What is a Fen?
Fens are among the rarest of wetland communities.
Fens
are a type of wetland fed by upslope sources through drainage
from surrounding soils and through groundwater movement. Fens
are characterized by their water chemistry, which is neutral or
alkaline. Fens differ from bogs because they are less acidic and
have higher nutrient levels. They are thus able to support a
diverse plant and animal community, and are often covered by
grasses, sedges, rushes, and wildflowers, which attract a richly
varied assortment of butterflies and moths.
Small changes in the amount of groundwater discharged into
a fen can modify its chemistry, negatively impacting the vegetation
that depends upon this uniquely balanced chemistry for survival. The
layer
of peat that forms in a fen creates a thick, rich mat that stores immense
amounts of water, providing an ideal environment for plants to grow and
reproduce.
Klein Fen is an especially unique fen known as a "hanging fen," which is a rare sloping wetland terrain. Fewer than twenty acres of these fens remain in Illinois. Klein Fen, which encompasses over five acres, is the only fen of its kind in DuPage County.