Impact of nitrogen deposition on the species richness of grasslands

A transect of 68 acid grasslands across Great Britain, covering the lower range of ambient annual nitrogen deposition in the industrialized world ( 5 to 35 kg N ha(-1) year(-1)), indicates that long-term, chronic nitrogen deposition has significantly reduced plant species richness. Species richness declines as a linear function of the rate of inorganic nitrogen deposition, with a reduction of one species per 4-m(2) quadrat for every 2.5 kg N ha(-1) year(-1) of chronic nitrogen deposition. Species adapted to infertile conditions are systematically reduced at high nitrogen deposition. At the mean chronic nitrogen deposition rate of central Europe (17 kgNha(-1) year(-1)), there is a 23% species reduction compared with grasslands receiving the lowest levels of nitrogen deposition.