Summary & Purpose
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.
Date of Publication or Submission
This study was conducted in collaboration and cooperation with the USDA Agriculture Research Service, Northwest Watershed Research Center, Boise, Idaho, and landowners within the Reynolds Creek Critical Zone Observatory (RC CZO). Support for this research was provided by NSF for RC CZO Cooperative agreement NSF EAR-1331872. The authors declare no conflicts of interest.
Single Dataset or Series?
Microsoft Excel (.xlsx), CSV (.csv)
Sap flux was continuously recorded using Dynagage sap flux sensors (Flow32-1K, Dynamax Inc., Houston, TX, USA). These sap flux sensors work on an energy balance approach, also known as stem heat balance (Dynagage sap flow sensor user manual). Constant heat is applied around the entire circumference of the portion of stem with a flexible heater. This Flow32-1K system has an auto-zero software; however, values of thermal conductance (i.e., 0.42 W m-2 K-1 for woody stems, Dynagage sap flow sensor user manual) and stem cross-sectional area (m-2) need to be entered manually in the program. The energy or heat carried by the sap flux is captured by thermocouples and is converted into real time sap flux in grams at both hourly and daily scales. We used 10mm diameter stem gages (SGA10-WS) in Wyoming big sagebrush and Mountain big sagebrush and 5mm diameter stem gages (SGA5-WS) for low sagebrush based on the size of branches in these species. The sensors were installed on the roundish branches with diameter range between 9.5-13 mm in Wyoming big sagebrush and Mountain big sagebrush and with diameter range of 5-7 mm in low sagebrush with minimum disturbance to the plant (Dynagage sap flow sensor user manual). These sensors were installed following installation procedure mentioned in the manual (Dynagage sap flow sensor user manual). The rough bark and scar tissues of branches were removed and smoothed with sand paper. Branches were cleaned with rag and canola release spray was applied around the circumference of branches. The sensors were installed after spray was evaporated and sensors were shielded with aluminum sheeting to avoid thermal gradient from direct radiation. These sensors do not require any calibration (Dynagage sap flow sensor user manual).
May 2015 - October 2017
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Sharma, Harmandeep; Reinhardt, Keith; and Lohse, Kathleen A.. (2019). Data for a Comparison of Sap Flux Among Three Sagebrush Communities Spanning Rain-to Snow-Dominated Precipitation Regimes [Data set]. Retrieved from 10.18122/reynoldscreek/15/