Comparative assessment of soil carbon stock of Ghodaghodi lake with its adjoining forest and grassland

Wetlands are dynamic ecosystems characterized by waterlogged or standing water conditions during at least part of the year. Productivity among wetlands varies depending on the type of the wetland, climatic condition and vegetation communities. Along with productivity, decomposition is another complicated process that involves both aerobic and anaerobic processes. Wetlands are also known to contribute in the release of methane to the atmosphere, representing about the 25% of the annual methane emissions on earth. The role of wetland-borne fluxes of carbon in the global carbon cycle is poorly understood, and more information is needed on different wetland types and their functioning as both sources and sinks of GHGs. The role of the wetlands as carbon sink locally as well as globally are still not realized and no scientific database on the stock of carbon deposited has been maintained. Therefore there is a need to assess and analyze thereby integrating scientific methods for sediment carbon, dissolved organic carbon and biomass calculation as well as the management practices of wetlands of Nepal. The objective of this study was to determine carbon stock in lake sediments of Ghodaghodi Lake as well as to determine and compare the soil carbon stock of adjoining forest and grassland. Similarly, the water quality and trophic status of the lake was also determined. The Soil Organic Carbon was determined by the wet-oxidation method given by Walkey and Black. The water quality parameters such as pH, DO, BOD, PO4, NO3 were examined and the trophic status of the lake was also determined. The mean Organic Carbon Stock of the Ghodaghodi Wetland soil was found to be 36.32 ton/ha and was found higher (p<0.05) than the adjoining Forest soil (21.28ton /ha) and Grassland soil (14.72 ton/ha). Similarly, the Dissolved Oxygen Content of the lake water was found below the tolerance limit at some sites. Similarly the Biological Oxygen Demand was found above the tolerance limit at all sites. The lake was found to be eutrophic in terms of phosphate concentration. From the study, it can be concluded that the soil organic carbon stock in wetland is higher than the soil organic carbon stock of forest and grasslands. Thus conservation of wetlands is necessary for the carbon sequestration and in turn mitigates climate change.