Effects of vegetation on the spatial and temporal variation of microclimate in the urbanized Salt Lake Valley

Abstract

Land cover characteristics can produce changes in spatial and temporal variability in potential temperature (θ) at scales that are relevant to city inhabitants. Using data from 60 sensors positioned in five urban parks and surrounding residential neighborhoods in the semi-arid Salt Lake Valley, we evaluated the effect of turfgrass cover versus tree shading on spatial and temporal variation in microclimate in a semi-arid urban area. Our results indicated that the replacement of vegetation by impervious surfaces plays a role in microclimatic homogenization. Tree shading was associated with higher spatial variability of θ during the day, while turfgrass cover was associated with higher spatial variability of θ at night. Contrary to our expectation of tree shading governing daytime θ, we also found turfgrass cover to have an efficient cooling effect. This suggests a prominent role of turfgrass evapotranspiration enhanced by high atmospheric evaporative demand, high soil moisture availability, and increased radiation loads that are characteristic of semi-arid urban landscapes. Given that turfgrass cover was also associated with reduced θ at night, mixed tree and grass landscapes may be effective in alleviating the urban heat island effect in semi-arid urban settings.