Sphagnum Swamps & Bog
We choose to separate these communities from other wooded swamps and fens because of the influence of their sphagnum substrate. While not true ‘ombrotrophic bogs’ (only nutrient input coming from atmosphere and rain water), the luxuriant growth of sphagnum in these swamps and fens both lowers the pH and the compressed underlying sphagnum peat reduces the input of nutrients from groundwater. Characteristic bog plants, including several species of Ericaceae, thrive under these conditions, and indeed are found nowhere else. Two categories of wetland with sphagnum substrate will be considered. They are distinguished more by their physiognomy than by their species associates. Sphagnum Tamarack Swamps dominated by Tamarack is the first. Nutrient Poor Fens are second. The Floating Sphagnum Mat bordering Beckman Lake is treated as a special feature.
Sphagnum Tamarack Swamp
Two large Sphagnum Tamarack Swamps that lie between Beckman Lake and Ice Lake have been affectionately named West and East Fairyland. Upon entering either of these tracts one is impressed by their openness and fragrance. They practically beg to be strolled through. Larix laricina (Tamarack) grows atop a lush mat of sphagnum moss. There is an abundance of ericaceous plants such as Ledum groenlandicum (Labrador Tea) and Vaccinium angustifolium (Common Blueberry). Eriophorum spp (Cottongrass) grows luxuriantly as does Betula glandulifera (Bog Birch). Conspicuous groundlayer forbs are Menyanthes trifoliata (Buckbean) and Smilacina trifolia (3-leaved False Solomon Seal). While not as rich floristically as the sphagnum margin of Beckman Lake, the large size of these two tracts makes them aesthetically almost unrivaled. Fewer than a dozen examples of this community exist in all of the North Metro counties.
Cedar Creek is a rare southern outpost for Black Spruce in Minnesota, but no true *Black Spruce Swamp* is found here. It is only along the perimeter of Beckman Lake where one finds Picea mariana (Black Spruce) co-mixed with Larix laricina (Tamarack). Ledum groenlandicum (Labrador Tea) is the most conspicuous understory shrub. Other ericaceous shrubs on sphagnum hummocks include Vaccinium angustifolium (Common Blueberry) and Vaccinium oxycoccus (Small-leaved Cranberry). Sarracenia purpurea (Pitcher Plant) thrives in depressions between hummocks. As in East and West Fairyland, conspicuous graminoids are Dulichium arundinaceum (3-way Sedge), Carex oligosperma (Few-seeded Sedge), and Eriophorum spp (Cottongrass).
*Black Spruce Swamps are common in northern Minnesota. Dense stands of often stunted Black Spruce grow atop a thick carpet of sphagnum mosses with several species of ericaceous shrubs dominating the understory. A common ericaceous shrub in northern Minnesota is Kalmia polifolia (Bog Laurel). This species does not reach Cedar Creek. The nearest locale for such a community is north of Hwy 48 in southern Pine County before crossing the St. Croix River into Wisconsin.
Nutrient Poor Fens
A second category of wetlands with sphagnum substrate are Nutrient Poor Fens. These fens sit atop sphagnum peat and most have a marshy moat surrounding them--a result of nutrient input from surrounding uplands. Most common are Wiregrass Meadows dominated by Carex lasiocarpa (Wiregrass) and with Chamaedaphne calyculata (Leatherleaf) as the most conspicuous ericaceous plant. The shrub Betula glandulifera (Bog Birch) is also commonly found. Representatives Poor Fens at Cedar Creek include Crane Marsh, Oval Marsh, and Road Cut Fen. A few others have additional ericaceous representatives such as Andromeda glaucophylla (Bog Rosemary) and Vaccinium macrocarpon (Large-leaved Cranberry). Non-ericaceous plants such as the Bog Willows (Salix pyrifolia, S. pedicellaris) may also be present. Several of these additional species can be found in Tower Bog and Remote Bog. However, neither of these ‘poor fens’ are as rich floristically as the bog margin of Beckman Lake. Only an exceptional few ‘bogs’ on the entire Anoka Sandplain have the insectivorous Pitcher Plants and Sundew found there. (See Special Features below.)
Nutrient Poor Fens are not uncommon on the Anoka Sandplain, but they are in a rather precarious position. They are fragile communities that are easily degraded by fires, and are extremely sensitive to ATV traffic and snowmobilers. In addition to cutting the sphagnum base into a soupy mess, such vehicular traffic introduces seeds of cattail, reed canary grass, and purple loosestrife from neighboring wetlands. Crane Marsh is a large wiregrass meadow immediately south of Fish Lake. It experienced a devastating wildfire in October 2000 and we fear that it may well be invaded by aggressive cattails in the very near future. Sandhill Cranes have nested on this and other fens and marshes on the Area since 1975.
The floating sphagnum mat bordering Beckman Lake is the best, and nearly only example, of a beautiful ‘bog’ mat surrounding open water in east-central Minnesota. Chamaedaphne calyculata (Leatherleaf) is the most conspicuous ericaceous shrub, but closer inspection yields a surprising variety of plants. In addition to Leatherleaf we find Andromeda glaucophylla (Bog Rosemary), and enormous patches of Vaccinium macrocarpon and V. oxycoccus (Large and Small leaf Cranberry). The two carnivorous plants Sarracenia purpurea (Pitcher Plant) and Drosera rotundifolia (Sundew) thrive on the mat. Farther out on the mat towards the open water one finds such noteworthy plants as Scheuchzeria palustris and Eriophorum chamissonis.
Rare insects of Beckman Lake Bog include Epidemia epixanthe (Bog Copper), Nannothemis bella (smallest dragonfly in North America), Melanoplus punctulata (Tamarack Grasshopper), and Gryllus palustris (Bog Cricket).