Pterocarpus angolensis growth rings and precipitation

A comparison between Zambezi and Otjozondjupa region, Namibia

Abstract

Pterocarpus angolensis is one of the most valuable species used for timber in Southern African countries. In Namibia, the species has been harvested for over 90 years for both commercial and domestic use. This is likely to lead to unsustainable management if efforts to understand the growth and response of the species to environmental conditions are not made. This study aimed to compare growth rings to precipitation in Zambezi and Otjozondjupa regions. Ten trees were sampled and from the disks, tree ring widths with two radii were measured with a microscopic device. Crossdating was carried out to construct the indexes, which was used to prepare the master of chronology. The findings show that the rainfall amount is not necessarily the limiting factor, as a weak correlation in both regions was found, regardless of the amount of rainfall received in the region. The results show a better correlation, though negative, between the months of September and December. Further studies are required that use precipitation data for stations near study sites and the consideration of other factors such as soil, temperature and fire regimes. The use of rainfall data from much less distance to the study site are recommended as well as the consideration of soil, temperature and fire aspects.