Climate-Constrained Attribution of Vegetation Carbon Sink Dynamics in a Karst Region: Disentangling Human and Climatic Contributions

In the context of increasing climate variability and carbon neutrality targets, understanding the relative roles of climate and human activities is essential for accurately assessing vegetation carbon sink dynamics. This study develops a climate-controlled attribution framework to disentangle human-induced effects from natural climatic variability in Guizhou Province, a representative karst region of Southwest China. Using multi-source remote sensing and climate data from 2004 to 2023, net ecosystem productivity (NEP) was estimated, and its spatiotemporal dynamics were analyzed. A two-step attribution approach was applied to isolate climate-driven variability and quantify the contribution of anthropogenic activities. Results indicate that mean NEP increased significantly from 273 gC·m−2·yr−1 in 2004 to 369 gC·m−2·yr−1 in 2023, with a provincial average of 318 gC·m−2·yr−1. Human activities are estimated to contribute a dominant share (approximately 60–75%), although uncertainties remain due to methodological limitations. Spatial analysis reveals pronounced heterogeneity, with stronger human-induced enhancement in eastern regions and mixed restoration–disturbance effects in ecologically fragile western areas. These findings suggest that ecological restoration policies in fragile karst ecosystems can generate amplified carbon sink responses beyond background climatic effects. These findings provide insights into understanding climate–carbon cycle interactions and improving region-specific climate mitigation strategies.