Increasing the number of street trees can be a promising method to reduce impacts of climate change currently impacting urban public health. However, the quantitative relationships between tree canopy cover and thermal comfort remains unclear, particularly in areas with high temperature and high humidity. This study aims to provide a better understanding of the effects of different degrees of tree canopy cover on human thermal comfort in shallow street canyons in a high temperature, high humidity area of China. Microclimatic measurements and qualitative surveys were conducted on sunny summer days in a shallow street canyon in Wuhan. The results suggest that microclimate benefits are greater for areas with a high-percentage tree canopy cover compared to medium- and low-percentage tree canopy cover—especially at noon. In streets with a high-percentage tree canopy cover, afternoon air temperatures and mean radiant temperatures can be reduced by up to 3.3 °C and 13.9 °C, respectively, compared to a similar street with no tree shade. The thermal sensation prediction formula is proposed and the relationship between human thermal sensation and microclimate factors is established. Blocking solar radiation and increasing wind speed are more feasible than controlling air temperature and humidity as ways to improve human thermal comfort.

Microclimatic condition is a fundamental indicator for evaluating outdoor space livability and vitality. Research has shown that poorly designed building layouts can lead to discomfort; however, the mechanisms influencing outdoor microclimate based on residential building layout are unclear for high temperature and high humidity regions. This study explores the relationship between residential building layouts and the outdoor wind and thermal environment at the pedestrian level in Wuhan, a city renowned for high temperatures and high humidity. Six typical residential building layouts were simulated, using the ENVI-met numerical model, to determine the spatial distribution of wind speed and air temperature. The Universal Thermal Climate Index was adopted as a comprehensive index with which to assess spatial and diurnal variations in microclimates surrounding each building layout. Results showed that parallel building layouts formed a ventilation corridor that increased wind speeds by approximately 0.3 m/s. A staggered building layout, in line with the prevailing wind direction, facilitated airflow in the ventilation corridor and further increased wind speeds. Windward buildings blocked high-temperature airflows and reduced air temperatures by approximately 1 ℃ in parallel layouts, and 1.4 ℃ in enclosed layouts. However, the cooling effect of windward buildings on high-temperature airflow was weaker than the warming effect caused by the wind shadow effect and direct sunlight. Additionally, the performance of the thermal comfort of the enclosed type layout was significantly better, for most of the day, than the parallel type layout.

Clearing of understory plants is a common management method in plantation forests, but its long-term impact on soil properties and understory plant diversity is still poorly understood. In order to uncover the potential relationship between understory diversity and soil properties, we categorized understory plants into herbs and shrubs, and took soil depth into consideration. We measured the soil variables and investigated the understory plant diversity in four stand age-classes (9-year-old for young, 18-year-old for intermediate, 28-year-old for near-mature, and 48-year-old for mature) in a Pinus massoniana plantation. We aimed to examine how the diversity of herbs and shrubs changed with stand succession and to determine which of the three soil depths (0–10 cm, 10–20 cm, 20–40 cm) had the strongest explanation for the understory plant diversity. Furthermore, structural equation modeling (SEM) was performed to assess the direct and indirect effect of understory clearing and stand age on understory diversity. We found that understory clearing influenced the trend of diversity of herbs and shrubs with stand age, and understory diversity showed a strong correlation with soil physical properties in all three soil layers. The soil properties in the 10–20 cm soil layer related with the diversity of herbs and shrubs most, while the 20–40 cm soil layer properties related with them the least. Understory clearing reduced soil available phosphorus (AP). Understory clearing and stand age were found to benefit understory plant diversity directly and decreased the understory diversity indirectly via AP. Consequently, to improve our understanding of the impact of understory clearing and stand age on biodiversity, we should take into account its direct and indirect effects.