Wood density of three oak species in East Tennessee : 1940-45 and 1970-75

The oak-hickory forests of East Tennessee were investigated at five locations in the vicinity of two coal-fired power generating facilities operated by the Tennessee Valley Authority. Three oak species (Quercus spp.) were sampled to determine whether wood cell density is related to air pollution (NO_x, SO₂) or acidified rain. Increment cores were collected and two periods (1940-45 and 1970-75) were analyzed by gamma-densitometric technique (Woods and Lawhon 1974). Wood densities were partitioned by latewood and earlywood and the component densities (density variables) which were average earlywood, average latewood, minimum earlywood, maximum latewood, and average period (1940-45, 1970-75) were statistically compared. When all trees of each species on all sites were analyzed, all com ponent densities for white (Quercus alba L.) and chestnut (Quercus prinus L.) oaks were greater for the period of 1940-45 than for the period 1970-75. Only for the minimum earlywood density of chestnut oak was the level of significance less than P=0.01. For black oak (Quercus velutina L.) differences between the two time periods were found only for the mean earlywood (P=0.05), maximum latewood (P=0.Q5) and mean period densities (P=0.01). There were no differences between mean latewood and minimum earlywood values.

Mean period density was less for period 2 (P=0.01) for all three species. Only for the components which comprise this measure of density were there any differences, and non-significant differences (P=0.05) were found in only two component densities for black oak.

The lower component densities In the period 1970-75 are discussed in terms of air pollution affects on tree growth rates and on forest productivity.