Trees in urban areas are important for their ecological functions in addition to their esthetic characteristics. Trees provide positive effects on urban microclimate by canopy, reflection, and transpiration activities; therefore, they help to decline formation of heat island. The objective of this study was to determine thermal effects of 15 different tree types: 4 coniferous and 11 deciduous species commonly found in the city of Erzurum located at the northeastern part of Turkey. The relationships between sky view factor and surface temperature regarding the differences in leaf density and tree species. In August 2016, the surface temperature of trees was measured using a thermal camera at 10:00 am and 4:00 pm hours. Sky view factor (SVF) was obtained by fisheye photos and physiologically characteristics of trees were determined. In all trees while the surface temperature was 20.1 °C at 10:00 am, it was 23.4 °C at 4:00 pm. Among the deciduous tree species, Betula verrucosa Ehrh. and Robinia pseudoacacia "Umbracuifera" had the lowest surface temperature; however, Abies concolor (Gord. & Glen.) had the lowest surface temperature among the coniferous tree species. The results indicated that the surface temperatures of different tree species varied considerably, and the SVF value had a significant effect on tree surface temperatures. However, it was obtained that the leaf types had no statistically significant effect on tree surface temperature.

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Natural areas are quickly degraded by opening new settlement and industrial areas in order to meet the increasing demand of the growing population. Concreting, modification of land surfaces, complex urban structures, and depressed urban environments contribute to the formation of an Urban Heat Island (UHI). In this study, the outdoor measurements, meteorological parameters related to the thermal indices such as humidity, temperature, wind velocity, and direction for 24 h measurements, were evaluated. The ENVI-met micro-scale model was performed for evaluating alternative scenarios for winter and summer on thermal comfort for better urban environments. Meteorological parameters together with vegetation characteristics were analyzed for making possible scenarios in botanical garden auto industrial area city center, and rural open area. The average of the vegetated simulations of the botanical garden was about 2.2 °C cooler than this of the mean of current situation in the city center. Based upon the average of all stations, it was determined that the temperature increased 1.4 °C with the simulation of both wooded areas in winter. However, the mean temperature of all stations with coniferous plants was 1.2 °C cooler, in summer. It was concluded that deciduous plants in city center produced more positive results than coniferous plants in winter. In general, it can be said that afforestation in cold climatic regions provides great advantages for both summer and winter and positively affects outdoor thermal comfort. However, it needs further measurement and further research in this regard.

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