Spatial and vertical variation in calorific value of two Quercus species and its correlation to wood chemical components

To compare the spatial and vertical variation in calorific value of two Quercus species (Quercus acutissima Carr. and Quercus variabilis Bl.) and analyze correlations between calorific values and wood chemical characteristics (lignin, cellulose, ash, benzene-alcohol extractive), an investigation was made in the 22 year-old plantations of the two species by sample tree techniques. Calorific values and wood chemical components were determined based on the sample discs taken at the stem height of 0.0m (base), 1.3m, 3.6m, 5.6m, 7.6m and 9.6m from the sample trees and also determined for ring groups (two rings) of each disc from pith to bark separately. The results indicated that there was a significant difference in calorific values among tree height (disc positions) as well as among ring groups within species. Calorific values of Quercus acutissima increased form pith to bark. In contrast to Quercus variabilis, calorific values tended to increase along the tree stem towards the tree top. Regression analysis indicated that the correlation between calorific values and wood chemical components of each disc position and ring group was generally weak, and calorific value dominantly positive for lgnin and cellulose, but negative for ash and benzene-alcohol extractive.