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

Abstract

With increasing private sector investments in commercial forestry, it is apparent that plantation forestry in Sri Lanka is moving in the direction of managing fast growing timber species for shorter rotations. However, there's a perceptionthat accelerated growth rates induced by improved forest management practices can result in inferior wood quality. This study tested this perceptionby studying the effect of growth rate on the specific gravity, as a proxy for wood quality, of three alternative timber species 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 ring width in K. senegalensis while S. macrophylla exhibited a slight increase in specific gravity from pith to bark. This increasing trend was more prominent in P. fortunei. Results revealed growth rates represented by ring width showed poor correlations with specific gravity in both S. macrophylla, and K. senegalensis. Although P. fortunei showed a statistically significant positive correlation, regression analysis indicated a poor relationship between growth rate and specific gravity. Hence it is unlikely that wood specific gravity of the studied species to be influenced by accelerated growth rates.