The soil, vegetation and the lower atmosphere are key compartments of the Earth, where almost all activities of mankind take place. This region is characterized by extremely complex patterns, structures and processes that act at different time and space scales. While the exchange of energy, water and carbon is continuous between the different compartments, the pertinent fluxes are strongly heterogeneous and variable in space and time. Therefore, the quantitative prediction of the systems behavior constitutes a major challenge to scientists and policymakers, especially in view of global climate change.