Carbon Storage Dynamics and Multi-Scenario Territorial Regulation in South China’s Karst-Coastal Transition Zones Under the “Dual Carbon” Target

In the context of low-carbon development targets, urban expansion within the karst ecoregions of southern China has intensified land-use-related carbon-stock losses, which highlights the necessity of scientific and sustainable land-use management strategies. Using multi-temporal land-use datasts spanning six periods from 2000 to 2025, this study integrates carbon-stock accounting and land-use transition-matrix analysis. Multicollinearity testing and spatial autocorrelation analysis are employed to reveal the driving mechanisms behind carbon-stock variations. Based on standardized beta coefficients (β), all driving factors are hierarchically classified into primary dominant factors, secondary constraint factors, and tertiary disturbance factors according to their regulatory intensity, and further grouped into topographic, ecological, and socioeconomic categories. On this basis, three differentiated land-management scenarios are constructed. By coupling the PLUS and InVEST models, this study simulates regional carbon-stock conditions for 2030 and 2035. The results show that regional carbon-stock exhibits a fluctuating pattern: it decreased from 2000 to 2005, rose continuously during 2005–2015 to reach its peak in 2015, and then declined persistently from 2015 to 2025. Spatially, obvious zonal differentiation can be observed: the northwestern mountainous areas maintain high carbon-stock levels, whereas southern coastal towns experience severe carbon-stock degradation. Topographic factors dominate regional carbon-stock dynamics; ecological factors exert critical buffering effects; human-induced land-use activities act as the secondary driver for carbon-stock loss. The conversion of farmland and woodland to construction land represents the major contributor to regional carbon-stock reduction. Under the “2035 Steep-slope Carbon-stock Protection Scenario”, the total regional carbon-stock increases by 1441.69 million tonnes relative to the “2035 Natural Development Scenario”. This scenario achieves the coordinated advancement of rocky desertification control and sustainable land use, facilitates synergistic low-carbon improvement and land-system sustainability, and provides practical references for low-carbon land governance in similar karst regions worldwide.