The vegetation of lichens and bryophytes on limestone outcrops in the Driftless Area of Wisconsin belongs to a single community consisting of two ecological groups, one on drier habitats and the other on moister ones. The vegetation was studied by a random sampling method involving 25 5-cm-square quadrats for each stand. Frequency data are used in the statistical analysis of the vegetation. An ordination technique analyzes the relationship of the 44 stands sampled and the ecological factors within them. Frequency data for selected species are presented on a three-dimensional ordination. The results show a vegetational continuum related to a moisture gradient. Frequency data present a better differentiation on the ordination than presence data. Relatively few studies concerning the quantitative ecology of lichens and bryophytes have been undertaken. American studies using random sampling techniques and statistical analyses of the results have been made by Hale (1955), Culberson (1955), Brodo (1961), and Looman (1962, 1964). The studies of Hale, Culberson, and Brodo pertain to corticolous bryophytes and lichens in southern Wisconsin, northern Wisconsin, and central Long Island respectively. Looman investigated the lichen and bryophyte flora of prairie grasslands in north-central United States and adjacent Canada. No similar studies have been made on saxicolous bryophyte and lichen vegetation. Aside from providing a quantitative description of 1 This work was partly supported by a grant from the Davis Fund of the Department of Botany and by a grant from the Research Committee of Graduate Schools of the University of Wisconsin. I thank Dr. J. W. Thomson for his support throughout this project and Mr. R. E. Berke for help in preparing the manuscript. 2 Biology Department, Wisconsin State University, Eau Claire, Wisconsin 54701. This content downloaded from 207.46.13.64 on Tue, 19 Apr 2016 05:58:49 UTC All use subject to http://about.jstor.org/terms 266 THE BRYOLOGIST [Volume 69 the rock-inhabiting vegetation of lichens and bryophytes of the Driftless Area, it is an aim of the present study to try to establish a quantitative method for the study of such saxicolous vegetation types so that objective comparisons among future investigations can be made. DRIFTLESS AREA: LAND AND CLIMATE The Driftless Area includes about 15,000 square miles situated mainly in the western upland region of Wisconsin with some extensions into the central plain and northern highland (Martin 1932). In Wisconsin the area covers 13,360 square miles and includes all or part of 22 counties. The remainder of the area is located in eastern Minnesota, northeastern Iowa, and northwestern Illinois. The area is drained in the west by the Mississippi River; the Black River in the northern part and the Wisconsin River in the southern part drain into the Mississippi. The theory that this area was never covered by glacial ice is old and well known. It was once believed that the area was completely surrounded by the glacier. Later, the idea was advanced that the ice of the eastern and western lobes of the glacier was present at different times, reaching the Driftless Area at its margin. In 1960, R. F. Black postulated that this area was covered by the ice, but that only the upper portions of the Wisconsin ice sheet covered the area. For this reason, the amount of drift carried into the area was much less than that found in surrounding areas subjected to the full depth of the glaciers (Black 1960). Whether glaciated or not, the area in many regions is heavily dissected, and much bedrock is exposed. The lowest exposed layer is Cambrian sandstone. It is overlaid by Lower Magnesian dolomite which is in turn overlaid by St. Peter sandstone. This is capped in many regions by Galena dolomite (Martin 1932). The Galena and Lower Magnesian dolomites investigated in this study were found in six of the southernmost counties in the Driftless Area where most of the limestone outcrops occur; namely, Crawford, Grant, Iowa, Lafayette, Richland, and Vernon Counties (Fig. 1). The elevations of the bedrock range from about 225 meters at the river edges in the west to 421 meters at the peaks more centrally located in the area. The dominant vegetation of the Driftless Area consists mainly of southern-hardwood forest and oak savannah with smaller areas of prairie, especially in the southern portion of the state where they are continuous with the great prairie grasslands to the west. The area has a rather homogeneous, continental climate with a mean annual temperature of 6.1-8.30 C and an average annual precipitation of 78.7-86.4 cm (Martin 1932). The temperature, however, as well as the light intensity and the radiation are undoubtedly extremely variable in the microhabitats. This content downloaded from 207.46.13.64 on Tue, 19 Apr 2016 05:58:49 UTC All use subject to http://about.jstor.org/terms 1966] FOOTE: LIMESTONE VEGETATION IN WISCONSIN 267