Models for Measuring Height-Diameter Relationships for Agarwood (AquilariamalaccensisLamk) Plantations in Bangladesh

Abstract

The relationship between tree height and diameter is an important element in growth and yield models, in carbon stock estimation and timber volume models, and in the description of stand dynamics.In this paper considered18 functional models and evaluated the performance that predict total tree height from diameter at breast height of agarwood. The models were applied to A.malaccensisLamk (Agarwood) which is economically important tree species planted in some potential forest areas of Bangladesh.A total of 5,866 tree heights and corresponding diameters at breast heights were extracted from many forest areas in Sylhet, Chittagong, Cox's Bazar and Chittagong Hill Tracts (Rangamati) forest division. The model goodness of fit values were evaluated in terms of adjusted coefficient of determination (R2), root mean squared error (RMSE), Akaike’s information criterion (AIC),Durbin- Watson statistic value,homogeneity of the residuals and significance of the regression parameters. The results of the study indicated that the height-diameter relationship can best be described by non-linear models. The best three models selected for the species with ranking in terms of goodness of fit. The Gompertz𝐻 = 17.0360 × exp⁡(−2.3614 × exp(−0.1009 × 𝐷)); Parabolic𝐻 = 0.4561 + 0.7735 × 𝐷 − 0.0089 × 𝐷2and Logistic (1 6.1156 ) 15.2424 0.1674 D e H      with R2=0.91 were height-diameter models performed better than other models.