Historical Biogeography of American Beech

American beech (Fagus grandifolia), now a centerpiece species of the eastern deciduous forest, has had a continually changing historical biogeography. This paper reviews the paleoecology, the presettlement occurrence, the modern range, and the current abundance pattern of beech. It synthesizes these four databases into maps representing the distribution and abundance of beech at specific periods from glacial maximum to the present. The post-glacial history of beech is a consistent broad northward expansion from refugia in the deep South. Beech reached its modern Canadian limits about 7,000 years ago and flourished with remarkable dominance south of the Great Lakes (regional >20% pollen) until 3,000 years ago. The contrast between presettlement (>35% witness trees) and modern beech abundance (<15% basal area) in the Northeast is just part of the regionally declining trend of beech dominance that began 2,000 years ago. The maxima of paleoecological representation, presettlement density, and current abundance are all centered in northern Pennsylvania and align in an broad axis of beech importance reaching northeast into Canada. The beech range has sharply defined boundaries and scattered southern and western populations are usually associated with riparian zones or on sheltered mesic slopes. The new distribution map extends the modern range more than 140 km north and identifies distinct outliers not found in the former mapped range. This detailed historical and geographic baseline of beech forests before it was affected by beech bark disease forms an important quantification of range, composition, and structure of beech that should be used to assess the effects of natural, land use, and new disturbances.