Sun Qianyu, Li Daicong, Tang Xiaolan, Ren Yujie
Department of Urban and Rural Planning, Nanjing Forestry University, Nanjing 210037, China.
Institute of Ecological Civilization Construction and Forestry Development, Nanjing Forestry University, Nanjing 210037, China.
Plants (Basel). 2025 Aug 8;14(16):2457. doi: 10.3390/plants14162457.
The urban heat island (UHI) effect has emerged as a growing ecological challenge in compact urban environments. Although urban vegetation plays a vital role in mitigating thermal extremes, its cooling performance varies depending on vegetation type and urban morphological context. This study explores the extent to which compact urban development-quantified using the Mixed-use and Intensive Development (MIXD) index-modulates the cooling responses of different vegetation types in Nanjing, China. A combination of landscape metrics, regression-based interaction models, and XGBoost with SHAP analysis is employed to uncover vegetation-specific and structure-sensitive cooling effects. The results indicate that densely planted trees exhibit reduced cooling effectiveness in compact areas, where spatial clustering and fragmentation tend to intensify UHI effects, particularly during nighttime. In contrast, scattered trees are found to maintain more stable cooling performance across varying degrees of urban compactness, while low-lying vegetation demonstrates limited thermal regulation capacity. Critical thresholds of MIXD (approximately 28 for UHI area and 37 for UHI intensity) are identified, indicating a nonlinear modulation of green space performance. These findings underscore the importance of vegetation structure and spatial configuration in shaping urban microclimates and offer mechanistic insights into plant-environment interactions under conditions of increasing urban density.
城市热岛（UHI）效应已成为紧凑型城市环境中日益严峻的生态挑战。尽管城市植被在缓解极端高温方面发挥着至关重要的作用，但其降温性能会因植被类型和城市形态背景而异。本研究探讨了以混合用途和高强度开发（MIXD）指数量化的紧凑型城市发展在多大程度上调节了中国南京不同植被类型的降温响应。采用景观指标、基于回归的交互模型以及结合SHAP分析的XGBoost方法，以揭示特定于植被且对结构敏感的降温效果。结果表明，在紧凑型区域，密集种植的树木降温效果降低，在这些区域，空间聚类和破碎化往往会加剧城市热岛效应，尤其是在夜间。相比之下，发现分散的树木在不同程度的城市紧凑度下能保持更稳定的降温性能，而低洼植被的热调节能力有限。确定了MIXD的临界阈值（城市热岛面积约为28，城市热岛强度约为37），表明绿地性能存在非线性调节。这些发现强调了植被结构和空间配置在塑造城市微气候中的重要性，并为城市密度增加条件下的植物 - 环境相互作用提供了机制性见解。
