%0 Journal Article
%T Quantifying trends and uncertainty in prehistoric forest composition in the upper Midwestern United States
%A Andria Dawson
%A Christopher J. Paciorek
%A Jason S. McLachlan
%A John W. Williams
%A Simon J. Goring
%A Stephen T. Jackson
%J Ecology - Wiley Online Library
%D 2019
%R https://doi.org/10.1002/ecy.2856
%X Forest ecosystems in eastern North America have been in flux for the last several thousand years, well before Euro©\American land clearance and the 20th©\century onset of anthropogenic climate change. However, the magnitude and uncertainty of prehistoric vegetation change have been difficult to quantify because of the multiple ecological, dispersal, and sedimentary processes that govern the relationship between forest composition and fossil pollen assemblages. Here we extend STEPPS, a Bayesian hierarchical spatiotemporal pollen¨Cvegetation model, to estimate changes in forest composition in the upper Midwestern United States from about 2,100 to 300 yr ago. Using this approach, we find evidence for large changes in the relative abundance of some species, and significant changes in community composition. However, these changes took place against a regional background of changes that were small in magnitude or not statistically significant, suggesting complexity in the spatiotemporal patterns of forest dynamics. The single largest change is the infilling of Tsuga canadensis in northern Wisconsin over the past 2,000 yr. Despite range infilling, the range limit of T. canadensis was largely stable, with modest expansion westward. The regional ecotone between temperate hardwood forests and northern mixed hardwood/conifer forests shifted southwestward by 15¨C20 km in Minnesota and northwestern Wisconsin. Fraxinus, Ulmus, and other mesic hardwoods expanded in the Big Woods region of southern Minnesota. The increasing density of paleoecological data networks and advances in statistical modeling approaches now enables the confident detection of subtle but significant changes in forest composition over the last 2,000 yr.  The presettlement data can be interpreted as a stable baseline and used to evaluate changes in the landscape caused by humans. Such an evaluation is possible because the geographic distributions of major tree speciesˇ­have changed little over the last 3000 years. (Frelich 1995)  Estimating the population and community dynamics of trees in the millennia before the rapid changes of the past two centuries is important for conservation biology and global©\change ecology. The rates and patterns of vegetation change preceding agroindustrial society offer baseline targets for management of natural areas (Barnosky et al. 2017) and benchmarks for assessing subsequent change (National Research Council 2005, Willard and Bernhardt 2011, Jackson 2012). Long©\term ecological time series provide constraints on processes in tree communities that play out over centennial
%U https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2856