CARBON SEQUESTRATION: ESTIMATION OF CARBON STOCK IN TEAK (Tectona grandis Linn. f.) ECOSYSTEM

Abstract

Carbon management in forest plantations will probably be the single most important agenda of the first half of the 21st century in India in the context of the greenhouse effect and mitigation of global climatic changes. Today teak (Tectona grandis) is widely planted in south-east Asia and in Africa, South and Central America as an exotic species. This teak based global sink would certainly increase because during the past 20 years most supplies of teak wood from natural forests have dwindled and increased interest has developed in the establishment of teak forest plantations.

Unlike in developed countries, developing countries do not have carbon inventories and data bank to monitor and enhance carbon sequestration potential of different plantations. In India attempts were made to assess carbon sequestration studies at macro level, mostly with the available data. No attempt has been made so far to assess the biomass and soil carbon sequestration at micro level. Therefore, a pilot study was taken up to estimate the carbon stock available in teak ecosystem. The study was conducted in a 12 year old teak planta tion planted at 2 m x 2 m spacing. Timber volume of about 100 trees was worked out by using height and gbh. Finally, the total biomass in the 1 ha area of teak plantation was estimated. Carbon estimation from the biomass was calculated based on the methodology described by Koch (1989) and the minimum value of 49.1 was adopted as the conversion factor.

Soil samples were collected at the surface (0-30 cm) and sub-surface (0-60 cm) layers. The collected soil samples were air dried in shade, broken the clods with wooden mallet and passed through 2 mm sieve, labeled and stored in cloth bags. The per cent of coarse fraction (> 2.0 mm size) for each layer was estimated. Undis turbed soil clods were collected from each layer and preserved for determination of bulk density. The deter mined bulk density was corrected for per cent coarse fractions. The corrected bulk density (Mg m-3) was used for the estimation of SOC density (Mg ha-1) and SOC stock.

The total biomass carbon of teak plantation was 5.52 t C /ha and total SOC was 6.71 t C /ha. The ratio between SOC and biomass carbon was 1.22. Post et al. (1990) reported that the ratio between SOC and biomass carbon is 2.5 to 3.0 times in the terrestrial ecosystem.

The present study indicates that the SOC is higher than that of biomass carbon but not 2.5 to 3.0 times of biomass carbon as recorded in well-managed terrestrial ecosystem. However, in the tropical forest, the carbon in the soil is roughly equivalent or lesser than the above ground biomass due to degradation. Hence, data bank on carbon stock will certainly help the foresters to enhance the soil carbon for sustainable management of forest plantations in the context of mitigating climate changes.