A multi-species density-dependent matrix growth model for the dry woodlands of Uganda

A density-dependent matrix growth model was constructed for the dry woodlands of Uganda basing on material collected from 42 sample plots with 7904 trees. The model was based on functions for individual tree upgrowth and mortality, and area-based ingrowth, with explicatory variables representing tree size, stand density and stand structure. The trees were pooled into three species groups basing on ecological and morphological criteria. For all groups, parameter estimates for tree size and stand density were found highly significant (p < 0.001) in predicting diameter increment and mortality except stand density for the upper storey species group (p = 0.067), while stand structure was found highly significant only for the intermediate storey species group. Ingrowth was modelled by a two-stage approach. Parameter estimates for a logistic function predicting the probability of ingrowth were statistically significant (p < 0.05) only for the intermediate storey species group, while no conditional ingrowth functions were built for any species group. A visual evaluation of the individual functions was carried out and the matrix model in totality was evaluated by comparing the number of trees ha−1 and basal area ha−1 for each plot at the time of the second inventory with the model predictions. Although the data used for model evaluation was not independent, it was concluded that the model is a reliable and fairly accurate tool for prediction of growth of dry woodland trees in of Uganda. The model may become a useful tool for a sustainable management of these woodlands, which are an important source of bioenergy for consumers in several urban centres.