Local Volume table for Acacia Mangium Plantations in the Southern Forest Divisions of Kerala

Abstract

An attempt was made to develop local tree volume equations based on diameter at breast-height (dbh) for Acacia mangium plantations in Thiruvananthapuram and Punalur Forest Divisions in Kerala. Trees of different size classes were sampled from plantations of A. mangium. Measurement of girth at breast-height (gbh) was taken before felling. The diameter at breast height (dbh) varied from 5 to 40 cm. Girth measurements (both over-bark and under-bark) were taken at the middle of each billet of length 3 m starting from the base. Billet volume was computed using Huber’s formula. Total commercial volume (over-bark) and pulpwood volume (under-bark) down to a lower limit of 15 cm girth were computed. The equations were based on data from 51 trees. Additionally, saleable timber volumes (both over-bark and under-bark) down to a lower limit of 70 cm girth (over-bark) were also computed. For computing the saleable timber volume, trees of girth at breast-height greater than or equal to 70 cm (over-bark) alone were considered. Altogether 28 trees were used for this purpose. Volume prediction equations were established using regression analysis. Dbh of the tree alone was included as a predictor variable as the equations based on diameter were good enough. The equations developed can predict the total commercial volume, pulpwood volume and saleable timber volume with justifiable precision, as the goodness of fit statistic was found higher than 80 per cent in all the cases. The equations are applicable only within the range of data used for the study. Local volume tables in terms of commercial, pulpwood, saleable timber and firewood volumes were prepared for the species based on developed equations.