Investigating the Kuan Kreng Peat Swamp Forest using Electrical Resistivity and Ground Penetrating Radar for Carbon Stock Estimation

Abstract

Peatlands, also known as bogs, fens, and especially peat swamp forests in tropical regions, are wetland ecosystems where peat layers are present due to anoxic conditions. Immense amounts of carbon are stored in peat layers, making it an important carbon sink for atmospheric carbon and playing a major role in carbon cycle. These peat layers are vulnerable to becoming a carbon emission source due to the disturbance of the peat layer by natural and anthropogenic processes. Southern Thailand comprises several peatlands that have encountered degradation due to cultivation and forest fires, especially the Kuan Kreng peat swamp forest, which is the second largest peatland in Thailand and serves for carbon storage. To evaluate the impact of peatland degradation, carbon stock estimation is necessary; thus, the thickness and distribution of the peat layers are necessary. This study utilizes ground penetrating radar and electrical resistivity imaging, along with conventional core studies, to investigate physical and chemical characteristics and also delineate peat layer. Significant relationships between chemical and physical properties of the peat layer are represented, which is useful for geophysical interpretation. The resistivity profiles show a high resistivity response, in the range of 21.9 to 145.0 ohm-m, which is interpreted as peat layers in the shallow subsurface. The high amplitude, contorted to sub-parallel reflection from GPR profiles, represents a peat layer that has a relatively lowest velocity with the highest dielectric constant. In order to evaluate carbon stock, average values of bulk density (0.19 g/cm­3) and TOC (31.18 wt. %) from the drilling core samples are advocated, resulting in 59.24 Kg C/m3 of carbon density. Then the peat layer average thickness of 18.00 cm from the geophysical survey and core samples are used to estimate the carbon stock per unit area. Therefore, considering the entire area of the Kuan Kreng peat swamp forest, the carbon stock is estimated at a minimum of 7.53 Mt.