Wet Meadows, Marshes and Rich Fens
Wet meadows, marshes and sedge fens are open wetland communities situated in topographic depressions in the Sandplain. They at times grade into one another and may not be readily distinguishable in the field. Wet Meadows tend to occur on mineral soil in shallow basins and do not accumulate much organic material. In contrast, Sedge Fens (also called rich fens) occur where plant remains can accumulate as peat, typically in closed basins or where cold groundwater limits decomposition. Marshes occur in deeper basins around open water or along streams and flowages where oxygen-rich water decomposes plant remains into a soupy organic muck. If one includes Shrub Swamps with these open wetlands, fully 1/4 of Cedar Creek would fall into this category. The most extensive tracts occur along Cedar Creek, the margin of Fish Lake, Bridge Marsh east of the Lab and Channel Marsh south of the Lab. Click here to view wetland graminoids.
Numerous wet meadows occur in small, shallow depressions in the southern, savanna portions of Cedar Creek. Here, the tussock-forming Hayden’s sedge Carex haydenii dominates. Common associates are Calamagrostris canadensis (Bluejoint Grass), Carex lanuginosa, Carex vesicaria, Iris versicolor (Blue Flag Iris), Spiraea alba (Meadow Sweet), Salix gracilis (Slender Willow), and Onoclea sensibilis (Sensitive Fern). A couple of these wet meadows grade into Wet Prairie where Spartina pectinata (Prairie Cordgrass) is found. In general, these shallow wet meadows at Cedar Creek are in superb natural condition, having an abundance of uncommon forbs that have been spared the disturbances caused by heavy grazing and invasion of reed canary grass. (See also Special Features of Sand Prairie & Savanna.)
A few large wet meadows at Cedar Creek occur along the creek itself as well as in Bridge Marsh east of the Lab, and in Channel Marsh south of the Lab. These wet meadows tend to be dominated by tussock sedge (Carex stricta) and bluejoint grass. They grade into peatier areas of rich fen, shrub swamp, alder swamp, or cattail marsh. These larger wet meadow types, if heavily pastured by cattle as is common elsewhere on the Sandplain, reveal the tussock nature of Carex stricta.
Sedge Fens are open wetlands that develop on a sedge peat (as opposed to the sphagnum peat of a poor fen) and have a water saturated substrate throughout most or all of the growing season. They are typically dominated by Carex lasiocarpa and Carex rostrata at Cedar Creek. In reality, they are difficult to distinguish from other community types because they grade into wet meadows, marshes, and nutrient poor fens. They also occur as small, sedgy openings in and around tamarack swamps, alder swamps, and mixed shrub swamps. This community is called a ‘rich fen’ (in contrast to ‘poor fen’) because the pH is near-neutral (or only slightly acidic) which allows essential plant nutrients to be more available. Another type of Rich Fen that is legally protected in Minnesota are *Calcareous Fens*. Here, carbonate-rich groundwater carrying calcium and/or magnesium creates conditions that are unfavorable for many common wetland plants but where certain rare species can thrive.
*No calcareous fens occur at Cedar Creek.
The largest examples of sedge fens at Cedar Creek occur in association with “wiregrass meadows” or nutrient poor fens (having a carpet of sphagnum and a “grassy” cover of the sedge Carex lasiocarpa). Examples occur north of Fish Lake in Martha’s Marsh, in the Bay of Tonkin SW of Crane Marsh, and in Bridge Marsh and Channel Marsh east and south of the Lab.
The most species-rich sedge fen near Cedar Creek is Reiling’s Fen—unfortunately, it is on adjacent private property. It is bounded by Co. Rd 24 to the north and west and by the creek to the east. Common flowering forbs of Reiling’s Fen are Spiraea tomentosa and S. alba (Steeple Bush, Meadowsweet), Eupatorium perfoliatum and E. maculatum (Boneset, Joe-Pye-Weed), and Solidago gigantea and S. canadensis (Giant and Canada Goldenrod). Noteworthy species include Chelone glabra (Turtlehead), Solidago uliginosus (Bog Goldenrod), Gentiana andrewsii (Bottle Gentian), Gentianopsis procera (Fringed Gentian), Spiranthes cernua (Nodding Ladies Tresses), Lathyrus palustris (Marsh Vetchling), and Parnassia palustris (Grass of Parnassus). Some of these same species also occur in Calcareous Fens. Reiling’s Fen has become densely shrubby over the past two decades with bog birch, willows, dogwoods, speckled alder,and the aggressive non-native shrub, Rhamnus frangula. The last wildfire occurred in 1955? and without another one soon, the herbaceous diversity will likely be lost.
Marshes occur along streams or the open water of lakes and ponds. They generally have standing water throughout the year and sit atop a rather deep layer of organic muck. Undecomposed peat does not accumulate because of the presence of warm oxygenated waters. Some of the ordinarily vernal pools and sedge fens on the Area may turn into Arrowhead Marshes in particularly wet years. These are dominated by Saggitaria latifolia (Broad-leaved Arrowhead). However, the most prevalent marshes of Cedar Creek Ecosystem Science Reserve are Cattail Marshes. These are probably more extensive on the Anoka Sandplain now than they were in pre-settlement times. Typha latifolia (Broad-leaved Cattail) was likely the dominant species at that time. However, such practices as dredging, damming, burning, and snowmobiling our wetlands have greatly increased the acreage of this community. These disturbed wetlands have been colonized by T. latifolia, T. angustifolia (Narrow-leaved Cattail) and the aggressive hybrid cattail, T. glauca.
The largest tract of Cattail Marsh at Cedar Creek Ecosystem Science Reserve is found in Peterson Marsh west of Fish Lake. Others surround Beaver Pond, Central Pond, and several other smaller ponds on the Area. In spite of their monotonous appearance, they do support a rather varied groundlayer community including such plants as Potentilla palustris (Marsh Cinquefoil) and species of Scutellaria (Skullcaps), Hypericum (St. John’s wort), and Lycopus (Bugleweeds). A common emergent aquatic is Broad-leaved Arrowhead. Common submerged aquatics are Utricularia spp (Bladderwort) and Lemna spp (Duckweed). Cattail marshes while being breeding grounds for hordes of noxious mosquitoes, do have some redeeming qualities. They provide nesting and food for Redwing Blackbirds, Marsh Wrens, Rails, Waterfowl, and muskrats.