Volume and Aboveground Biomass Models for Dry Miombo Woodland in Tanzania

Abstract

Tools to accurately estimate tree volume and biomass are scarce for most forest types in East Africa, including Tanzania. Based on a sample of 142 trees and 57 shrubs from a 6,065 ha area of dry miombo woodland in Iringa rural district in Tanzania, regression models were developed for volume and biomass of three important species, Brachystegia spiciformis Benth. (n = 40), Combretum molle G. Don (n = 41), and Dalbergia arbutifolia Baker (n = 37) separately, and for broader samples of trees (28 species, n = 72), shrubs (16 species, n = 32), and trees and shrubs combined (44 species, n = 104). Applied independent variables were log-transformed diameter, height, and wood basic density, and in each case a range of different models were tested. The general tendency among the final models is that the fit improved when height and wood basic density were included. Also the precision and accuracy of the predictions tended to increase from general to species-specific models. Except for a few volume and biomass models developed for shrubs, all models had R2 values of 96–99%. Thus, the models appear robust and should be applicable to forests with similar site conditions, species, and diameter ranges.