Two studies by Boise State University geoscientists provide new information about how snowmelt is stored and used in mountain environments.
Global warming is said to be reducing snowpacks across the western U.S., with potentially far-reaching implications for downstream water resources. In the studies, Boise State researchers wanted to know how changing snowpacks will impact upland ecosystems in areas of the mountains that aren't near streams.
The Boise State geoscientists found the benefit of winter snow accumulation to high-elevation ecosystems is limited by the soil's ability to store water. While mountain snowpacks are important natural reservoirs extending spring and summer water delivery to downstream users and ecosystems, the study found that the coarse-grained, shallow soils can store only a fraction of the snowmelt into the summer when the water is needed. This means that declines in snowpack may have a minimal impact on summer water availability in these locations.
In a related study, researchers found a large difference in the capacity of the soil to store water on north-and south-facing slopes. The study found soils on north-facing slopes in a semi-arid mountain region in Idaho can hold up to 50 percent more water than soils on south-facing slopes. Because south-facing slopes dry out faster, the ability of vegetation to survive the dry summers is limited.
The study also found that the more heavily vegetated north-facing slopes have the capacity to store more water because of finer-grained and deeper soils, which in turn produce drastically different soil water retention capacity. The researchers concluded that these differences are driven by various levels of solar radiation; the south-facing soils receive considerably more light and energy than their north-facing counterparts.
Researchers say these studies don't suggest that upland ecosystems will be less sensitive to climate change, but rather that changes to winter snowpack may not be the primary reason for the impact.
"What is interesting about these studies is they suggest that the soils might be more sensitive to changes in precipitation timing rather than amount," says Jim McNamara, co-author of the studies and a professor of geosciences. "The limited ability of soils to store water from snowmelt highlights the potential importance of spring and early summer precipitation, and changes in spring precipitation may have a profound impact on upland water availability."
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