University of Minnesota
University of Minnesota
College of Biological Sciences
http://www.cbs.umn.edu/
Upland forest.View of Cedar Creek.Oak savanna at Cedar Creek.

Cedar Creek habitats

Cedar Creek lies on a sandy outwash plain formed during the last stages of the Wisconsin Glaciation some 11,000 years ago.

Relief is slight, having an elevational gradient of only 10 meters. The area of about 2,200 hectares (5,400 acres, or about nine square miles) is roughly equally divided into four parts: wooded uplands, abandoned fields, lowland wooded swamps, and open fens and marshes. Uplands consist of fine, nutrient poor, outwash sand. Lowlands with a muck-peat substrate atop sand were formed by the filling in of ice-block basins following the late Wisconsin glacial retreat. Climate is continental. Winters are cold, long, and filled with snow. Summers are short, warm, humid, and filled with biting flies. Springs are short, cool, and rather wet. Falls are cool, colorful and exhilarating.

3 BiomesMinnesota lies at the juncture of three great biomes of North America: Northern Conifer Forest, Eastern Deciduous Forest, and Tallgrass Prairie. Cedar Creek contains elements of all three, and in consequence is floristically and faunally quite diverse. Among the Vertebrates, 52 species of mammals, 229 species of birds (133R, 58M, 38V) are reported for the Area. Roughly 4,000 species of insects have been collected here, and it is likely that an additional 4,000 await discovery. The spiders and other invertebrates of Cedar Creek have not been adequately surveyed. The same can be said for the Area’s fungi, lichens and mosses. More than 800 species of vascular plants have been collected here; and although much of the area has been cleared, farmed, logged, or pastured in the past, a number of uncommon species have survived, and indeed flourish here. It is a special treat to be able to explore a pristine sand savanna with 100-year-old bur oaks, pasque flowers, false heather; and just a mile away walk into a black spruce-tamarack swamp with Labrador Tea, pitcher plants and sundew.

Prairie, savanna and woodlands

Upland habitats include more than 100 fields that had been cleared for agricultural use, but the sterile soils soon resulted in abandonment of these fields. Some of the oldest fields, abandoned in the 1920s and 1930s, have been colonized by native prairie species and are now respectable Sand Prairie with Little Bluestem (Schizachyrium scoparium) a dominant grass and with a diverse assemblage of prairie forbs. The more recently abandoned fields have a rather weedy character and are dominated by Kentucky Bluegrass and Quackgrass (Poa pratensis and Agropyron repens). Tracts of Savanna with Bur Oak (Quercus macrocarpa) the dominant tree are found on the Area, and many of these are included in a Burn Program that was initiated in 1964 and continues to the present. Several tracts of Dry Oak Woodland are also present. Former savanna areas that have not been burned have ‘brushed up’ in the absence of fire and have been transformed into Overgrown Savanna. Others with infrequent but intense burns have changed into Scrub Oak Woodland.

Dry Oak Forest is the most common wooded upland community found on the Anoka Sandplain. These forests are dominated by Northern Pin Oak (Quercus ellipsoidalis), are rather open below, and have a rather meager ground flora. Many of them had been logged and/or grazed in the past and most have experienced historical burns. However, very few of these are included in the Cedar Creek Burn Program. There are only a few fire-protected knolls of Mesic Upland Forest with Basswood (Tilia americana) and Sugar Maple (Acer saccharum) present. The groundlayer is more diverse with a small show of spring ephemerals. Occurring on the uplands in North Section, which is buffered from wildfires by extensive areas of wetland to the south and west, are tracts of Mixed Conifer-Hardwood Forest with pines growing amongst hardwoods. Most common is White Pine (Pinus strobus) mixed with hardwoods. A single natural stand of Red Pine (Pinusresinosa) is found northwest of Cedar Bog Lake. One might expect Jack Pine Barrens to occur on this sandy outwash given our proximity to extensive tracts of such habitat in western Wisconsin, but the few Jack Pine (Pinus banksiana) present in North Section are not reproducing. This tree requires fire for reproduction, but our Burn Program contains no tracts with this species present. Lowland Hardwood Forest flanks many of the wooded uplands where the transition to wetland is not abrupt. Characteristic trees are Red Maple (Acer rubrum), Paper Birch (Betula papyrifera), and Trembling Aspen (Populus tremuloides).

