PRESETTLEMENT LANDSCAPE HETEROGENEITY - EVALUATING GRAIN OF RESOLUTION USING GENERAL LAND OFFICE SURVEY DATA

General Land Office Survey (GLOS) records from the A.D. 1840s provide data for quantitative characterization of presettlement vegetation acr oss western Mackinac County, Michigan, located within the mixed conife r-northern hardwoods forest region. We analyzed data from land survey plat maps and 1958 bearing, witness, and line trees from 162 surveyed section and quarter-section corners in order to map vegetation cover t ypes at a level of spatial resolution appropriate for characterizing l andscape heterogeneity using standard landscape ecological metrics. As also demonstrated by a number of both classic and contemporary plant- ecological studies, the distribution of landforms, soils properties, h ydrology, and location of fire breaks all contribute to the heterogene ity in vegetation observed at a landscape scale in the region. Through a series of spa tial landscape analyses with differing grain of resol ution, in this study we determine that a grid cell size of 65 ha (0.5 mix0.5 mi or 0.25 mi(2) to 259 ha (1 mi(2)) gives a conservative chara cterization of landscape heterogeneity using standard metrics and is t herefore appropriate for use of GLOS data to study historical landscap e changes.