Xeriscaping is an increasingly popular strategy to curb water use in arid regions. During this process, turfgrass is replaced with a mixture of mulching and 'water wise' plant species. While metering studies have demonstrated that turfgrass removal results in reduced water demand on average, xeriscape designs can vary widely in their form, plant cover, and species present. There is a need for more accurate information about in situ evapotranspiration (ET) rates in heterogeneous urban landscapes in order to predict water demand and adequately inform planning efforts. Recent in situ studies have demonstrated that the urban microclimate (i.e. variations in shading) is an important factor in landscape water use. Variation in plant physiology and atmospheric boundary conditions may further influence plant water relations as urban landscapes become more diverse. We sought to evaluate species-specific variability of water use by plants commonly utilized in xeriscaping.
Results/Conclusions
In collaboration with a local botanic garden (Red Butte Gardens in Salt Lake City, UT), we measured in situ ET rates using a clear chamber fitted with relative humidity sensors on a well-watered Kentucky Bluegrass (Poa pratensis) lawn (shaded and unshaded), and four turfgrass alternative species. These species (Thymus lanuginosus, Veronica oltensis, Sedum spurium, and Bouteloua dactyloides) were also well-watered. We measured hourly ET diurnally for 5 replicates of every species during 3 days in Summer and Fall, 2018, and used a loess smoothing and integration algorithm to calculate daily rates. Chamber measurements were calibrated using gravimetric water loss from potted subset of each species. ET rates were highest in full-sun Kentucky Bluegrass and lowest in shaded Kentucky Bluegrass. ET rates from turfgrass alternatives (in full sun) were generally comparable to Kentucky Bluegrass in full sun despite 'water wise' label, suggesting that well-watered turfgrass alternatives utilize available water.