Spatiotemporal Dynamics of Carbon Sequestration in IntensiveAgricultural Floodplains: Bridging the Gap Between Monocultureand Ecosystem-Based Adaptation in Phichit Province, Thailand

Abstract

The Agriculture, Forestry, and Other Land Use (AFOLU) sector occupies a critical nexus in the global carbon cycle, acting simultaneously as a source of greenhouse gas emissions and a potential terrestrial sink. This study quantifies the carbon dioxide ($CO_2$) sequestration potential across three administratively distinct sub-districts—Sam Ngam, Tha Lo, and Kamphaeng Din— in the Lower Northern region of Thailand. By integrating 2023
Land Use/Land Cover (LULC) datasets with species-specific allometric carbon coefficients derived from stratified 40x40 meter field sampling plots, we assessed the standing carbon stocks of these rice-dominated landscapes. Results indicate a profound landscape homogenization, with rice paddies accounting for over 85% of the agricultural area. While Sam Ngam exhibits the highest aggregate carbon sequestration (~177,870 t $CO_2$) due to its extensive land area, its sequestration efficiency per hectare (7.60 t $CO_2/ha$) is orders of magnitude lower than that of perennial systems such as Eucalyptus camaldulensis plantations (2,964 t $CO_2/ha$) and mixed orchards. This study moves beyond static biomass accounting by critically evaluating the results through the lens of recent advancements in Soil Organic Carbon (SOC) microbial dynamics and the PLUS-InVEST modeling framework. We argue that the current monocultural trajectory presents a “carbon density paradox,” where vast vegetative cover masks a functional deficit in long-term carbon storage. We propose a transition towards “Teal Carbon” strategies—managing freshwater wetland/canal interfaces—and agroforestry to enhance resilience without compromising food security.