How to Spot a Prairie Fen

By Jake McCarthy

The next time you’re out walking in nature and surrounded by sedges with damp feet, take a look around. You might find yourself in a fen, one of Michigan’s most diverse habitats. Prairie fens are nutrient-rich wetlands that use groundwater to support a wide range of plants and animals. Globally scarce, they are home to species including Eastern massasauga rattlesnake and pink and white lady slipper. Fens also improve water quality and reduce the risk of flooding.

Fens are fragile, though, and need to be recognized and protected in order to thrive. MNA protects and manages a number of fens in Michigan, including the Bullard Lake Fen Plant Preserve in Livingston County and the Robert T. Brown Nature Sanctuary in Houghton County. It can take 10,000 years for a fen to form naturally, so it’s important to do what we can to conserve the fens we have.

Here are a few ways to identify a fen:

Soil – Peat and marl are common soil types in fens. Peat, made of decaying plant matter, is spongy and bounces when you walk on it. Marl is a gray-colored and clayish soil.

Water Source – Unlike bogs and swamps, which are rainwater-fed, fens receive water from seeps and springs. Seeps and springs are sources of ground water that have reached the surface. It’s easier to spot both in winter because steady temperatures means they’re unlikely to freeze.

Water Level – The water level in a fen remains fairly constant. Even after a heavy rain, it won’t show significant standing water like a swamp. This is because fens draw water from the ground, not precipitation.

Hummocks – Fens are rife with hummocks, small mounds of sedges that haven’t decomposed because of the water. Hummocks are a great place for a variety of plants to grow, and dot the face of any healthy fen.

For more information on prairie fens in Michigan, how to spot them and restoration tips for landowners, visit MSU’s Prairie Fen Companion website.

To learn more about MNA’s fens and efforts to conserve them, visit our website. To join MNA staff in managing fens with prescribed burns, contact regional stewardship organizer Matt Schultz for more information at mschultz@michigannature.org.

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