There is a small rise on the boundary of Lake and McHenry counties that was once the shore of a lake. On a winter’s day it overlooks a large expanse of dry cattails, their brown flower heads still disintegrating into the white fluff that bears the plants’ seeds on the wind. Beyond the cattails a raft of leafless shrubs surrounds a wrack of barren tamaracks, their crowns tossed on most winter days by harsh winds. From a distance Volo Bog looks lifeless.
Walk closer over the bright green hummocks of moss, though, and you will see waxy red berries clinging to the branches of the winterberry holly. Chickadees, cardinals, and other birds of the north woods, such as the white-winged crossbill, flit among the bushes, drawn by the abundant berries. They’re also attracted by the tamaracks, whose seeming solidity belies the instability of the bog’s soil. Below the trees’ wide, shallow roots is water–a fact not readily apparent in the winter, when the frozen ground and water feel solid. In the summer the ground shakes and vibrates. Visitors to Volo view the bog from the relative stability and safety of a wooden boardwalk.
The boardwalk traverses the concentric rings of vegetation that distinguish the bog’s various stages of ecological succession. In the outer rings there are the cattails, then shrubs such as the winterberry holly, then the tamaracks. Inside the tamarack zone are shrubby species that tolerate acidic water, such as Willow and leatherleaf; then a reedy circle of sedges, ferns, and sphagnum moss; and in the center, the pond, an area of less than an acre.
The tamarack is one of the few conifers that loses its needles in the winter. They fall in October, after turning a bright gold, leaving the branches dotted only with tiny cones that look like flower buds. The fallen needles join the other dead vegetation that litters the bog’s surface. Little decays in the water, which is made acidic by sphagnum moss and the tannic acid that leaches from the tamarack needles. Instead, the plant matter becomes peat. Through the centuries the peat builds up, supporting new plant life and shrinking the open pond further.
Thus each plant sows the seeds of its own demise. As tamarack seedlings sprout on the new peat near the bog’s center, the old trees on the filled-in areas furthest from the center die, no longer able to compete with other species on the less and less acidic soil. Over centuries the concentric rings of vegetation move inward. Someday the open water will be covered by a tamarack forest, then shrubs, then the marsh plants that now make up the outermost ring. In the Chicago area only the Indiana Dunes are as graphic an example of ecological succession.
A visitor to the bog in winter notices seasonal changes more readily than such long-range cycles. But in the berries and cones lie the seeds of next year’s growth, which will further choke the open water. In this battle of land and water, the land is winning. Though the course of its victory may seem interminably slow to us, it is swift in geological terms.
Volo Bog’s history goes back to the retreat of the last ice age some 12,000 years ago, when a great block of ice–a landlocked iceberg–broke off a glacier and was pressed into the ground as the glacier retreated. When the block later melted, it formed a steep-sided and poorly drained lake. Dead vegetation that drifted into its waters remained there. The sphagnum moss that grew among the cattails at water’s edge formed the beginning of the floating mat of vegetation; as its growth turned the water more acidic, unusual bog plants grew: sundew, leatherleaf, blueberry, and arrowhead.
Volo Bog is the only bog in Illinois that still exhibits all the stages of ecological succession. Pistakee and Brandenburg bogs, part of the same nature preserve, have no open water remaining. Further north, bogs are more common. Many of the plants found at Volo, including the tamarack, are at the southernmost limit of their range here. Some are locally rare. The bog’s staff and volunteers are currently compiling an herbarium of preserved plant samples, a project that is expected to include some 100 species. “There are suspicions that there are things out there that we don’t know about yet,” says Stacy Miller, the site naturalist, citing the story of a visitor who came back from an unauthorized hike away from the boardwalk clutching a branch that may have come from a black spruce, a species otherwise unknown in the area.
In winter, bog visitors see not only bird life, but also evidence of mammals–sometimes in the flesh, more commonly in the form of tracks in the snow. At 1 PM on Monday, December 26, Stacy Miller is leading a “winter wonderland” walk through the bog. Other nature walks are conducted at 11 AM and 1 PM every Saturday and Sunday, Visitors can see the bog on their own 8 AM to 4 PM daily (except December 25 and January 1). Admission is free. The bog is on Brandenburg Road just west of Highway 12 in Ingleside; call 815-344-1294 for details.
Art accompanying story in printed newspaper (not available in this archive): photo/Peter Friederici.