Community shifts in grassland due to more extreme intra-annual precipitation variability and warming

Background/Question/Methods

Greater intra-annual precipitation variability is predicted for many regions on earth, leading to longer dry periods and more intense rainfall events. Their effects on vegetation and ecosystem functions are widely unknown. Although currently, climate change effects on species distributions are frequently reported, it remains unclear for many regions of the world how local extinction and immigration will be balanced under increased precipitation variability. Here, we present results from the field experiment EVENT II in which Central European grassland is subjected to increased spring and summer rainfall variability (low, mid and extreme rainfall variability without any change to the annual rainfall amount) in combination with summer and winter warming. Data on aboveground biomass and species abundance was collected since 2008. Changes in species abundance patterns (Bray–Curtis Dissimilarity) were analysed by linear mixed effect models.

Results/Conclusions

Relative abundance and biomass production of single species was altered by more extreme variability in spring. Further, we detected deviation and turnover in the dominance of structure of plant communities in response to more extreme precipitation variability. Additional summer warming intensified the effects of altered precipitation variability. Grass species seemed to be more vulnerable to precipitation changes than forbs. However, legume species remained unaffected.These changes in relative species abundance may serve as an early indicator of long-term climate change effects altering community composition and biogeographic patterns before local extirpations occur.