Phytosociology of the Lowland Forests of Northern Wisconsin

Abstract

land forests. The composition and floristic relationships of the upland forests have been described by Brown and Curtis (1952). The present study is concerned with the second type, with the forests which are found on poorly drained sites which receive runoff waters from adjacent uplands or which are subjected in other ways to temporary or permanent high levels of soil moisture. Such sites are a prominent feature of the heavily glaciated terrain in northern Wisconsin. They are found in partially filled lake basins, along stream terraces, or on flat lands of glacio-lacustrine origin. They support forests which vary from stands of pure conifers in the wettest situations to stands of nearly pure hardwoods on the most mesic sites.- The substrate in these lowland forests is rich in organic matter, frequently in the form of peat which may be present in beds many feet in thickness. The climate of the area is the Type I of Bochert (1950); it is characterized by cold snowy winters, reliable summer rains, and low rates of evaporation. The snow cover is usually deep enough to protect the soils from frost penetration to any great depth and often prevents any freezing of the soil. Cold air drainage into the lowland forest basins serves to increase the severity of the temperature microclimate and may result in frost on any day of the year. The importance of these lowland forests is greater than their areal extent might indicate. Perhaps less than 10 percent of the land area in northern Wisconsin is occupied by them, but they have received far less disturbance than any of the upland types. Their direct economic potential as sources of lumber or other forest products is low, but they are of great importance in stabilizing the water supply of the region. Their role in providing wintering grounds for the white-tailed deer is also of high significance in the over-all conservation program (Christensen, 1954).