Temperature Reduction Mechanisms Based on Planting Characteristics† - Focusing on Isolated Trees and Group Plantings -

The purpose of this study is to quantitatively analyze the effects of structural characteristics of single-tree planting and clustered tree planting on summer air temperature based on observations in urban forests. Air temperature and humidity were monitored during two observations from June to August 2025 at urban parks located in Jung-gu and Dalseo-gu, Daegu, South Korea. A total of 21 observation points representing single-tree planting and 7 points representing clustered planting were selected, and air temperature variations were analyzed across daytime, nighttime, and early morning periods. For single-tree planting, key structural attributes of individual trees, including canopy area, crown base height, and tree height, were examined. For clustered planting, planting- and space-related structural variables, such as sky view factor (SVF), impervious surface area, and crown base height, were analyzed. Correlation analysis and multiple regression analysis were conducted to identify the dominant variables influencing air temperature under each planting type. The results showed that both planting types exhibited the most pronounced cooling effects during the daytime. In single-tree planting, canopy area and crown base height were the primary cooling-related variables (canopy area and crown base, Acer: β = –0.585 to –0.197 and β = –0.461 to –0.231, Zelkova serrata: β = –1.199 to –0.672 and β = 0.038 to 0.342), whereas in clustered planting, air temperature was mainly influenced by sky view factor(SVF: β = 0.485 to 0.863) and impervious surface area(β = 0.204 to 0.556). This study provides insights into the thermal mitigation mechanisms of different planting configurations and offers foundational evidence for establishing planting structure and spatial configuration strategies aimed at reducing summer air temperature in urban forest planning.