The effect of acid deposition on American beech growth.

Abstract

Human induced acid precipitation has been shown to cause large negative effects on sensitive ecosystems in areas that have a direct association with a large-scale producer of pollution. However, the effects of acid deposition on forests in non-industrial, calcareous areas remain relatively unexamined. Thirty American beech (Fagus grandifolia) trees from Colonial Point in Pellston, MI were cored and their annual rings were measured. These measurements were then compared to SO4 and nitrogen wet deposition data collected over the past twenty years. We hypothesized that increased SO4 deposition would correspond to lower annual growth, while nitrogen deposition could either correlate positively or negatively with growth. Our results show a significant positive relationship between average annual tree growth and SO4 wet deposition, and no significant correlation between nitrogen deposition and annual growth. We attribute these unexpected results to the highly calcareous nature of the soil and the nature of the pollutants.