Abstract
Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity–ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity–productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity–productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions.
Highlights
Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood
We find that interspecific variability stress tolerance and the strength of per capita species interactions in unstressed conditions can explain how stress alters biodiversity effects on ecosystem functions
Confirming other studies[7,9,13,14,15,16], we found that envionmental stress changed the biodiversity–ecosystem function relationship (Fig. 1, Table 1)
Summary
Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. While the majority of studies reported a decreased effect of biodiversity on ecosystem functions with increasing stress[7,8,9,10,11,12,13,14,15,16], others reported no change[17,18] or even an increase[19] The mechanisms underlying these stress-induced changes in biodiversity effects—and possibly explaining the observed differences among studies—remain virtually unexplored. Stress is assumed to alter the effect of species interactions by causing species-specific effects on fitness[32,33] Both theories, by consequence, make different predictions on how stress can modulate biodiversity effects
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