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CHAPTER 23 The effect of man on the vegetation INDIAN EFFECTS Nature of archaeological evidence Our knowledge of the possible influence of early Indian populations on the vegetation of Wisconsin is based entirely upon archaeological evidence concerning their cultural habits that has been deduced from tools and other artifacts that have been found and have been associated with their habitations. The archaeologist gathers this evidence by painstaking excavations of old village sites, burial grounds, refuse piles, cave shelters, and other places used by the Indians, and to a lesser extent from artifacts discovered in plowed fields and other places not necessarily connected with a population center. Tools, such as spear points, arrowheads, and other weapons lIsed in the hunt, and Copyrighted Material EFFECT OF MAN ON THE VEGETATION 457 fishhooks or harpoon points used for aquatic animals, tell of foodgathering habits. Pottery pieces, both cooking and storage vessels, imply a fairly sedentary population and are usually associated with an agricultural economy. Corncobs, smoking pipes, and other remains give some indication of the kinds of crops raised. Conch shells from Florida, obsidian from the Rocky Mountains, and copper from Isle Royale, found together in a Wisconsin village site, indicate a welldeveloped trade system and probably a more-or-Iess stable political system. Traces of palisades around villages, and house plans reconstructed from the patterns of post impressions, can be used to interpret the probable population size of the villages. Charcoal from the fireplaces of the village can be used to date the time of occupancy, using the technique of analysis for radioactive carbon. Another means employed to learn the time sequence for various cultures is based upon the occurrence of artifacts in stratified layers, as in the debris on the floor of cave habitations, where the oldest materials are on the bottom and the youngest toward the top. A source of strength of the stratigraphic method is the inherent conservatism of all peoples, so much so that a particular culture tends to make one or a few special kinds of arrowheads or pots, or tends to mark their artifacts with certain distinctive symbols, and continues to make the S:Jtion of the prairies by 1880 and the southern savannas were taken up almost as thoroughly. In the savanna country. however, there was a tendency to al10w the rougher sections of the farm to develop in forest, as a source of fuel and building materials. One result was the widespread occurrence of [arm wood lots, 10 to 60 acres in size on the average, composed of a dense growth o[ oaks and associated species on lands that were formerly open brushland or widely spaced savanna. Thus it happened that by 1950, after a century of intense utilization, there was more closed forest in many southern \Visconsin counties than there had been at the time settlement began 120 years earlier. Some impression of the rate of conversion of native communities to farm land can be obtained from the interesting studies of Shriner and Copeland (1904). These investigators presented a map showing the land cover of four townships in Green County as it appeared in ]83], 1882, and 1902. By adding information from the Wisconsin Land Eco· nomic Inventory of 1935 and from aerial photographs of these town· ships in 1956, it is possible to gain a clear picture of the pace and ex· tent of deforestation. The four townships originally contained 16.8 per cent prairie and 83.2 per cent forest and oak opening. Using the arbi· trary criterion of a 50-foot or greater spacing between trees as an indication of openings, the surveyors' records can be interpreted to show that 38.2 per cent of the wooded land was in savanna and 61.7 per cent in closed forest. By 1850 all of the prairie land had been entered in farms, with an almost complete destruction of the original community. By 1882, the savanna area had been reduced to 34 per cent of its original extent and the dense forest to 29 per cent. In Jordan Township, which was 86 per cent oak opening, 12 per cent oak forest, and 2 per cent prairie in 1831, the wooded areas of both types were reduced to an average of 33.6 per cent by ]882, but the remaining acreage contained more wood than the original, due to the conversion of savanna to forest. Tentative estimates, based on known tree densities and calculated basal areas as determined from known ages, indicate that...

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