title: Novel and Lost Forests in the Upper Midwestern United States, from New Estimates of Settlement-Era Composition, Stem Density, and Biomass.
abstract: BACKGROUND
  EuroAmerican land-use and its legacies have transformed forest structure and composition across the United States (US). More accurate reconstructions of historical states are critical to understanding the processes governing past, current, and future forest dynamics. Here we present new gridded (8x8km) reconstructions of pre-settlement (1800s) forest composition and structure from the upper Midwestern US (Minnesota, Wisconsin, and most of Michigan), using 19th Century Public Land Survey System (PLSS), with estimates of relative composition, above-ground biomass, stem density, and basal area for 28 tree types. This mapping is more robust than past efforts, using spatially varying correction factors to accommodate sampling design, azimuthal censoring, and biases in tree selection.
  We compare pre-settlement to modern forests using US Forest Service Forest Inventory and Analysis (FIA) data to show the prevalence of lost forests (pre-settlement forests with no current analog), and novel forests (modern forests with no past analogs). Differences between pre-settlement and modern forests are spatially structured owing to differences in land-use impacts and accompanying ecological responses. Modern forests are more homogeneous, and ecotonal gradients are more diffuse today than in the past. Novel forest assemblages represent 28% of all FIA cells, and 28% of pre-settlement forests no longer exist in a modern context. Lost forests include tamarack forests in northeastern Minnesota, hemlock and cedar dominated forests in north-central Wisconsin and along the Upper Peninsula of Michigan, and elm, oak, basswood and ironwood forests along the forest-prairie boundary in south central Minnesota and eastern Wisconsin. Novel FIA forest assemblages are distributed evenly across the region, but novelty shows a strong relationship to spatial distance from remnant forests in the upper Midwest, with novelty predicted at between 20 to 60km from remnants, depending on historical forest type. The spatial relationships between remnant and novel forests, shifts in ecotone structure and the loss of historic forest types point to significant challenges for land managers if landscape restoration is a priority. The spatial signals of novelty and ecological change also point to potential challenges in using modern spatial distributions of species and communities and their relationship to underlying geophysical and climatic attributes in understanding potential responses to changing climate. The signal of human settlement on modern forests is broad, spatially varying and acts to homogenize modern forests relative to their historic counterparts, with significant implications for future management.
authors.affiliation: Department of Geography, University of Wisconsin-Madison, Madison, Wisconsin, United States.
authors.forename: Simon J
authors.identifier: http://orcid.org/0000-0002-2700-4605
authors.initials: SJ
authors.lastname: Goring
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Mladenoff
authors.affiliation: Harvard Forest, Harvard University, Petersham, Massachusetts, United States.
authors.forename: Charles V
authors.initials: CV
authors.lastname: Cogbill
authors.affiliation: Harvard Forest, Harvard University, Petersham, Massachusetts, United States.|Department of Biology, Bryn Mawr College, Bryn Mawr, Pennsylvania, United States.
authors.forename: Sydne
authors.initials: S
authors.lastname: Record
authors.affiliation: Department of Statistics, University of California, Berkeley, California, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Paciorek
authors.affiliation: Department of the Interior Southwest Climate Science Center, U.S. Geological Survey, Tucson, Arizona.|School of Natural Resources and the Environment and Department of Geosciences, University of Arizona, Tucson, Arizona, United States.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Jackson
authors.affiliation: Department of Earth and Environment, Boston University, Boston, Massachusetts, United States.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Dietze
authors.affiliation: Department of Statistics, University of California, Berkeley, California, United States.
authors.forename: Andria
authors.initials: A
authors.lastname: Dawson
authors.affiliation: Department of Geography, Dartmouth College, Hanover, New Hampshire, United States.
authors.forename: Jaclyn Hatala
authors.initials: JH
authors.lastname: Matthes
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States.
authors.forename: Jason S
authors.initials: JS
authors.lastname: McLachlan
authors.affiliation: Department of Geography, University of Wisconsin-Madison, Madison, Wisconsin, United States.|Center for Climatic Research, University of Wisconsin-Madison, Madison, Wisconsin, United States.
authors.forename: John W
authors.initials: JW
authors.lastname: Williams
mesh_terms: D018533:Biomass; D028203:Cedrus / Q000502:physiology; D003247:Conservation of Natural Resources; D017753:Ecosystem; D016468:Forestry / Q000639:trends*; D065928:Forests; D018652:Hemlock / Q000502:physiology; D006801:Humans; D028221:Larix / Q000502:physiology; D015146:Midwestern United States; D058974:Phylogeography; D063148:Plant Dispersal / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology; D029963:Quercus / Q000502:physiology; D032384:Tilia / Q000502:physiology; D014197:Trees / Q000502:physiology*; D034403:Ulmus / Q000502:physiology