Sagebrush (Artemisia spp.) is a widespread and locally dominant shrub throughout much of western North America, occupying >66 million ha. Sagebrush steppe provides many important ecosystem services including water and carbon (C) storage, as well as providing critical habitat for several threatened and endangered animal species. Because these systems are water limited, changes in precipitation regimes associated with climate change are predicted to alter ecosystem processes such as water and C storage and cycling. However, such changes are hard to predict due to lack of fundamental information on plant water use in sagebrush. While a few studies have been conducted that analyze differences in water budgets in sagebrush ecosystems at landscape scales using eddy covariance methods, data on plant water use at organismal scales are few. Therefore, we quantified seasonal patterns in plant water use in three different sagebrush communities dominated by A. tridentata ssp. wyomingensis, A. arbuscula, and A. tridentata ssp. vaseyanaspanning the rain- to snow-dominated elevation zones in the Reynolds Creek Critical Zone Observatory in Southeastern Idaho. We used thermal dissipation type sap flux sensors installed on 5-6 shrubs/site to measure sap flux during summer 2015.
Results/Conclusions
The preliminary data showed greater absolute sap flux in both A. tridentata species compared to A. arbuscula. Cumulative sap flux was greatest in A. tridentata ssp. vaseyana (6783g/stem/d) followed by A. tridentata ssp. wyomingensis (4376 g/stem/d), and least in A. arbuscula (3806 g/stem/d) during June to October, 2015. However, per unit leaf area, sap flux was greatest in A. arbuscula in comparison to A. tridentata ssp. vaseyana and wyomingensis. Monthly sap-flux data showed maximal sap flux in June, and minimal sap flux during October, consistently in all three sagebrush communities. Mean monthly sap-flux sharply declined from 76 g/d to 20 g/d in A. tridentata ssp. vaseyana from 60 g/d to 16 g/d in A. tridentata ssp. wyomingensis, and from 9 g/d to 4 g/d in A. arbuscular. Our preliminary data suggests that environmental variables controlling sap flux differs between rain vs. snow dominated systems. The rain-dominanted sites are mainly controlled by soil moisture while snow-dominanted by soil temperature. Our findings indicate that transitions from snow to rain may alter fundamental controls on sap flux and understanding of the ecohydrology of different sagebrush species and subspecies may be key to predicting ecosystem responses to changes in climate.