Lay summary
The scope of this proposal is to complete a field experiment started in 2004, and to explain observed vegetation dynamics after recent extreme summer droughts in the Southern Alps.In the field experiment, rainfall was manipulated by automated equipment (rain shelter and irrigation) to realistically simulate extreme droughts in summer/autumn and spring. The aim of the experiment is to firmly establish our concept, based on circumstantial observational evidence, that occasional droughts and particular conditions for establishment from seed are key aspects for an understanding of species coexistence, community structure and ecosystem functioning. Three main hypotheses will be tested:(1) Seasonality of droughts affects the outcome of regenerative succession after drought(2) Dry meadows show high resistance to drought and low resilience after drought(3) Drought and seed limitation affect productivityThe experiment had a successful start in 2004/2005. Well-working technical instruments have created (and measured) the conditions aimed at for this study. Data sampling periods had a correct timing and sampling was completed for a whole community based on totally 11'200 small quadrats. Frequency was sampled separately for established and newly regenerated populations, in July before (2004) and after drought treatments (2005, 2006, 2007), seedlings were also checked in additional periods (October 2004, April 2005, October 2005, April 2006, April 2007).In the context of global climate change research, our project addresses highly relevant questions dealing with impacts on ecosystems. With our population-based approach under field conditions we hope to make a substantial complementary contribution to Swiss research in the framework of the Swiss NCCR Climate.For further information see http://www.botany.unibe.ch/associated/grass/index.php