Fen Wetlands

Description:

Fens are uncommon but widely distributed in western Montana, occurring on small to mid size lakes or low gradient slopes with an elevated water table. Fens are one of two types of Peatlands, the other being bogs, and are generally defined as wetlands with waterlogged substrates that promote the accumulation peat. In Montana no extensive areas of true bogs are known to occur3. Peatlands are characterized by having accumulated a minimum of 40 cm of organic soils (peat). Studies have recorded peat accumulation in Montana to be as much as 5.9 meters. Fens differ from bogs in their hydrologic inputs are from precipitation1,2,3. As a result Fens are generally less acidic and are one of the most floristically diverse habitats in Montana. Still, the accumulation of peat and saturated conditions present a variety of floristic growth challenges and thus these wetland types generally support rare and vulnerable plant species.

Function and Values:

Fens, like bogs, provide important benefits in a watershed, including preventing or reducing the risk of floods, improving water quality, and providing habitat for unique plant and animal communities.

Photos of Fen Wetlands:

Example of a Carr Fen on the Rocky Mountain Front Range
Photo by Alex Gladstone
"Example of a "Carr" Fen on the Rocky Mountain
Front Range, Blackfeet Indian Reservation, Montana"

Example of a Fen with an elk wallow in the middle, near the Big Snowy Mountains, Montana
Photo by Lynda Saul
"Example of a Fen with an elk wallow in the middle,
near the Big Snowy Mountains, Montana"

Fen in Glacier County, MT showing multiple different wetland vegetation types
Photo By: Cat McIntyre
"Fen in Glacier County, MT showing multiple different
wetland vegetation types"

Distribution Map of Fen Wetlands:
Distribution Map of Fen Wetlands

Potential Stressors:

Ditching and Draining:

An example of an wetland that has been drained via piping
Photo by: Larry Urban
"An example of an wetland that has been drained via piping."

Invasive Species:

Reed Canarygrass infestation of a small wetland in Lewis and Clark County, Montana
Photo By: Lynda Saul
"Reed Canarygrass infestation of a small wetland
in Lewis and Clark County, Montana"

Reference:

1 Chadde, S. W. et. al. 1998. Peatland on national forests of the northern Rocky Mountain: Ecology and conservation. USDA Forest Service General Technical Report RMRS-GTR-11

2 http://www.epa.gov/wetlands/wetlands-classification-and-types#fens

3 Hansen, P. L. et. al. 1995. Classification and Management of Montana's riparian and Wetland Sites. Montana Forest and Conservation Experiment Station. University of Montana, Missoula, MT.