Objective With the rapid expansion of urbanization, activities such as population growth, changes in land use, and extensive use of fossil fuels have led to significant CO₂ emissions, resulting in a series of climate issues such as global warming. Plant communities, through photosynthesis, act as the only natural carbon sink in urban areas, holding crucial significance for mitigating climate change. In urban environments, the configuration of plant communities is influenced by intrinsic factors such as species composition, tree size, and community structure, as well as external factors such as site conditions and anthropogenic disturbances. The limited space in urban areas further constrains the unrestricted expansion of urban green spaces. Therefore, optimizing the planting of urban plant communities to maximize carbon sequestration and oxygen release under current conditions is one of the key approaches to mitigating urban climate change issues and achieving the “carbon peaking” and “carbon neutrality” goals.

Methods This research focuses on Tianjin People’s Park, a typical century-old urban park in Tianjin, and selects 60 representative plant communities. The photosynthetic rate was measured using the FK-GH60 photosynthesis meter, while the leaf area index was determined using the live leaf area meter YMJ-D and the LAI-2200C canopy analyzer. Based on the obtained data, daily carbon sequestration and oxygen release data for each plant community are calculated. Hierarchical structure of plant community , average diameter at breast height, average tree height (DBH), average crown width, three-dimensional green biomass, and community density are selected as plant community characteristic factors. Pearson correlation analysis is performed using SPSS software to analyze the correlation between plant community characteristic factors and carbon sequestration and oxygen release capacity. Furthermore, principal component analysis of plant community characteristic factors is conducted using SPSS software.

Results The average carbon sequestration and oxygen release capacity of different plant communities can be ranked from high to low as follows: Arbor-shrub-grass, arbor-grass, arbor-shrub, shrub-grass, arbor, and shrub plant communities. There exists a highly significant moderate positive correlation between the average DBH and carbon sequestration and oxygen release capacity of plant communities (r=0.574, p<0.01). There exists a highly significant strong positive correlation between the average tree height of plant communities and carbon sequestration and oxygen release capacity (r=0.631, p<0.01). There exists an extremely significant strong positive correlation between the average crown width and carbon sequestration and oxygen release capacity (r=0.852, p<0.01). There exists an extremely significant strong positive correlation between the three-dimensional green biomass of plant communities and carbon sequestration and oxygen release capacity (r=0.844, p<0.01). There exists a highly significant positive correlation between plant community density and carbon sequestration and oxygen release capacity (r=0.681, p<0.01). Based on this, the research further proposes optimization design strategies to enhance the carbon sequestration and oxygen release benefits of plant communities. This research draws the following results: 1) The more complex the hierarchical structure of a plant community, the stronger its carbon sequestration and oxygen release capacity; 2) plant communities with specific specifications (average DBH: 0 − 0.2 m; average tree height: below 6.0 m; average crown width: 0 − 2.0 m) have stronger carbon sequestration and oxygen release potential; 3) 0.2 − 0.4 plants/m² is the optimal density range for achieving high carbon sequestration and oxygen release benefits; 4) among various plant community characteristic factors, three-dimensional green biomass has the most significant positive impact on carbon sequestration and oxygen release benefits.

Conclusion This research systematically explores the influence of different plant community characteristic factors on carbon sequestration and oxygen release benefits, identifies key influencing factors, and proposes optimization design strategies for plant communities, with a view to providing theoretical support and guidance for the design of plant communities with high carbon sequestration and oxygen release capacity in urban green spaces. However, this research also has limitations: 1) Field research is concentrated during the period from August to October, lacking data from other seasons; 2) in the process of field research, photosynthetic rates of plants in all sample plots fail to be measured simultaneously during the collection of some data, and the influence of surrounding ground cover on the results is not considered. Future dynamic and long-term monitoring of plant communities is needed to more fully understand their dynamic ecological processes. In addition, the influence of the surrounding environment on research results needs to be further considered to improve the scientific validity of the research.