The impact of climate variability on the phenology and productivity of managed grasslands in Alpine environments

In many European countries grasslands occupy a large fraction of the agricultural area and deliver important provisioning and regulating ecosystem services to society. Managed grasslands are sensitive to climatic variations and shocks. Understanding their responses to adverse climatic conditions is therefore of paramount importance for supporting decision making in agriculture. In view of the possibility of increasing climatic variability warming and more frequent occurrence of unfavorable spells, quantitative knowledge of these responses is also necessary to inform adaptation.

With a geographical focus on Switzerland, this contribution presents a retrospective analysis of the effects of climate variability on grassland phenology and productivity, dating back to the mid-20th century. Material used for developing the analysis includes long-term experimental and monitoring data, as well as on the results of numerical experiments conducted with a mechanistic model of herbage growth. Results are obtained for a selection of locations that illustrates the variety of environmental conditions encountered across the Swiss territory.

Inter-annual variations in seasonal growth dynamics and the occurrence and timing of growth limitations are discussed along with underlaying long-term trends in phenology and productivity caused by the rise in temperature, shifts in the precipitation regime, decadal variations in solar radiation, increasing evaporative demand during the recent decades, and long-term changes in snow coverage. The overarching questions guiding the analysis and presentation are: Have the frequency, intensity and seasonality of adverse conditions already changed over the recent past, and if so, what have been the implications for grassland-based agriculture in Switzerland? And, to what extent do changes in phenology, productivity and their variability reflect an impact of large-scale atmospheric circulation patterns?