Das Projekt "Kohlenstoff- und Stickstoffkreislaeufe in Waldoekosystemen (CANIF)" wird vom Umweltbundesamt gefördert und von Universität Hohenheim, Fakultät III Agrarwissenschaften I, Institut für Pflanzenernährung durchgeführt. Introduction: In CANIF, we investigate effects of climate and soil-borne and deposited nitrogen on carbon and nitrogen assimilation and turnover as well as on forest organism functioning in broad-leaved and coniferous forests along a climatic transect through Europe extending from northern Sweden to central Italy. This will contribute to the European and global research programmes envisaged by the EC Environment and Climate Programme (Framework IV, TERI). The subproject of the Institute of Plant Nutrition, Hohenheim University, is focused on nitrogen uptake by, and transport of photosynthetic carbon to the root system of trees. Objectives: The time-course of root growth is monitored at the different sites. To determine the contribution of ectomycorrhizal hyphae to the nitrogen uptake of trees and the corresponding carbon supply from these trees to the fungi, compartment experiments are carried out, labelling not only nitrogen supplied to the compartments (15N), but also C incorporated by the shoots of young trees (13C). Scientific progress to-date: The root growth data set has been completed except for one more monitoring (spring 1997). Detailed data on root growth will be available in second half of 1997. Double-labelling experiments (15N, 13C) have been carried out at five locations (three Norway spruce sites, two beech sites) in 1996. Samples are in analysis.