What is a fen?

    Sandhills wetlands are connected to the region's abundant groundwater and exhibit great diversity, from extremely alkaline lakes to small freshwater ephemeral wetlands. Fens are a rare type of wetland first documented in the Sandhills in the 1980s.

    Fens are characterized by a high water table and peat soils that take thousands of years to form. The moist, cool micro- climate of fens, plus the high mineral content of the water, support a broad diversity of plants, including 16 species considered rare in Nebraska.

    Many fens form at the headwaters of streams. The continual discharge of grandwater provides habitat for four state- threatened fish species: blacknose shiner, pearl dace, finescale dace, and northern redbelly dace.

Extensive biological studies have not yet been done within Nebraska, but in surrounding states, biologists have documented numerous examples of rare snails, dragonflies, damselflies, spiders, and butterflies associated with fens.

    The movement of groundwater in the Sandhills is not completely understood, particularly at fens. Fens tend to develop at sites where groundwater "mounds" have formed under dunes. Seepage from these mounds sometimes surfaces low on hillsides at the edges of a valley. The downward pressure of groundwater mounds under dunes may also result in water surfacing as seeps in the valley floor. Where seeps have flowed to the surface at the same site for hundreds or thousands of years, impeding the decomposition of plant material, deep deposits of peat and muck soils have formed, and fens have been created. (Illustration used with permission of NEBRASKAland Magazine.)