Assessing the impact of climate change on grassland ecosystem services using DayCent

Grasslands deliver a range of ecosystem services to society that are potentially threatened by climate change. Assessing climate change impacts on grassland ecosystem services is essential for developing adaptation strategies. This is particularly important for a country like Switzerland, in which grasslands represent about two thirds of its agricultural land. Among grassland ecosystem services, fodder production (provisioning) and soil carbon sequestration (regulating) are most vulnerable to drought and other extreme events. Process-based ecosystem models, such as DayCent, are suitable tools for assessing concomitant impacts of climate change on different ecosystem services. DayCent simulates fluxes of C and N among the atmosphere, vegetation, and soil and allows the prediction of the effect of increasing temperature and CO₂ levels and decreasing rainfall on herbage growth and soil carbon stocks. We have been using DayCent to simulate the dynamics of herbage growth and soil organic carbon pools with varying degree of stability in managed permanent grasslands in Switzerland. For the present study, we selected an experimental grassland site located at Oensingen, Canton of Solothurn. We calibrated DayCent using inverse modeling (PEST tool) and verified the model performance based on several years of field data. We then applied the model to examine how future shifts in climatic conditions are likely to affect yields and carbon stocks, and what are the associated uncertainties. For this exercise, we developed local climate change scenarios using a stochastic weather generator (LARSWG). After reviewing the results, we discuss how process-based modeling can contribute for development of climate-smart agriculture tools, which can support better definition of agricultural policies and payment systems for grassland ecosystem services.