All trees form associations with mycorrhizas. In temperate forests ectomycorrhizas are dominant, and form complex communities of a large number of different species. Ectomycorrhizas are one of the major pathways of carbon into soils and are thus important for carbon storage in ecosystems, but also the principle pathway by which trees acquire nutrients from the soil. This talk will explore the community structure of ectomycorrhizas in forests, and their functions as regulators of ecosystem processes. Douglas Godbold is Professor of Forest Ecology at the Universität für Bodenkultur Vienna. His principle research interests are linking belowground biodiversity to ecosystems functions for both trees and mycorrhizas. This work has been carried out in a number for ecosystem types from boreal to tropical forests. He currently focusses on alpine tree line systems.