Research Progress on Carbon Source-Sink Transition Characteristics and Driving Factors in Terrestrial Ecosystems

Against the backdrop of global climate change, the dynamics of carbon sources and sinks in terrestrial ecosystems play a pivotal role in regulating atmospheric CO₂ concentrations and mitigating climate change. Drawing on the latest domestic and international research findings in recent years, this study systematically synthesizes the quantitative characteristics, spatiotemporal patterns, and driving factors of carbon source-sink transitions in terrestrial ecosystems, while identifying current research gaps and future directions. The key conclusions are as follows: 1) The global terrestrial ecosystem has generally shifted from a carbon source to a carbon sink, with an average carbon sequestration capacity of 2.4±0.8 Pg(C) a^-1 during the period 2015–2024. China’s terrestrial ecosystem constitutes a significant global carbon sink, currently exhibiting a carbon sink intensity of 0.20–0.25 Pg(C) a^-1, where ecological initiatives such as afforestation expansion and vegetation restoration serve as critical contributing factors; 2) Carbon source-sink transitions are comprehensively driven by multiple factors, including climatic variables (temperature, drought, ENSO), CO₂ fertilization effect, wildfires, land use/cover change, and forest age. Notably, these transitions exhibit marked regional and scale-dependent heterogeneity, as well as distinct threshold effects; (3) Future research should focus on enhancing the accuracy of carbon source/sink accounting, deepening investigations into meso- and micro-scale process mechanisms, and identifying key thresholds. These efforts aim to provide robust scientific support for ecosystem management and climate governance in the context of the carbon neutrality goal.