abraded surfaces more effectively than fine sand travelling primarily in suspension. The observed pattern of biomass loss was similar to that reported in flume studies of the effects of suspended sediment on periphyton. The negative relationship between sand transport rate and post-flow event biomass was nearly identical to that found on the Skona River, Norway, for larger flow events. Sand constitutes a large percentage of the bedload of gravel-bed rivers and is susceptible to transport during frequent flow events. Even small increases in sand loadings to the gravel-cobble river bed can cause large increases in streambed abrasion.

Copyright © 2012 John Wiley & Sons, Ltd.

Hydraulic redistribution has been widely confirmed to occur in the arid and semi-arid ecosystems. However, no research has documented the existence of such a water use/sharing mechanism in the desert riparian forests of the lower reaches of the Tarim River. The current study continuously monitored the sap velocity of roots, micro-meteorological factors and volumetric soil water content at different soil depths and different distances from the trunk to verify whether Populus euphratica Oliv., the dominant species of the riparian forest, has a hydraulic redistribution mechanism and to document its influence factors and ecological effects. We also sampled the stable isotope δ¹⁸O in both soil and plant samples. On the basis of this data, the magnitude of hydraulic redistribution, its driving factors and ecological effects were estimated statistically. The results demonstrate that P. euphratica possesses clear hydraulic lift properties, and the effect of hydraulic lift was distinct at depths of 60–120 cm in the soil within a distance of 4 m from the trunk. This soil moisture spatial variation was attributed to the spatial distribution of the root system. Furthermore, hydraulic lift can improve soil moisture, providing approximately 10–20% of daily water used in the upper soil layers (0–120 cm). By increasing the availability of water in the upper soil water, hydraulic lift can facilitate the existence of some herb species in the Populus community. For the first time, we have estimated the extent of hydraulic redistribution in these ecosystems, and the data indicate that hydraulic lift is an important process in the desert riparian forests in the extremely arid regions of Central Asia. Copyright © 2012 John Wiley & Sons, Ltd.

Riparian ecosystems are required to be preserved to achieve a good ecological status. The Water Framework Directive (2000/60/EC) specifically supports the assessment of new management tools that allow the European Member States to achieve good ecological status of river-related ecosystems. Within several approaches, a dynamic riparian vegetation distributed model (CASiMiR-vegetation), with a time step of 1 year, has been selected as a useful first-step tool to achieve the Water Framework Directive requirements. The model has been implemented into three river reaches with different climatic and hydrologic settings, located in three European countries. Common bases were established in the model setup. The model was calibrated independently in the Kleblach reach (Drau River, Austria), the Ribeira reach (Odelouca River, Portugal), and the Terde reach (Mijares River, Spain) with simulation periods of 8, 11 and 41 years, respectively. The parameter values and the results were comparable between the different countries. The calibration performance achieved high correctly classified instances (60%). Additionally, weighted kappa values ranged from 0·52 to 0·66 in distinguishing riparian succession phases. The model behaved similarly in the validation, even offering better results in most cases. This work demonstrates the applicability of this model in the simulation of the riparian vegetation dynamic distribution over a wide range of environments. As it performs in a robust manner and with good results in reaches with different hydrological characteristics, the model could be also applied to analyse different hydrological scenarios or to predict changes after restoration measures within a reach. Copyright © 2012 John Wiley & Sons, Ltd.

The recent mountain pine beetle epidemic in the Colorado River Basin has resulted in widespread tree mortality in pine stands across the Colorado Plateau. Because of complex micro-scale (i.e. tree well scale) interactions between vegetation and snow processes, one of the most significant issues resulting from this epidemic is the potential hydrologic impacts of the effects of changing forest structure. Using SNTHERM, we conducted a comparative modelling scenario analysis of the snowpack along a transect between two trees over the course of the snow ablation season (28 February–30 June) under four forest stand conditions to assess changes in snowpack characteristics because of loss of canopy biomass. We found that the red phase scenario (intermediate phase of tree death) exhibited a 4-day earlier snow disappearance date than the living stand scenario and grey phase scenario (advanced phase of tree death), although the timing of isothermal conditions at 0 °C was identical. The modelled clearcut scenario snowpack became isothermal at 0 °C 10 days earlier than the living, red phase, or grey phase scenarios. The clearcut modelling scenario also exhibited the greatest homogenization of snow properties, and the spatio-temporal distribution of snow disappearance at the tree well scale was 70% as variable as the living, red phase and grey phase modelling scenarios. These results provide insight to the processes responsible for changing hydrologic dynamics in snow-dominated forest ecosystems with the onset of vegetation stress and death and may help inform future forest management strategies.

Copyright © 2012 John Wiley & Sons, Ltd.

A large number of wetlands, lakes and ponds exist in northern Canada, Alaska and Siberia, and the hydrologic and ecological processes in these water bodies are now responding to a changing climate. A large wetland, Polar Bear Pass (PBP), situated in the middle of Bathurst Island is considered to be one of the most important ecological sites in the region. Numerous ponds exist at PBP and are connected to their surrounding watersheds by streams and groundwater inflow, receiving varying amounts of water and nutrients. In 2008 and 2009, the representative hydrology of typical ponds at PBP along with their quantity of dissolved organic and inorganic carbon (DOC and DIC, respectively) was evaluated. Pond DOC and DIC loads and composition differ depending on the presence or absence of one or more hydrologic linkages that a pond has with its catchment. Elevated DOC loads were mostly of terrestrial origin and occurred in ponds receiving meltwater from snowbeds and discharge from hillslope creeks. The seasonal shift in connectivity of a pond to its catchment was critical in controlling DOC loads and concentrations. The frequency and duration of summer precipitation had a strong control on pond hydrologic connectivity and elevated the contribution of terrestrial DOC from wetland to ponds, especially ones that were hydrologically connected. The estimated DOC yields from wet meadow catchments highlight their importance as a source of carbon to pond ecosystems downstream. These wetland areas and ponds are potentially significant pools of carbon and are sensitive to future climate changes in permafrost-dominated environments. Copyright © 2012 John Wiley & Sons, Ltd.

Riparian corridors in semi-arid Mediterranean environments are ecosystems of high biodiversity and complexity. However, they are threatened because of high levels of human intervention. River damming and related flow manipulation is considered as one of the most prominent human impacts on riparian corridors. This study combines historical time series information on river flows and their human manipulation, historical aerial images depicting changes in riparian land cover and ground observations of the species – age composition and morphology of the riparian corridor of a Mediterranean river (the Mijares River, Eastern Spain) over the last 60 years. In this sense, we explored how to integrate information from a wide variety of data sources, and we extracted a variety of indices and undertook analyses that identified and summarized spatio-temporal changes in riparian structure and in the driving flow processes. Results revealed an increase in the cover and density of woody vegetation and a decrease in bare sediment areas (essential for recruitment of riparian pioneer species), with a synchronous reduction in the complexity of the riparian corridor of the middle reaches of the Mijares River. These vegetation changes have accompanied a decrease in the magnitude and variability of river flows over the last six decades, with higher severity since dam closure. This study illustrates the effectiveness of combining disparate historical data sources and the effectiveness of processing these sources to extract informative metrics that can improve the understanding and management of riparian systems. Copyright © 2012 John Wiley & Sons, Ltd.

Two new ecological niche clustering approaches are presented in this paper: first, an importance/dominance evaluation model, based on both density and biomass, is devised to evaluate the importance (contribution) of a specific species in its community; second, an integrated index encoding approach is constructed to spatially cluster all dominant species at a sampling site. Two approaches are employed to study ecological niche clustering of the Huai River Basin zoobenthos in order to identify key regions for ecosystem restoration. Results show that habitat changes will significantly impact Corbicula fluminea (Müller), whereas influences on Corbicula nitens (Philippi) will be the least significant. Total phosphorus has the greatest impact on zoobenthos, and high-concentrated ammonia nitrogen is also detrimental. Decreasing the discharge of both phosphorus and ammonia nitrogen in the Huai River Basin is therefore required to facilitate restoration. Changing habitat parameters has only a limited effect on alteration of zoobenthos structure. The application of these niche clustering approaches has identified priority locations for ecological restoration in the Huai River Basin. Copyright © 2012 John Wiley & Sons, Ltd.

We investigated the spatial and temporal changes of benthic macroinvertebrate communities in response to floods and droughts in three different stream types: perennial, intermittent, and ephemeral. Benthic macroinvertebrates were collected monthly (or biweekly) at six different sampling sites from July 2006 to January 2008. Species richness and abundance were extremely low at all sampling sites during the flooding period, but the communities subsequently recovered rapidly within 1 month. The effects of floods and droughts on benthic macroinvertebrates manifested differently among the three different stream types. Species richness and abundance had a negative relationship with the amount of precipitation in the perennial stream type, whereas no significant relationship was observed in the ephemeral stream type. A Self-Organizing Map, an unsupervised artificial neural network, classified the samples into four clusters based on the similarities of community composition, reflecting the different effects of floods and droughts on the different stream types. Our results suggest that floods and droughts are the defining characteristics of streams, spatial heterogeneity (i.e. the perennial stream type) can decrease the effect of temporal heterogeneity, and both spatial and temporal heterogeneities are important for structuring the environmental condition and benthic macroinvertebrate assemblages. Copyright © 2012 John Wiley & Sons, Ltd.

Maintaining sufficiently high surface (capitula) soil-water pressures to avoid the draining of hyaline cells (desiccation) is paramount to hummock-forming Sphagnum species' survival; however, the mechanisms of capitula water supply are poorly understood. This study investigates how the hydraulic characteristics of different Sphagnum species (Sphagnum fuscum, Sphagnum rubellum and Sphagnum magellanicum) contribute to desiccation avoidance, on the basis of numerical simulations parameterized with measured soil hydraulic characteristics for each species. Although having similar unsaturated hydraulic conductivity values, the upper 5 cm of S. magellanicum retains ~20% less moisture under tension than S. fuscum and S. rubellum; in fact, S. rubellum on average retained slightly more water than S. fuscum. Hydrus-1D was used to simulate daytime and nighttime conditions over a 7-day period, where daily potential evaporation was 4 mm, to explore the governing mechanisms controlling water supply to the capitula. The simulations showed that S. fuscum and S. rubellum were able to retain sufficiently high moisture content under the prevailing simulated water demand to sustain surface soil-water pressure heads (greater than −100 cm), whereas S. magellanicum could not prevent depressurization and the concomitant desiccation of its surface layer. A similar number of the same size pores were observed in all species; however, there was lower pore connectivity in S. magellanicum leading to the desiccation of the capitula. Contrary to previous studies, the results of this study indicate that it is not only soil-water retention but also pore connectivity that allows hummock species to thrive above the water table.

