Joe LeMonnier 



VlOOMiJ.es 175) 



•ILUNOIS .1 ' ' r :, "^ '■ 



flowers grow on the sphagnum-dominated 

 soil, all species adapted to saturated soils, 

 cool summers, and frigid winters with 

 long durations of snow cover. They in- 

 clude bushy-branched horsetail, winter- 

 green, starflower, and bunchberry (a four- 

 inch-tall, nonwoody type of dogwood). 

 Carnivorous sundews and pitcher plants, 

 as well as a wide variety of slender, deh- 

 cate sedges, are also common. 



After making our way for a few hun- 

 dred feet through this fragile, watery ter- 

 rain — being careful not to step on the 

 flowering plants — we left behind most of 

 the scraggly trees and faced a meadowlike 

 area with small rivulets of water running 

 between ridges covered by sphagnum 

 moss and other vegetation. This was the 

 patterned fen, although the pattern was not 

 immediately visible. If we could have 

 looked down from above, however, we 

 would have seen that the ridges and 

 rivulets were all more or less parallel to 

 one another, oriented east-west at right 

 angles to the sUght slope of the terrain. 



Peatlands all across the more northerly 

 regions may contain patterned fens. Scien- 

 tists in Europe recognized them many 

 years ago, calling them aapamires. The 

 rivulets are referred to as flarks, while the 

 adjacent ridges of soil and vegetation are 

 called strings. Biologists have come up 

 with several hypotheses concerning the 

 origin of patterned fens. One suggestion is 

 that the alternate freezing and thawing of 

 the soil over a long period of time eventu- 



Bunchberry is a nonwoody type of 

 dogwood. 



Doug Locke: Dembinsky Photo Associates 



ally gives rise to the altemating flarks and 

 strings. 



While freezing and thawing may play a 

 role in creating patterned fens, there may 

 be a more important factor. Patterned fens 

 usually arise where the terrain has a grad- 

 ual, nearly imperceptible grade of about 2 

 percent. Through time, soil slides down 

 this small gradient. When one edge of the 

 slipping soil hooks onto something, such 

 as a small tree or even a rock, flie soil 

 tears, forming a flark along the tear hne. 

 After many years of constant sliding and 

 tearing, a distinct pattern of altemating 

 flarks and strings becomes evident. 



At Shingleton Bog, the strings and 

 flarks may be as narrow as one foot or as 



Shingleton Bog 



For visitor information write: 

 Forest Supervisor 

 Hiawatha National Forest 

 2727 N. Lincoln Road 

 Escanaba, Michigan 49829 

 (906) 786-4062 



much as thirty feet wide and are usually 

 from ten to one hundred or more feet long. 

 The strings may stand as much as three 

 feet higher than the flarks, but usually the 

 contrast is more subtle. The amount of 

 water in the flarks varies with rainfall, 

 ranging from inconspicuous amounts up 

 to pools six inches deep. The water is 

 nearly neutral, with a pH of about 6. 



Several plants seem confined to the 

 flarks: a tufted httle sedge known as Carex 

 exilis, the intermediate sundew, one kind 

 of bladderwort, and the white beaked rush. 

 The strings, on die other hand, provide 

 habitat for Kalm's lobeha, bog rosemary, 

 shrubby cinquefoil, a wild Uly, and several 

 flowering plants exceptionally rare for the 

 region. Most of the rarities, including a 

 sedge, an orchid, a sundew, a tiny rasp- 

 berry, and a willow herb, are arctic species 

 that were left behind when the great glaci- 

 ers of the Ice Age receded northward. 



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 4/94 



