Achieving the goal of "dual carbon" involves two main aspects: carbon emission reduction and carbon sequestration. As key entities in carbon accounting and policy making, cities should not only monitor their carbon emissions, but also give due consideration to their carbon sequestration functions. Based on a systematic review of carbon sequestration accounting methods applicable to different types of cities, the total carbon sequestration within the Third Ring Road of Shenyang is estimated to be 4.42 million tons, which offsets approximately 7.92% of the carbon emissions from energy consumption in the same year. The study analyzes the basic principles of carbon sequestration by different types of carbon sinks in urban ecosystems, such as vegetation, soil and buildings, and reveals significant spatial variation in their distribution. Specifically, vegetation carbon density increases progressively from the city center to the urban periphery, whereas soil and building carbon density exhibit a decreasing trend. Urban ecosystem carbon sequestration is influenced by land use types, with notable differences in both carbon sequestration and carbon density across different land use types. Natural carbon sinks display relatively consistent characteristics, while artificial carbon sinks show marked variability. Among all land use types, residential land contributes the highest carbon storage, while industrial land demonstrates the highest carbon density. By exploring the interactions among urbanization, land use types, and urban carbon sinks, this study elucidates the characteristics of urban ecosystem carbon sequestration. The findings provide a scientific basis for enhancing urban carbon sink capacity, realizing the value of carbon sequestration, and advancing the goal of urban carbon neutrality.

Urban morphology significantly affects the ecological effects of urban heat islands, ventilation, and atmospheric pollution. Here, we reveal the mechanisms linking the ecological effects of urban morphology to develop a planning approach for the collaborative optimization of multiple ecological effects. Considering Shenyang, a cold city in northern China, as the study area, a multiple regression model of morphological parameters and ecological effects was established, and the impact of morphological parameters on ecological effects was explored. The results show that the aspect ratio of the streets, building density, and vegetation coverage are sensitive to multiple ecological effects. The inflection point of the ecological effect function curve occurs when the aspect ratio of the building and building density are 0.2 and 0.3, respectively. In addition, for optimal design applications in typical areas of the city, to obtain a Pareto-optimal urban morphology, Grasshopper is used to establish a parametric platform, wherein a genetic algorithm solves the multiple regression equation set. Ultimately, five ecological effect indicators are optimized and show 8.4%, 5.0%, 31.6%, 33.1%, and 12.5% improvement. The study effectively constructs a collaborative optimization planning and design method for multiple ecological effects.