Wetfall Deposition and Precipitation Chemistry for a Central Appalachian Forest

Abstract

Although extensive research on acidic deposition has been directed toward 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 deposition. Emphasis was placed on seasonal patterns of ionic concentrations (H+, Ca++, NH4+; NO3-, and SO4=) and spatial variability of ionic concentrations and deposition among sites. Seasonal patterns of most ions showed 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 montane 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 uniformly 3-4 times higher in H+ and SO4= concentration than the mid-western and western sites. Precipitation at FEF was chronically acidic, more so during the growing season, and highest at higher elevations where environmental stresses can be most severe. Furthermore, there were occasional large discrepancies between the low-elevation site and the higher-elevation forested sites for precipitation chemistry and acidic deposition. These results suggest that synoptic-scale (network) data may greatly underestimate the pollutant conditions to which highelevation forest trees are exposed, since network data rarely take elevation into account and typically are based on annual ionic concentration and deposition means that may be considerably lower than those of the growing season.

Global assessment of nitrogen deposition effects on terrestrial plant diversity: a synthesis

“…N concentrations in the dominant species were significantly higher in treatment plots, whereas cation concentrations were generally lower, supporting the conclusions of Gilliam and Adams (1996). Density and biomass declined 80% and ;90%, respectively, for all herb-layer species; particularly notable was the dominant species, Maianthemum canadense.…”

“…Increased N inputs of 16-48% (Fowler et al 1999) can be further enhanced in high altitude forests from orographic effects (Dore et al 1992). Gilliam and Adams (1996) found wet N deposition to be 50% higher at 750 m than at 500 m in eastern U.S. hardwood forests. Thus, high-altitude forests are at particular risk from the impacts of N deposition.…”

“…Salient details of these studies are summarized in Appendix A. N has been added to an entire watershed at the Fernow Experimental Forest (FEF), West Virginia, since 1989. Foliar analysis of a common herb-layer species, Viola rotundifolia, revealed higher N in the treatment vs. control watersheds, accompanied by lower Ca and Mg, in response to four years of treatment, suggesting that N additions increased N availability and decreased Ca 2þ and Mg 2þ availability to herb-layer species (Gilliam and Adams 1996). Hurd et al (1998) added N at three hardwood sites in the Adirondack Mountains, New York, finding that cover of dominant herbaceous species declined significantly after three years of treatment, partly from increased shading by fern species.…”

Effects of Nitrogen on Temporal and Spatial Patterns of Nitrate in Streams and Soil Solution of a Central Hardwood Forest

“…We tested the following hypotheses: (1) changes in stream NO 3 − for both untreated and Ntreated watersheds will follow recent observations of decline in stream NO 3 − at various sites in the eastern United States, and (2) experimental additions of N will decrease spatial heterogeneity in soil N processing at the watershed scale in a central Appalachian hardwood forest. [29]; dry deposition of N is ∼2 kg N ha −1 yr −1 [31]. Tree species were generally similar on these watersheds, with the primary difference being one of dominance.…”

Acidification and Nutrient Cycling

“…For these analyses, inputs were calculated on a calendar year basis, using data from the Fernow Fork Mountain deposition monitoring site, located near the top of WS4, and from the Parsons NADP site located in the Nursery Bottom in Parsons, West Virginia. Both of these sites and methods are described in Adams et al (1994) and Gilliam and Adams (1996). Briefly, precipitation samples were obtained using Aerochem Metric automated wet/ dry collectors, and open bucket "bulk" collectors.…”