Vegetation-Specific Cooling Responses to Compact Urban Development: Evidence from a Landscape-Based Analysis in...

Area of Science:

• Urban ecology
• Environmental science
• Climate change adaptation

Background:

• The urban heat island (UHI) effect poses ecological challenges in cities.
• Urban vegetation is crucial for mitigating extreme urban temperatures.
• Vegetation's cooling performance is influenced by its type and the surrounding urban structure.

Purpose of the Study:

• To investigate how compact urban development, measured by the Mixed-use and Intensive Development (MIXD) index, affects the cooling performance of different vegetation types.
• To understand the relationship between urban morphology, vegetation structure, and UHI mitigation in Nanjing, China.

Main Methods:

• Utilized landscape metrics to quantify urban development.
• Employed regression-based interaction models to analyze cooling responses.
• Applied XGBoost and SHAP analysis to identify vegetation-specific and structure-sensitive cooling effects.

Main Results:

• Densely planted trees showed reduced cooling in compact urban areas, exacerbating UHI effects, especially at night.
• Scattered trees maintained consistent cooling across different urban densities.
• Low-lying vegetation had limited thermal regulation capacity.
• Identified critical MIXD thresholds (approx. 28 for UHI area, 37 for UHI intensity) indicating nonlinear green space performance.

Conclusions:

• Vegetation structure and spatial configuration significantly impact urban microclimates.
• Urban planning must consider vegetation type and arrangement for effective UHI mitigation in dense environments.
• Findings provide mechanistic insights into plant-environment interactions under increasing urban density.