Copyright © 2012 John Wiley & Sons, Ltd.

Soil acidity is well known to affect the species composition of natural vegetation. The physiological adaptations of plants to soil acidity and related toxicity effects and nutrient deficiencies are, however, complex, manifold and hard to measure. Therefore, generally applicable quantifications of mechanistic plant responses to soil acidity are still not available. An alternative is the semi-quantitative and integrated response variable ‘indicator value for soil acidity’ (R_m). Although relationships between measured soil pH and R_m from various studies are usually strong, they often show systematic bias and still contain high residual variances. On the basis of a well-documented national dataset consisting of 91 vegetation plots and a dataset with detailed, within-plot, pH measurements taken at three periods during the growing season, it is shown that strong spatiotemporal variation of soil pH can be a critical source of systematic errors and statistical noise. The larger part of variation, however, could be explained by the moisture status of plots. For instance, Spearman's rho decreased from 93% for dry plots and 87% for moist plots to 59% for wet plots. The loss of relation between soil pH and R_m in the moderately acid to alkaline range at increasingly wetter plots is probably due to the establishment of aerenchyma-containing species, which are able to control their rhizosphere acidity. Adaptation to one site factor (oxygen deficit) apparently may induce indifference for other environmental factors (Fe²⁺, soil pH). For predictions of vegetation response to soil acidity, it is thus important to take the wetness of plots into account. Copyright © 2012 John Wiley & Sons, Ltd.

Evapotranspiration (ET), ecosystem water use efficiency (EWUE), and energy partitioning in switchgrass (Panicum virgatum L.) ecosystems are crucial to understand its water and energy balances since switchgrass acreage is expanding for cellulosic biofuels. We measured CO₂, H₂O, and energy fluxes over a switchgrass field in Chickasha, OK, USA, using eddy covariance method. The objective of this study was to quantify seasonal variations in ET, EWUE, and seasonal distributions of energy partitioning in response to controlling factors. Seasonal (May to mid-November) cumulative ET (450 mm) was similar to cumulative rainfall (432 mm). During June to September, ET was 1·92 times of rainfall, indicating that the crop experienced severe drought during the mid-growing season. ET showed clear seasonality with 3–4 mm day⁻¹ during the active growing season (late May and June) to low rates of about 0·5 mm day⁻¹ during the late growing season (November). The ET rate decreased during dry periods. On seasonal scale, more energy was partitioned to sensible heat flux (H) than latent heat (LE) because of drought. Estimation of EWUE by dividing time integrals of gross ecosystem photosynthesis (GEP) by respective H₂O fluxes (ET) at monthly time scale provided EWUE from 10·46 (August) to 14·08 g CO₂ mm⁻¹ ET (October) with a seasonal average of 12·01 g CO₂ mm⁻¹ ET. Seasonal patterns in EWUE were observed with smaller values during drought because of more rapid reduction in carbon assimilation (GEP) than ET. These findings confirm the major role of precipitation in determining water and energy balances in switchgrass.Copyright © 2012 John Wiley & Sons, Ltd.

To determine the effects of anthropogenic pressures on the ecology of rivers in the Segura Watershed, we examined stream physicochemistry and the macroinvertebrate community in relation to land use, flow regulation by reservoirs, and the Tajo-Segura Inter-basin Transfer. The inter-basin transfer is thought to be the most important stressor because it affects the flow regime as well as water quality and quantity in an arid, typically water-stressed environment. The concentrations of major ions were strongly impacted by agricultural and urban land uses and the inter-basin transfer. There was a significant increase in conductivity and the concentrations of SO₄²⁻ and other major ions downstream of the Tajo-Segura Transfer. The macroinvertebrate community was less diverse and composed of more pollution-tolerant taxa in areas affected by flow regulation and the inter-basin transfer. The rivers of study are at risk for salinization because of inputs from land use and the Tajo-Segura Transfer. Therefore, major ion and nutrient concentrations should be monitored. Currently, there is no limit specified for SO₄²⁻ concentration in relation to aquatic ecosystem health in Spain. Measures are needed to reduce the effects of contamination and flow regulation to protect the aquatic ecosystem within the Segura Watershed. Copyright © 2012 John Wiley & Sons, Ltd.

Evergreen plants inhabiting ephemeral wetlands endure long dry spells interspersed with periods of flooding (or inundation). Inundation events are likely to be important for plant water use and growth, but few studies have linked the physiology of plants to hydrological processes during flood. We investigated the link between changes in the soil physical environment and plant water use traits in a stand of Casuarina obesa Miq and Melaleuca strobophylla Barlow trees during a controlled inundation event at Toolibin Lake. Toolibin Lake is an internationally recognized ephemeral wetland, which is under threat from altered hydrology and salinization. During flood, the velocity of water movement through the clay-dominated soil profile suggested that macropores and plant root preferential flow paths aided water distribution. C. obesa was more capable than M. strobophylla to capitalize on the inundation event, suggesting preferential use of macropore water and a concentration of roots near the soil surface. Sap flux (Q_S) and tree diameter (ϕ) were interdependent and there was a correlation between increasing ϕ and increasing pre-dawn leaf water potential (Ψ_pd). These observations link the movement of water through the soil profile with changes in tree water use and tree girth in C. obesa and M. strobophylla. Changes in the soil physical environment observed in this study also highlight the risks associated with hydrological management in salinity-affected ecosystems. Although floods provide fresh water to the root zone of trees, the resulting recharge may also elevate saline groundwater into the region of plant water uptake. Copyright © 2012 State of Western Australia

Water use of a dominant desert species, Haloxylon ammodendron, growing in the southern edge of Gurbantünggüt Desert in northwest China, was measured using sap flow technologies at both tree and branch scales. Daily sap flow at whole-tree scale showed a good relationship with atmospheric evaporation demand (P < 0·001), whereas daily sap flow at branch scale showed good relationships with the variable of transpiration rate (P < 0·01). Hysteresis in hourly sap flow at both scales was observed as a function of micro-meteorological variables, in which the hysteresis between sap flow and vapour pressure deficit was clockwise rotation, suggesting that the water use of H. ammodendron was related to not just the stomatal behaviour but also use of stored plant water. The hysteresis between sap flow and photosynthetic photon flux density was counter-clockwise after precipitation, but turned to be clockwise under dry conditions, which was ever clearer at whole-tree scale. Different responses of sap flows at branch and whole-tree scale to climate factors were identified, which strongly indicated that H. ammodendron had some mechanisms to reduce whole-tree water use at high transpiration demand, while maintaining part of canopy under relatively high water use, which resulted in canopy scale patchiness. Copyright © 2012 John Wiley & Sons, Ltd.

Reforestation of previously deforested landscapes often increases soil organic matter content and porosity as the plantation forest ages, leading to increased soil saturated hydraulic conductivity (K_H). However, the time required for a reforested soil's K_H to recover to that of the original forest differs considerably between locations because of variations in forest, climatic and soil properties. We examined a chronosequence of sites on similar soils in a managed forest landscape in southern Ontario, Canada, ranging from open fields deforested in the late 19th century, through red pine (Pinus resinosa) stands of varying age, to 100+ year-old mixed conifer–hardwoods. Soil texture, organic matter content, bulk density, K_H, and overstory and understory forest characteristics were measured. For sites with similar soil textures, there was a general increase in K_H in the following sequence: open fields → red pine plantations → mixed conifer–hardwood stands. There were no significant changes in near-surface organic matter contents or soil bulk densities with forest age, and neither factor was related to temporal changes in K_H. Temporal trends in K_H were associated with increased understory density with forest age, suggesting that increases in K_H were driven by understory root development and greater macroporosity. It may take ~25 years before reforestation begins to affect soil infiltration characteristics at the stand scale and at least 40 years following planting before the K_H of soils under red pine plantations begins to equal that for undisturbed mixed conifer–hardwood stands. This recovery may be assisted by management activities such as thinning of red pine stands, which promotes understory development.

Copyright © 2012 John Wiley & Sons, Ltd.

Coupled hydrology and water quality models are an important tool today, used in the understanding and management of surface water and watershed areas. Such problems are generally subject to substantial uncertainty in parameters, process understanding, and data. Component models, drawing on different data, different concepts, and different structures, are affected differently by each of these uncertain elements. This paper proposes a framework wherein the response of component models to their respective uncertain elements can be quantified and assessed, using a hydrological model and water quality model as two exemplars. The resulting assessments can be used to identify model coupling strategies that permit more appropriate use and calibration of individual models, and a better overall coupled model response. One key finding was that an approximate balance of water quality and hydrological model responses can be obtained using both the QUAL2E and Mike11 water quality models. The balance point, however, does not support a particularly narrow surface response (or stringent calibration criteria) with respect to the water quality calibration data, at least in the case examined here. Additionally, it is clear from the results presented that the structural source of uncertainty is at least as significant as parameter-based uncertainties in areal models. Copyright © 2012 John Wiley & Sons, Ltd.

Native hardwood trees are frequently planted to restore forest cover to abandoned agricultural lands in the Neotropics. Few studies compare rainfall interception in such plantations and the vegetation the trees are planted to replace. We compared throughfall (TF) and stemflow (SF) in a mature stand of wild sugar cane Saccharum spontaneum L. and six tropical hardwoods growing in a restoration trial in the Republic of Panama. Interception in trees was dominated by TF, with SF accounting for less than 3% of gross rainfall (Pg). By contrast, SF was a dominant means by which rainfall reached the ground in S. spontaneum, and this dominance became greater at higher Pg. Slopes of Pg/SF regressions were considerably steeper in S. spontaneum than among tree plots. We tentatively concluded that trees intercept more rainfall than S. spontaneum. However, median total I was negative in S. spontaneum when SF was estimated using the median and the median plus maximum absolute deviation of stem densities as a multiplier. Sources of potential bias in S. spontaneum measurements include overestimation of stem density, high inter-event variability of water volumes in individual SF collectors, and contact between stems diverting SFs. To our knowledge, ours is the first study to compare I in restoration plantings of tropical hardwoods and in S. spontaneum. It is also only the second study to quantify TF and SF in a sugar cane, likely due to the methodological difficulties involved in retrieving reliable estimates of these variables in very dense grass stands. Copyright © 2012 John Wiley & Sons, Ltd.

