B53D-0599
Interactive effects of altitude and management on resistance and resilience of permanent grasslands to drought: combining agronomic, functional and ecophysiological approaches Buttler, A., Deleglise, C., Signarbieux, C., Meisser, M., Mosimann, E., Mills, R.

Friday, 18 December 2015
Poster Hall (Moscone South)
Alexandre Buttler1,2, Claire Deléglise2,3, Constant Signarbieux1,2, Marco Meisser3, Eric Mosimann3, Robert Mills4,5, Anita Risch4, Amarante Vitra1,2 and Sylvain Delzon6, (1)École Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental, Engineering (ENAC), Laboratory of Ecological Systems (ECOS), Lausanne, Switzerland, (2)WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Laboratory ECOS, Lausanne, Switzerland, (3)Agroscope, Institute for Livestock Sciences, Changins, Nyon, Switzerland, (4)WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland, (5)University of Lancaster, Lancaster, United Kingdom, (6)Université de Bordeaux-INRA, UMR BIOGECO, Talence, France
Abstract:
The expected increase in extreme climatic events will cause significant constraints on grassland systems and, as a result, farmers must adapt grassland management. Identifying potential interactive effects of factors such as altitude and management, with different water availability scenarios is therefore a major challenge to anticipate the performance of mountain grasslands.

Using rain shelters across grassland systems in the Swiss Jura, we simulated the effects of severe droughts in spring and summer periods, at different altitudes, and compared realistic management types such as grazing by sheep, and intensive and extensive mowing. When comparing grazing and mowing management under an extreme drought event at a similar altitude, minor short-term changes of species composition, and almost no persistent effects were observed. However, significant changes were observed in plant functional traits, reflecting a strong decline in plant growth during the drought, and a partial recovery two months later. Forage yields, and its nutritive value, thus declined during the drought period, and both were still affected in the following months, but had recovered in the following spring. Negative drought effects were stronger in the grazing management, although recovery was slightly improved in this management. Concerning soil biogeochemistry, we compared microbial biomass C and N, as well as the activity of extracellular enzymes at peak drought, and during the rewet phase. Both indices remained comparable to control treatments under drought. During the rewet phase, some enzymes were stimulated in the grazed-control, but microbial biomass remained comparable. These systems showed considerable resistance to extreme drought, with only minor short term impacts due to management. However, cascading effects from the aboveground to belowground function may be observed if such events increase in frequency and these processes are expected to be different at the various altitudes.