HERBACEOUS LAYER AND SOIL RESPONSE TO EXPERIMENTAL ACIDIFICATION IN ACENTRAL APPALACHIAN HARDWOOD FOREST

The herbaceous layer (vascular plants less-than-or-equal-to 1 m in hei ght) is an important component of forest ecosystems and a potentially sensitive vegetation stratum in response to acid deposition. This stud y tested several hypotheses concerning soil and herbaceous layer respo nse to experimental acidification at the Fernow Experimental Forest in north-central West Virginia. Fifteen circular sample plots (0.04 ha) were established in each of three watersheds: WS3 (an almost-equal-to 20-yr-old watershed receiving acidification treatment with (NH4)2SO4), WS4 (>80-yr-old control), and WS7 (almost-equal-to 20-yr-old control) . The herb layer was sampled intensively in 10 1-m2 subplots within ea ch sample plot, including determination of species composition, cover, and random biomass harvests. Harvested plant material was separated b y species and analyzed for macronutrients, micronutrients, and Al. Soi l was sampled from harvest subplots and analyzed for texture, pH, orga nic matter, and macro- and micronutrients. Few differences among water sheds for virtually all measured soil variables indicated minimal resp onse of soil fertility to the acidification treatment. The herbaceous layer was also quite similar among watersheds with respect to cover-bi omass and species diversity; WS7, however, had almost-equal-to 70% hig her herb layer cover that both Ws3 and WS4, a result of the predominan ce of a few high-cover fern species and attributable to the north-faci ng aspect of WS7 vs. south-facing aspects of WS3/WS4. There was a high degree of species similarity among watersheds, suggesting no shift in species composition in response to acidification. There was also mini mal response of element concentrations to acidification, although Fe a nd Al exhibited evidence of increased uptake in WS3. We conclude that, contrary to our expectations, there has been little substantive respo nse of the soil and herb layer to acidification, but hypothesize that herbaceous layer species may experience toxicity problems with increas ed mobility of Al and micronutrients in the future.