Das Projekt "Ressourceneffiziente landwirtschaftliche Produktionssysteme, Drought legacy effects on grassland invasibility" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Berner Fachhochschule, Hochschule für Agrar-, Forst- und Lebensmittelwissenschaften.
Das Projekt "Invasibility of Swiss Grasslands" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Berner Fachhochschule, Hochschule für Agrar-, Forst- und Lebensmittelwissenschaften.Ecological processes resulting from global change, such as more frequent extreme summer drought or increased propagule pressure of exotic species, often affect plant communities gradually at time scales of years or decades and may therefore not often be distinctly recognized. The effects of potential interactions of such processes are largely unknown. Interactions may partly compensate single effects and contribute to constancy of communities and ecosystems. However, ecologists are increasingly concerned about potentially adverse interactions that may stimulate cascades of species extinctions. Over the last decade sowing experiments have found reliable evidence for seed-availability related effects on the local occurrence of species, the size of populations and the richness and productivity of communities. This implies that processes influencing the production and dispersal of seeds and/or the establishment of seedlings are important for the functioning of ecosystems. Although major cases of adverse invasions have not occurred so far, we suspect that species-rich meadows that show a high seedling turnover are potentially susceptible to invasion. Current invasibility theory predicts increased invasion during temporary resource pulses that could be associated with increased variability of rainfall. Successful invasion may primarily depend on the propagule pressures of local resident and potential invader species. A new multi-factorial seed-addition experiment will investigate hypotheses concerning the main and interactive effects of productivity, summer drought, origin of species, and propagule pressure. The experiment will be started in 2010 in meadows covering a wide productivity gradient in different Swiss regions. The knowledge gained from this experiment will be used to predict grassland invasibility in Switzerland.
Das Projekt "Influence of droughts on regeneration, vegetation change and ecosystem functioning" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Universität Bern, Departement Biologie, Institut für Pflanzenwissenschaften.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 productivity The 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
