Simulation Experiments with Late Quaternary Carbon Storage in Mid-Latitude Forest Communities

The assumption was tested that forest biomass in communities on the modern landscape is equivalent to that in similar communities on the late Quaternary landscape. Forest carbon storage dynamics during the past 16,000 years were derived from a mathematical model of forest processes and individual tree species behavior. Modern pollen and climate data sets provided pollen-climate transfer functions to generate model driving variables from fossil pollen records. Climate variables were estimated from fossil pollen stratigraphies in Tennessee, Ohio, and Michigan. Only simulated early postglacial warming produced the large carbon gains one would expect in mixed deciduous-coniferous forests from unglaciated regions. The simulated mid-Holocene warming generated little carbon storage response by temperate deciduous forests and large carbon gains in northern hardwood-conifer forests, unlike the linear relationship expected when equivalence is assumed between modern and prehistoric forests. Late-glacial, mid-latitude forests may have contained more biomass than would be expected from equivalent forests on the modern landscape. Simulations of alternate hypotheses to explain the enhanced late glacial biomass cannot distinguish effects of reduced seasonal temperature extremes from effects of changing species' temperature tolerances.