Optimizing the pattern of land space development and protection as well as improving regional ecological security are significant tasks in the construction of an ecological civilization. The Lancang River Basin is a significant ecological barrier in Southwest China, and its ecological security is critical to the Natural World Heritage Site of “Three Parallel Rivers” and even to Southeast Asia. In this study, the InVEST model and MSPA method were used for the identification of the ecological sources; the resistance surface was corrected by the night light coefficient; and the ecological linkages, pinch points, obstacles, and ecological breakpoints were extracted using the circuit theory to construct the ecological security pattern of the Lancang River Basin. The major study results indicated that: (1) A total of 23 ecological sources were identified in the watershed, covering an area of 9019.56 km², mostly large-scale irregular patches. (2) A total of 39 ecological corridors were identified in the study area; 15 key corridors, 17 important corridors, and 7 general corridors were extracted based on the gravity model, which together formed a ecological security network for the watershed. (3) Sixteen ecological pinch points, one primary ecological improvement area, twelve secondary improvement areas, and twenty-nine ecological breakpoints were identified in this study. The ecological protection and restoration of different important ecological areas are conducive to the protection of biodiversity and the construction of the ecological security pattern in the Lancang River Basin.

Continuous urban expansion and the resulting land use and land cover (LULC) changes significantly exacerbate the urban heat island effect and intensify heatwaves. While the cooling effects of blue–green spaces are widely documented, most studies focus on single landscape types or specific time frames. Few investigations systematically explore the comprehensive thermal regulation mechanisms of gray–green spaces, or their nonlinear driving factors and interactive effects across coupled seasonal and diurnal scales. To address these gaps, this study focuses on Chengdu, a typical expanding city in China, to establish a comprehensive indicator system for urban gray–green spaces. This system encompasses four key dimensions: coverage, fragmentation, aggregation, and morphological spatial pattern. After evaluating 12 machine learning models, the optimal model was selected for further analysis using SHapley Additive exPlanations (SHAP) and Partial Dependence Plots (PDP). This research investigates the nonlinear thresholds and interactive effects of composite gray–green space indicators on land surface temperature (LST) across varying seasonal and diurnal cycles. The results indicate that: (1) The impact of gray–green spaces on LST varies significantly across seasonal and diurnal contexts. Green spaces primarily exert a cooling effect during spring, summer, and autumn, whereas gray spaces dominate heat retention during winter and across all nocturnal periods. (2) The morphological spatial pattern of green spaces (GMSPA) outperforms traditional coverage indicators (G1) in providing cooling benefits across multiple scenarios. (3) The cooling efficiency of GMSPA peaks between −0.8 and −0.5, reaching saturation at 0.53. Conversely, LST exhibits a sharp, step-like increase when gray space aggregation (B3) exceeds −0.58. (4) Optimizing areas with high GMSPA can significantly mitigate heat exposure risks in expanding cities. These findings offer robust theoretical insights and actionable guidelines for spatial planning aimed at thermal resilience, urban thermal environment management, and building energy conservation in rapidly growing urban areas.