Nature-based solutions: Assessing the carbon sink potential and influencing factors of urban park plant communities in the temperate monsoon climate zone.

As nature-based solutions, urban park plant communities play a pivotal role in regulating urban carbon cycles, alleviating global climate change, and fostering sustainable urban development. However, the factors influencing the carbon sink efficiency of plant communities in urban parks within temperate monsoon climate zones have not been fully investigated. This study used multivariate heterogeneous data to evaluate plant communities' carbon storage (CS) and annual carbon sequestration (ACS) in 25 urban parks across different biotope types in Jinan, a city located in China's temperate monsoon climate zone. The driving mechanisms affecting carbon sink efficacy were revealed using Spearman correlation, regression, principal component analyses, and structural equation modeling. Results demonstrated that: 1) Closed broadleaf multi-layer green space has significant carbon sink potential compared to other vegetation structures. 2) The carbon sink efficiency of the plant communities negatively correlated with the sky view factor and planting layout density. Three-dimensional green quantity (3DGQ), the ratio of trees and shrubs, species richness, and vertical structures positively correlated with plant communities' carbon storage and sequestration. 3) Whether increasing 3DGQ, the ratio of trees and shrubs, or the total number of individuals of all species, there is a certain threshold bottleneck in enhancing the carbon sink benefits of plant communities. 4) Plant community structure, species composition, and species diversity influenced carbon sink efficiency, collectively forming the first principal component. The 3DGQ affected carbon sink efficiency as the second principal component. Synergistic effects existed among these driving factors, jointly explained 64.3 % and 90.1 % of the CS and ACS of plant communities, respectively. Optimization design strategies for different plant communities in urban parks were proposed.