DISTRIBUTION OF BIOMASS IN AN INDIANA OLD-GROWTH FOREST FROM 1926 TO 1992

We examined the structural and spatial distribution of woody biomass i n relationship to disturbance in an Indiana old-growth deciduous fores t over a 66-yr period. Analysis was done on the core 7.92 ha of a 20.6 -ha forest in which every tree 10 cm dbh and over has been tagged and mapped since 1926. Five years are compared-1926, 1976, 1981, 1986 and 1992. Dry weight of living biomass for the 7.92-ha area for these 5 vr was 154 Mg/ha, 207 Mg/ha, 220 Mg/ha, 216 Mg/ha and 211 Mg/ha, respect ively Biomass of dead trees was 1 Mg ha(-1) yr(-1) from 1977 through 1 981; 4 Mg ha(-1) yr(-1) from 1982 through 1986; and 3 Mg ha(-1) yr(-1) from 1987 through 1992. Biomass of trees that died between 1976 and 1 992 was greatest for midseral species. Living biomass of dominant earl y to midseral species is declining while that of late seral species is increasing. In 1926 biomass of trees 10 to 25 cm diam consisted of 14 % Quercus spp. and 12% Acer saccharum. By 1992 biomass in this diamete r range consisted of 1% Quercus spp. and 43% A. saccharum. Equilibriun parch size was estimated for biomass at each of the five inventory da tes to determine ii there was a change. Equilibrium patch size for bio mass was estimated to be 0.64 ha during all five inventory dates based on the coefficient of variation (CV) of biomass for 16 different grid cell sizes. Grid cell size refers to tile size of adjacent cells in a grid that covered the entire study area. The grid with the smallest c ells had cells of 0.01 ha. This grid of 0.01-ha cells was aggregated t o 15 additional grid cell sizes, where the largest grid cell size was 1.98 ha. CV for all grid cell sizes was highest in 1926 due to effects of prior grazing. There data indicate an increase in deadwood biomass , a drift in stand composition, recovery from grazing by an increase i n small diameter trees and no change in equilibrium patch size over th e five inventory dates.