5.6. SR 06-07-2004 - Laserfiche WebLink

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on the Marschner map, based on data from 1895 (Map 4).47 The Marschner vegetation types have been simplified as follows: I Sir.::.plified Category I Mixed Deciduous Forest I Oak Savannah I Prairie I Wetland M:li!3Chner Catego~~s I I Aspen -Oaks, Big Woods-Hardwoods, River Bottom Forest I Oak Opens and Barrens I I Prairie I I Conifer Bogs and Swamps, Wet Prairie The model functions by weighting areas that fall along the border of any of these ecosystems (forest, savannah, prairie, and wetland). As most desirable is to have access to all these systems, the more ecotones present in any given area, the more heavily weighted the area is in the probability model. As mentioned above, the farther back in time one goes, the less accurate the vegetation map is. Because of the environmental changes discussed earlier, the vegetation maps do not apply to any period pre-A.D. 300. Thus two versions of the model have been produced: a generalized model for all period, and a post 300 A.D. model that' considers vegetation, Parameters not included: Some parameters often included in a model are not included in this Elk River model. Many models emphasize river terraces; in the Elk River model, which initially heavily weights proximity to river and also considers hill and ridge tops, using river terraces as a modeling factor proved to be redundant. Proximity to organic soils and glacial sediments are often used as parameters but these proved to have a minor effect on the Elk River model, in part because most of Elk River is in sandy outwash areas, and in part because the glacial till, important for lithic resources, is exposed in this areas by rivers and streams which are heavily weighted. For the early historic period, it would be expected that the model would use proximity to the Red River Oxcart trail and the Military Road as a parameter. Both of these routes, however, run so closely to the already heavily weighted rivers systems, that the addition of these trails as a parameter has no appreciable effect on the model: essential they are redundant. For this reason the generalized model is functional for both prehistoric and early historic periods. 23