Modeling above-ground bole biomass of selected tree species within the Forestry Research Institute Of Nigeria (FRIN)

Abstract

The objective of this study was to develop species-specific allometric models and pooled above-ground bole biomass models for selected tree species within the Forest Research Institute of Nigeria (FRIN). The objective was met by obtaining, Diameter at Breast Height (DBH), Diameter at Top (DT) and Bole Height (BH) of tree species. The collected variables were used and two selected species in terms of their basal area coverage: Khaya senegalensis and Pinus caribaea were selected for biomass modeling. The allometric models were developed from a two-step stratified sampling approach. Population dimensions were determined from sample plots, where-after trees were sampled for biomass representing the collected dimensions. The dry mass of the sampled components were used in a regression modeling approach to develop a set of species-specific and combined species linear models. The best models were selected based on goodness-of-fit model evaluation criteria and a two-step upscaling  process was used to upscale samples to tree level and from tree to stand level. DBH and basic density were significant predictors of total  aboveground bole biomass (AGBB) and diameter as single predictor produced consistently good results. Diameter was used throughout the up scaling process to determine the biomass per ha. The R² fit for the models were high (0.99). Models 5 and 10 had low RMSE (9.38 and 7.55) and BIC values of 83.4 and 77.1. The parameter p-values of all models were significant (p <0.05). Future research can investigate remote sensing applications with field data to estimate forest biomass over larger areas.

Keywords: Khaya senegalensis, Pinus caribaea, species-specific models, combined-species models, diameter, basic density.