Abstract:

【Objective】This study explores the correlation between summer comfort evaluation indexes, namely the S index, and wet bulb globe temperature (WBGT) index, and microclimate and plant landscape factors to assess microclimate effects. The goal is to enhance the environmental quality and usability of urban waterfront green spaces by optimizing human thermal comfort under varying plant landscape characteristics.【Method】 Nine representative plots and one control site along the urban section of the Qinhuai River in Nanjing were selected for analysis. Key plant elements (large tree coverage, small tree coverage, shrub coverage, and ground cover) were surveyed alongside meteorological factors (air temperature, relative humidity and wind speed). Comfort levels were calculated, and visual charts were used to illustrate changing patterns. Correlations between thermal comfort and the selected variables were analyzed. 【Result】Waterfront spaces were classified into three plant layout types: point, strip and surrounding layouts. Key findings include the following: comfort variations by layout, namely the point and surrounding layouts exhibited higher microclimate comfort, while the strip layout was less favorable. The point layout demonstrated the most significant cooling and humidifying effects. Contribution of factors to comfort: air temperature and relative humidity were major contributors to the microclimate’s integrated variables, while the WBGT index had a prominent influence on comfort. Air temperature positively correlated with comfort, relative humidity showed a significantly negative correlation, and wind speed had the weakest impact. Plant element correlations: comfort was most strongly correlated with large tree cover, followed by shrub cover, small tree cover, and ground cover. For optimal spatial comfort in 20 m × 20 m quadrats, a large tree-to-shrub coverage ratio between 2∶1 and 6∶1 was ideal. Ratios below 2∶1 negatively impacted the comfort index.【Conclusion】Quantitative analysis of microclimate effects under different plant spatial layouts reveals the interplay of key factors influencing summer thermal comfort. Based on these findings, the following strategies are proposed for optimizing plant configurations in urban waterfront green spaces: prioritize point layouts: Employ point layouts to maximize the regulatory effects of plant spaces on the microclimate. Optimize coverage ratios: ensure a large tree-to-shrub coverage ratio greater than 2∶1 to enhance thermal comfort. Flexible planting strategies: select tree species and planting densities based on site-specific conditions. Leverage water-plant synergy: maximize the combined microclimate benefits of water bodies and vegetation.

Key words: waterfront green space, comfort index, plant layout, summer microclimate, Nanjing Inner Qinhuai River