Over 18, 000 ha of degraded wet lowland areas in Sri Lanka have been converted to Pinus caribaea plantations through an afforestation program. These plantations are poorly managed and subject to frequent fires, set by local people who do not see much value in them for their subsistence. Consequently, these plantations remain under-productive and under-utilized, particularly due to the paucity of plant and economic diversity for rural development. In response to this a Pinus enrichment trial has been launched to restore plant and economic diversity in these biodiversity poor monoculture plantations. In this field trial, in Hantana on land belonging to the University of Peradeniya, selected rows of Pines were removed. We used this opportunity to estimate the above ground biomass of P. caribaea.
Total tree height, stem diameter at the two ends of the stem, middle and immediately below the lowest live branch were recorded at the time of logging. From each tree, fresh samples of stem discs at the root collar, middle and the end were collected, sealed in polythene bags and dry weights were measured at 700 C. Fresh weight of the branches, needles and cones were determined. Sub samples of these were taken for determination of fresh weight: dry weight ratios.
In our study we predicted the tree form. Pine tree trunks are cylindrical at the lower part and conical at the upper part. Empirical formulae were derived separately to estimate biomass for the cylindrical part and the conical part of the tree. These formulae are site specific to the P. caribaea plantations in Hantana. Using the formulae, the above ground biomass of a 25-yr-old P. caribaea stand was calculated as 194 tha-1. Of the live standing crop the stem represented 60%, the branches 17%, the leaves 13%, the cones 3% and dead branches 7%. This Pine stand had 695 Pine trees ha-1, a mean dbh of 20.1 cm, a mean height of 20.7 m and mean basal area of 23.6 m2 ha-1. The estimated values showed that the P. caribaea plantation studied is good source for carbon sequestration.
I M Ambagahaduwa, I A U N Gunatilleke, G Seneviratne and C V S Gunatilleke
Department of Botany, University of Peradeniya, Sri Lanka