Changes in mass element fluxes and their importance for critical loads: GEOMON network, Czech Republic

Three years (1994-1996) of runoff, bulk deposition, and throughfall S and N data obtained from GEOMON, a network of 14 small forest catchments in the Czech Republic, are presented. In this paper, we assess regional differences and temporal trends in S and N fluxes under changing regional burdens. Decreases in S deposition have occurred in the emission-burdened northern and western parts of the Czech Republic, where remedial measures have been applied. For example, at the Uhlirska catchment (Jizerske hory Mtns., northern Czech Republic), throughfall S fluxes decreased from 72.7 to 48.5 kg ha(-1) yr(-1). In contrast, the relatively clean central and southern parts of the Czech Republic showed an increase in S deposition; for example at the Na lizu catchment (Sumava Mtns., southern Czech Republic) throughfall S fluxes increased from 9.0 to 18.8 kg ha(-1) yr(-1). In burdened catchments with damaged forests, high runoff of N was observed. Using fluxes of S and N measured at the GEOMON sites, we calculated critical loads and exceedances for both S and N in the catchments. The critical loads of S ranged from 505 to 3,631 mol L-1 yr(-1) during 1994-1996; in about 80 % of the catchments the critical loads were exceeded by atmospheric deposition; half of the catchments showed an exceedance for N.