Ecosystems are an expression and a condition of life on earth. Ecosystems are the sites of interaction of organisms and their environment. Terrestrial ecosystems are the decisive interface between the atmosphere and solid earth. They influence the climate and the water balance on a local up to a global scale and, with their services and goods, constitute the basis of human society. This clearly indicates the importance of securing the benefits of ecosystems and thus the knowledge of their functions and processes.
Uncertainties in the quantitative description of ecosystem processes loom large. The reasons lie in the complexity of the entire earth system and also in the broad spectrum of exchange processes in terrestrial systems effective on different scales of time and space. In particular, the manifold systems feedbacks between soil, vegetation, atmosphere, and climate still contain many riddles. In the light of growing population pressure, urbanization, and the increasing requirements to be met by agriculture, the interaction of ecosystems functions and land use and climate change are of growing importance. However, these mechanisms and their consequences are not yet understood well enough.