Tree-ring analysis for sustainable harvest of Millettia stuhlmannii in Mozambique

Abstract

Millettia stuhlmannii (Taub.) is a highly desirable timber species throughout its range in southeastern Africa and one of the three most important timber trees in Mozambique where it is intensely harvested. Relatively little is known with regard to the species' long-term radial growth rates, leaving open the question of whether current harvest schemes are sustainable. Tree-ring analysis is a useful method for obtaining accurate estimations of age and growth rate of tropical tree species. This paper presents results of tree-ring analyses of M. stuhlmannii from a large timber concession in the Sofala Province of central Mozambique. The analyses include estimates of: (1) tree age, (2) radial growth dynamics, and (3) the relationship between tree diameter and the percentage of heartwood relative to diameter. Our findings indicate that annual radial growth can be highly variable among and within individual M. stuhlmannii trees at the site. We also find that the relationship between stem diameter and percentage heartwood is significantly positive, suggesting that optimal harvesting diameters for this characteristic can be reliably determined. Given the lack of information on growth history and the potential for unsustainable exploitation, these findings are highly relevant to the sustainable management of this important timber species.