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Tree Volume Tables for Acacia Mangium in the Plantations of Bangladesh

M. A. Latif
Senior Research Officer
Forest Inventory Diovision, BFRI, Chittagong.

M. A. Habib
Forest Inventory Diovision, BFRI, Chittagong.

S. Das
Forest Inventory Diovision, BFRI, Chittagong.

Abstract/ Executive Summary:

Acacia mangium Willd. (mangium) is a promising fast growing multipurpose tree species of the family Leguminosae. The species has been successfully introduced to Bangladesh and is being planted since 1983. An attempt was made to prepare the volume tables for the species. Diameter at breast height (Dr-volume and D-height-volume relationships were determined to estimate the total volumes over bark and under bark. It was observed that the logarithmic function to the base e gives a good fit model for the same .

Keywords: Plantation, Acacia mangium Willd, Data, Measurement.

Location: Felled trees.

Start Date: 01-07-1979

End Date: 30-06-1983

Program Area:

Commodity:

Objectives:

To attempt was made to prepare volume tables for the species in Bangladesh.
To estimate the volume of the tree.

Methodology:

Collections of data: Data were collected from the felled trees. Diameters at breast height (dbh) were measured first. Then the trees were felled leaving 7-10 cm stump and the total heights were measured. The trees were marked at one metre intervals from one metre above ground level to a top end diameter of approximately 3.0 cm over bark and diameters over bark were taken. The barks were then removed from each point of diameter measurement and underbark diameter measurements were taken. Compilation of data: The volumes of all the sections except the top and bottom portions were computed by using the mean cross-sectional area of the two ends of each section. The bottom section was assumed cylindrical. The top most section was assumed a cone and volume was computed as one third of the cylindrical volume of the portion. The top end diameter measurement for each tree was considered as the base diameter of the cone. The volume of the cone was ignored for estimation of under bark tree volume. The individual tree volume was then estimated by summing up the volume of each section of a tree. Regression equations were used to relate these individual tree volumes (V) and were related to dbh (0) and total height (H) using various functions and transformations as required in the models. Computation of volume function: Multiple regression analysis were done to select the best suited equations. The following 10 models were tried to select the equation of best fit with different variables as follows: 1. V = bO+ b1D, 2. V =bO + b1D + b2 D², 3. V = bO + bl D², 4. V = bO + bl D² H, 5. V = bO + bl D² + b2 H + b3 D²H, 6. V = bO + b1 D² + b2 DH + b3 D²H, 7. log (V) = bO + b1log (D) 8. log (V) = bO + b1 log (D) + b2 log (H) 9. V /02 = bO + bl HD²+ b2 /H + b3/D² 10. V /02 = bO + bl /02 + b2/H + b3/D The equations of the best fit were chosen based on the highest multiple coefficient of determination, F-ratio, lowest residual mean square and low Furnival index. Models were selected for estimation of the total volume over bark and total volume under bark to a top end diameter of approximately 3.0 cm over bark. The selected equations were also transformed for estimation of volume from the girth at breast height (G). Validation of the selected models: The best suited regression equations were tested with a set of independent data on 33 trees collected and compiled in the same procedure. The actual volumes of these trees were collectively compared with the corresponding volume predicted by the selected models. The independent tests for validation were the absolute deviation percent, paired t-test, chi- square test and 45 degree line test.

Source of Information: Bangladesh Journal of forest science, vol. 22,(page no: 23-29), Nos. 1 & 2, Jan-Jul 1993, BFRI, Chittagong.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The equations for the total volume over bark and the total volume under bark to a top end diameter of approximately 3.0 cm over bark (Vub) were selected after the validation of the selected models. The mean sum of squares, multiple coefficient of determination, F-ratio and Furnivall index as selection statistics and the error mean sum of squares, percent absolute deviation percent (%AD), t-value. Validation of the selected models: The selected models satisfied all the validation criteria. The most vivid ones are the slopes and percent total deviations. They are nearly 45 degree and less than 5% respectively. This nature was considered sufficient to mark the importance of minor discrepancies in the horizontal bands of deviations. From the results of the validation of the' models, it can be concluded that the selected models can safely be used for estimation of the volumes of mangium tree in the plantations of Bangladesh. These volume tables should not be used to estimate volumes of individual trees in a stand. These tables may be used for the mean tree of a stand which may be multiplied by the number of stem to get the total volume of the stand. Estimation of volumes for trees much outside the height and dbh ranges shown in the stand table should only be done with caution.

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