GRASSVISTOCK: modeling water fluxes in agro-pastoral systems

Climate change is currently threatening agro-pastoral systems around the world. Increased temperature and prolonged drought periods are reducing the capacity of these environments to provide several ecosystem services and their potential to mitigate climate change. In this context, grasslands and pastures monitoring gains a relevant importance for improving farm management and productivity, farmer incomes and to reduce input wastage and greenhouse gases emissions. In these perspectives, many crop models have been adopted with the purpose of allowing an accurate grassland monitoring, to promptly detect the impact of eventual abiotic stresses (e.g. thermal and water stresses) and to identify adequate adaptation strategies to cope with climate change. In this study, the grassland growth model GRASSVISTOCK was implemented for simulating the soil water dynamics and fluxes as well as their impacts on leaf area index (LAI) and above-ground biomass (AGB) in three Alpine (A, B and C) and three Mediterranean (D, E and F) grasslands. The results showed good model performances at simulating soil fractional transpirable soil water (FTSW) in the Alpine sites (site B: r=0.81; RRMSE=44.42%; site C: r=0.78; RRMSE=33.43%) while no comparisons between observed and simulated FTSW were performed for the other grasslands due to less data availability. The model also showed satisfactory performances at estimating LAI and AGB in both Alpine (LAI: r=0.66; RRMSE=33.03%; AGB: r=0.60; RRMSE=35.54%) and Mediterranean (LAI: r =0.85; RRMSE=43.58%; AGB: r=0.77; RRMSE=28.02%) sites. On these bases, this study proposes a prognostic tool for estimating water fluxes with the purpose of supporting agronomic decisions and to improve the sustainability of agro pastoral systems.