Comparison of water use by Artemisia tridentata spp. wyomingensis and Chrysothamnus viscidiflorus spp. viscidiflorus

Abstract

With the reduction of fire frequency in the northern Great Basin, shrubs have increased in abundance at the expense of the herbaceous component. The ability of shrubs to acquire limited soil water resources is probably an important process in determining plant succession and composition. Water use by Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) and green rabbitbrush (Chrysothamnus viscidiflorus subsp. viscidiflorus) was measured during the growing season. I tested the hypothesis that Wyoming big sagebrush utilizes soil water at a more rapid rate, early in the growing season than green rabbitbrush. Water use by these 2 shrubs was compared by determining total water potential (ψ), leaf conductance, transpiration per unit leaf area, and transpiration per unit of canopy throughout 2 growing seasons. Soil water depletion around isolated plants was also measured during both growing seasons. Both plants initiated spring growth at approximately the same time; however, Wyoming big sagebrush maintained a larger leaf area index within the canopy throughout the growing season. Leaf conductance and transpiration were significantly (P is lesser than or equal to 0.05) higher in green rabbitbrush, while transpiration per unit of canopy was higher in Wyoming big sagebrush. Soil water depletion was significantly (P is lesser than or equal to 0.05) more rapid at the canopy edge of isolated Wyoming big sagebrush than green rabbitbrush plants. Wyoming big sagebrush has a greater capacity to exploit early spring soil water than green rabbitbrush.