Jentsch, A; Beierkuhnlein, C: Simulating the future - responses of ecosystems, key species and European provenances to expected climatic trends and events, Nova Acta Leopoldina, 112(384), 89-98 (2010)
Key words: EVENT 1, EVENT 2, EVENT 3, EVENT 4, EVENT 5
Future climate chane ist expected to rapidly modify the long-term average and variation in temperature and precipitation regimes. The local climate that has been experienced by organisms and ecosystems does no longer exist. More frequent and more pronounced extreme weather conditions are expected in the near future. Monitoring both future climate and the ecological responses will be important. However, monitoring can not supply the necessary insights for the design of adaptation strategies in time. Ecological modeling is heuristically limited due to the simple fact of hitherto not available evaluation and adjustment of results. Thus, the experimental sumulation of climatic trends and events is urgently needed in order to identify responses of important communities and species that are exposed to anovel climate. Experimental appraches are artificial to some degree, but they can yield fundamental insights into crucial mechanisms of reponse to rapid climate change. In the ENENT experiments (EVENT I to V), we simulate expected future climatic conditions including extreme weather events along a gradient ranging from highly standarized and replicated pot experiments over manipulation of strongly controlled artificial plant communities (with defined number of specimen and with standarized substrate) to manipulation of semi-natural established grassland communities on old-grown soils. We are testing the effects of summer warming, winter warming, increased winter precipitation, recurrent extreme summer drought, excessive summer rain, and modified frost-thaw-cycles. In addition, we are combining different drivers in multi-factor experiments (e.g. land use intensity and warming or more extreme precipitation regimes.) The main focus of the EVENT-experiments in on grasslands, but also shrubland (heath) on the community level and important tree species on the within-species diversity level are experimentally exposed to future climatic scenarios. The role of biodiversity - in terms of species richness and richness of various growth forms and functional groups - for the buffering of extreme wather events is of special interst for us. Surprise occur! Total biomass did not respond as strongly as expected, but single species performance was very specific. For particualr specie, significant effects of drought, heavy rain and increased freeze-thaw cycles were found in parameters related to e.g. nutrient cycling, gas exchange, phenology and reproductive fitness. Biodiversity did both, buffer extremes in some cases and accelerate stressin other cases.

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