We have conducted a field experiment to ascertain the role of ecohydrological interactions between run-off source areas and sink patches in the dynamics of artificial slopes derived from open cast coal mining in central-eastern Spain. We analysed the effects of run-off interruption on soil moisture, on the leaf water potential of woody species and on the herbaceous biomass in vegetation patches of three reclaimed slopes subjected to a different disturbance degree resulting from different overland flow volumes running down the slopes. Soil moisture and plant performance were seriously affected by run-off exclusion, and this effect was more intense as level of disturbance increased. In fact, run-off redistribution appeared to be determinant for plant performance in the more disturbed slope, whereas the presence of the shrub Genista scorpius appeared to be more determinant for plants in the less disturbed slope. Our results confirm the validity of the Trigger–Transfer–Reserve–Pulse model in artificial slopes during the aggradation process. These results point out the importance of run-off redistribution between vegetation patches in the evolution of artificial slopes by creating fertility islands that improve the performance of vegetation. Restoration practices in drylands may thus significantly improve if a ‘run-off expert management’ strategy is adopted. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we investigated the influence of contrasting riparian forest types on upland stream temperatures and the links between thermal regime and standard indices of forest cover. Stream temperature was measured for two hydrological years at multiple sites along two tributaries of the River Dee, Scotland. Riparian cover in the upper reaches of both streams was dominated by Calluna moorland while the lower sections comprised either dense alluvial broadleaved forest (Girnock Burn) or native Scots Pine stands (Tanar). The Point-Centered-Quarter Method was used to quantify stem density (SD) and tree coverage (TC) as an indicator of channel shading comprising either dense alluvial broadleaved forest (Girnock Burn) or native Scots Pine stands (Tanar). The greatest reductions in maximum temperature (4 °C) and diel amplitude (6·6°C) were observed where TC and SD were greatest in areas of relatively dense broadleaved riparian cover. Analysis of the relationship between forest characteristics and temperature summary statistics revealed that SD and TC were significant predictors of mean and maximum temperatures, as well as daily temperature ranges for both rivers during the summer. The relationship between summer thermal indices and indicators of channel shading (SD or TC) was independent of forest type. However, as SD and TC were greater in the deciduous reaches of Glen Girnock than the mature Scots pine reaches of Glen Tanar, maximum reductions in stream temperature were greater in Glen Girnock. Given that maximum temperatures were strongly influenced by measures of shading, it suggested that riparian planting may offer a suitable mitigation against high temperatures under climate change. Copyright © 2012 John Wiley & Sons, Ltd.

The disruptive potential of floods, drought, ice, and high water temperature on fishes in streams have been well documented. We examined the relationship between unexpected high flow events, low flow events coupled with low and high air temperature events, and a variety of ecological measures frequently used to quantify fish communities in streams, e.g. density. We developed a severity index to quantify concurrent extreme disturbances occurring over annual and summer periods. We anticipated that years or summers of high severity would result in changes in the fish community measures, e.g. low abundance. Despite the occurrence of severe events, there were relatively few instances of environmental severity resulting in consistent negative/positive changes in fish communities. Of the fish community measures, young-of-the-year (YOY) growth was most responsive to extremes. Low flow in combination with high temperature events significantly lowered YOY growth; whereas, unexpected high flows increased growth. Unexpected high flow events were associated with a significant negative effect on fish abundance and positive effects on biomass, YOY growth, and diversity during the summer period. The predictive power of abiotic–biotic regressions from the summer time period was generally greater than that from the annual time period. We suggest that high amounts of groundwater flow into the streams may buffer the impact of extreme environmental conditions. Our methodology of measuring extremes in flow and air temperature could be implemented over much larger scales for use in long-term monitoring impacts related to climate and land use change. Copyright © Her Majesty the Queen in Right of Canada 2012

Apart from being water limited during the dry season, some tropical dry forests are also phosphorus (P) limited. For these systems, throughfall contributes an important source of P. Leaf leaching of P would confound the quantification of external P in throughfall; and thus, it is necessary to determine the importance of leaf leaching for such systems. In this study, we used a modification of the classic methodology to determine whether P is leached from common tree species found in a tropical dry forest. Our modification of washing the leaves allowed us to also examine the amount of organic phosphorus (P_O) and inorganic phosphorus (P_I) yielded instantaneously from the leaves, representing P deposited on leaf surfaces. We compared leaves from mature and successional forests to understand how canopy structure affects deposition. Although we saw no evidence for leaching, the decline in rinsate P between sample times may suggest that microbes on the surfaces of leaves take up P dissolved in intercepted canopy water. The washing of leaves during the experiment yielded measurable quantities of P_O and P_I. The quantity of P_O or P_I yielded from the surfaces of leaves differed between species and forest types. Scaled-up estimates suggested that 0·8 g P_I ha⁻¹ per rainfall event and 2·8 g P_O ha¹ event⁻¹ were yielded from the successional forest and 4·4 and 10·7 g P_O ha¹ event¹ from the mature forest, the latter of which is very similar to measured throughfall values for this area. Copyright © 2012 John Wiley & Sons, Ltd.

Dwarf succulents persist in the arid Succulent Karoo despite the low-water storage capacities of their contracted leaves and stems that are inadequate for enduring severe and prolonged drought. We examined the contribution of non-rainfall moisture (fog, dew, water vapour) to the water budgets and relative abundance of two endemic dwarf succulents Agyroderma pearsonii and Cephalophyllum spissum. Non-rainfall moisture was measured with automated lysimeters containing bare quartz-gravel soils and introduced A. pearsonii and C. spissum individuals at hourly intervals spanning an 8-month wet winter to dry summer period. Total non-rainfall atmospheric moisture intercepted by the bare quartz-gravel substrate of 137·6 mm, of which water vapour adsorption contributed 56·2 mm, fog 78·2 mm and dew 3·4 mm, was virtually equivalent to the rainfall amount of 142·7 mm. Agyroderma pearsonii intercepted 228·4 mm of non-rainfall moisture of which water vapour adsorption contributed 117·1 mm, fog 104·4 mm and dew 6·9 mm. This was nearly three times the non-rainfall amount of 88·7 mm y⁻¹ intercepted by C. spissum, of which water vapour contributed 44·3 mm, fog 41·3 mm and dew 3·1 mm. The greater quantity of non-rainfall moisture intercepted by A. pearsonii corresponded with its threefold greater leaf abundance and twofold greater canopy cover than that of C. spissum. We conclude that non-rainfall moisture, especially the absorption of atmospheric water vapour by soils and its uptake by the extensive network of superficial roots of dwarf quartz-field succulents are vital in sustaining their growth and survival and in determining their distributions and relative abundance. Copyright © 2012 John Wiley & Sons, Ltd.

The role of turbulence in the dislodgment of benthic stream invertebrates from the riverbed was investigated experimentally in a laboratory flume. For the first time, technological advances allowed measuring the spatio-temporal patterns of turbulent flow around two free-moving invertebrates (Aeshna cyanea and Somatochlora flavomaculata). A specific methodology was developed for the analysis of turbulence around benthic invertebrates. The results confirmed two hypotheses: (i) on the contrary to sediment particles, invertebrates are not only sensitive to the peak values of the turbulent flow forcing but also to the temporal fluctuations in this flow forcing; and (ii) the dominant temporal fluctuations are not due to local turbulent structures of the size of the invertebrate, but to turbulent structures that scale with the flow depth and are inherited from upstream. In 15 of the 17 conducted tests, important turbulent events that scale with the flow depth accompanied by rapid temporal flow fluctuations occurred at the moment of dislodgement. The dominant forcing was consistently a threefold increase in shear stress, and was related to a sweep event in 12 of the 17 tests. Thereby, the increase in longitudinal velocity was typically about 40%, which led to a 100% increase in drag force in comparison with the time-averaged drag force. These results enable a new understanding of the detailed hydraulic conditions leading to passive drift of stream invertebrates. In addition, they open new perspectives to improve models predicting the distribution of benthic invertebrates based on hydrodynamics by accounting for turbulence. Copyright © 2012 John Wiley & Sons, Ltd.

This study presents the first application of fibre-optic distributed temperature sensing (FO-DTS) for analysing the impact of spatially heterogeneous vegetation patterns on the thermal conditions of an ecosystem. It analyses the spatial patterns and temporal dynamics of canopy and ground temperatures at unprecedented spatial and temporal resolution to showcase the potential as well as limitations of the FO-DTS technology for ecohydrological applications. By using the partial rhododendron coverage of a deciduous UK woodland as a model system, FO-DTS surveys were carried out to demonstrate the detection of different dynamic thermal patterns in the presence/absence of rhododendron (Rhododendron ponticum L).

The high-resolution temperature measurements of this study provide strong evidence for the moderating impact of rhododendron coverage on air, ground and soil temperatures in forest ecosystems, which has important implications for ecological and biogeochemical process dynamics.

The results successfully demonstrate the significant potential of FO-DTS for high-resolution, spatially detailed, transient temperature monitoring in forest environments. The survey performance and its very efficient signal-to-noise ratio proves the capability of FO-DTS networks to provide highly accurate information on temporal dynamics in spatial temperature patterns with great prospect for substantially improving spatial coverage and sensitivity of temperature observations in a range of ecological applications. Copyright © 2012 John Wiley & Sons, Ltd.

