MAPPING HISTORICAL FOREST TYPES IN BARAGA COUNTY MICHIGAN, USA AS FUZZY-SETS

Data on tree location and species in a portion of Northern Michigan we re gathered from General Land Office (GLO) survey notes (ca. 1850), di gitized, and generalized to represent forest types. Fuzzy membership v alues describing the degree of membership of each species in each fore st type were derived from (a) semantic information in the forestry lit erature and (b) a fuzzy clustering routine applied to data from random ly placed circular plots. The fuzzy membership values assigned to each tree point for each forest type were interpolated to form continuous surfaces using kriging and co-kriging. Advantages of this method over traditional discrete mapping methods include: (a) multiple options are available for the display and analysis; (b) classification uncertaint y and the continuity of natural vegetation can be represented; and (c) the classification scheme is applied systematically across the entire map area and can be altered to produce alternative maps. The subset o f available display and analytical products presented include: discret e forest type maps; a surface representing the confusion between fores t types; fuzzy logical overlays of forest types; and discrete class ma ps with color value altered within each class to indicate degree of co nfusion at each location.