RCCZO -- Sap Flow, Vegetation -- Sap flux among sagebrush communities -- Reynolds Creek Experimental Watershed -- (2015-2017)

Artemisia spp. play a significant role in hydrological cycling of sagebrush steppe ecosystems. These sagebrush ecosystems cover a wide elevation gradient and are dominated by different species and subspecies of sagebrush. Water balance of sagebrush ecosystems varies along an elevation gradient with pulse-driven ecosystems located at lower elevation and drier sites and water storage (i.e., snow-dominated precipitation) ecosystems located at higher elevation and wetter sites. Thus, it is difficult to predict how water fluxes in these ecosystems will respond to changing climatic conditions along an elevation gradient. The primary objective of this study was to characterize sap flux in three sagebrush communities located along a rain- to snow-dominated regime by comparing hourly, daily, and seasonal sap flux patterns and their relationships with environmental factors. Sap flux was monitored between June 2015 and October 2017 using heat balance sensors. Meteorological data was also measured from adjacent weather stations, including air temperature (Tair), vapor pressure deficit (VPD), solar radiation (SR), and relative humidity (RH). Soil moisture content was also monitored at different depths in three communities during study period. We hypothesized that sap flux would be greater in the shrubs located at the highest, snow-dominated site compared to lower, rain-dominated sites. Our results indicated that daily sap flux was greater (~ 17%) in A.t. wyomingensis at the rain-dominated site (WBS) compared to A.t. vaseyana at the snow-dominated site, likely due to a comparatively longer growing season at the lower site. Sap flux drives several physiological response of desert plants (i.e., gas exchange, water transport, plant hydraulics) and will be impacted by climatic changes. Therefore, accurate estimation of plant water use (i.e., sap flux) and how various environmental factors influence sap flux in different sagebrush communities will help in predicting the role of sagebrush in hydrological cycling in future scenarios.