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Fens and rare plants in the Beartooth Mountains, Wyoming

Date: August 08, 2018

A review of botanical characteristics of 18 fens in the Beartooth Mountains of Wyoming.


Photo of a fen with floating mats on the water
Overview of Swamp Lake Fen in 1987 (photo: Hollis Marriott, WYNDD).

Mountain fens (peat-accumulating wetlands) are groundwater-dependent habitats (i.e. groundwater dependent ecosystems or GDEs) protected under the Clean Water Act and other federal mandates in the United States. There is increasing interest in documenting and monitoring the occurrence and characteristics of fens. In addition to supporting unusual plants, fens are sites of carbon and water storage and long-term ecological stability, since the underlying peat requires thousands of years to accumulate. This report describes 18 fens in the Beartooth Mountains of Wyoming; they were chosen for review because they contain unusually large numbers of rare plants, and have been surveyed or sampled for more than 40 years. Information from the report provides baseline information for future research in the Beartooths, and comparison data for other ranges.

Authors summarized information from past surveys of 18 fens in the Beartooth Mountains of Wyoming, conducted from 1962 to 2009. The cumulative information is presented as a reference that can be used by botanists, wetland ecologists, hydrologists, and soil scientists. While the floristics elements, especially the documentation of rare plant species, are the main focus of the report, information on each fen’s general vegetation types, geology and soils, hydrology, and environmental disturbances, is also reported.

Key Findings

Photo of a rare plant, arctic cottongrass, at Wyoming Creek
Arctic cottongrass (Eriophorum callitrix) at Wyoming Creek (photo: Bonnie Heidel, WYNDD).

Observations included:

  • 32 Wyoming vascular Plant Species of Concern, plus one bryophyte have been documented in the fens.
  • Wetland flora from the fens includes 58 plant families, 156 genera, and 336 vascular plant species—more than 10 percent of the known Wyoming flora.

Current and Potential Disturbances on the Beartooth fens:

  • Three of the 18 fens are located along or adjacent to U.S. Highway 212 corridor.
  • Past livestock grazing may have affected populations of some rare plant species.
  • The fens are mostly free of invasive, non-native plant species.
  • Fieldwork from 2002 to 2007 coincided with moderate to exceptional drought. At two of the fens, water was depleted during a 2005 field visit, and occurrence of upland vegetation was observed near the wetlands. 

Featured Publications

Heidel, Bonnie ; Fertig, Walter ; Mellmann-Brown, Sabine ; Houston, Kent E. ; Dwire, Kathleen A. , 2017

Principal Investigators: 
Principal Investigators - External: 
Bonnie Heidel - University of Wyoming
Forest Service Partners: 
Sabine Mellman-Brown, Region 1
External Partners: 
Kent Houston, Shoshone National Forest
Bonnie Heidel, University of Wyoming
Walter Fertig, Moenave Botanical Consulting
Research Location: 
Beartooth Mountains, Shoshone National Forest, Wyoming