Wetlands

Lowland habitats with a peaty substrate atop sand are diverse and include a variety of wooded swamps. Present on the Area are extensive tracts of White Cedar Swamp (Thuja occidentalis), MinerotrophicTamarack Swamp (Larix laricina), Black Ash Swamp (Fraxinus nigra), Alder Swamp (Alnusincana), and Mixed Shrub Swamp with Red-osier Dogwood (Cornusstolonifera), Willows (Salix spp), and Poison Sumac (Rhus vernix).

Of special significance are areas having a Sphagnum substrate atop peat. While not true ‘ombrotrophic bogs’ (nutrient input only from precipitation and atmospheric deposition) the accumulated sphagnum lowers the pH and reduces nutrient availability from surrounding uplands. Surrounding many of these areas is a charactistic moat (lagg area) where elevated nutrient input favors a marshy community. Two large tracts of Sphagnum Tamarack Swamp are found to the west of Beckman Lake. Labrador Tea (Ledum groenlandicum) grows luxuriantly on the sphagnum hummocks in this ‘bog swamp’, and Bog Birch (Betula glandulifera) is a common understory shrub. Along the perimeter of Beckman Lake there is a small tract of Tamarack (Larix laricina) and Black Spruce (Piceamariana) atop sphagnum, a community characteric of northern Minnesota, but extremely rare this far south. The floating sphagnum mat extending toward the lake has many other characterisic ‘bog species’ such asBog Rosemary (Andromeda glaucophylla), Cranberries (Vaccinium spp), Pitcher Plant (Sarracenia purpurea), Sundew (Drosera rotundifolia), and Cottongrass (Eriophorum spp). Several Nutrient Poor Fens with sphagnum substrate that are dominated by Wiregrass (Carex lasiocarpa) and have Leatherleaf (Chamaedaphne calyculata) as the primary ericaceous plant also occur on the Area.

Open wetlands lacking a continuous sphagnum substrate are extensive at Cedar Creek and are here categorized as Wet Meadows (situated in small basins, having little organic substrate over mineral soil, and generally dominated by Calamagrostiscanadensis), Sedge Fens (in larger basins with an underlying sedge peat, Carex stricta a common sedge, and grading into shrub swamp), and Emergent Marsh (flanking open water, having a mucky organic substrate, and here dominated by Typha spp).

Lakes and ponds

Aquatic communities consist of four ‘lakes’ and numerous smaller ponds. Fish Lake is a large shallow, sand-bottomed lake. The other three—Beckman Lake, Cedar Bog Lake, and Ice Lake—are small and marsh margined. Numerous smaller ponds are also present. Many of these are temporary and are among the most dynamic, compositionally speaking, of all the plant communities on the Area. CedarCreek, a small, marsh-margined, meandering stream, flows along the western portion of the Area.

Disturbed areas are common. Many of the younger abandoned agricultural fields have a rather weedy character and are dominated by Kentucky Bluegrass (Poa pratensis) and Quackgrass (Agropyronrepens). A number of introduced garden and ornamental plantings persist at several homesites, both active and abandoned. Several Pine Plantations were established in the 1950s. Small tracts of Reed Canary Grass Wetland (dominated by the introduced Phalaris arundinacea) are also present. Roadsides, ditches, and parking lots are routinely disturbed and weedy in character. Finally, several experimental plots have been established for research purposes and sometimes seeded with non-native species.

As mentioned earlier in the introduction, Cedar Creek is a Registered Natural Landmark, recognized in 1975 as ‘possessing exceptional value in illustrating our nation’s natural heritage’. The initial purchase of White Cedar Swamp surrounding Cedar Bog Lake, the Tamarack-Black Spruce margin of Beckman Lake, and tracts of Bur Oak Sand Savanna was inspired by the recognition of their rare and exceptional status in this region of the state. Their protection is a mandate placed on this and future generations. The task will not be an easy one given the encroachment of suburbia and threats by such aggressive invaders as Glossy-leaved Buckthorn (Rhamnus frangula), Black Locust (Robinia pseudacacia), Purple Loosestrife (Lythrumsalicaria), Leafy Spurge (Euphorbia esula), and Reed Canary Grass (Phalaris arundinacea). Future generations will hold us accountable for the vigor of our stewardship.

References

Wovcha DS, BC Delaney, and GE Nordquist (1995). Minnesota’s St. Croix River Vally and Anoka Sandplain: a guide to Native Habitats. 234 pp. Univ. of Minnesota Press.

Eggers, SD and DM Reed (1997). Wetland Plants and Plant Communities of Minnesota and Wisconsin. 264 pp. US Army Corps of Engineers, St. Paul District.