Multi-pathway vegetation restoration drives differential carbon sequestration regulated by hydrogeological conditions in Lijiang River Basin

Karst ecosystems represent a vulnerable yet significant component of the global carbon sink. Although vegetation restoration is recognized as fundamental to boosting the carbon sequestration of karst ecosystems, the regulatory mechanisms by which heterogeneous hydrogeological conditions mediate the efficacy of different restoration pathways on terrestrial carbon sequestration remain poorly constrained. To address this knowledge gap, we conducted a case study in the Lijiang River Basin, a typical karst watershed in Southwest China that has undergone severe rocky desertification followed by extensive vegetation restoration efforts over recent decades. This study integrated multi-source remote sensing data, a refined hydrogeological classification model, and the CASA model to quantify spatiotemporal dynamics of carbon sequestration. Based on land-use change trajectories, six vegetation restoration pathways were delineated, encompassing the full spectrum of restoration approaches. The results revealed that spatial heterogeneity in carbon sequestration was primarily regulated by hydrogeological conditions. A synergistic interaction between soil organic carbon and terrain roughness was identified as the core driver of net ecosystem productivity, with hydrological connectivity providing a substantial compensatory effect in areas with limited soil fertility. The effectiveness of restoration pathways was highly context-dependent. Artificially planted forests yielded high short-term carbon gains, while natural regeneration exhibited superior long-term potential in well-drained habitats. Temporally, vegetation cover in karst areas surpassed that of non-karst regions after 2007, demonstrating a pronounced late-mover advantage following large-scale restoration policies. This study identifies a synergistic regulatory mechanism, providing a spatially explicit scientific basis for the precision optimization of ecological restoration strategies in karst areas. • Hydrogeology and restoration pathways co-determine the spatial heterogeneity of carbon sequestration. • Hydrological connectivity compensates for low soil fertility to boost carbon sinks. • Natural regeneration outperforms artificial plantations in high-drainage karst areas. • Karst ecosystems demonstrate a pronounced late-mover advantage, surpassing non-karst vegetation coverage after 2007.