Spatial Heterogeneity and Nonlinear Influencing Mechanisms of Vegetation Carbon Sequestration Capacity in the Southwest China Karst Region

Abstract

Understanding of the spatiotemporal dynamics of vegetation carbon sequestration capacity (VCSC) in Southwest China's contiguous karst region is critical for regional carbon cycling. Using MOD17A3 data from 2001 to 2023, we analyzed spatial heterogeneity in vegetation net primary productivity (NPP) and applied Geodetector to evaluate nonlinear influencing mechanisms across 32 factors. The results showed that the multi‐year average NPP in the southwest karst was 725 g C m ⁻²  yr ⁻¹ , exhibiting a southward‐increasing gradient. Recovery areas expanded at a rate of 3.21 g C m ⁻²  yr ⁻¹ , covering 79.3% of the region. Comparative analysis revealed that Engineering Governance Areas (EGA) significantly outperformed Natural Recovery Areas (NRA) in enhancing VCSC. In EGA, the mean recovery rate (3.67 g C m ⁻²  yr ⁻¹ ), significantly improved areas (51.3%), extremely stable area (71.7%), and future sustainable recovery (72.0%) were 1.38, 1.23, 1.22, and 1.18 times higher than those in NRA, respectively. However, natural factors played a greater role than anthropogenic activities in explaining the spatial heterogeneity of NPP. Environmental interactions exhibited both nonlinear and bivariate enhancement, with combined effects exceeding those of individual factors. The dominant interactions were AET ∩ ELE (77.7%) for the whole region, AET ∩ PRS (61.8%) in EGA, and AET ∩ ELE (87.3%) in NRA. The optimal environmental thresholds for vegetation growth were AET of 1,244–1,397 mm, precipitation of 2,025–2,259 mm, temperature of 18.5–20.8°C, and elevation of 1,094–1,438 m. Integrating restoration strategies with these environmental thresholds helps identify priority zones, providing a scientific basis for the precision management of karst desertification and supporting China's “dual carbon” goals.