Effects of vertical vegetation layering and canopy closure on microclimate in plant based habitat patches

This study examines how canopy closure and vertical vegetation layering within habitat patches in an urban park shape microclimatic conditions and thermal comfort. Habitat patches were identified using a plant-based habitat classification approach. The sky view factor (SVF) was calculated, and microclimate measurements were conducted using fixed and portable sensors. Thermal comfort was assessed using the Universal Thermal Climate Index (UTCI), Humidex, and mean radiant temperature (Tₘᵣₜ), while the park's contextual cooling effect relative to the surrounding urban fabric was quantified through park cooling intensity (PCI) based on control point comparisons. The results indicate that single-layer patches exhibited the highest maximum temperatures during summer, whereas three- and five-layered structures tended to reduce daytime temperature peaks. Although increased layering in summer reduced daytime temperatures, it was associated with elevated nighttime maxima under certain conditions. In autumn, five-layered structures produced the lowest average temperatures, while permeable three-layered patches composed of tree, shrub, and groundcover combinations. Regarding the radiative environment, multi-layered and evergreen-dominant patches showed reduced Tₘᵣₜ and substantially suppressed midday heat stress, whereas more open and weakly layered patches exhibited increased Tₘᵣₜ and heat stress exposure ≥ 26 °C during periods of intense solar radiation. In winter, higher SVF increased daytime heat gains but amplified nighttime temperature variability through radiative loss and wind exposure. Overall, the findings offer a seasonally and spatially applicable framework for understanding how multi-layered vegetation structures contribute to thermal comfort in urban park environments.