NCCR Climate (Plant/Soil)
Keywords: climate change, drought, temperate grassland, stable isotopes
Context
With increasing clarity, results of different climate models show that the frequency of extremely dry summers like 2003 will increase in Switzerland. For 2070, models predict an average reduction in Swiss summer precipitation of around 20% and a maximal reduction of 50% compared to today. As Switzerland holds large water reserves in the Alps, drought has not been considered a problem for a long time. Additionally, due to the topographic diversity of the country, drought might be a regional rather than a national problem. However, there is no doubt that future summers will generally be drier. Since grasslands cover a large part of Switzerland at all elevations and are the base to agricultural milk and meat production the focus of Plant/Soil is on this ecosystem type. While the consequences a decrease in summer precipitation will have on temperate grassland ecosystems are not very well understood, we need a better understanding of the response of grasslands to drought to be able to develop viable adaptation strategies in advance. Besides the most obvious harvest reduction, drought can also considerably affect the carbon cycle.
Objectives
Assess the effect of experimental summer drought on temperate grassland systems at different altitudes, focusing on:
- above-ground biomass production
- below-ground biomass production
- species composition
- vegetation structure (height, LAI)
- C and N concentrations and C/N ratio in biomass
- mechanisms involved using stable isotopes
- water sourcing of species using 18O signature of root crown water
Experimental Design and Methods
The effects of drought on productivity and community structure of grasslands is studied in a field experiment at three different altitudes in Switzerland. At the ETH research stations rain shelters are built up to keep the rain out. These shelters are supposed to manipulate nothing but soil humidity. This is controlled with continuous measurements of soil and vegetation microclimate (temperature, humidity, evapotranspiration and PAR). Rainfall data are obtained from an external source. The vegetation structure is described with its height and LAI. Biomass is sampled throughout the growing season (corresponding to the normal mowing dates of the stations) and separated into species. Root biomass is estimated using ingrowth cores. The dried biomass is then weighed and analysed for C/N, 13C and 15N. Especially the analysis of the stable carbon isotope will give insight into the severity of the water stress for different species. Root crown and soil water are sampled in campaigns and analysed for 18O to learn more about the actual source of water for the plants.
Publications
2017
Wilcox K R, Shi Z, Gherardi L A, Lemoine N P, Koerner S E, Hoover D L, Bork E, Byrne K N, Cahill Jr. J, Collins S L, Gilgen AK, Holub P, Jiang L, Knapp A K, LeCain D, Liang J, Garcia-Palacios P, Peñuelas J, Pockmann W T, Smith M D, Sun S, White S R, Yadjian L, Zhu K, Luo Y (2017) Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments. Global Change Biology 23: 4376-4385 external pageDOI: 10.1111/gcb.13706
2015
Prechsl UE, Burri S, Gilgen AK, Kahmen A, Buchmann N (2015) No shift to deeper water uptake depth in response to summer drought of two lowland and sub-alpine C3 grasslands in Switzerland. Oecologia 177: 97–111 doi:external page10.1007/s00442-014-3092-6
2014
Gilgen AK, Feller U (2014) Effects of drought and subsequent rewatering on Rumex obtusifolius leaves of different ages: reversible and irreversible damages. Journal of Plant Interactions 9: 75–81 doi:external page10.1080/17429145.2013.765043
Prechsl UE, Gilgen AK, Kahmen A, Buchmann N (2014) Reliability and quality of water isotope data collected with a low budget precipitation collector. Rapid Communications in Mass Spectrometry 28: 879–885 doi:external page10.1002/rcm.6852
2013
Finger R, Gilgen AK, Prechsl U, Buchmann N (2013) An economic assessment of drought effects on three grassland systems in Switzerland. Regional Environmental Change 13: 365–374
2010
Gilgen AK, Signarbieux C, Feller U, Buchmann N (2010) Competitive advantage of Rumex obtusifolius L. might increase in intensively managed temperate grasslands under drier climate. Agriculture, Ecosystems and Environment 135:15-23
Joos O, Hagedorn F, Heim A, Gilgen AK, Schmidt MWI, Siegwolf RTW, Buchmann N (2010) Summer drought reduces total and litter-derived soil CO2 effluxes in temperate grassland – clues from a 13C litter addition experiment. Biogeosciences 7: 1031–1041
Zeeman MJ, Hiller R, Gilgen AK, Michna P, Plüss P, Buchmann N, Eugster W (2010) Management, not climate, controls net CO2 fluxes and carbon budgets of three grasslands along an elevational gradient in Switzerland. Agricultural and Forest Meteorology 50: 519–530
2009
Gilgen AK, Buchmann N (2009) Response of temperate grasslands at different altitudes to simulated summer drought differed but scaled with annual precipitation. Biogeosciences 6:2525-2539
2008
Gilgen AK, Buchmann N (2008) Effects of summer drought on temperate grassland performance. Grassland Science in Europe 13:913-915
2007
Buchmann N (2007) Biodiversität als Versicherung. Artenreiche Wiesen trotzen dem Klimawandel. Hotspot Biodiversität und Klimawandel vol. 16, 16
2006
Barnard RL, de Bello F, Gilgen AK, Buchmann N (2006) The δ18O of root collar water best reflects source water δ18O in different types of herbaceous species. Rapid Communications in Mass Spectrometry 20:3799-3802