- Johnson, Arthur H.
University of Pennsylvania, Department of Earth and Environmental Science University
In the early 1930’s, Carl C. Heimburger measured soil pH and dilute-acid extractable Ca at approximately 100 sites across the Adirondacks. In 1984, we located more than 60 of those plots, and measured the same variables, repeating his procedures. The 1984 samples were stored for the comparisons done in this study. In 2004 we located 54 of the plots, and repeated the vegetation and soil studies done in 1984. The result of this time series showed depletion of plant-available Ca in organic and upper mineral horizons in spruce-fir, northern hardwood, and pine forests between 1930 and 2006 of 49%, 52% and 59%, respectively. Between 1984 and 2004 there was a significant region-wide loss of Ca from the Oe horizons. The average annual rates of forest floor Ca loss measured between 1930 and 1984, and between 1984 and 2004 in spruce-fir stands were 7.6 and 9.4 kg ha-1y-1, remarkably similar to the annual rate of Ca loss measured in a 4-yr study conducted in the spruce-fir forest on Whiteface Mt., NY (8.4 kg ha-1y-1).
In 1984 we established permanent vegetation plots at the soil sampling sites, and we measured the trees again in 2004. In spruce-fir plots, there was a large (35%), statistically significant reduction in live red spruce basal area between 1984 and 2004, and in the northern hardwood plots, a significant reduction in sugar maple sapling density. Both of those species are known to be adversely affected by low soil Ca levels.