County-level land use carbon budget dynamics and heterogeneous driving mechanisms in Chengdu plain, China: integrating FLUS and GTWR model

BACKGROUND: Against the backdrop of global warming, land use change critically shapes regional carbon budgets by altering both emission sources and carbon sinks. Existing studies predominantly focus on macro-scales, overlooking county-level heterogeneity and future trajectories, thus limiting precise carbon balance management. The Chengdu Plain, as a key economic agglomeration and upper Yangtze ecological barrier, faces severe carbon imbalance challenges due to rapid urbanization. This study contributes three novel insights: (i) integrating county-scale analysis with future land use simulation to project carbon budget dynamics; (ii) applying GTWR to reveal spatiotemporally heterogeneous driving mechanisms that macro-scale studies mask; and (iii) developing a county typology-based carbon management framework. RESULTS: (1) From 2000 to 2030, construction land expanded significantly while cropland, forest, and grassland continuously contracted; (2) The net carbon budget (net emissions) followed a trajectory of initial increase and subsequent decline, peaking at 6673.122 × 10⁴ t in 2020 before declining to a projected 6409.177 × 10⁴ t by 2030. Construction land was the dominant carbon source, while forests served as the primary carbon sink, together accounting for over 95% of the gross budget; (3) County-level net carbon budgets exhibited strong positive spatial autocorrelation, dominated by High-High and Low-Low agglomeration patterns; (4) GTWR results indicated that consumption level (mean coefficient: 0.466), urbanization level (0.392), population size (0.388), and industrial structure (0.196) positively drove net carbon emissions, while investment level (-0.048) exhibited an inhibiting effect not captured in average macro-scale models. Spatiotemporal heterogeneity was notable. CONCLUSION: Achieving a managed regional carbon balance requires differentiated county-level strategies: For urban core counties, low-carbon community transformation and optimized urban layout; for industrial counties, carbon intensity thresholds and green industrial land policies; for underdeveloped southwest counties, green consumption promotion; and cross-regional carbon compensation mechanisms to strengthen sink protection. This county-scale, mechanism-based framework provides a scientific toolkit for precise carbon balance management in ecologically and economically vital regions.