[Carbon Sequestration Zoning and Management in Megacities from a Sustainable Perspective: A Case Study of Beijing]

To address the contradiction between the development of megacities and ecological restoration, as well as the carbon sequestration capacity guarantee, this study was based on the sustainable development framework and adopted the research approach of "clarifying carbon sequestration characteristics, evaluating carbon sequestration suitability, and comprehensively dividing carbon sequestration areas" to propose carbon sequestration zoning and management measures for Beijing under the sustainable development framework. First, we used the improved Carnegie Ames Stanford Approach （CASA） model and soil microbial respiration equation to quantitatively estimate the net ecosystem productivity （NEP） of vegetation in Beijing from 2001 to 2020. The spatiotemporal distribution pattern and evolution characteristics were analyzed and trend, volatility, and continuity were used as evaluation indicators for carbon sequestration characteristics. Second, from a sustainable perspective, considering the natural, social, and economic conditions of Beijing, the driving factors of NEP in Beijing were analyzed from the perspectives of single-factor detection and interactive detection using geographic detector methods. Finally, the driving factors were used as suitability evaluation indicators for sustainable carbon sequestration. Risk detection was used to assign values to different intervals of the driving factors based on their corresponding NEP mean values. Combined with the NEP carbon sequestration characteristics in Beijing, the sustainable carbon sequestration zones in Beijing were determined. The results showed that： ① On the time scale, the overall trend of NEP change in Beijing from 2001 to 2020 was fluctuating upward, and on the spatial scale, NEP in the northwest was larger than that in the southeast. The overall trend showed a divergent expansion from the center of Beijing, and 79.6% of the regional NEP showed an increasing trend； however, the scope of the region with a sustainable growth or a reversal from a decrease was still relatively small. The region with the least volatility among the carbon sequestration regions included Huairou, Yanqing, and Fangshan Districts. ② The major drivers of spatial variability of NEP in Beijing were, in descending order of explanatory degree, vegetation cover, land use type, elevation, degree of human interference, slope, level of economic activity, population density, GDP, and average temperature. The interaction of the drivers was a two-way enhancement or non-linear enhancement and the characteristics of spatial variability of NEP were affected by the joint action of multiple drivers. ③ Combined with the evaluation of the suitability of sustainable carbon sequestration and the characteristics of the evolution of carbon sequestration, Beijing was divided into five categories： carbon sequestration core areas, carbon sequestration key areas, carbon sequestration priority areas, carbon sequestration potential areas, and carbon sequestration supplemental areas, which accounted for 47.5%, 17.7%, 15.4%, 11.4%, and 8.0% of the municipal area, respectively. The results of this study can provide a basis for the delineation of carbon sequestration areas and the formulation of management measures in Beijing. To realize sustainable development and carbon neutrality, megacities should define carbon sequestration zones by combining the effects of multiple drivers and the evolutionary characteristics of carbon sequestration, to adopt targeted carbon sequestration strategies.