Mapping correlations between nitrogen concentrations in atmospheric deposition and mosses for natural landscapes in Europe

Recent investigations proved that nitrogen (N) concentrations in mosses are primarily determined byatmospheric deposition. The correlations are country- and N compound-specific and agree well withspatial patterns and temporal trends across Europe as a whole and in single European countries. Thisstudy investigates whether correlations between the concentration of N in atmospheric deposition andmosses within the units of an ecological land classification of Europe can be established. To this end, N measurements from the 2005 European moss survey and modelled N atmospheric deposition in 2005were intersected with a map of European landscapes. Then, considering minimum numbers of samplingsites required across Europe, in single European countries and within the landscapes of Europe andaccounting for spatial auto-correlation, the correlations between the N concentration in mosses andcorresponding deposition were calculated and mapped for each of those landscape units containingmoss sampling sites. Using an example of one landscape with positive correlation and one landscape withno correlation between N concentrations in deposition and in mosses, influencing factors were rankedbased on investigating the multivariate interactions between moss concentrations and, amongst others,atmospheric deposition, land use, elevation or moss species by classification and regression trees. Fromthis study it could be concluded that the numbers of sampling sites within Europe and most participatingcountries as well as within most of the landscapes covering Europe are sufficient. Spatial patterns ofcorrelations between the atmospheric N deposition and N concentration in mosses could be provento vary across the landscapes of Europe. Where clear positive correlations between N concentrationsin deposition and mosses exist in landscapes, multivariate ranking identifies the deposition as maininfluencing factor. In cases with no correlation between deposition and N concentrations in mosses,other factors such as e.g. moss species collected may be of importance. Therefore, mosses were proved toserve as biological indicators for atmospheric depositions and ecologically defined land classes could beidentified as more complex indicators which allow relating exposure monitoring with effects assessment.