Effect of Growth Rate on Wood Specific Gravity of Three Alternative Timber Species in Sri Lanka; Swietenia macrophylla, Khaya senegalensis and Paulownia fortunei

With increasing private sector investments in commercial forestry, it is apparent that plantationforestry in Sri Lanka is moving in the direction of managing fast growing timber species for shorterrotations. However, there’s a perceptionthat accelerated growth rates induced by improved forestmanagement practices can result in inferior wood quality. This study tested this perceptionby studyingthe effect of growth rate on the specific gravity, as a proxy for wood quality, of three alternative timberspecies grown in Sri Lanka; Swietenia macrophylla, Khaya senegalensis and Paulownia fortunei.Specific gravity remained more or less uniform from pith to bark regardless of the fluctuation of ringwidth in K. senegalensis while S. macrophylla exhibited a slight increase in specific gravity from pith tobark. This increasing trend was more prominent in P. fortunei. Results revealed growth rates representedby ring width showed poor correlations with specific gravity in both S. macrophylla, and K.senegalensis. Although P. fortunei showed a statistically significant positive correlation, regressionanalysis indicated a poor relationship between growth rate and specific gravity. Hence it is unlikely thatwood specific gravity of the studied species to be influenced by accelerated growth rates.