|Williams, Christopher - Jason|
|Bates, Jonathan - Jon|
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2016
Publication Date: 1/1/2017
Citation: Kormos, P.R., Marks, D.G., Pierson, F.B., Williams, C.J., Hardegree, S.P., Havens, S.C., Hedrick, A., Bates, J.D., Svejcar, A.J. 2017. Ecosystem water availability in juniper versus sagebrush snow-dominated rangelands. Rangeland Ecology and Management. 70(1):116-128. https://doi.org/10.1016/j.rama.2016.05.003.
Interpretive Summary: This paper describes a modeling experiment conducted to determine the sensitivity of snow deposition and catchment hydrology to removal of juniper from the landscape. The experiment is based on 6 years of data collection in a series of instrumented catchments on South Mountain, near the Oregon – Idaho boarder. Simulations were based on the current juniper distribution, and on a hypothetical juniper-free, sagebrush land cover. Results indicate that juniper capture blowing snow, which results in a deeper and more extensive snowcover, while sagebrush do not capture as much snow, allowing the development of large snow drifts, with some areas scoured snow free. However the deeper snow in the juniper-dominated scenario melts out earlier in the year, while the drifts that develop under the sagebrush scenario last well into spring, providing water for ecosystems and sage grouse well into the growing season. Juniper removal is complicated and interacts with the snowcover energy balance in ways that are not always anticipated.
Technical Abstract: Western Juniper (J. occidentalis Hook.) now dominates over 3.6 million ha of rangeland in the Intermountain Western US. Critical ecological relationships among snow distribution, water budgets, plant community transitions, and habitat requirements for wildlife, such as sage grouse, remain poorly understood. The goal of this study is to better understand how juniper encroachment effects water availability for ecohydrologic processes and associated wildlife habitat in snow-dominated sagebrush (Artemisia spp.) steppe ecosystems. A six-year combined measurement and modeling study is conducted to explore differences in snow distribution, water availability, and annual water balances between juniper-dominated and sagebrush-dominated catchments. Although there is large interannual variability in both measured weather data and modeled hydrologic fluxes during the study, results indicate that juniper-dominated catchments have greater peak accumulations of snow water equivalent and earlier snow melt versus sagebrush-dominated catchments. The day on which 75% of the modeled surface water input enters the catchments is delayed by an average of 9 days for the sagebrush-dominated scenario compared to the juniper-dominated scenario. Water delivery is delayed in the sagebrush-dominated scenarios as a result of increased water storage in snowdrifts. The lone exception to this trend is a water year with above average precipitation and below average wind speeds. In that year, the juniper-dominated scenario retains snow longer, which contributes to soil water input and streamflow later in the year compared to the sagebrush-dominated scenario. The delayed water input to sagebrush-dominated ecosystems in typical water years has wide ranging implications for available surface water, soil water, and vegetation dynamics associated with wildlife habitat for sagebrush obligates such as the greater sage grouse.