Comparing Water Use in Semi-Arid Montane Aspen, Conifer, Sage and Grass/Forb Ecosystems

Evapotranspiration (ET) is one of the most critical land surface processes in regional climate models. Because there are few ET measurements and monitoring capabilities in high elevation mountain ecosystems, this study used numerical modeling to estimate evaporation and transpiration from four common semi-arid montane vegetation types (Aspen, Conifer, Grass/Forb and Sagebrush). A numerical model was used to simulate soil moisture-based estimates of evaporation, transpiration and ET using 2010 measurements of environmental conditions from the instrumented T. W. Daniel Experimental Forest (TWDEF), in Northern Utah. The patterns of evaporation, transpiration and ET were simulated and compared based on vegetation type, location and soil texture. The transpiration and ET revealed significant differences between trees and the Grass/Forb and Sage ecosystems. But soil evaporation estimates showed no significant difference among vegetation types. There was significant spatial variability in tree transpiration but not observed in Grass/Forb and Sage. The soil texture seemed to play an important role in controlling the transpiration rate of aspen and conifer. The ratio of the modeled ET to the reference ET was observed to be a function of soil moisture for each type of vegetation. Our next step will be to compare year to year (2009 – 2011) water use rates in these same ecosystems.