Fen Mapping for the Salmon-Challis National Forest

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Abstract:

The Salmon-Challis National Forest (SCNF) covers 4.3 million acres in five discontinuous units within east-central Idaho. Wetlands within the SCNF provide important ecological services to both the Forest and lands downstream. Organic soil wetlands, known as fens, are an irreplaceable resource that the U.S. Forest Service has determined should be managed for conservation and restoration. Fens are defined as groundwater-fed wetlands with organic soils that typically support sedges and low stature shrubs. In the arid west, organic soil formation can take thousands of years. Long-term maintenance of fens requires maintenance of both the hydrology and the plant communities that enable fen formation. <br>

In 2012, the U.S. Forest Service released a new planning rule to guide all National Forests through the process of updating their Land Management Plans (also known as Forest Plans). A component of the new planning rule is that each National Forest must conduct an assessment of important biological resources within its boundaries. Through the biological assessment, biologists at the SCNF identified a need to better understand the distribution and extent of fen wetlands under their management. To this end, U.S. Forest Service contracted Colorado State University and the Colorado Natural Heritage Program (CNHP) to map all potential fens within the SCNF. <br>

Potential fens in the SCNF were identified from digital aerial photography and topographic maps. Each potential fen polygon was hand-drawn in ArcGIS based on the best estimation of fen boundaries and attributed with a confidence value of 1 (low confidence), 3 (possible fen), or 5 (likely fen). The final map contained 3,401 potential fen locations (all confidence levels), covering 5,749 acres or 0.1% of the total land area. This total included 385 likely fens, 1,037 possible fens, and 1,979 low confidence fens. The average fen polygon is just 1.69 acres, but the largest likely fen polygon is over 140 acres. <br>

Fen distribution was analyzed by elevation, bedrock geology, Land Type Association, and watershed. The vast majority of mapped potential fens occurred between 6,000 to 9,000 feet. This elevation range contained 78% of all potential fen locations and 74% of likely fen locations. The majority of likely fen locations occurred in the Strongly Glaciated Lands in Granite Land Type Association. Likely fens were concentrated in three particular watersheds: Upper Elk Creek had 24 likely fens, Swamp Creek-Marsh Creek had 18 likely fens and Cape Horn Creek had 16 likely fens. <br>

This report and associated dataset provide the SCNF with a critical tool for conservation planning at both a local and Forest-wide scale. These data will be useful for the ongoing SCNF biological assessment required by the 2012 Forest Planning Rule, but can also be used for individual management actions, such as planning for timber sales, grazing allotments, and trail maintenance. Wherever possible, the Forest should avoid direct disturbance to the fens mapped through this project, and should also strive to protect the watersheds surrounding high concentrations of fens, thereby protecting their water sources.

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Reference Code: U17SMI01IDUS <br>

Full Citation: Smith, G., Lemly, J. and Schroder, K. 2017. Fen Mapping for the Salmon-Challis National Forest. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado. <br>

Location: ELECTRONIC FILE - BOTANY: OTHER <br>

Keywords: Salmon-Challis National Forest, fen, mapping <br>