Estimating soil organic carbon sequestration in rice paddies as influenced by climate change under scenario A2 and B2 of an i-EPIC model of Thailand

Abstract

Carbon sequestration in soils constitutes an important option that can be used to reduce CO2 emissions to the atmosphere and reduce environmental impacts. Soil organic carbon (SOC) is both a source of carbon release and a sink for carbon sequestration. Our objectives in this study were to validate the interactive Environmental Policy Impact Calculator (i-EPIC) model version 0509, as well as to estimate SOC sequestration under climate change scenarios A2 and B2 SRES emission scenarios in Thailand. The SOC estimated by i-EPIC was compared with data from the Office of Soil Resources Survey and Research, Land Development Department. The results indicated that performance testing of i-EPIC is able to estimate SOC. Validation of SOC proved to be satisfactory with a resulting root mean square error (RMSE %) value of 34.60. The SOC content showed a decreasing trend under B2 and A2 climate scenarios (average 0.87% and 0.85%, respectively) compared to the reference from 2007 (average 0.92%). Stepwise regression analysis also revealed that carbon from residue decomposition, biomass pool carbon, and the total change of the carbon pool were directly correlated with the SOC (R2= 0.99, p< 0.01). Furthermore, the change from rain supplied water to irrigation also resulted in an increase of carbon inputs but a decrease in the SOC sequestered during the 2007-2017 period. Regression analyses indicated that soil carbon sequestration responds linearly to carbon input. Significant changes in carbon input as well as decreases in SOC levels were observed as temperature and precipitation increased. Based on the testing and analysis, we concluded that i-EPIC is capable of reliably simulating effects of climate change on SOC sequestration. Based on the results, this knowledge and information can increase effectiveness in the promotion of integrated rice management for rice production in Thailand.