Simulation of Water and Carbon Fluxes in Agro- and forest Ecosystems at the Regional Scale

To investigate effects of different land use management practices on carbon fluxes at the regional scale we developed an integrated model by coupling an ecohydrological river basin model SWIM (Soil and Water Integrated Model) and a soil organic matter model SCN (Soil-Carbon-Nitrogen model). The latter is a submodel of the forest growth model 4C. The extended integrated model combines hydrological processes, crop and vegetation growth, carbon, nitrogen, phosphorus cycles and soil organic matter turnover. It is based on a three level spatial disaggregation scheme (basin, subbasin and hydrotopes), whereas a hydrotope is a set of elementary units in the subbasin with a uniform land use and soil type. The direct connection to land use, soil and climate data provides a possibility to use the model for analyses of climate change and land use change impacts on hydrology and soil organic matter turnover. Aim of this study is to test the model performance and its capability to simulate carbon pools and fluxes in right magnitude and temporal behaviour at the regional scale. As a first step, the model was parameterised and validated for conditions in East Germany, incorporating values known from literature and regionally available times series of carbon pools and fluxes. This provides verification of carbon pools and fluxes in the landscape and verifies the correct representation of the environmental processes therein. Based on this, different land management strategies (e.g. soil cultivation techniques, crop residue returns) and land use change options (e.g. conversion of agricultural areas to forest or to set-aside areas) can be simulated to assess the behaviour of water and carbon fluxes as well as carbon sequestration options.