Modelling the water balance of a grassland soil

Sammanfattning: Expected future climate change characterized by higher temperatures and more frequent summer droughts may cause significant changes in soil hydrological processes leading to limited nutrient and water availability and reductions in plant growth. Soil hydrological and plant growth models attempt to reproduce the complex interactions in the plant-soil water system in terms of mathematical equations, parameters and coefficients. If these models are able to capture the behaviour of the plant-soil-atmosphere continuum, in terms of soil water fluxes in the vadose zone and plant growth, they could help users to understand and predict the effects of climate change. In the scope of this study, a numerical soil water balance model was applied to three soil lysimeters located in Rollesbroich, Germany to analyse the accuracy of model predictions for temperate grassland. The model output showed some differences in calibrated model parameters and goodness-of-fit for the three lysimeters with identical soil profiles. The numerical analysis of the simulated results showed a satisfactory degree of model plausibility with R2 values between 0.52 and 0.99, RMSE between 0.01 and 0.05 cm3 cm-3 for water contents and 0.067 to 0.072 cm d-1 for actual evapotranspiration. The graphical model analysis showed a good explanation of the main seasonal patterns in the observations, despite some errors revealed by an analysis of the model residuals. It can be concluded that, with some additional improvements, this soil hydrological model could be applied to simulate the effects of future climate change scenarios.