trapping nutrients so that they are no 

 longer recycled. Such fens end up as bogs, 

 as the waterlogged peat slows down oxy- 

 gen movement and reduces the rate of de- 

 composition. Fewer and fewer plant spe- 

 cies other than sphagnum are able to 

 survive in the habitat. Some, perched on 

 the peat, must obtain their water and nutri- 

 ents strictly from rain, absorbing these ne- 

 cessities mostly through above-ground tis- 

 sues rather than through roots. 



As a bog matures, more and more 

 shrubs invade it, most of them members of 

 the heath family. In northern Michigan, 

 bogs eventually become dominated by 

 black spruces, forming a type of swamp 

 referred to as a muskeg. This process may 

 take several thousand years. 



Unlike peatlands, marshes and swamps 

 are flooded at least part of the year, so 

 sphagnum has little chance to become es- 

 tablished and to accumulate. Their soils 

 are well aerated and rich in minerals. 

 Marshes are dominated by grasses, with 

 few woody plants. Similar habitats, when 

 dominated by sedges, are called sedge 

 meadows, and when forested, they are 

 called swamps. 



In Crum's terms, Summerby Swamp 

 consists of both rich fen and cedar swamp 

 zones. (Another type of wetland found in 

 Hiawatha National Forest will be explored 

 in next month's article on Shingleton 

 Bog.) I toured the area in early July, ac- 



companied by botanist Donald Henson. 

 The fen, on the north side of Michigan 

 Highway No. 123, was dotted with sphag- 

 num hummocks. Although the fen's sur- 

 face water and groundwater are charged 

 with magnesium and calcium, these 

 sphagnum hummocks are acidic enough 

 to accommodate the growth of acid-loving 

 plants, including wintergreen, leatherleaf, 

 cranberry, and Labrador tea, all members 

 of the heath family. Scattered throughout 

 were thickets of stunted tamarack, white 

 cedar, and black spruce. 



The fen was colorful with the orange 

 flowers of wood lily, the yellow and or- 

 ange blossoms of Indian paintbrush, and 

 the purplish pitchers of pitcher plants. 

 Closer observation revealed the much 

 smaller flowers of arrowgrass (not a true 

 grass) and a diversity of sedges and 

 rushes. 



After surveying the fen, we crossed to 

 the south side of the road. Here we ob- 

 served a mature white cedar swamp with 

 occasional stands of black spruce. Beneath 

 the trees grew royal fern and many species 

 of flowering plants that had bloomed ear- 

 lier in the year, including starflower, 

 goldthread, and bunchberry (a dwarf type 

 of dogwood). Henson speculates that the 

 construction of the road has restricted the 

 draining of water from the north to the 

 south side, speeding the establishment of 

 the swamp zone. 



Summerby Swamp 



For visitor information write: 

 Forest Supervisor 

 Hiawatha National Forest 

 2727 N. Lincoln Road 

 Escanaba, Michigan 49829 

 (906) 786-4062 



Joe LeMonnier 



Wood lily 



Rod Planck; Photo Researchers, Inc. 



While most of the plants in the fen and 

 cedar swamp are common throughout 

 northern Michigan, several are rare for the 

 region. Black crowberry, bird's-eye prim- 

 rose, butterwort, and the hyssop-leaved 

 fleabane (which looks like a small daisy), 

 all more common much farther to the 

 north, have found the right conditions to 

 thrive in Summerby Swamp. 



Worldwide, peatlands are often found 

 in cool temperate zones near oceans. This 

 is because mild winters and long growing 

 seasons with cool, humid, foggy condi- 

 tions favor the growth of sphagnum moss. 

 Peatlands also arise in poorly drained 

 topography sculpted by glacial action. 

 This is true of the Great Lakes area, where 

 the poor drainage of the shallow soil, com- 

 bined with an even distribution of rainfall 

 throughout most of the year, allows peat- 

 lands to form despite short growing sea- 

 sons, low humidity, and long, cold winters. 



Robert H. Mohlenbrock, professor emeri- 

 tus of plant biology at Southern Illinois 

 University, Carbondale, explores the bio- 

 logical and geological highlights of the 

 156 U.S. national forests. 



22 Natural History 3/94 



