Effect of Agricultural Land-Use Patterns on Soil Organic Carbon Stock in the Upper Vietnamese Mekong Delta

In the mitigation strategies of climate change, improving soil carbon storage is considered as one of the main tasks to enhance agricultural sustainability and sequester atmospheric carbon dioxide. Agricultural patterns have been changing significantly and causing many impacts on soil organic carbon (SOC) storage in the upper Vietnamese Mekong Delta (VMD). Therefore, this study aims to evaluate how typical agricultural pattern changes are affecting SOC by estimating the SOC stock and identifying the correlation with soil physic-chemical properties. Soil samples were collected in both depths of 0-20 cm and 20-50 cm and analyzed physic-chemical properties such as soil texture, bulk density, pHKCl, EC and SOC. In topsoil layers, the SOC stock of the wetland forest was the highest in the opened depression of floodplain (24.42 +/- 1.38 kg C m(-2); p<0.05) while that of paddy rice was the richest at depth of 20-50 cm (27.69 +/- 2.97 kg C m(-2); p<0.05). In other agro-ecological areas, SOC stock in croplands was lower than forest and grassland in topsoil layer, especially in mountainous areas. SOC stock correlated positively with SOC content, clay, bulk density, and EC (p<0.05) but had a negative correlation with sand and pHKCl (p<0.05). The decrease in SOC stock in dry cultivating patterns indicated the impact of agricultural management practices and soil fertility on SOC storage. Thus, improving SOC stock