- 1The consequences of globally declining biodiversity and climate change for ecosystem functions are intensively debated topics in ecological research. However, few studies have investigated potential interactions, or the combined effects of both scenarios, for ecosystem functioning. In the work presented here we tested the hypothesis that increasing plant diversity acts as insurance for ecosystem functions during extreme weather events which are predicted by climate change scenarios.
- 2We measured the effect of plant diversity on above- and below-ground productivity in semi-natural grasslands following experimentally induced early summer drought. To test the insurance hypothesis directly, we determined in each community the range of δ13C values of individual plant species as drought stress indicators.
- 3Increasing plant diversity significantly enhanced below-ground productivity as a consequence of simulated drought, while above-ground productivity was reduced independently of plant diversity.
- 4Plants shifting carbon allocation to below-ground compartments during drought maintain various aspects of ecosystem services and functions. Although we were not able to detect physiological evidence for the insurance hypothesis, we conclude from our below-ground results that plant diversity is an essential entity of ecosystems for maintaining ecosystem functions in a changing climate.