Soil and Biomass Carbon Accumulation in Abandoned Paddy Wetlands (APWs): Implications for Sustainable Land Management

Abandoned paddy wetlands (APWs) develop after rice cultivation ceases and may support carbon sequestration, soil conservation, and sustainable management of abandoned agricultural land. This study quantified soil and biomass carbon in six reference APWs in the central region of the Republic of Korea. Following the Intergovernmental Panel on Climate Change (IPCC) Good Practice Guidance for Land Use, Land Use Change and Forestry (GPG-LULUCF), soil samples were collected to a depth of 30 cm to estimate soil organic matter (OM), soil organic carbon (SOC), and soil organic carbon storage per unit area (SOCS). Land cover-based carbon absorption was evaluated within 300 m hydro-ecological impact zones for 2000, 2013, and 2021, and biomass carbon was estimated for woody, herbaceous, and mixed communities using field measurements and drone LiDAR-derived vegetation structure. The mean OM and SOC contents were 33.7 and 19.54 g/kg, respectively. The corrected mean SOCS was 61.20 ± 22.28 kg/m2 (unadjusted mean: 67.97 kg/m2), approximately 8.5–40 times the reference values reported for South Korean forest soils and urban parks. The mapped mean carbon absorption was 20.45 tCO2/ha in 2000, 35.30 tCO2/ha in 2013, and 38.14 tCO2/ha in 2021. Because only three mapped years were analyzed, these values describe observed differences and do not establish a continuous temporal trajectory or a stable plateau. The findings suggest that APWs may contribute to sustainable land management, wetland restoration, soil conservation, and climate-change mitigation through carbon retention in soils and vegetation. These field data provide region-specific evidence for evaluating sustainable management strategies and complementing broader-scale soil–vegetation carbon models.