Elevated acid deposition has been a concern in the central Appalachian region for decades. A long-term acidification experiment on the Fernow Experimental Forest in central West Virginia was initiated in 1996 and continues to this day. Ammonium sulfate was used to simulate elevated acid deposition. A concurrent lime treatment with an ammonium sulfate treatment was also implemented to assess the ameliorative effects of base cations to offset acidification. We show that the forest vegetation simulator growth model can be locally calibrated and used to project stand growth and development over 40 years to assess the impacts of acid deposition and liming. Modeled projections showed that pin cherry (initially) and sweet birch responded positively to nitrogen and sulfur additions, while black cherry, red maple, and cucumbertree responded positively to nitrogen, sulfur, and lime. Yellow-poplar negatively responded to both treatments. Despite these differences, our projections show a maximum of 5% difference in total stand volume among treatments after 40 years.

The long-term effects of soil acidification on the development of a young aggrading Appalachian forest were examined after 21 years of continuous treatment. Beginning with a clearcut harvest in 1997, annual ammonium sulfate (N+S) and ammonium sulfate with lime (N+S+LIME) treatments were aerially applied to a developing forest. The lime treatment was designed to counteract the acidification of the nitrogen and sulfur amendments. After 21 years, the N+S and N+S+LIME treatments had little impact on total woody biomass accumulation relative to the control. There were significant differences among species and treatment responses with respect to woody biomass accumulation, however. Biomass of Prunus pensylvanica was about twice as much as any other species in N+S and N+S+LIME treatments but was similar to Liriodendron tulipifera and Betula lenta on control areas. Treatment effects were not significant for average tree diameter or stem density, although both varied among the six tree species with the highest importance values. The importance value of P. pensylvanica decreased by almost half in the last 6 years due to mortality, but this was not associated with either the N+S or N+S+LIME treatments. The dynamic nature of this short-lived tree species is potentially masking any effects of the N+S or N+S+LIME treatments to date. Study Implications: We examined the long-term impact of nitrogen and sulfur additions with and without lime on forest stand development. After 21 years, the forest showed little change in aboveground woody biomass, although the distribution of biomass among species was affected by the treatments. Prunus pensylvanica (pin cherry) accumulated the greatest biomass on N+S and N+S+LIME treatments relative to the untreated areas. However, P. pensylvanica is a short-lived species, and our data show it is declining. It is unclear whether the treatments are having minimal impacts or they are being masked by the early dominance and subsequent mortality of P. pensylvanica.