One of the biggest challenges in predicting ecohydrologic fluxes is scaling from easily measured variables to more difficult, often emergent patterns and processes. This is especially true in spatially heterogeneous systems such as black spruce (Picea mariana)-dominated boreal forests containing excessive and low soil moisture conditions. Traditional hypotheses suggest that transpiration is controlled by hydraulic responses to vapor pressure deficit (D) and soil moisture; however, these may potentially be misinformed because of omission of soil drainage gradients. Thus, we predict that 1) spatial heterogeneity in tree transpiration along a soil drainage gradient is positively correlated with D, 2) sap flux (J_S) and leaf-level transpiration (E_L) are higher and whole-tree transpiration (E_C) lower in the poorly drained than well-drained stands, and 3) spatial heterogeneity of E_C is regulated primarily by tree-related covariates such as sapwood and leaf area and secondarily by environmental covariates including peat and moss depth. With the use of 122 black spruce sap flux measurements, the range of autocorrelation (inverse of spatial variation) decreased from 20 m at low D (<0.7 kPa) to 2 m at midday D values (>0.9 kPa). J_S and E_L were significantly greater and E_C less in poorly drained than well-drained stands; controlled primarily by tree-related covariates (sapwood and leaf area) representing long-term growth conditions and secondarily by soil moisture and spatially sampled D reflecting shorter-term environmental variation. Quantification of spatial heterogeneity informs predictive models of the distance at which homogeneity can no longer be assumed and will improve mechanistic predictions of transpiration at multiple spatial scales. Copyright © 2012 John Wiley & Sons, Ltd.

In a semiarid sedimentary catchment of central Argentina, we describe a recent process of landscape dissection, abrupt canyon and watercourse formation and soil salinization. We link these adverse hydrological and geomorphological transformations to three potentially important drivers: precipitation increase, seismic activity and deforestation. Remote sensing imagery in the last 48 years showed an exponential increase in the length of streams, with drainage density values tripling to reach 0.22 km km². During the same period, forest area declined from 47% to 10%, at the expense of agriculture expansion. A 3.4-fold expansion of surface water bodies and water table level raise of 0.15 m y⁻¹ over the last 35 years was observed. Discharge of a new stream at the middle of the basin ranged between 0.25 and 0.45 m³ s⁻¹ accompanied by a large and stable load of salts (~0.7 g l⁻¹). Nil recharge and large vadose accumulation of salts in dry forests stands contrasted with recharge rates of ~16 mm y⁻¹ and salt-leached profiles under agriculture. Although the process of landscape dissection occurred during decades of higher than average precipitation, extreme rainfall events and seismic activity were not exceptional in that period. Results suggest that the replacement of forests by annual crops played a more important role, reducing evapotranspiration, triggering the onset of groundwater recharge and favouring subsurface through piping/sapping processes. The abrupt landscape dissection shows no signs of stabilization at the present and may only be ameliorated through changes in vegetation that restore the original non-flow condition of the forest. Copyright © 2012 John Wiley & Sons, Ltd.

The long-term tower-based eddy covariance measurements of CO₂/H₂O fluxes are carried out in a temperate mature forest in Northeast China. The current study investigates the atmospheric (net radiation and vapour pressure deficit) and vegetation (surface conductance) controls of the evapotranspiration (ET) within the two observational years with different water conditions. The results show that the ET during the short dry season of 2004 was higher than that during the wet season of 2005. The ET is mainly driven by the meteorological factor of vapour pressure deficit. The mixed forest did not show clear signs of ET suppression during the summer drought because of its slightly reduced surface conductance, whereas its water demands from the atmosphere significantly increased. Thus, the annual ET slightly varied (416·2 to 462·1 mm) despite the large interannual variation in precipitation (488·7 to 761·6 mm). The 0–100 cm deep soil water storages are important sources of water supply for ET during dry seasons. The findings of this study suggest that the possible reduction in precipitation under future climate change scenarios with invariable or even enhanced ET will decrease the replenishment of groundwater and outflow and, consequently, the downstream water supply. Copyright © 2012 John Wiley & Sons, Ltd.

The quality of ecotope maps of five districts of main water courses in the Netherlands was assessed on the basis of independent validation samples of field observations. The overall proportion of area correctly classified, and user's and producer's accuracy for each map unit were estimated. In four districts, the validation samples were selected purposively in the past. For the fifth district, a stratified two-stage probability sample was designed, such that the spatial pattern resembles that of the purposive samples. For the purposively sampled districts, measures of map quality were estimated following a model-based approach, using a model for the spatial variation of classification errors. For the randomly sampled district, measures of map quality were obtained following a design-based approach, using the inclusion probabilities of the sampling points. The overall proportions of area correctly classified vary from 61% to 76%. Both user's and producer's accuracies show large variation among the map units. Model-based predictions of producer's accuracies from two models differed strongly, indicating that with the model-based approach the validation results strongly depend on model assumptions. We demonstrate that stratified two-stage random sampling answers to the same practical and budgetary constraints as purposive sampling. Stratified two-stage sampling combined with a design-based estimation method results in model-free estimates of the overall proportion of area correctly classified, user's and producer's accuracies. This means that the inferential validity of the estimated overall proportion of area correctly classified and user's and producer's accuracies is rigorously established if a design-based approach is followed. Copyright © 2012 John Wiley & Sons, Ltd.

Fish Index of Biotic Integrity (IBI), macroinvertebrate North Carolina Biotic Integrity Index (NCBI) data, and Tennessee Macroinvertebrate Index (TMI) data were collected in 2009 and 2010 along with the hydrology to determine if a golf course water withdrawal was degrading the stream's aquatic life. Campostoma anomalum dominated the stream, and there were low numbers of Ephemeroptera–Plecoptera–Trichoptera (EPT) taxa. Richland Creek is a 28-square-mile watershed located in a highly urbanized area. The golf course withdraws a daily average of 400 000 (1514 cubic metre) gallons of water over a 60 to 155 day period. McCabe Golf Course withdraws >10% of the flow in the low-flow months of June through October. Fish IBI scores were poor throughout Richland Creek with the upstream IBI being higher than downstream of the withdrawal. TMI scores were moderately impaired upstream and downstream of the golf course withdrawal, with the TMI being marginally better upstream of the withdrawal than downstream. The natural flow regime (Annear et al., 2004) is not maintained in Richland Creek because of the urban nature of the stream and the increased stormwater runoff into the stream. Tennessee Wildlife Resources Agency's instream flow policy statement states that flow should not be <20% above the September median flow, which is 12 cfs (0·39 cms). The hydrology of the stream is altered by one major water withdrawal with its associated low-head dam as well as urbanization, which affects the fish and macroinvertebrate diversity. Copyright © 2012 John Wiley & Sons, Ltd.

This study measured water-use efficiency of wildland vegetation at the whole-plant level during two contrasting years to better understand ecosystem responses to precipitation fluctuations in the Great Basin, USA. Biome-representative species included grasses (Distichlis spicata, Leymus triticoides, and Sporobolus airoides), desert shrubs (Artemisia tridentata, Atriplex confertifolia, and Ericameria nauseosa), wetland/riparian plants (Glycyrrhiza lepidota, Juncus arcticus, and Salix exigua), and an exotic annual (Salsola tragus). Plants were grown in 5·8 m² plots in a common garden in eastern California. Four watering treatments were applied monthly during two summers: control (no water other than natural precipitation), low (1·3 cm), medium (2·6 cm), and high (3·9 cm). Water-use efficiency, here termed water to production (WTP_a), was the ratio of water transpired to aboveground biomass produced. Biomass production was 50% lower and WTP_a was five times higher during 2009 than 2010. WTP_a decreased with watering during 2009 but increased with watering during 2010. Year differences determined vegetation productivity and response to summer watering and were related to the lower winter/spring precipitation during 2009 than 2010. Desert shrubs were more drought tolerant than grasses and wetland plants. Yet, an increase in summer precipitation would primarily benefit herbaceous species and not desert shrubs. Desert shrubs achieved greater standing crop but lower root-to-shoot ratio (RSR) than herbaceous species. Nonetheless, the grass S. airoides had the greatest standing crop overall, mainly because of its greater root production (RSR 5·5). Species differences in growth, WTP_a, and biomass allocation should be considered in land management and conservation practices. Copyright © 2012 John Wiley & Sons, Ltd.

Knowledge of soil moisture dynamics at reasonable temporal and spatial resolutions is required to improve hydrological understanding and modelling. However, in the Mediterranean area, considered as one of the most vulnerable areas to global change, there is a severe lack of detailed soil moisture data sets. The objective of this study is to investigate the inter-annual and intra-annual spatial and temporal distributions of soil moisture in a Mediterranean mountain area, using the detailed hydrological data set gathered in the Vallcebre Research catchments (NE Spain). With the use of time-domain reflectometry, soil moisture was measured weekly between 1998 and 2003 at eight representative profiles. Time series of soil moisture showed a clear seasonal pattern. Results obtained revealed that soil moisture on hillslopes under forest cover was lower than in downslope areas covered with grasses. However, differences were not persistent through the year but were minimal during the driest and wettest conditions and maximal during the drying and wetting-up periods. During the wetting-up and drying-down periods, the soil moisture distribution depended mainly on local controls. However, during wet conditions, soil moisture patterns were controlled by nonlocal factors that limited the vegetation-related variability of soil moisture. In this mountain area, forest cover is likely to increase as the climate changes, which will most probably reduce the average soil moisture at the catchment scale as well as its spatial variability. These changes may ultimately be seen as a threat to the future of water resources in this area. Copyright © 2012 John Wiley & Sons, Ltd.

Microcrustacean emergence from the dry sediments is an important colonization pathway that allows these microfauna to recover and repopulate temporary aquatic habitats after months or years of dryness. Viable microcrustacean propagules in sediments of three different temporary aquatic habitats – rainpools located within the rarely flooded portions, frequently flooded floodplains and rarely flooded floodplains – were assessed experimentally by flooding the soils. Three major groups of microcrustaceans – cladocerans, copepods and ostracods – emerged from the sediments. Species richness and mean total numbers of emerged microcrustaceans per sample varied across the studied temporary aquatic habitats (Kruskal–Wallis, p < 0.05). Both species richness and mean total number of emerged microcrustacean per sample were lowest in sediments of rarely flooded floodplains. The highest species richness of microcrustaceans emerged from the treatments with soils of the frequently flooded floodplains. The mean total number of emerged microcrustaceans per sample was highest from sediments of rainpools followed by frequently flooded floodplains. Findings of this experiment suggest that high flooding frequency of temporary aquatic habitats may be important to sustain high viability of microcrustacean propagules in the sediments. Reduction of regular inundation of temporary floodplains due to the threats of increasing human water abstractions and climate change may have some negative effects on the microcrustaceans of the Okavango Delta by reducing the viable propagules within these systems. The findings of this experimental study will be relevant towards efforts that are aimed at reconciling anthropogenic pressures and conservation of microcrustaceans in the Okavango Delta. Copyright © 2012 John Wiley & Sons, Ltd.

