Height-Diameter Allometry for Tree Species in Tanzania Mainland

Abstract

Total tree height (H) and diameter at beast height (D) are important independent variables in predicting volume, biomass, and other forest stand attributes. However, unlikeDmeasurement, which is easy to measure with high accuracy,Hmeasurement is laborious. This study, therefore, developedH-Drelationships for ten different forest types in Tanzania Mainland. Extents in which climate and forest stand variables explain the variation inH-Dallometry were also assessed. A total of 31782 sample trees covering miombo woodlands, humid montane, lowland forests, bushlands, grasslands, mangroves, cultivated land, wetlands forests, and pines andEucalyptusspecies plantations were used for model development. TheHestimating model without climate and forest stand variables referred herein as “base model” was first developed followed by “generalized model” which included climate and stand variables. All the data were fitted using nonlinear mixed effect modelling approach. Results indicated that generalizedHestimating models had better fit than the base models. We therefore confirm a significant contribution of climate and forest structure variables in improvingH-Dallometry. Among the forest structure variables, basal area (BA) was far more important explanatory variable than other variables. In addition, it was found that the mean treeHtends to increase with the increase of mean precipitation (PRA). We therefore conclude that forest specific generalizedHmodel is to be applied when predictingH. When forest type information is not available, generalized regional model may be applied. Base model may be applied when forest stand or climate information are missing.