Diversity–stability relationships in plant communities of contrasting habitats
To what extent are small-scale (<200 m2) plant species dynamics related to biotic (species richness, proportion of short-lived species) and abiotic (soil nitrogen and moisture) factors? Are species-rich plant communities more stable in terms of their species composition? Do species-rich communities exhibit more variation in the number of individuals at both the population and community level?
Coastal dunes, peatlands and marshlands, western Netherlands.
We analysed small-scale species dynamics in naturally assembled plant communities from dune grassland, dune scrubland, dune slack, moist oligotrophic grassland and marshland, differing in species richness, soil nutrient and hydrological conditions. The analysis was based on long-term data sets comprising 61 permanent plots (scale: 2 x 2 m–14 x 14 m), monitored over a period of 14–52 yr, encompassing 992 relevés. Species dynamics was expressed using different measures, i.e. species turnover, species dissimilarity, cumulative species number and variation in species abundances, at the population and community level. Plot size and length of the monitoring period were included as explanatory variables to make clear that the results were not confounded by these factors.
Generalized linear modelling revealed that the variation in species dynamics among plots was largely explained by biotic factors, i.e. differences in species diversity (19–54%) and the proportion of short-lived species in the vegetation (<3%), and to a small extent (<10%) by abiotic factors, i.e. differences in abiotic conditions. Species-rich plots were more stable in terms of species composition and year-to-year variation in species abundances and total species abundances.
The naturally assembled communities, spanning a broad gradient of resource availability (dry to moist and nutrient-poor to -rich soils), conformed to the same positive relationship between diversity and stability, both at the population and the community level. Although observational studies do not allow drawing of conclusions on mechanisms behind observed patterns, possible explanations are briefly discussed.