Objective The construction of high-carbon-sequestration urban green space has become a key component of high-quality built environment development under the carbon neutrality strategy. Systematic quantitative analysis and digital mapping of carbon sequestration efficiency provide an essential scientific basis and practical guidance for precision enhancement of urban green space quality and refined ecological resource management. As one of the primary natural carbon sinks in the built environment, urban green space effectively mitigates carbon emissions and improves human settlement quality. Carbon sequestration efficiency—expressed per unit time or per unit area—captures the spatio-temporal dynamics of carbon sequestration processes and serves as an integrated indicator for evaluating the multi-path carbon cycle performance of landscape green spaces. In the context of rapid urbanization, fragmented and heterogeneous green space patterns have increasingly constrained the carbon sequestration function of cities. Therefore, conducting quantitative analysis of carbon sequestration efficiency to assess enhancement strategies has become an important means of addressing carbon sequestration pressure and promoting high-carbon-sequestration development. However, traditional methods for measuring the carbon sequestration efficiency of urban green spaces often face problems such as unstructured consideration of carbon sequestration paths, incomplete analytical frameworks, low measurement accuracy, and insufficiently explicit enhancement strategy identification. These limitations highlight the urgent necessity of developing landscape-architecture-oriented, layered-carbon-sequestration-path-based, fine-grained, and quantitative analytical methods to improve the reliability, validity, and spatial precision of carbon sequestration efficiency measurement and visual representation.
Methods Grounded in urban green space development characteristics and layered carbon sequestration principles, this study establishes A quantitative analysis framework for the carbon sequestration efficiency of urban green spaces, integrates the Layered Carbon Sequestration Path Method into measurement modeling, and applies the framework to the Yanziji Blocks, Nanjing as an empirical case under construction original conditions and redevelopment plan. The workflow includes five major steps: 1) constructing the carbon sequestration efficiency analysis system; 2) identifying and classifying urban green space; 3) layered sampling and field survey; 4) carbon sequestration efficiency measurement using the layered carbon sequestration path algorithm; and 5) digital mapping and spatial pattern analysis.First, the carbon sequestration mechanisms of landscape green space were examined, with particular attention to carbon fixation, biomass accumulation, soil carbon storage, litter decomposition, and rhizosphere carbon cycling. This provided the theoretical foundation for developing a layered carbon sequestration path model and guided the construction of the carbon sequestration efficiency analysis system. Second, landscape green space within the study area was extracted and categorized based on carbon sequestration characteristics, transforming them into hierarchical geospatial datasets consistent with the Urban green space classification system. Third, layered sampling plots were designed for vegetation, soil, and micro-habitat surveys, supplemented by literature data to construct a comprehensive carbon sequestration plot database. Fourth, carbon sequestration characteristic coefficients were calculated using the layered carbon sequestration path formulas, and combined with terrain and vegetation structural data to build carbon sequestration efficiency measurement models under both the Original Conditions and the Redevelopment Plan, forming the basis for multi-dimensional spatial analysis. Finally, using the Yanziji Blocks as the case, the study implemented grid-based spatial quantification, visual mapping, and statistical evaluation of carbon sequestration efficiency, focusing on composition, spatial distribution, contribution proportion, improvement potential, and hotspot analysis.
Results The empirical results indicate the following: 1) The layered-path-based carbon sequestration efficiency measurement model demonstrates strong applicability for urban block-scale analysis. It enables accurate quantification of carbon sequestration characteristic coefficients, total carbon sequestration, and multi-dimensional carbon sequestration efficiency under both the Original Conditions and the Redevelopment Plan. 2) Comparative digital mapping showed that the Redevelopment Plan substantially improved overall carbon sequestration efficiency relative to the Original Conditions, transforming the spatial pattern from an uneven distribution into a more balanced and optimized one. Multiple hotspot regions emerged, reflecting enhanced spatial clustering of high-efficiency areas. Meanwhile, carbon sequestration improvement potential decreased significantly and tended toward theoretical saturation, suggesting that the redevelopment plan achieved nearly optimal carbon sequestration levels. 3) The results further demonstrate that reasonable planning—such as increasing the green space ratio, optimizing vegetation structure through multi-layered canopy configuration (tree−shrub−groundcover), and integrating vertical greening (e.g., roof gardens)—effectively enhances carbon sequestration efficiency under new urban development scenarios.
Conclusion This study establishes a layered-path-based carbon sequestration efficiency analysis system, develops a fine-scale measurement model, and implements a digital mapping toolkit for urban green space carbon sequestration efficiency at the urban block scale. The proposed approach effectively addresses the limitations of low measurement accuracy, incomplete analytical frameworks, and insufficient spatial representation in current research. It significantly improves the reliability and validity of carbon sequestration efficiency quantification and visualization. The findings provide theoretical foundations, methodological guidance, and technical support for the organic renewal and redevelopment of the built environment under carbon neutrality objectives, and offer a replicable framework for the planning, evaluation, and design of high-carbon-sequestration urban green spaces.
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