Context: In terrestrial ecosystems, soils act as buffers in a hydrological, chemical and biological sense. They play an important role in ecosystem behaviour and the response to environmental change. Models can be used to integrate results of detailed process studies at the ecosystem level. Aim: Quantifying physical and chemical processes in the unsaturated soil and the role of transport processes in biogeochemical transformations, optimization of the interaction between the use and development of simulation models on the one hand and the interpretation of data obtained from monitoring programmes or laboratory experiments on the other hand. Methods: Simulation models, laboratory column/incubation experiments, development of new measurement techniques, monitoring programmes, automated data acquisition and processing. Present topics: Monitoring and modelling forest hydrological processes, optimization of TDR for measurements of soil water content and electrical conductivity.