Tree girth increment pattern in three medicinally important Pterocarpus species in Kerala, India

Pterocarpus indicus Willd., Pterocarpus marsupium Roxb., and Pterocarpus santalinus L.f. are commercially important medicinal trees, which are also having conservation concern and listed under the IUCN Red list of threatened category. However, information is not available on their tree girth increment pattern. In the present study, species-wise data pertaining to GBH (tree girth measured at 1.37 m from ground level) of trees were periodically collected till they attained the age of 34 years from the species trial plots established in 1984. The mean annual increment in GBH at 34 years was maximum in P. marsupium, followed by P. santalinus and P. indicus with no significant difference in the values of P. indicus and P. santalinus. The relation between tree age and the mean GBH of all the three species were modeled using simple linear regression models which have significant coefficients of determination (R²). Thus, the fitted equations can be used for estimating the tree age from the GBH of standing tree.