Management implications of annual growth rings in Pterocarpus angolensis from Zimbabwe

Dendrochronological analyses indicate that Pterocarpus angolensis produces anatomically distinctive annual,growth rings in the indigenous forests of western Zimbabwe. Annual growth rings in P, angolensis can be identified on highly polished cross-sectional surfaces on the basis of the semi-ring porous tree rings; the reasonably continuous band of initial parenchyma; and by smaller changes in vessel diameter, wood density, and color from the early-wood to late-wood portion of the growth rings. Together, four lines of evidence indicate that these growth bands are annual: P. angolensis is strongly deciduous and the phenology of this species is tightly synchronized with the seasonality of rainfall in western Zimbabwe; the growth rings are semi-ring porous; ring-width time series are highly correlated between trees at a single forest location, and between forests separated by >100 km; and also because the mean ring-width chronologies derived from these trees are significantly correlated with regional rainfall totals during the wet season from 1901-1990. P. angolensis is one of the most valuable timber species in south tropical Africa, and the discovery of exactly annual growth rings will allow detailed analyses of the growth and yield under different ecological and management settings. It may also be possible to develop centuries-long tree-ring chronologies from P. angolensis, which would be useful for the reconstruction of past climate and streamflow. (C) 1999 Elsevier Science B.V. All rights reserved.