We investigated the intra-annual variability and environmental controls over transpiration (E) in a planted, even-aged (58 years; 537 trees ha⁻¹), experimental forest of invasive native Juniperus virginiana in the Nebraska Sandhills, with three canopy classes (dominant, co-dominant, and suppressed) by using sap flux techniques, in a year where drought was absent (2008, 34% above average precipitation). Daily E was closely linked to growing-season length and variability in the environment. Minimum and average daily air temperatures, photosynthetically active radiation, and precipitation explained the majority of the intra-annual daily variability in E. Vapour pressure deficit was a significant factor in spring and summer, shallow volumetric soil water content (VSWC 0·2 m) was important during summer particularly June, and deep VSWC (0·6 m) was a significant factor in January and August. E was highest in the dominant trees and contributed to the majority (~77%) of stand transpiration (E_c) on site because of their larger canopy size, greater tree density, more leaf area, and accessibility to water resources compared with the co-dominant and suppressed tree canopies, which contributed to 16% and 7%, respectively. E_c averaged ~413 mm year⁻¹, corresponding to ~24% of potential evapotranspiration. Soils were significantly drier in the J. virginiana stand than in adjacent C₄-dominated grasslands, which could be due to the longer growing season over which physiological activity extends in J. virginiana compared with C₄-dominated grasslands in the region and precipitation interception by the canopy and forest floor, which evaporates before reaching the soil. Copyright © 2012 John Wiley & Sons, Ltd.

Fragmentation of freshwater systems is one of the more common human-induced impacts on the environment, and one of the most dramatic because it leads to disconnections among riverine habitats, severely affecting fish populations. To counter this form of ecological abuse, there has been a significant increase of the number of restoration actions. This work approached stream restoration from a holistic point of view, combining habitat modelling with laboratory experimental research. A 2D hydrodynamic model was used to test the increase in weighted usable area (WUA) created by different boulder placement (BP) scenarios in a disturbed site, with a widespread potamodromous cyprinid fish – the Iberian barbel (Luciobarbus bocagei) – as the target species. This was complemented by experimental trials in a full-scale experimental fishway with different bottom substrata arrangements, in order to assess the effects of boulders on barbel movements. Results show that instream BP increases WUA for barbel and facilitates fishway negotiation. The findings reflect the importance of placing instream boulders in fragmented systems in order to enhance suitable habitat area and river connectivity. However, BP must be specifically designed for each case and should always be preceded by a comprehensive study for each site and target fish species. Copyright © 2012 John Wiley & Sons, Ltd.

Mediterranean regions are characterized by a large intra-annual and inter-annual variability in rainfall and associated hydrological regime patterns. Predictions of changes in climate indicate that mean precipitation and annual temperature will both increase, with a concentration of precipitation and the existence of extended and harsher drought periods with profound implications for river ecosystems. Our aim in this study was to predict the response of Mediterranean riparian vegetation to different climate change scenarios, using a dynamic riparian vegetation model that relates flow regime with riparian vegetation dynamics. In our case study, mapped riparian patches were significantly distinct in between, and altitude, height above water table, patch age and stem diameter were the most important of the factors that distinguished succession phases. A floodplain vegetation model was calibrated and achieved a good strength of agreement between simulated and observed maps. Model results with the expected flow regime under the effect of climate change demonstrate that nonwoody sparsely vegetated areas expand outwards and mature succession patches expand inwards, whereas pioneer and young riparian patches decrease in area. Our results suggest that extreme climatic change in Mediterranean rivers will promote the disappearance of the pioneer and young succession stages of riparian woodlands, thus making efforts to conserve these ecosystems a challenging task. Copyright © 2012 John Wiley & Sons, Ltd.

Vegetation pattern and landscape structure intersect to exert strong control over ecohydrological dynamics at the watershed scale. The hydrologic implications of vegetation disturbance (e.g. fire, disease) depend on the spatial pattern and form of environmental change. Here, we investigate this intersection at Tenderfoot Creek Experimental Forest (TCEF), Montana, with a focus on the mountain pine beetle (Dendroctonus ponderosae) epidemic currently affecting the Rocky Mountains. We calibrated QuickBird remote sensing imagery with a leaf-level spectral library of local vegetation. We used this spectral library to determine diagnostic vegetation indices for differentiating stages of beetle infestation within the 37 km² TCEF watershed. These indices formed the basis of a three-component mixing model to establish the extent and magnitude of beetle infestation across the TCEF watershed. We compared disturbance patterns with spatially distributed topography and vegetation variables derived from a light detection and ranging-based digital elevation model of TCEF. We determined that certain landscape characteristics (low vegetation density, south-facing slopes, steep slopes, locations with small contributing areas and locations with lower values of the topographic wetness index) were significantly more likely to exhibit the effects of beetle infestation. Our efforts to monitor vegetation mortality across space and time provide a context for assessing landscape susceptibility to initial mountain pine beetle infestation and how outbreak (i.e. landscape scale infestation) patterns may affect watershed ecohydrology via altered water and biogeochemical cycles. Copyright © 2012 John Wiley & Sons, Ltd.

In drylands across the globe, grasslands and savannas have succumbed to encroachment by woody plants. There is a concern that, in some cases, these changes may lead to lower groundwater recharge and streamflow. In karst landscapes, the effect of woody plants on recharge is difficult to determine because of the shallow and rocky soils. In our study, we estimated the amount of water entering a shallow cave (3–5 m deep) as a surrogate measurement for groundwater recharge, to evaluate whether the removal of Ashe juniper (Juniperus ashei) above the cave would affect recharge. Three sets of large-scale rainfall simulations were conducted in 2005, before removal of the overstory juniper; seven were conducted in 2008, soon after the juniper were removed; and two were conducted in 2009, one year after juniper removal. We found that recharge occurred mainly via conduits or macropores and, as such, was extremely dynamic and responsive to rainfall. The amount of recharge ranged from 3% to 17% of the water applied, the higher percentages being measured when antecedent soil conditions were wet. At least in this case of recharge taking place via conduit flow, removal of the juniper had little if any effect. Copyright © 2012 John Wiley & Sons, Ltd.

Since the late 1990s, drought-driven dieback has affected more than a million hectares of pinyon pine-juniper woodlands in the southwestern USA. Analysis of annual aerial surveys by the US Forest Service and soil survey data shows that most of the mortality occurred between 2003 and 2004 and that 70% was restricted to soils mapped as having available water storage capacities (A_c) <100 mm. We conducted a more refined analysis and found that as A_c increased in increments of 50 mm up to 300 mm, the distribution of areas with observed mortality decreased exponentially from 42% to 3% (n = 6 classes, r² = 0.93). We used this information in a process-based stand growth model, physiological principles predicting growth, to assess year to year variation in gross photosynthesis between 1985 and 2005 with climatic data at monthly intervals from four weather stations where pinyon-juniper woodlands were confirmed by satellite imagery. A sensitivity analysis identified sustained periods of drought and supported field observations that once canopy leaf area approaches a maximum value, the majority of mortality should be restricted to soils with A_c values <100 mm. Additional analyses indicated that differences in soil texture played a small part (<10%) in the variation of gross photosynthesis and that consecutive years of drought may have a cumulative effect on pinyon pine vulnerability to bark beetle attack. Disturbances reducing canopy leaf area index should result in less pine mortality in the future, although conversion to shrub and grassland may occur if climate conditions continue to become less favorable. Copyright © 2012 John Wiley & Sons, Ltd.

Biological soil crusts are a key component of many dryland ecosystems. Following disturbance, biological soil crusts will recover in stages. Recently, a simple classification of these stages has been developed, largely on the basis of external features of the crusts, which reflects their level of development (LOD). The classification system has six LOD classes, from low (1) to high (6). To determine whether the LOD of a crust is related to its ecohydrological function, we used rainfall simulation to evaluate differences in infiltration, runoff, and erosion among crusts in the various LODs, across a range of soil depths and with different wetting pre-treatments. We found large differences between the lowest and highest LODs, with runoff and erosion being greatest from the lowest LOD. Under dry antecedent conditions, about 50% of the water applied ran off the lowest LOD plots, whereas less than 10% ran off the plots of the two highest LODs. Similarly, sediment loss was 400 g m⁻² from the lowest LOD and almost zero from the higher LODs. We scaled up the results from these simulations using the Rangeland Hydrology and Erosion Model. Modelling results indicate that erosion increases dramatically as slope length and gradient increase, especially beyond the threshold values of 10 m for slope length and 10% for slope gradient. Our findings confirm that the LOD classification is a quick, easy, nondestructive, and accurate index of hydrological condition and should be incorporated in field and modelling assessments of ecosystem health. Published in 2012. This article is a U.S. Government work and is in the public domain in the USA.

Surface water resources are important components of savanna landscapes, supplying large populations of wildlife with drinking water critical for thermoregulation and digestion. However, little is known about the behavioural or physiological influence of water quality on wildlife health. East African savannas are well known for their migrating populations of ungulates coinciding with seasonal and spatial patterns of forage. In the Serengeti ecosystem, seasonal rainfall, high wildlife abundance and spatially variable soil composition result in temporal and spatial differences in surface water quality. Furthermore, nutrient enrichment from dissolved minerals and animal waste transported in runoff drive bacterial and algal blooms. Previous studies have suggested that water quality may be a factor in the migratory behaviour of wildebeest as poor quality water can have significant health consequences for ungulates, including depressed milk production and reduced food conversion. This paper examines the hypothesis that water quality in the southern Serengeti plains exceeds expected maximum tolerance limits at the end of the wet season – when migratory wildlife move northward, away from this region. Data collected during the migration's movement over 3 years are examined to determine if regional differences in water quality are physiologically meaningful and how the consumption of poor quality water may influence wildebeest nutrient intake. With increased demand for surface water resources from human populations, growing climatic uncertainty and significant changes in land cover outside of protected areas, the influence of water quality on animal behaviour needs to be considered for future management strategies. Copyright © 2012 John Wiley & Sons, Ltd.

