Warming alters hydrologic heterogeneity: Simulated climate sensitivity of hydrology-based microrefugia in the snow-to-rain transition zone

Authors: MARSHALL, ADRIENNE - University Of Idaho; LINK, TIMOTHY - University Of Idaho; ABATZOGLOU, JOHN - University Of Idaho; Flerchinger, Gerald; Marks, Daniel; TEDROW, LINDA - University Of Idaho

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2019
Publication Date: 3/18/2019
Citation: Marshall, A.M., Link, T.E., Abatzoglou, J.T., Flerchinger, G.N., Marks, D.G., Tedrow, L. 2019. Warming alters hydrologic heterogeneity: Simulated climate sensitivity of hydrology-based microrefugia in the snow-to-rain transition zone. Water Resources Research. 55:2122-2141. https://doi.org/10.1029/2018WR023063.
DOI: https://doi.org/10.1029/2018WR023063

Interpretive Summary: In mountainous terrain, drifting snow contributes to water available to plant ecosystems. In this study, we assessed the climate sensitivity of a drift-subsidized water availability to plant ecosystems in a small, semi-arid mountainous catchment in the snow-to-rain transition zone. We conducted climate experiments using a physically based hydrologic model and set of potential changes in temperature and precipitation to understand hydrologic responses to a sagebrush plant community that receives no drift subsidies and an aspen grove that does. The drift-subsidized aspen plant community was generally more sensitive to warming than the surrounding sagebrush landscape, with reduced potential for the effects of warming to be offset by increased precipitation. These changes suggest climate warming will increase hydrologic homogeneity across the landscape and potential large changes in drift-subsidized plant communities.

Technical Abstract: In complex terrain, drifting snow contributes to ecohydrologic landscape heterogeneity and hydrologically-induced refugia. In this study, we assessed the climate sensitivity of a drift-subsidized refugium in a small, semi-arid mountainous catchment in the snow-to-rain transition zone. We conducted climate experiments using a physically based hydrologic model and set of potential changes in temperature and precipitation to understand responses of a suite of hydrologic metrics across the watershed. Experiments with an imposed 3.5 °C warming showed reductions in average maximum snow water equivalent of 58-68% and total water available for streamflow by 72%. While relative decreases were similar across sites, much greater absolute decreases in snowpack occurred in the drift-subsidized site than the surrounding landscape. In the drift-subsidized site, warming resulted in a shift from a regime that included both energy and water limited years to one that was exclusively water-limited. Warming also resulted in altered interannual variability of hydrologic variables that was as large or sometimes greater than changes in mean values. For example, with warming of 3.5 °C, mean potential discharge in the drift-subsidized unit decreased by 252 mm (71%), while the interquartile range decreased by 255 mm (65%). The drift-subsidized unit was generally more sensitive to warming than the surrounding landscape, with reduced potential for the effects of warming to be offset by increased precipitation. These changes suggest an increase in hydrologic homogeneity across the landscape and relatively large changes in drift-subsidized refugia.