Diversity-Stability Relationships of an Alpine Plant Community under Simulated Environmental Change

Abstract

We examined the relationship between plant community diversity (species richness, evenness) and stability in an alpine Dryas octopetala heath exposed to four years of warming (open top chambers) and nutrient addition at Finse, southern Norway. Furthermore, we examined if different functional types responded differently to the interaction between environmental change and initial community diversity. We used the temporal change in species composition, calculated as the sum of change in sample scores in detrended correspondence analyses, as a measure of variability (opposite of stability). Under ambient conditions, a high initial species richness was associated with less stability of the total species composition. Under experimental warming, initial high species richness and evenness were associated with a more stable subsequent vascular species composition. Vascular stability decreased, however, with higher species richness under nutrient addition. When warming and nutrient addition were combined, high initial evenness was associated with more stable bryophyte composition, whereas high species richness was associated with reduced lichen stability. Thus, the degree and direction of the diversity-stability relationship depended on the type of environmental perturbation, the responding functional type, and on the diversity parameter used. The large variation in diversity-stability relationships is likely an outcome of complex species interactions and environmental factors influencing community diversity.