Growth responses of riparian trees to changes in water availability are poorly understood, thereby limiting understanding of regional drought implications in river corridors. We used dendrochronological methods to develop growth series and analysed oxygen isotopic ratios (δ¹⁸O) in α-cellulose from individual tree rings for two co-occurring riparian species, Fraxinus excelsior and Populus nigra. Trees were sampled along the Ain River (France) to assess growth and annual source water availability, inferred from tree-ring δ¹⁸O, compared with variations in streamflow and precipitation. Both species exhibited decreased growth during drought years, but F. excelsior demonstrated less variation in annual growth across sites compared with P. nigra. The latter species expressed a smaller range of δ¹⁸O among individuals and years, but greater δ¹⁸O sensitivity to river discharge, indicating a more consistent hyporheic water source. P. nigra also suffered more growth inhibition than F. excelsior in dry years when water tables were suppressed. These differences suggest contrasting patterns of water use, wherein F. excelsior uses primarily water from the vadose zone to maintain moderate growth rates, and P. nigra demonstrates more consistent phreatic water usage and suffers in drought years when water tables are suppressed. These observations are consistent with data on floodplain rooting depths, which show that F. excelsior maintains its roots above the gravel layer, whereas P. nigra generally roots deeply into phreatic zone gravels. These results indicate that surprisingly, poplars may be more sensitive to drought than ash trees and may be vulnerable to climate changes affecting water availability in riparian corridors. Copyright © 2012 John Wiley & Sons, Ltd.

The four main Chinese carps, collectively abbreviated as MCHA, include the black carp (Mylopharyngodon piceus), grass carp (Ctenop haryngodon idellus), silver carp (Hypoph thal michthys molitrix), and the big-head carp (Aristichyths nobilis). MCHA constitutes a significant catch of China's fresh water fishery. The construction of the Gezhouba and Three Gorges Dams greatly affects the physical habitat conditions of these four main carp species. This paper presents a time-series model for the assessment of instantaneous physical conditions in MCHA habitats. The model incorporates the effects of various hydrological variables (e.g. water level fluctuation, water temperature and sediment concentration) on MCHA habitat quality. The model is tested for the Yichang-Zhijiang reaches of the Yangtze River – a suitable region for analysing the effects of dam construction on the physical conditions of MCHA habitat. The model analyses instream ecological flow (IEF) characteristics of the study area in the spawning season of MCHA. On the basis of the analysis, the min, max and optimal IEFs are 6200, 51000 and 14 500 m³/s, respectively. The model introduces an efficient method for calculating the instantaneous habitat area on the basis of IEF and other physical conditions. If properly applied, the model is an efficient tool for assessing the effects of variations in flow conditions on MCHA habitat quality. The model could also be used in real time to analyse the combined effect of ecological regulations (e.g. as induced by the Three Gorges and Gezhouba Dams) on MCHA spawning conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Canopy storage capacity is influenced by several variables, including canopy surface area, canopy architecture, and wind. Different species with the same canopy area, but with differences in leaf hydrophobicity and water droplet retention, may produce different values of canopy storage capacity. The objective of this study was to investigate if leaf hydrophobicity and water droplet retention are additional influences on canopy storage capacity. Specifically, this study tested the hypothesis that species with the highest leaf hydrophobicity and the lowest water droplet retention had the lowest canopy storage capacity on a per leaf area basis. Seven tree species from Colorado, United States were selected for experimentation. Five branches from each species were lopped, positioned under a rainfall simulator, and connected to a balance to record the mass gain of the branches by rainfall interception during 17 min of rainfall simulation. Each branch was destructively sampled following rainfall simulation to calculate the leaf and woody surface areas. The rank order of leaf surface storages at canopy storage capacity for each species corresponded to the rank order of leaf hydrophobicity and water droplet retention for each species. Species with the highest leaf surface storage had the lowest leaf hydrophobicity and the lowest water droplet retention. The significance of leaf hydrophobicity and water droplet retention as variables that influence canopy storage capacity is a largely unexplored topic in ecohydrology. Copyright © 2012 John Wiley & Sons, Ltd.

Sudden instream releases of hypolimnetic water from hydropower plants [i.e. hydropeaking (HP)] can cause abrupt temperature variations [i.e. thermopeaking (TP)], typically on a daily basis. The propagation of discharge and thermal waves is asynchronous, causing the benthic community to undergo two different but consecutive impacts. Invertebrates respond to sudden increases in discharge with catastrophic drift, and respond to sudden changes of temperature with behavioural drift. Owing to the time lag separating discharge and thermal wave peaks, catastrophic and behavioural drift can occur as distinct events. We conducted simulations in a set of open air flumes directly fed by an Alpine stream, and analysed drift induction in benthic invertebrates caused by a HP wave followed by a cold TP wave, and compared it with drift induced only by a cold TP wave. Drift propensity increased during HP and TP simulations, with a synergic effect: drift was higher when the TP wave followed the HP one. We also recorded a selective effect: some taxa did not respond to the alterations, some taxa responded to the discharge variations and to the thermal variations, or to the thermal variations alone. The most abundant taxa in benthos were Chironomidae and Baetidae, followed by Simuliidae. Simuliidae and Chironomidae were the most abundant drifting taxa. Copyright © 2012 John Wiley & Sons, Ltd.

Seasonal availability of water is a key controlling factor in semi-arid savanna vegetation structure, function and interactions. Understanding of woody plant interactions with grasses in savannas has long been underpinned by Walter's two-layered niche differentiation hypothesis that postulates that grasses and trees source water from different depths. The Walter hypothesis persists in the literature, despite contrary evidence and a lack of quantitative empirical tests of the theory. We conducted a greenhouse experiment to determine the following: (1) whether tree seedlings and grasses obtain water from different depths on rocky and sandy soils; (2) whether interspecific competition affected tissue water content of clipped grasses; and (3) the influence of repeated grass clipping on soil moisture. Grass competition significantly reduced tree seedling rooting depth on both rocky and sandy substrates. Trees had significantly longer roots on rocky substrates than on sandy substrates for all combinations (trees only, trees with unclipped grasses and trees with clipped grasses). Results indicated a three-tier soil moisture depletion pattern, with a top layer (15 cm) exclusively exploited by grasses, an intermediate zone (25–35 cm) utilised by both grass and tree seedling roots and deeper subsoil exclusively tapped by tree seedling roots. Our results are consistent with Walter's hypothesis, but we distinguished between three rather than two layers of tree and grass root interactions in acquiring soil moisture. Copyright © 2012 John Wiley & Sons, Ltd.

The investigation of flow–ecology relationships constitutes the basis for the development of environmental flow criteria. The need to understand hydrology–ecology linkages in natural systems has increased owing to the prospect of climate change and flow regime management, especially in water-scarce areas such as Mediterranean basins. Our research quantified the macroinvertebrate community response at family, genus and species level to natural flow regime dynamics in freshwater streams of a Mediterranean semiarid basin (Segura River, SE Spain) and identified the flow components that influence the composition and richness of biotic assemblages. Flow stability and minimum flows were the principal hydrological drivers of macroinvertebrate assemblages, whereas the magnitude of average and maximum flows had a limited effect. Perennial stable streams were characterized by flow sensitive lotic taxa (Ephemeroptera, Plecoptera and Trichoptera) and intermittent streams by predominately lentic taxa (Odonata, Coleoptera, Heteroptera and Diptera). Relatively minor biological changes were recorded for intermediate flow regime classes along a gradient of flow stability. Seasonal variation and minimum flows are key hydrological components that need to be considered for river management and environmental flows in the Segura River basin and other Mediterranean basins. The anthropogenic modification of these parameters, due to both human activities and climate change, would probably lead to significant changes in the structure and composition of communities in perennial stable streams. This would be characterized by a reduction of flow sensitive Ephemeroptera, Plecoptera and Trichoptera taxa and an increase in more resilient Odonata, Coleoptera, Heteroptera and Diptera taxa. Copyright © 2012 John Wiley & Sons, Ltd.

Small glaciers are more sensitive to climate change and can drive remarkable runoff variation in local catchments. Here, the recent shrinkage and hydrological response of Urumqi Glacier No.1, a typical continental glacier, situated in the arid region of northwest China, were investigated using glacier data, hydrological and meteorological data collected near the glacier during the past 50 years. The results showed that annual air temperature and precipitation increased by 0·9 °C and 91 mm (17.5%), respectively. Glacier length shortened by about 215·2 m (9·7%) and its area diminished by 0·304 km² (15·6%). The cumulative mass balance of the glacier was −13 693 mm, equivalent to 15·2 m of glacier ice. Annual glacier runoff calculated by using a water balance model and the runoff measured at the outflow gauging station increased remarkably. The percentage of the increased river flow being derived from the increased glacier runoff reached 69·7% especially after 1994. Temperature and precipitation during the ablation season were the governing factors affecting the runoff at the glacierized (Glacier No.1) and non-glacierized (Empty Cirque) catchments, respectively. Temperature rise and precipitation increase between 1959 and 2008 have had a combined effect on glacier mass loss and runoff change. Copyright © 2012 John Wiley & Sons, Ltd.

