Biometric assessment of early stem growth at a commercial stand of African mahogany (Khaya grandifoliola)

Abstract

African mahogany species (Khaya spp.) have proven to be promising in the Brazilian forestry scenario, replacing native mahogany owing to their medium-fast growth and relevant timber value. This study aimed to carry out forest inventory and assessments of a Khaya grandifoliola plantation in the first years after planting, test hypsometric models to describe tree growth, and identify the maximum commercial stem yield (i.e., greater than 6 m in height). The stand was located in the municipality of Piracanjuba (GO), where seedlings of seed origin were used. Twenty random plots with a 15 m radius were allocated, and the total height (HT), stem height (HS), diameter at breast height (DBH), crown area, and forest canopy were measured. Four hypsometric models were employed in this study. The best equation was selected based on determination coefficients and standard errors. Further, the models were cross-validated to evaluate predictability and bias. At four years of planting, the largest class of HS was found to range from 3.1 to 4.1 m, and most trees had a DBH ranging from 0.084 to 0.126 m. The percentage of trees with stems > 6 m was 8.35%. The linear model ensured more consistent results for estimating HT, while the quadratic and Weibull models led to more consistent results for HS. By using models, stem measurements can be measured based on DBH, ultimately aiding the selection of stem management strategies for the growth of forests with greater commercial value.