In the transition zone between open atmosphere and forest floor the canopy layer is modifying energy and mass exchanges. Through interception at the canopy layer and leaf fall, a specific situation is created at the forest floor concerning nutrient input, water availability und microclimatic parameters. These processes, however, are far from being static, but are subject to a dynamic development, which can be observed in many places (succession, desertification). Therefore, these interdependencies are relevant for both ecological as well as meteorological studies. Measurement data under the forest canopy allow conclusions to be drawn concerning the amount of biomass on the one hand and the growing conditions for forest vegetation on the other hand.