Abstract In the CLIMEX project, two catchments are manipulated to investigate the effects of elevated temperature and CO 2 on decomposition of soil organic matter. Litterbag studies do not show a clear treatment effect after five months of manipulation. Due to the treatment, however, the contribution of orgnaic anions to the total charge balance of the soil solution appears to decrease. Laboratory experiments show that C loss from soil columns as CO 2 and TOC increases with temperature. Because N uptake by vegetation is absent, nitrification increases with temperature resulting in increased acidification of the outflow water.