Introduction to the NITREX and EXMAN projects

Abstract European concern over the cause and consequences of forest decline, acidification of soils and surface waters, and the nutrient enrichment of terrestrial and aquatic ecosystems, led to the establishment of the NITREX (Nitrogen saturation experiments) and EXMAN (Experimental Manipulation of Forest Ecosystems in Europe) projects, two research networks of large-scale manipulation experiments under the auspices of the EU Commission of European Communities. NITREX comprises 10 experiments at 8 sites in 7 countries at which nitrogen is either added to or removed from ambient atmospheric deposition to simulate major changes in nitrogen deposition. EXMAN comprises experiments at 6 sites in 4 countries at which ambient atmospheric deposition is experimentally altered in chemical composition and/or quantity. The ultimate goal of this research is to contribute to the scientific basis required for the refinement of EU policy on atmospheric quality, and the legislation which will emanate from that policy.