Allometric Modelling of Tectona grandis for Diameter at Breast Height and Crown Collar Diameter Estimations in the Dry Semi-Deciduous Forest Zone of Ghana

Abstract

The increased rate of deforestation and forest degradation in developing tropical countries like Ghana, necessitated massive afforestation and reforestation as the approach for mitigating this menace with mostly short rotational tree crops like Tectona grandis (teak). Teak poles have been noted worldwide for their durability especially for electrification projects. However, its usage for electrification projects in Ghana has attracted immense attention and concern in Ghana primarily because of massive demand but frequent rejection of the poles due to unsuitable crown collar diameter and length of the tree required for electric poles. Currently, the relationship between the diameters at breast height, collar diameter and height - parameters that can be adopted for easy determination of crown collar diameter on field has not been well established in Ghana. This study was carried out to determine the relationships between and among diameter at breast height, height and crown collar diameter and diameter at breast height, height and crown collar diameter of teak in the dry semi-deciduous forest zone of Ghana to ease the determination of crown collar diameter to avoid its waste due to rejection. The study was carried out in compartment 5 of Chirimfa Forest Reserve. Diameter at breast height, total height and crown collar diameter variables were measured on hundred (100) felled trees. Regression analysis performed at a confidence level of 95% revealed no significant relationship (R² = 0.00, p > 0.05) between diameter at breast height and total height. However, significant relationship (R² = 73.40, p < 0.05) was found between crown collar diameter and diameter at breast height. The significant relationship (R² = 76.60, p < 0.05) among crown collar diameter, diameter at breast height and height as indicated by the model CD _(cm) = 0.6625DBH _(cm) – 0.563H _(m) + 3.83, indicates that the appropriate determination of crown collar diameter of teak is a function of height and DBH growth. However, relationship between DBH and collar diameter was the strongest and suggest the DBH as the most important determining parameter for correlating Collar diameter of teak trees in the dry semi-deciduous forest zone of Ghana The study has thus provided a baseline equation that could be used to predict and determine teak trees crown collar diameters with diameter at breast heights in Ghana and also for further exploration for better predictions.

Keywords: Deforestation, degradation, reforestation, electrification, diameter, collar