WETFALL DEPOSITION AND PRECIPITATION CHEMISTRY FOR A CENTRAL APPALACHIAN FOREST

Although extensive research on acidic deposition has been directed tow ard spruce-fir forests, less research has been done on the impacts of air pollution on eastern montane hardwood forests. The purpose of this study was to describe precipitation chemistry for several Appalachian hardwood forest sites at or near the Fernow Experimental Forest (FEF) to assess the potential for problems associated with acidic depositio n. Emphasis was placed on seasonal patterns of ionic concentrations (H +, Ca++, NH4+, NO3-, and SO4=) and spatial variability of ionic concen trations and deposition among sites. Seasonal patterns of most ions sh owed highest concentrations during the summer months and deposition of H+ was especially pronounced during this time. Deposition of all ions was generally greater (related to greater precipitation) at three mon tane forested sample sites compared to a nonforested riverbottom site. Precipitation chemistry at FEF was similar to other sites throughout the eastern United States and contrasted sharply with mid-western and western sites. Eastern sites, including means for FEF sites, were unif ormly 3-4 times higher in H+ and SO4 = concentration than the mid-west ern and western sites. Precipitation at FEF was chronically acidic, mo re so during the growing season, and highest at higher elevations wher e environmental stresses can be most severe. Furthermore, there were o ccasional large discrepancies between the low-elevation site and the h igher-elevation forested sites for precipitation chemistry and acidic deposition. These results suggest that synoptic-scale (network) data m ay greatly underestimate the pollutant conditions to which high-elevat ion forest trees are exposed, since network data rarely take elevation into account and typically are based on annual ionic concentration an d deposition means that may be considerably lower than those of the gr owing season.