Prairie Fens of Michigan
All of the plants that Hillary and I collected came from
prairie fens in southern Michigan. Once finished with identity confirmations,
over 800 new specimens will be added to the CMC Herbarium. We even have a few
specimens that did not have any representation in the CMC Herbarium yet.
We traveled to ten prairie fens across five counties to collect our specimens. We visited the sites two times: once in late spring, the other in late summer. The sites looked very different between two periods with completely different plants in bloom: In spring, Carex sp., some grasses, and a select few dicots (Figure 1); in later summer, Asteraceae and practically everything else (Figure 2).
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Figure 1. In a sedge meadow of a prairie fen in Oakland County, Michigan, in June the Carex sp., other Cyperaceae, and Poaceae show their dominance. White cedar (Thuja occidentalis) and tamarack (Larix laricina) thickets surround the sedge meadow. A stand of the invasive narrow-leafed cattail (Typha angustifloia) is spreading across the central stream. |
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| Figure 2. Above is the same prairie fen of Oakland County, Michigan, in August. The sedge meadow zone of a prairie fen blooms in many different colors. In this photograph many wildflowers – Eutrochium maculatum, Eupatorium perfoliatum, Solidago - are blooming amongst the dominant sedges (Cyperaceae) and grasses (Poaceae). A few Asclepias species (A. syriaca in the foreground on the left) are also seen in sedge meadows. On the left in the middle-ground are a few dogwood shrubs (Cornus), and in the background are tamarack (Larix laricina) and white cedar (Thuja occidentalis) trees. Beware: Poison sumac shrubs (Toxicodendron vernix) are also common in prairie fens. This photograph was taken at a prairie fen in Oakland County, Michigan. |
Prairie fens are a groundwater-fed wetlands dominated by
grasses, sedges, and asters, found mostly in the glaciated Midwest. They are
one of the most diverse ecosystems in the temperate region. These wetlands also
are often source waters for major rivers: the Grand River, Shiawassee River,
and River Raisin all begin in prairie fens. Fen existence also helps reduce the
effects of global climate! Since prairie fens are fed by a nearly constant
source of groundwater, they are wet almost all year long. All this groundwater
reduces the rate of decomposition, so carbon and other compounds are trapped in
the dead vegetative matter.
There are many different vegetation zones in the fens, each
housing a different assortment of species. Typically sedge meadow zones cover
the greatest area of a prairie fen (Figures 1 & 2). Sedge meadows are
dominated by Cyperaceae, usually Carex
sp. and contain many flowering dicots, mostly Asteraceae, and Poaceae, commonly
big blue stem (Andropogen gerardii)
and Indian grass (Sorghastrum nutans).
Shrubs and small trees (Rosaceae, Cornus,
and Toxicodendron vernix) are also
common in sedge meadows.
Inundated flat is the zone near lakes and streams usually
dominated by sedges (Cyperaceae) with few other small species (Figure 3). In
times of heavy precipitation the inundated flat can become flooded. Walking in
these zones is often “bouncy” because there is a mat of dead, non-decomposed
vegetation you walk on. Sometimes these mats have more water than soil beneath
them. These are the zones you may suddenly sink up to your thigh and not feel a
bottom, only water and mud in your boot.
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| Figure 3. An inundated flat is a wet zone bordering lakes and streams dominated by Cyperaceae species (upper left). Clockwise from the top are some common and dominant species of inundated flat: Schoenoplectus sp. and Cladium mariscoides, on the lower right Eleocharis elliptica, and on the lower left a mat of Eleocharis rostellata around a Sagittaria latifolia plant and other sedges. |
A calcareous groundwater seep is where a spring is allowing
the groundwater to seep directly to the surface (Figure 4). These areas are wet
all year round and are typically nitrogen and phosphorus poor. Carnivorous
plants and other common bog species are found in this area of the prairie fen
since it is lacking in nitrogen and phosphorus. Some prairie fens lack these
zones; in others the seep may span acres; in others there are several small
pockets with no one more than 25 square feet.
The wooded prairie fen zone is commonly along the edge of
the prairie fen, transitioning the wetland into upland habitat (Figure 5). Some
are dominated by tamarack (Larix laricina), other white cedar (Thuja occidentalis) or red cedar (Juniperus virginiana). One
sure thing is that they are smelly: Skunk cabbage (Symplocarpus foetidus) is a common and sometimes dominating species
in wooded prairie fen zones.
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| Figure 5. A wooded prairie fen zone is still dominated by sedges, grasses, and asters, but has a canopy layer and other more shady wetland species like skunk cabbage (Symplocarpus foetidus). The most common tree species of wooded prairie fen is tamarack (Larix laricina, a sapling pictured right). Other species include poison sumac (Toxicodendron vernix), dogwood (Cornus spp.), white cedar (Thuja occidentalis), red maple (Acer rubra), and willow (Salix spp.). |
As you can see, prairie fen communities are very diverse. The
specimens we collected will support our field identification of the plant
species for our theses and papers. A great specimen must have all the plant
parts, including the roots (a tough job with some Carex and wetland species). These specimens must be pressed and
dried for at least two weeks and frozen in a no-frost freezer to prevent insect
and mold contamination of the Herbarium collection. For more information on
collecting see the CMC Herbarium website (http://cmcherbarium.bio.cmich.edu/collections.html).
After confirmation of species identity and properly mounted and labeled, they
will be submitted to the Herbarium as specimens.
Rachel
Photos
by Hillary Karbowski and Rachel Hackett
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