Vegetation dynamics are very sensitive to climate change, especially in arid and semiarid regions. The Tarim River Basin, the largest and the most arid basin in northwest China, is a typically closed, independent, and self-balanced hydrological system. In this study, the Mann–Kendall trend test, partial correlation analysis, and gray relation analysis were used to investigate the vegetation dynamics and their response to hydroclimatic change in the Tarim River Basin from 1982 to 2006. The results indicated that vegetation vigour and coverage in the majority of the study area improved over the study period. However, vulnerable ecological regions including the margin of oases, the southeast of the Kunlun Mountains, and riparian zones were stressed by water shortage. Vegetation in these vulnerable zones tended to experience a decreasing trend, and water diversion was necessary to protect the important vulnerable ecological regions. The results of partial correlation analysis in space indicated that vegetation variation had a significantly positive correlation with mean annual temperature overall and a significantly positive correlation with local precipitation in most of the mountain regions. The results of gray relation analysis demonstrated that temperature was the main stress factor for mountain vegetation and runoff for oasis vegetation. Under the direct and indirect effects of temperature rise over the study period, vegetation vigour and coverage area have been improved because of more favourable hydroclimatic conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Vegetation is sensitive to changes in the ecological environment in arid and semiarid regions, so information on the dynamics of vegetation cover changes can provide important information for ecological environmental protection and early warning of ecosystem degradation. With the SPOT/VEGETATION normalised difference vegetation index dataset of the typical semiarid land in Inner Mongolia (IM) during 1998–2008, this study applied an integrated statistical method combing asymmetric Gaussian filtering, seasonal Kendall test, R/S analysis, correlation analysis and regression analysis, to investigate the impact of climatic factors on trends in vegetation cover. The main findings are as follows: (1) Over the 1998–2008 period, the vegetation coverage is relatively stable in IM, with only 24.5% of the total area exhibiting a significant variation in cover. The spatial distribution of the vegetation cover change has the following regional characteristics: in the northeast forest region, the vegetation cover is stable; in the middle steppe region, significant changes are observed and in the southwest desert region, the vegetation exhibits significant degradation. (2) Normalised difference vegetation index time series in most regions of IM reveal a vegetation change trend. In the high vegetation covered regions, the change trend will be reversed, whereas in the low vegetation covered regions, the original change trend will be preserved. (3) Analysis of correlation coefficients and stepwise linear regression reveals relationships between vegetation change and climatic factors. Temperature and precipitation have a direct influence on vegetation change, acting as the main climatic driving forces for the regional vegetation evolution. Copyright © 2012 John Wiley & Sons, Ltd.

Relationships between water depths and density of submergent vegetation were studied in montane wetlands using statistical techniques based on clustering and an extension of regression trees. Sago pondweed (Stuckenia pectinata) was associated with lower average water depths than water milfoil (Myriophyllum sibiricum). We detected a nonlinear relationship when average water depths were used to predict percent cover in S. pectinata, with depths of 30–40 cm, producing the highest predicted average percent cover of S. pectinata; higher and lower depths resulted in lower percent cover predictions. For M. sibiricum, higher water depths were monotonically associated with higher average percent cover. To foster more S. pectinata and less M. sibiricum, managers might employ water control structures to reduce water depths below 1 m, using both temporary drawdowns and average depths of 30–40 cm. Other species responded less markedly to water depth variation. Should decreased water depths become more common, these results suggest an increase in S. pectinata and a decrease in M. sibiricum. Published in 2012. This article is a US Government work and is in the public domain in the USA.

In this study, we have analysed the series of daily air temperatures from 1977 to 2009 measured in a sedge-grass marsh ecosystem near the town of Třeboň, Czech Republic (Central Europe). Annual averages of daily mean, minimum and maximum temperatures were analysed. Possible significant increases were recorded for all these values during the study period. The annual average of daily maximum temperatures increased on average by 0.0827 °C per year. The annual average of daily mean air temperatures increased by 0.0544 °C per year. The rise of the annual average of daily minimum air temperature was the lowest, namely by 0.0374 °C per year. The air temperature rise was not the same in all periods of the year, and different increases were found in individual months. The daily mean air temperature rose significantly in the growing season (April–August). In all the other months except December, a statistically non-significant rise of daily mean air temperatures was recorded. From the ecological point of view, the different monthly increases are more important for the wetland ecosystem than the slow gradual rise of air temperature over the years. The air temperature rise recorded in the wetland studied was lower than that predicted by climatic models. Copyright © 2012 John Wiley & Sons, Ltd.

The study of the patterns of plant species diversity and the factors influencing these patterns is the basis of ecology and is also fundamental to conservation biology. Groundwater-dependent vegetation (GDV) must have access to groundwater to maintain their growth and function, and this is especially common in arid and semi-arid regions, including north-western China. In this paper, plant species diversity and groundwater attributes (composition and depth) were investigated in 31 plots in the Ejina Delta in north-western China to determine whether groundwater attributes influenced patterns species diversity in GDV. Detrended canonical correspondence analyses and generalised additive models were performed to analyse the data. A total of 29 plant species were recorded in the 31 plots; perennial herbs with deep roots had an advantage over all other groups, and GDV species diversity was primarily affected by groundwater depth (GWD), salinity (SAL) and total dissolved solids (TDS), HCO₃⁻, Ca²⁺, pH, and SO₄²⁻. The herb layer species diversity and total species diversity reached their maximum in similar, moderate environmental conditions. The diversity of the tree species was influenced by SAL and TDS and was maximal at large values of GWD and low values of SAL and TDS. The diversity of shrub species was affected by Ca²⁺ and Mg²⁺ and was maximal low GWD and high SAL and TDS. Patrick's and Shannon–Wiener's index of the total community diversity presented a bimodal pattern along gradients of GWD and SAL, whilst Simpson's and Pielou's index showed a partially unimodal pattern. On the basis of field investigation and the analysis of field data, we concluded that the perfect combination of GWD and SAL for GDV species diversity is 2 m and 1·8 g l⁻¹, respectively. The appropriate combination range is 2–5 m and 1·8–4·2 g l⁻¹, and the critical combination for the damaged GDV species diversity is 5 m and 4·2 g l⁻¹. Copyright © 2012 John Wiley & Sons, Ltd.

Forecast changes in irrigation practices and climate are likely to result in changes to surface and ground water availability for floodplain woodland remnants; however, the potential effects of such changes are poorly understood, with implications for management of woodland remnants for long-term biodiversity persistence. This paper examines Eucalyptus largiflorens floodplain woodland structure and condition in two contrasting regions within the same catchment. It assesses the effects of varying levels of irrigation land use intensity surrounding woodland sites and of flood history within sites, testing the following propositions: (i) floodplain woodlands with greater intensity of surrounding irrigation land use will be in worse condition and have less structural complexity than other floodplain woodlands; (ii) floodplain woodlands with flood histories closer to ‘natural’ regimes will be in better condition and will have greater structural complexity than other floodplain woodlands. This paper demonstrates that where groundwater tables have fallen, rainfall is in deficit and surface flooding occurs less than once every two years, E. largiflorens trees will be in poor condition and are more likely to die. In the absence of sufficient rainfall and groundwater, more frequent flooding is required to maintain E. largiflorens in good condition (less crown death and greater crown density) than would normally be required. Irrigation land use intensity affects variables that create habitat complexity in woodlands, such as the presence of old and young trees, and the abundance of shrubs such as lignum and Sclerolaena. Flow regimes (particularly prior wetting frequency) affect both structure and condition. These results have implications for understanding and management of elements of biodiversity dependent upon the resources provided by floodplain woodlands. They emphasize the importance of maintaining healthy black box remnants in irrigation areas for biodiversity persistence, and suggest that rehabilitation of black box communities in the Lowbidgee using managed flooding could bring significant biodiversity benefits to the region. Copyright © 2012 CSIRO

The reestablishment of productive forests over mining waste and overburden is a primary reclamation goal in oil sands mining in Northern Alberta, Canada. Soil water conditions in coarse-textured soils can be limiting to forest growth. The objective of this study was to evaluate the effect that textural variability may have on plant-available water and concomitant forest productivity on coarse-textured reclamation soils. The ecophysiological and biogeochemical processes model, Biome-BGC (Thornton et al., Agricultural and Forest Meteorology 113: 185–222, 2002), was employed to simulate forest dynamics. The water flow sub-model in Biome-BGC was replaced by a field-validated physically based formulation for transient unsaturated water flow. The modified model was assessed using validated physiological parameters, and model predictions were compared with measurements of aboveground biomass dynamics for jack pine (Pinus banksiana Lamb), white spruce [Picea glauca (Moench) Voss], and trembling aspen (Populus tremuloides Michx.). The modified Biome-BGC model was then used to evaluate the response of leaf area index and net primary production to available water holding capacity on texturally variable, coarse-textured soils. The results indicate that textural variability could increase the available water holding capacity within a 1-m profile of coarse-textured soil by 8 to 16 mm. This enhanced available water holding capacity could increase forest leaf area index by 0·3 to 0·8 and net primary production by 14–30% depending on the specific soil texture and tree species. Copyright © 2012 John Wiley & Sons, Ltd.

Short records of naturally fluctuating Pacific salmon (Oncorhynchus spp.) populations elicit challenges for the long-term management of North American fisheries. A dendrochronologic approach was used to reconstruct long proxy histories of regional Pacific salmon populations returning to streams along west central British Columbia coastlines. Tree rings from five tree species collected at 18 sites were found to be sensitive to interannual fluctuations in large-scale ocean and atmospheric circulation patterns. Using a regional network of climate-sensitive ring-width and ring-density tree-ring chronologies in linear regression models, multi-century long-term abundance records for populations of sockeye, chinook, chum and pink salmon were generated. Models explained between 27% and 39% of the variability in escapement records and were more proficient at capturing trends than annual magnitudes. The reconstructions vary in length, dating from 1400, 1536 and 1638 ad and extending to 2009 ad. Notable fluctuations in salmon abundance over the past six centuries are described, with significant population collapses shown to occur during the early 1400s, the late 1500s, the mid-1600s, the early 1700s, the early 1800s and parts of the 1900s. These models are the first to utilize climate-sensitive tree-ring records to reconstruct regional abundance histories and thus contribute potentially valuable information for salmon fisheries managers. Copyright © 2012 John Wiley & Sons, Ltd.

