Foliar nitrogen as an indicator of nitrogen deposition and critical loads exceedance on a European scale

The foliar N content of bryophytes and Calluna vulgaris (L.) has been shown to be an indicator of atmospheric N deposition in the UK at a regional sca le (1000km) and more recently on a smaller scale in the vicinity of intensi ve livestock farms. This work extends the geographical scale of the relatio nship between foliar N concentration of Calluna vulgaris and other ericaceo us shrubs and N deposition with 2 measurement transects, one extending from northern Finland to southern Norway (2000km) and the other extending from central Sweden to Stockholm, south east Sweden (330km). Included in the sec ond transect is a region of complex terrain in the Transtrand uplands, wher e the variation in N deposition with altitude and canopy cover was quantifi ed using Pb-210 inventories in organic soil. The relationship between folia r N (F-N) and N deposition was shown to increase linearly with N deposition (N-D) over the range 0.8% N to 1.4% N according to F-N = 0.040N(D) + 0.793 (r(2) = 0.70). The data are entirely consistent with earlier studies which together provide a valuable indicator of critical loads exceedance, the th reshold value being approximately 1.5% N, which is equivalent to a N deposi tion of 20 kg N ha(-1) y(-1).