2. Summary of National Data

The first part aimed at initiating a European database of empirical critical loads of nitrogen. Empirical critical loads are based on effects of (elevated) nitrogen deposition on ecosystems. A compilation of all relevant studies led to well established ranges (UBA, 2004). The value for the empirical critical load can be picked from this range, depending on other local factors, such as temperature, soil wetness, base cation availability. Some NFCs applied empirical critical loads in earlier submissions, mixed with loads calculated using the Simple Mass Balance (SMB) model. In this call, a clear distinction has been made and a database for empirical critical loads has been established, next to a database based on SMB or other models. These ‘classic’ critical loads are referred to as modelled critical loads to make a clear distinction between the two approaches. Another novelty of this call is the focus on Natura 2000 areas. These areas, for which the Habitats directive (92/43/EEC) and/or the Birds directive (79/409/EEC) apply, are of special interest for the conservation of natural habitats and bird species, and the maintenance of biodiversity. Therefore it is also important to know the sensitivity to nitrogen deposition of these areas.