Indifference of Mountain Big Sagebrush Growth to Supplemental Water and Nitrogen

Abstract

The responses of mountain big sagebrush (Artemisia tridentata ssp. vaseyana (Rydb.) Beetle) to small annual additions of water and/or nitrogen were investigated in southwestern Wyoming. A factorial field experiment with 2 levels of water (0 or 4 liters per plant in May) and 2 levels of ammonium nitrate fertilizer (0 or 31 kg N ha-1) was conducted with mountain big sagebrush tubelings from 1981 through 1984. End-of-season aboveground biomass and relative growth rate were not affected during 1982-84. Twig growth, ephemeral leaf survival, plant phenology, plant water potential and its components were likewise unaffected by the water and nitrogen treatments during the 1983 and 1984 growing seasons. Lack of a supplemental water main effect or a water × nitrogen fertilizer interaction probably were not evident because of above-average precipitation at the research site during the experimental period. The most likely explanation for the observed lack of nitrogen effect is that the nitrogen additions were small in relation to the total amount available to the plants.