Assessing Water Use in Semi-Arid Montane Aspen, Conifer, Sage and Grass/Forb Ecosystems Using Measurements and Numerical Simulation.

Title: Assessing Water Use in Semi-arid Montane Aspen, Conifer, Sage and Grass/Forb Ecosystems using Measurements and Numerical Simulation

Author: Ling Lv, Scott B. Jones¹, Lawrence E. Hipps

Utah State University, department of plants, soil and climate, Logan, UT

Content: The main source of fresh water in the western US is derived from snow melt from montane ecosystems, which often become water-limited later in the summer. To gain insight into water use processes of these montane ecosystems, we used field measured water content coupled with HYDRUS-1D numerical simulations. Our objectives were to estimate evaporation, transpiration and ET from four common semi-arid montane vegetation types (Aspen, Conifer, Grass/Forb and Sagebrush) at the instrumented T. W. Daniel Experimental Forest (TWDEF) located in Northern Utah. We estimate the growing-season variation in evaporation (f_e), transpiration (f_t) and ET fluxes (f_et) and relate the variability in f_e, f_t, and f_et to the soil water content (θ) and reference ET (ET₀).  The patterns of evaporation, transpiration and ET were also compared based on vegetation types, calendar years and green canopy duration. Results show the timing of the annual peak f_e, f_t, and f_et cycles, which vary among years for each vegetation type. For each vegetation type, the length of time green canopy was present changed annually, however, total annual evaporation, transpiration and ET have no significant difference among years for specific vegetation.  For the specific year, Aspen showed significant difference compared with sagebrush and Grass/Forb, and Conifer had no significant difference compared with other vegetation types.   For each vegetation type, the length of time green canopy was present changed annually, but the ET exhibited no significant differences among. The f_et is positively correlated with the ET₀, which is mainly governed by controlled by solar radiation and saturation deficit at TWDEF. 

Abstract Citation: Ling Lv, Scott B. Jones¹, Lawrence E. Hipps. 2012. Assessing Water Use in Semi-arid Montane Aspen, Conifer, Sage and Grass/Forb Ecosystems using Measurements and Numerical Simulation. Soil Science Society of America Annual Meeting, Cincinnati, Ohio, October 21-24, 2012.