University of Colorado at Boulder

Colloquia Event

Friday December 03, 2010. 03:30 pm. GUGG 205

Sedge Meadows of the Wyoming Basin Shrub-Steppe—Are they Wetlands?

The Wyoming Basin shrub-steppe is a semiarid cold-desert ecosystem. Average annual precipitation is approximately 300mm and surface water is scarce. However, the Wyoming Basin does contain riparian areas, playa lakes, and extensive sedge-dominated wet meadows in ephemeral and intermittent stream channels. The meadows, locally referred to as sloughs, are linear features several kilometers in length and anywhere from 50 to 300 meters in width. They are found at 2000 to 2500 meters altitude in south-central Wyoming and contain sedges, rushes, willows, and other hydrophytes.

One of the larger sloughs is peat-forming and is considered a fen. This may represent the lower limit of peat-forming wetlands in the Rocky Mountain Cordillera.

The predominant land uses are livestock grazing and oil and gas development. Where these uses involve the wet meadows, there are conflicts with water quality and sage grouse habitat. Sedge meadows in good ecological condition provide important sage grouse brood habitat.

The longitudinal gradients of the stream channels are important. Above a certain threshold gradient, the channels are erosional. Channels with lower gradients are depositional, accumulating both inorganic and organic sediments. Wet meadows develop when upstream springs and groundwater seeps provide sufficient water to create hydric soils.

Current studies of the sedge meadows will determine whether these systems are wetlands under the accepted Federal and state criteria.