Construction of a stem volume prediction model for mature Eucalyptus grandis plantation in Pidurutalagala of Nuwara Eliya, Sri Lanka
by
Kandiah Selvarathnam and Upul Subasinghe
by
Kandiah Selvarathnam and Upul Subasinghe
Timber volume is the most crucial variable in commercial forest plantations. Therefore a precise volume prediction model was constructed for the mature Eucalyptus grandis plantation located in the Pidurutalagala mountain of Nuwara Eliya District, Sri Lanka.
0.02 ha circular samples were used for the data collection. Breast height diameter (dbh) and total height (h) were measured as the preliminary measurements. Then the stems of the standing trees in the sample plots were divided into sections and section lengths, end-diameters and mid-diameters were measured in order to use the Newton's formular for the stem volume estimations. Altogether 14 samples were used for the data collection.
A basic relationship was then developed by assuming the stem volume (v) can be predicted as a function of h, basal area (g) which is calculated using dbh and site quality as given below.
0.02 ha circular samples were used for the data collection. Breast height diameter (dbh) and total height (h) were measured as the preliminary measurements. Then the stems of the standing trees in the sample plots were divided into sections and section lengths, end-diameters and mid-diameters were measured in order to use the Newton's formular for the stem volume estimations. Altogether 14 samples were used for the data collection.
A basic relationship was then developed by assuming the stem volume (v) can be predicted as a function of h, basal area (g) which is calculated using dbh and site quality as given below.
v = f (g, h, site quality)
In order to represent the site quality, top height and top height / age functions were used. Regression analysis (linear) was used to quantify the relationships. In order to obtain the best models, the variables in the above equation were transformed into different forms that can biologically be accepted. R2 and standard residual distrinbution were used to evaluate the model quality. After a careful study, two models were selected to predict the stem volume of E. grandis trees in the selected plantation.
In order to represent the site quality, top height and top height / age functions were used. Regression analysis (linear) was used to quantify the relationships. In order to obtain the best models, the variables in the above equation were transformed into different forms that can biologically be accepted. R2 and standard residual distrinbution were used to evaluate the model quality. After a careful study, two models were selected to predict the stem volume of E. grandis trees in the selected plantation.
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