Plant species richness and the exceedances of critical loads for N deposition: an overview

Roland Bobbink
Landscape Ecology, Institute of Environmental Biology,
Utrecht University


The emissions of ammonia (NH3) and nitrogen oxides (NOx) have strongly increased in the second half of the 20th century. Because of short- and longe-range transport of these nitrogenous compounds, atmospheric nitrogen (N) deposition clearly increased in many natural and semi-natural ecosystems. N deposition is now a major threat to biodiversity. Empirical N critical loads are effect tresholds for the environmetal impacts of N deposition. After a short introduction of the ecological consequences of N enrichment and the empirical critical load approach, an overview will be given on the relationship between the exceedances of N critical loads and plant species richness in several groups of ecosystems (grasslands, arctic/alpine communities and forests). Finally, the use of the empirical load approach will be discussed.