EXMAN is a joint project funded by the Commission of the European Communities (CEC) Directorate XII, Science and Research (DG XII), with research partners in five European countries. The aim of EXMAN is experimental manipulations of the water and nutrient cycles in forests. These experiments are aimed at testing hypotheses on ecosystem reactions to altered inputs and boundary conditions. EXMAN developed along with the 'roof method' as a means for the manipulation of water and solute fluxes into the forest soil on an ecosystem scale. Large roofs are built underneath the forest canopy to collect the throughfall. This amount of water is then, by means of technical equipment, altered in its chemical composition and/or its quantity and/or its temporal flux distribution and reapplied by sprinkler systems to the soil. The reactions of the soil chemical and hydrological parameters, as well as the physiological reactions of the forest stand and the soil fauna and microflora, are investigated in an integrated manner. Such patch-scale roof studies are running in Denmark, the Netherlands, Ireland and Germany (EXMAN sites), as well as in Norway and Sweden. Concerted planning and evaluation of results is secured by periodic contacts between the groups. Results from the manipulation studies may contribute considerably to the progress of the projects GCTE (Global Change and Terrestrial Ecosystems) and BAHC (Biological Aspects of the Hydrological Cycle, e.g, the soil-vegetation-atmosphere transfer (SVAT) models). Relevant BAHC Foci are Focus 1, Activity 1, Tasks 1.1.2, 1.1.3 and 1.1.5.
