Abstract:
Volume of trees is an important parameter in forest management, but only volume models with limited geographical
and tree size coverage have previously been developed for Tanzanian miombo woodlands. This study
developed models for estimating total, merchantable stem and branches volume applicable for the entire miombo
woodlands of Tanzania. We used data from 158 destructively sampled trees, including 55 tree species collected
from wide geographical and biophysical ranges. We developed general and site-specific models with diameter at
breast height only as the independent variable, together with models with both diameter at breast height and tree
height. Leave-one-out cross-validation was used to evaluate the models. The total tree volume models that included
diameter at breast height and tree height had appropriate predictive capabilities with relative root mean square
errors (RMSEr) ranging from 30.5% to 47.6%. The RMSEr for total tree volume models with diameter at breast height
only ranged from 39.9% to 48.0%. The site-specific models had slightly lower RMSEr values relative to the general
models. The relative mean prediction error of the general total tree volume model with diameter at breast height and
tree height was lower (0.6%) than those of the previously developed models (−30.7% to 31.2%). Based on the evaluations,
we recommend the general total tree models to be applied over a wide range of geographical and biophysical
conditions in Tanzania.
