The Vegetation of Wisconsin: An Ordination of Plant Communities

12. Northern forests - lowland

Northern forests-lowland NATURE AND GENERAL DISTRIBUTION The swamp forests of the northern lowlands have the distinction of being the first vegetation type to be described for Wisconsin. Nicolas Perrot, nearly three hundred years ago in 1667, gave a general account of the swamps, with remarks on their extent and composition. Two centuries later, T. C. Chamberlin in 1877 described them more fully and showed their relations to the glacial topography of the region, as shown in the quotations in Chapter 9. The two segments of the compositional gradient, the wet and the wet-mesic communities, include the tamarack-black spruce bog forests, the white cedar·balsam fir conifer swamps, and the black ash-yellow birch-hemlock hardwood swamps. They are found largely on two topographic types-lake beds and river floodplains. The pitted glacial outwash of north central 'Visconsin has numerous depressions whose bottoms are below the surface of the water Copyrighted Material 222 NORTHERN FORESTS table. These may be small kettles or potholes in regions of recessional moraines, or larger, more extensive basins in areas of ground moraine or outwash. rvlany of these are still occupied by open-water lakes, especially in and ncar Vilas County and in tbe northwestern portion 01 the state. Others are partially or completely filled by the action of encroaching vegetation and consist of a spongy, organic substrate called peat, which is formed by the dead but undecomposed remains of mosses, sedges, or woody plants. These peat beds may be covered either by forest or by non-forest vegetation. The latter is usually either open sphagnum bog or sedge meadow, both of which will be described in later chapters. The forests may occur also on the lowlands which border the rivers and streams of the region. True floodplains, in which the annual or seasonal rise of the water floods the bordering lands and deposits a fresh layer of mineral sediments, are relatively rare in northern Wisconsin . More commonly, the streams meander sluggishly through a valley of varying width or are rapidly flowing with "white water" on numerous cascades and rocky rapids. The latter type commonly has very little streamside vegetation of the lowland kind. The meandering streams, on the other hand, are frequently dammed by beaver or by wind-thrown logs with the resultant formation of ponds and flowages . These ponds accumulate organic sediments or are filled by vegetational encroachment in a manner similar to the glacial lakes. They, also, may be occupied either by open or forest vegetation. The former type, called a "beaver meadow," is one of the characteristic features of the northern landscape. The typical tree of the forested streamside is white cedar although black ash is also very common. Because of the rather specialized topographic requirements of the northern lowland forests, they tend to be distributed as small discrete bodies and rarely cover any extensive contiguous areas (Figure XII-2). The total area on the map is 2,241,400 acres or 6.40 per cent of the land surface. Certain large or locally well-known swamps include those in the bed of former Glacial Lake Wisconsin in Juneau and surrounding counties, the Cedarburg Swamp in Ozaukee County, the Sheboygan and Manitowoc Swamps in counties of the same names, and the New London Swamp in Waupaca County. Perhaps the greatest concentrations of swamps are to be found in southern Iron County, northern Forest County, Price County and Oconto County. A number of conifer swamps are found in the prairie-forest province south of the tension zone. These are most numerous east of the Rock River in the glaciated area but a few occur in the Driftless Area on streams that ,,,ere dammed by outwash from the melting glaciers. Copyrighted Material LOWLAND 223 These southern swamps are largely covered by tamarack forest with a groumllayer of herbs and shrubs typical of the region north of the lone. For various reasons these southern tamarack swamps are frequently considered to be relic outliers of the northern forest. They will be so treated in the present chapter since their floristic affinities are obviously with the northern lowlands or even the boreal forest of spruce and fir, but it is recognized that their relic status is by no means definite or simple. The major P.E.L. studies of the northern lowland forests were made by Christensen (1954) and Jones (l955-see Clausen, 1957). Much of the material in the present chapter...