Carbon Sequestration in Relation to Topographic Aspects and Land Use in Northeast of Thailand

With the aim of investigating carbon sequestration and its relationship with land use in different topographical conditions, the present study carried out during March-November/2013 in mixed vegetation cover areas under forest condition, eroded bare land and cultivated lands of corn, cassava and paddy rice in Nakhon Ratchasima province, Northeast of Thailand. A total number of 72 samples {3(transects) X 6 (sampling points spreading over different land uses along toposequence) X 4 (different depths)} together with 72 undisturbed soil samples using Soil Core Samplers for the determination of soil bulk density were collected from four different depths, 0-15, 15-30, 30-45 and 45-60 cm with each comprising six spot of mini soil pit located from three transect (tran-1, tran-2 and tran-3) for laboratory analysis in this study. The estimation of soil organic carbon and calculation of the amount of carbon sequestration on the basis of transects and landscape positions up to 60 cm soil depth revealed a positive significant correlation (r = .66**) between carbon sequestration and elevation. A non-significant but positive correlation (0.269 NS) was also observed between carbon sequestration and slope but the combined effect of slope and elevation was found to be significant with CSeq (r = .56*). Among land uses, the highest amount of carbon sequestration was observed in trees and forest followed by corn, cassava, paddy rice while the lowest being in bare land with respective values of 26.10, 23.70, 19.50, 16.80 and 6.20 Mg C ha-1. Carbon sequestration was also found to be significantly correlated with depth within soil profile, showing the highest amount in surface soil and decreased gradually with increasing depth in all land use types. The highest concentration of organic carbon (4.74 g kg-1) and rate of carbon sequestration (11.07 Mg C ha-1) was found in native forest at the surface soil (0-15 cm depth) and the lowest (1.84 g kg-1 and 4.37 Mg C ha-1) mostly at the lowest depth (45-60 cm) studied. Variation in soil organic carbon under different land uses and topographic condition along toposequence are of significance for understanding the process of soil carbon sequestration.

Considering the steadily increasing threats to the environment and biodiversity, especially facing the on-going climatic change, time has come now with ever greater urgency to go beyond the apparent limits of non-exhaustive sampling and make the most of what is available in terms of recorded field data, whatever the degree of incompleteness of species inventories.

As a modest and limited attempt to concretise this wish at the local level, I try, hereafter, to highlight the importance of additional information that may be unveiled through adequate post-analysis of a set of eight frog communities, recently inventoried by Katwate, Apte & Raut in an amphibian hot-spot in the north-western Ghats of India. At last, the likely variations of both total species richness and the intensity of hierarchical structuring of species abundance are simulated as an answer to the steadily increasing influence of the ongoing climatic change.