Phased responses of urban tree canopy cover changes to urbanization process within Beijing's built-up area: An analytical framework coupling state, transition, and drivers

Urban canopy coverage (UTCC) is a measure that reflects both the quantity and quality of urban green spaces. Understanding how UTCC responds to urbanization is crucial for developing comprehensive strategies to achieve sustainable urbanization. Our study presented a framework for understanding the response of UTCC changes to the urbanization process coupling state, transition, and drivers. Using high-resolution remote sensing interpretation data in 2002-2013-2019, we examined the spatiotemporal heterogeneity and comparative characteristics of UTCC status indicators, UTCC transition indicators, and urbanization factors within Beijing's urban area in 2002-2013 and 2013-2019. These indicators included annual UTCC change (AUTCCPC), annual mean patch size change (AMPSC), annual Euclidean minimum distance change (AEmnC), UTCC loss (UTCCloss), UTCC gain (UTCCgain), UTCC stability index (UTCCSI), impermeable surface proportion (P_IMP), road density (D_ROAD), population density (D_POP), and distance from urban center (DIS_UC). The findings indicated a "deceleration and balance" trend in UTCC changes from 2002 to 2019. The UTCC proportion, patch size, connectivity, and stability continued to increase, accompanied by a deceleration in increasing rate. The UTCC spatial distribution shifted from a ring road gradient pattern to a balanced pattern. The urbanization factors that impacted UTCC most were P_IMP and D_Road. The interaction impact intensity between factors was enhanced, with P_IMP boolean AND D_READ and P_IMP boolean AND DIS_UC having the most substantial impact on UTCC changes. Our study unveiled the phased response of UTCC changes to the urbanization process, providing a theoretical foundation for "how to promote more effective UTCC planning during rapid urban development" and aiding planners/managers in implementing sustainable forest management.