PROCEEDINGS: Index of Abstracts

THIRTY-THREE YEAR CHANGES IN ABOVE- AND BELOW-GROUND BIOMASS IN NORTHERN HARDWOOD STANDS IN VERMONT

A. H. Johnson-1 and G. R. Strimbeck-2

1-University of Pennsylvania Department of Geology, Philadelphia, PA 19104. 2-University of Vermont, Burlington, VT 05405.

In 1957-1960, R. O. Curtis and B. W. Post surveyed 81 even aged (45-90 y old) northern hardwood stands on acid till soils over the length of Vermont's Green Mountains. The purpose of the original study was to determine predictive relationships between site index and site characteristics, including latitude, elevation, soil drainage class, soil organic matter content and soil nutrients. The sites were not randomly selected in the 1950s. Rather, they were chosen to represent a range of stand ages and the range of environmental conditions associated with northern hardwood forests growing on acid till. In 1990-92 we were able to reliably relocate 40 of the original plots using sketch maps and witness trees. In 1990-91 we sampled 23 of the plots which were relocated exactly by blazed witness trees. These plots showed no signs of human disturbance other than possible minor removal of red maple for stand improvement. In 1992, we relocated 17 sites that had been selectively logged. The original witness trees had been removed in most cases, and these plots were located from roadside monuments, measured distances and compass bearings. Remeasurements of tree and soil characteristics allowed comparison of tree heights, basal areas, volumes, above-ground biomass, and soil organic matter pools.