Patterns of trace metal concentration and acidity in montane forest soils of the northeastern United States

Abstract

Forest floor and mineral soil samples were collected from subalpine spruce-fir forests at 1000 m above mean sea level on 19 mountains in the northeastern United States to assess patterns in trace metal concentrations, acidity, and organic matter content. The regional average concentrations of Pb, Cu, and Zn in the forest floor were 72.3 (2.9 s.e.) μg g−1, 8.5 (0.7) μg g−1, and 46.9 (2.0) μg g−1, respectively. The regional average concentrations of Pb, Cu, and Zn in the mineral soil were 13.4 (0.8) μg g−1, and 18.2 (1.2) μg g−1, respectively. The regional average pH values of the forest floor and mineral soil were 3.99 (0.03), and 4.35 (0.03), respectively. The Green Mountains had the highest concentrations of Pb (105.7 μg g−1), and Cu (22.7 μg g−1), in the forest floor. They also had the highest concentrations of Cu (18.0 μg g−1), in the mineral soil. Site aspect did not significantly influence any of the values. Concentrations of Pb were lower than concentrations reported earlier in this decade at similar sites while concentrations of Cu and Zn remained the same. We believe that these lower Pb concentrations reflect real changes in forest Pb levels that have occurred in recent years.