Poster, International Symposium Soil processes under extreme meteorological conditions, Bayreuth: 25.02.2007 - 28.02.2007
Abstract:
Soil water plays a major role in the dynamic of most ecosystem processes, but the influence of extreme weather events on soil water budgets has been poorly understood. Using the one dimensional model WHNWIN (Huwe, 1992), volumetric water contents, matric potentials und soil water fluxes were simulated for a spruce stand at the Fichtelgebirge, Germany. Two field experiments were carried out: (i) exclusion of throughfall by roof constructions below the canopy over 7 weeks and subsequent rewetting within 2 days (80 mm) and (ii) soil frost by removal of snow cover. The F and H layer were integrated into the model because the forest floor may yield large amounts of water and is of particular importance for many chemical and biological processes. The model was calibrated by using measured water contents and matric potentials from the previous year on the control plot. There was excellent accordance between measured and simulated volumetric water contents and matric potentials in the upper mineral soil and in the forest floor. In deeper soil horizons, however, differences appeared at times between measured and simulated values which could be explained by preferential flow. Water flowing through preferential flow paths could rapidly increase water contents and reduce matric potentials in deeper horizons. An infiltration experiment on a control plot with brilliant blue solution confirmed this presumption by clearly showing preferential flow paths through the profile. The adjusted simulation was applied to the manipulated plots by changing the boundary conditions snow cover and rainfall, respectively.