Evolution and driver analysis of forest carbon stocks in karst mountainous areas of southwest China in the context of rocky desertification management

Forest carbon pools within karst regions are pivotal in the global carbon cycle, and elucidating the dynamics and principal drivers of forest carbon stocks is crucial for enhancing carbon sequestration in these areas. With the amelioration of karst ecosystems through rocky desertification control projects, the factors influencing forest carbon storage have become increasingly intricate. In this study, the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model was corrected for forest age to estimate forest carbon stocks, and the Multi-scale Geographically Weighted Regression (MGWR) model was used to investigate the mechanisms of natural and socio-economic factors affecting forest carbon stocks during different ecological engineering periods. The results show that: Ecological engineering has made a significant contribution to the enhancement of forest carbon sinks in karst regions, with an increase in forest carbon stock of 34.82 t/hm(2) observed between 2001 and 2020. The ecological benefits exhibit a lagging effect, with the rate of carbon stock increase being markedly higher in the later stages of the project than in the initial and intermediate phases. There are substantial variations in the ecological benefits of ecological engineering across different karst landforms. The proportion of areas with significantly increased carbon stocks in the faulted basin (II) and karst valley (I) regions exceeding 70 %, while the karst trough valley (IV) has contributed the most to the increase in forest carbon sequestration. Moreover, the driving factors of carbon storage in forests in karst mountain areas exhibit spatiotemporal heterogeneity, with DEM and the human activity intensity of land surface (HAILS) significantly affecting the carbon sequestration function of regions IV and karst plateau (V) in the prior interim of ecological engineering; GDP has a significant positive effect on the karst peak cluster area (III) in the interim period; and in the late period, the inhibitory effect of HAILS on forest carbon sequestration weakens, while afforestation activities significantly enhance carbon sequestration in regions V and I. The research results have important reference value for improving the ecological benefits of ecological engineering in karst landforms, developing the potential of forest carbon sequestration, and addressing climate change.