This study was undertaken in a watershed at a dry Spanish Mediterranean location. The effects of the north-facing and south-facing aspects on atmospheric parameters, soil water contents (SWCs) and plant water balances were assessed during 18 months including two dry seasons and one wet season. The species studied were the evergreen sclerophyll Quercus suber and the semi-deciduous shrubs Cistus albidus, Cistus monspeliensis and Lavandula stoechas. Atmospheric parameters were similar in both exposures, but water content of the 30-cm uppermost soil layers was higher under canopy in the south-facing slope during the wet season. Water balances of both slopes were different, and this was related to the lower shrub abundance and the vegetation patchiness observed in the south-facing slope. Autumn plant recovery was faster in the north-facing hillslope and occurred first in shrubs. During the whole study, Quercus suber displayed a hydrostable strategy maintaining an optimum water balance in both hillslopes. This was not the case of shrubs that avoided drought using a phenological adjustment and were more affected by aspect. Differences between tree and shrub water economies relied mainly on their respective root systems. The faster recovery of shrubs after the first autumn rainfalls allows them to avoid competition with other functional groups for water and nutrients during some days. Leaf-drying curves distinguished the functional behaviour of the tree and the shrubs because stomatal closure occurred at higher relative water content in the former. The coexistence of both functional strategies ensures an efficient use of water and nutritional resources. Copyright © 2012 John Wiley & Sons, Ltd.

Coastal dunes support a biodiverse wetland habitat, dune slacks, which depend on a seasonally fluctuating, but near-surface, groundwater level. Any long-term change in the hydrological regime will impact the ecology. Analysis of long-term water level hydrographs, using a methodology prescribed for surface water flow gauging data, provides a set of ecohydrological ‘indicators of alteration’. These indicators collectively form a robust quantified measure of change that provides a basis for assessing the ecological impact that may result from a changed hydrological regime. This method was tested using monthly frequency water level data from three west coast UK coastal dunes, over periods of up to 37 years. Mean hydrological variables derived from the hydrographs were compared pre-impact and post-impact for a variety of perturbations: medium-term climate variation and pre-shoreline and post-shoreline erosion. The method provided a valid quantification of hydrological change. The low frequency of water-level data measurements compared with continuous flow-gauge data precluded analysis of change in inter-annual variability or perturbation (coefficients of variability) because of the likelihood of missed extreme flood and drought. Principal components analysis was used to identify associations between hydrological indicators and highlighted redundancy among some indicators such as measures of frequency and duration but orthogonality, i.e. independence, of others such as mean water levels and duration of drought. The hydrological effects of climatic variation over a 37-year period, of management interventions and erosion events that occurred at the three coastal dunes were small compared with the likely impact from projected climate change predictions. Copyright © 2012 John Wiley & Sons, Ltd.

Revegetation was one of most successful measures to restore desert sand dunes and to improve regional eco-environments in the Tengger Desert, Northwest China. The potential for soil moisture replenishment by precipitation in the revegetation restored desert ecosystems is influenced strongly by the hydraulic properties of the surface soils. Steady-state infiltration rates from tension disc infiltrometer were measured at revegetation restored desert soils (VS) and unvegetated sand dunes (SD), respectively. Results indicated that the site specific VS and SD hydraulic properties differed significantly. Compared with SD, the long term VS has the effect of decreasing the hydraulic conductivity of the surface soil, while increasing the capillary effect on the infiltration rate. Averagely, the hydraulic conductivity of VS was 0·43 times of SD at the near saturation conditions. At VS, tension infiltration were dominated by capillarity effect more than that of SD, which were ascribed to the differences in soil properties where the former has a higher amount of finer particles, organic matters content and lower bulk densities. Accordingly, the hydraulically functioning mean pore sizes were larger at SD, where the gravity effect dominated the tension infiltration process. Therefore, in the study area under the pulse precipitation events in the growing seasons, VS contains more soil water by capillarity effect than SD does, which would contribute to shallow rooted herbage and cryptogam water consumption. Nevertheless, looking at the whole soil profile, for the actual rainfall water regimes, VS has insignificant effects on the soil profile water regime, with unchanged deep fluxes. Copyright © 2012 John Wiley & Sons, Ltd.

Alligator (Alligator mississippiensis) holes are a key feature in the Everglades landscape providing aquatic refuge for alligators and other aquatic organisms. The morphology of the hole as well as its location in the landscape may influence its function as an aquatic refugium. Morphologic and hydrologic characteristics and dynamics of 50 alligator holes in Everglades National Park, Florida were examined based on 1-m resolution digital images and field measurements from 1994 to 2007. Major morphometric parameters of alligator holes calculated for the study area included surface area, diameter, major axis orientation, basin depth, and circularity index. We used basin depth along with surface water modelling from the Everglades Depth Estimation Network to describe alligator hole hydroperiod and examine relationships among morphologic features, habitat, and hydrology. Alligator holes in this study were similar morphologically (pond surface area, basin depth, and sediment depth) among locations and habitats, and for the most part over time with the exception of holes in the Rocky glades. Alligator holes with greater surface area were not necessarily deeper holes. Hole hydroperiod was not correlated with surface area, and larger holes did not dry out less frequently than smaller holes. Although marsh hydroperiods varied by location and habitat, alligator hole hydroperiod did not, illustrating that across the landscape alligator holes provide aquatic refugia under a range of hydrologic conditions. Published in 2012. This article is a US Government work and is in the public domain in the USA.

Vulnerability of wetland vegetation to water table changes is a widely studied topic in the field of ecology. Extreme flood or drought conditions imposed on wetlands cause disappearance of plants or shift in the vegetation regime. The recovery of such plant compositions is of particular importance when the wetland is subjected to frequent water table fluctuations resulting from land use changes and requires knowledge of mechanisms underlying evolution of plant growth to changing hydrologic conditions. We used a spatially varying, coupled groundwater–vegetation growth model to investigate the survival mechanism of wetland herbaceous plants. The plants were subjected to long-term water table drainage because of land use changes that caused the disappearance of one of the species composition. In an effort to revive the disappeared species, hypothetical soil saturation was introduced onto the study domain through elevated water table level. Even though the system had returned to hydrologically favourable environment, the disappeared species was unable to recover, which in turn led to the evaluation of factors that determine the re-emergence of the species through sensitivity analysis. The results of the sensitivity analysis showed that the disappeared species recovered during scenarios of reduced duration of drawdown, increased assimilation rates and increased competitiveness. The analysis also showed that the competitiveness of the plants, which was modelled by the classic Lotka–Volterra algorithm, supersedes any of the unfavourable plant growth characteristics. The results of this study demonstrated the ability of the groundwater–vegetation response model to facilitate an understanding of plant development and a hierarchy of important factors that promote their growth in altered hydrologic conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Lakeshores are under increasing pressure from human activities, which cause extensive hydromorphological alterations. In this article, a method is described for assessing those alterations by using physical criteria developed in relation to the response by the lakeshore ecosystem, using benthic invertebrates as indicators. Two alpine lakes (Lake Bled and Lake Bohinj, Slovenia) were used as a case study. Both lakes are subjected to varying levels of physical alterations and lakeshore uses, which are described using alteration variables for four lakeshore zones: littoral zone, shoreline zone, riparian zone and lakeshore region. On the basis of these four variables, a Lakeshore Modification Index (LMI) was developed as a weighted sum of all variables. The weights were based on each variable's explanatory power regarding the distribution of benthic invertebrate taxa using canonical correspondence analyses. Both the LMI and all four lakeshore zone alteration variables showed significant (p < 0.01) negative correlations with species richness, but the LMI showed the strongest correlation (Pearson r = −0.086, p < 0.01). Differences existed in the level of alteration of the two lakes, with Lake Bled being more altered than Lake Bohinj; Lake Bled also exhibited the highest values for all four alteration variables and the highest LMI score. With the use of a classification system with five equidistant LMI classes, a difference was observed between the lakes in the distribution of LMI classes (two-sample Kolmogorov–Smirnov test Z = 5.714, p < 0.01). An assessment and classification of lakeshore modifications based on physical criteria, similar to that given by the LMI, can provide an important tool for lake management in practice, where a reliable method for assessing pressures is needed to support decision-making. Copyright © 2012 John Wiley & Sons, Ltd.

Floodplain wetlands in the wet–dry tropics are under increasing pressure from water resource development, and there is a need for methods to assess the biophysical dynamics of these extensive and often remote ecosystems. This study assessed the capacity of optical remote sensing methods to monitor the seasonal dynamics of inundation, turbidity, and aquatic vegetation cover for a northern Australian savanna catchment. MODIS data were used to map seasonal flood inundation patterns, and Landsat 5 TM data were used to map dry-season waterbody dynamics. A network of water-depth loggers and temperature sensors provided ground observations of surface inundation dynamics, and was used to validate the inundation mapping. Post-flood waterbody surface area declined by 89% over the dry season, with 70% of the decline occurring for Palustrine (floodplain) waterbodies. All aquatic systems became increasingly disconnected as the dry season progressed. Statistical relationships were developed between seasonal measurements of turbidity, aquatic vegetation cover, and Landsat spectral data. Catchment wide predictions showed that turbidity increased and macrophyte cover decreased for the Palustrine and Lacustrine (lake) systems, while the Riverine systems became less turbid over the dry season. These results show that, for open savanna landscapes where cloud cover does not limit waterbody detection, optical remote sensing methods can be effectively applied to assess seasonal patterns of inundation and accompanying biophysical dynamics. This provides an effective tool to evaluate the impact of river flow regime changes from water resource use or climate change in these regions. Copyright © 2012 John Wiley & Sons, Ltd.

Few quantitative experimental studies have been carried out on the influence of subterranean termite activity on the water infiltration capacity of crusted soils in the semi-arid Sahelian region. These studies found increased infiltration rates on soils that were affected by foraging galleries of subterranean termites. In this paper, remarkable results are presented from crusted agricultural fields in the Sanmatenga region in Burkina Faso with clear termite activity compared to reference fields without termite activity. Fine-scale rainfall experiments were carried out and general topsoil (upper 5 cm) characteristics were measured. Infiltration rates were found to be significantly slower on plots affected by subterranean termite activity. These results are contradictory to the findings reported in general literature. On the basis of topsoil property measurements, the reduced infiltration rates cannot be indisputably explained, and we suggest that the main responsible factor for a reduction of infiltration was related to differences in topsoil surface (upper 3 mm) properties. Two hypotheses are formulated in an attempt to explain the reduced water infiltration rates on termite plots. Copyright © 2012 John Wiley & Sons, Ltd.