Integrating Non-Park Green Space into Urban Green Infrastructure: A Community-Scale Assessment of Ecological Supply–Demand Balance and Structural Performance

Green spaces (GS) play a pivotal role in promoting ecological sustainability and enhancing public well-being. However, traditional park green spaces (PGS), characterized by centralized layouts, often fail to meet the spatially diverse needs of urban residents. Non-park green spaces (NPGS) have therefore emerged as important supplements to urban forest and green infrastructure systems, yet systematic evaluations of their performance contributions remain limited. Using a multidimensional Supply–Demand Ratio (SDR) framework, we compared park-only (PGS) and integrated (All_GS) scenarios across 609 communities in the central urban area of Nanjing, China, to quantify changes in urban forest service capacity, accessibility, and equity. Results show that integrating NPGS increased the mean SDR by 46.88%, with 59.28% of communities exhibiting improved green service performance. The Deviation Reduction Index (DRI) indicates a 13.67% reduction in deviation from the ideal service range, demonstrating improved overall balance and spatial equity. Community transition analysis further reveals that accessibility improvements are accounted as the key pathway to enhance overall performance, while capacity and quality displayed higher spatial heterogeneity. Overall, NPGS integration substantially enhances service equity and spatial balance in green provision, providing a robust analytical framework for integrated urban forest management and targeted optimization of urban green infrastructure.