Spatiotemporal distribution and attribution of carbon sequestration in karst rocky desertification land in southern China

To mitigate the intensification of desertification and land degradation in karst areas of southern China, since the late 1990s, the Chinese government has implemented a series of ecological restoration projects. In the past couple of decades, the carbon sequestration potential of karst rocky desertification land increased significantly. However, few studies have explored the characteristics and driving mechanisms of carbon sequestration in karst areas. This study aimed to quantify the spatiotemporal patterns, trends, and drivers of carbon sequestration in the Huajiang River Basin, a typical karst basin, in southern China during 2000-2020 and its five geographic zones via the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The five zones of the karst basin exhibited the following characteristics: (I) good natural background condition with positive feedback human intervention; (II) poor natural background condition with increased negative and decreased positive feedback human interventions; (III) poor natural background condition with increased positive and decreased negative feedback human interventions; (IV) non-karst land; and (V) poor natural background condition with no significant positive and negative feedback human interventions and with heavy reliance on natural ecosystem recovery. The results were four-fold. First, the Huajiang River Basin showed a significant increasing trend of carbon sequestration. The spatiotemporal variation of carbon sequestration significantly differed among the five zones (Ⅴ > Ⅲ > Ⅳ > Ⅱ > Ⅰ). The stability of carbon sequestration was lowest in zone III. Second, a 20-year land-use/cover change directly affected the level of carbon sequestration. The conversion of cropland, grassland, and woodland to shrubland was the main reason for the increased carbon sequestration in zone I. Third, carbon sequestration was negatively correlated with the desertification level of karst rocky areas. The spatial distributions of moderate, serious, and extremely strong desertification levels in zone II showed an increasing trend. Zones I, III, and V exhibited no significant desertification. Finally, the integrated ecological management against desertification increased carbon sequestration. Negative feedback human interventions (e.g., quarrying) exerted a significant disturbing impact on carbon sequestration that needs to be addressed in the formulation of management practices.