CONSTRUCTION OF A GROWTH MODEL TO PREDICT INDIVIDUAL STEM VOLUME FOR Eucalytus grandis PLANTATION IN PIDURUTALAGALA AREA IN NUWARA ELIY A
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Timber volume is the most crucial variable in commercial forest plantations. Therefore model construction for Eucalyptus grandis to predict the main stem volume for individual trees precisely. The study was carried out in Pedruthalagala area in Nuwara Eliya district because the selected plantation is well matured and at the felling age. The circular sampling plots of 0.02 hectare were decided to obtain the required tree measurement. Diameter at breast height, total height, diameter at different height levels were taken by usingthe instruments such as diameter tape, Blume Leiss altimeter, and Spiegel relaskop. All together 14 such plots were used to take the measurements. The basic relationship was developed using the equations volume = form factor * basal area * height. Because form factor is difficult to quantify, it was tried to replace it by usingthe plantation attributes such site quality, age etc. At the first phase of this study 12 equations were selected and after a series of rigorous testing, such average model bias, efficiency, residual distribution and R2, two models were selected for the use in the field. These models are follows 1. vol=O.147(g*h)+O.00839top 2. vol=O.147(g*h)+O.637topiage Where: g*h = basal area tpp = top height to/age = top height / age g = diameter
Timber volume is the most crucial variable in commercial forest plantations. Therefore model construction for Eucalyptus grandis to predict the main stem volume for individual trees precisely. The study was carried out in Pedruthalagala area in Nuwara Eliya district because the selected plantation is well matured and at the felling age. The circular sampling plots of 0.02 hectare were decided to obtain the required tree measurement. Diameter at breast height, total height, diameter at different height levels were taken by usingthe instruments such as diameter tape, Blume Leiss altimeter, and Spiegel relaskop. All together 14 such plots were used to take the measurements. The basic relationship was developed using the equations volume = form factor * basal area * height. Because form factor is difficult to quantify, it was tried to replace it by usingthe plantation attributes such site quality, age etc. At the first phase of this study 12 equations were selected and after a series of rigorous testing, such average model bias, efficiency, residual distribution and R2, two models were selected for the use in the field. These models are follows 1. vol=O.147(g*h)+O.00839top 2. vol=O.147(g*h)+O.637topiage Where: g*h = basal area tpp = top height to/age = top height / age g = diameter