Settlement-Era Gridded Tree Composition, Midwestern US: Level 1

Gridded forest composition data for Minnesota, Wisconsin, Michigan, and portions of Illinois and Indiana from survey notes from the Public Land Survey System (PLSS), prior to widespread land use conversion by EuroAmerican settlers. The Public Land Survey System in this region was carried out from approx. 1800 - 1904, in a time transgressive manner from east to west. Trees identified at section and quartersection points within the PLSS are aggregated to a regular 8km grid on a Great Lakes St. Lawrence Albers projection (EPSG:3175). For all points only the closest two trees are used in estimating composition and then summed within the 8km grid cell. The raw count of trees is reported, including "No trees" where surveyors found no trees within 300 links of the point. Methods and data are described in Goring et al., 2015 (http://biorxiv.org/content/early/2015/10/24/026575), except for data from Illinois and Indiana which are described in the methods below. This material is based upon work supported by the National Science Foundation under grants #DEB-1241874, 1241868, 1241870, 1241851, 1241891, 1241846, 1241856, 1241930.