Comparative Analysis of Dynamic Changes and Scenario Predictions of Carbon Storage in a Small Watershed Driven by Social-Natural Factors in Cold Regions

Carbon storage (CS) influences the balance and stability of the carbon cycle in global terrestrial ecosystems. Research on changes in CS and scenario forecasting is essential for developing sustainable socioeconomic policies. To more accurately predict the CS in small watersheds in cold regions, this study takes the Ashi River watershed (ARW) as a case to explore the “past–present–future” in CS. We quantify the dominant factors affecting CS and further focus on the prediction of CS under four SSP–RCP scenarios considering the dominant factors from a new perspective by coupling the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) and Patch-generating Land Use Simulation (PLUS) models, which is important for implementing the dual carbon policy in cold regions. The findings revealed a pattern of growth followed by reduction in CS between 1990 and 2020, resulting in an overall increase of 2.68% to 3947.40 × 10⁴ Mg in 2020. Both natural and socioeconomic factors drove changes in CS, with natural factors having a direct positive impact and socioeconomic factors a direct negative impact. Climate factors and land use types were significantly correlated with CS. The simulations showed a significant increase in CS across all four scenarios, with the largest increase of 52.39% occurring under the ecological protection scenario and 18.36% under the black soil cropland conservation scenario. A carbon management strategy was developed based on land use and land cover change (LUCC) and the ARW's developmental trajectory to establish an economic–ecological balanced development model. The results of this study can provide a valuable reference for decision-makers in formulating sustainable development strategies for CS units in cold regions.