CLIMATE AND LAND USE IMPACTS ON THE HISTORICAL ECOLOGY OF THE UPPER MIDWESTERN UNITED STATES - IMPLICATIONS FOR PALEOECOLOGICAL RESEARCH

Historic land use and forest change over the centuries since Euroamerican settlement have significantly changed the structure and composition of forests in the upper Midwestern United States and associated pollen assemblages. The extent to which this change has affected the realized climate niche for key taxa is less well known.

Predictions for future species range shifts are predicated largely on correlative models that relate modern species distributions to climate parameters in the modern era. Given the extent of regional forest change and recent losses to key forest taxa including Hemlock, Elm and Chestnut it is possible that certain taxa have shiften with respect to climate change over the last century. The additional pressure of climatically biased land use conversion for agriculture along the western and southern border of the upper Midwest means that the shift in climate space may be most pressing in a region of climate space that is critically important for understanding future species responses to climate change.

These changes have important implications for the use of modern datasets in reconstructing past climate and vegetation patterns. The use of modern composition and vegetation-climate relationships to calibrate paleoclimate models may be compromised if modern forests represent novel co-occurence and climate relationships.