/ The Historical Development of the Tension Zone Concept in the Great Lakes Region of North America
ï~~136 THE MICHIGAN BOTANIST Vol. 44 Hansen and di Castri 1992, Holland et al. 1993, Risser 1995, and Ward and Wiens In Press). These functions include serving as frontiers for successional change (Rusek 1992), governing ecological flows and patterns (Wiens 1997), and preservation of biodiversity (Yoon 1997). It is important to understand how and why the tension zone concept developed because it is part of one of the major themes in ecology-the search for pattern or distribution in space of species and individuals and understanding their relationships with other organisms and the environment (McIntosh 1976), and understanding change and uniformity within ecosystems (Hagen 1992). This search has been going on since the time of Darwin. In On the Origin of Species (1859), Darwin presented the contrasting views of change brought about by the struggle of competition and "a high degree of uniformity, stability, and interdependence" (Hagen 1992) that nature's complex web sometimes produces. ACKNOWLEDGMENTS The author gratefully acknowledges the comments provided by A. A. Reznicek and two anonymous referees on earlier drafts of this work. LITERATURE CITED Barbour, M. G., J. H. Burk, and W. D. Pitts. 1980. Terrestrial Plant Ecology. Menlo Park, California: Benjamin/Cummings Publishing Company. Cheney, L. S. 1894. Is forest culture in Wisconsin desirable? Transactions of the Wisconsin State Horticultural Society 24: 163-170. Clements, F. E. 1905. Research Methods in Ecology. Lincoln, Nebraska: University Publishing Company. Curtis, J. T. 1959. The Vegetation of Wisconsin. Madison, Wisconsin: University of Wisconsin Press. Curtis, J. T. and R. P. McIntosh. 1951. An upland forest continuum in the prairie-forest border region of Wisconsin. Ecology 32: 476-496. Darwin, C. R. 1859. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. London: John Murray. de Laubenfels, D. J. 1975. Mapping the World's Vegetation: Regionalization of Formations and Flora. Syracuse, New York: Syracuse University Press. di Castri, F., A. J. Hansen, and M. M. Holland (Eds.). 1988. A new look at ecotones: emerging international projects on landscape boundaries (special issue 17). Biology International. Egerton, F. N. 1976. Ecological studies and observations before 1900. In Issues and Ideas in America (B. J. Taylor and T. J. White, eds.), pp. 311-351. Norman, Oklahoma: University of Oklahoma Press. Fassett, N. C. 1929. Preliminary reports on the flora of Wisconsin. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters 24: 249-68. Fassett, N. C. 1930. The plants of some northeastern Wisconsin Lakes. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters 25: 157-168. Fassett, N. C. 1931. Notes from the herbarium of the University of Wisconsin. VII. Rhodora 33: 224-228. Fassett, N. C. 1939. The Leguminous Plants of Wisconsin. Madison, Wisconsin: University of Wisconsin Press. Fassett, N. C. 1943. Another Driftless Area endemic. Bulletin of the Torrey Botanical Club 70: 388-399. Fassett, N. C. 1944. Vegetation of the Brule Basin, past and present. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters 36: 33-56. Fassett, N. C. 1945. Juniperus virginiana, Juniperus horizontalis and Juniperus scopulorum, IV. Hy
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