Critical loads of nitrogen and sulphur to avert acidification and eutrophication in Europe and Chna

Introduction Forests and other (semi-)natural ecosystems
provide a range of ecosystem services, such as
purifyingwater, stabilizing soils and nutrient cycles, and
providing habitats for plants and wildlife. Critical loads
are a well-established effects-based approach that has
been used for assessing the environmental consequences
of air pollution on large regional or national scales.
Materials and methods Typically critical loads of
sulphur (S) and nitrogen (N) have been derived
separately for characterizing the vulnerability of
ecosystems to acidification (by S and N) and eutrophication
(by N). In this paper we combine the two
approaches and use multiple criteria, such as critical
pH and N concentrations in soil solution, to define a
single critical load function of N and S.
Results and conclusions The methodology is used to
compute and map critical loads ofNand S in two regions
of comparable size, Europe andChina.We also assess the
exceedance of those critical loads under globally modelled
present and selected futureNand S depositions.We
also present an analysis, in which the sensitivity of the
critical loads and their exceedances to the choice of the
chemical criteria is investigated. As pH and N concentration
in soil solution are abiotic variables also linked to
plant species occurrence, this approach has the potential
for deriving critical loads for plant species diversity.