Forest ecosystems represent a major type ofland use in Germanyand in Europe. They provide a number of functions, or ecosystem services, beneficial to humans, namely biomass production, regulation of the water- and energy cyde, C and N sequestration, erosion control, recreation, and they act as habitat for numerous species. The stability of forest ecosystems in Europe as influenced by the deposition of air pollutants has been a matter of debate for more than 20 years. Besides atmospheric deposition, other environmental conditions affecting forest ecosystems, such as temperature, CO content of...