Riparian and valley-margin hardwood species of pre-colonial Piedmont forests: A preliminary study of subfossil leaves from White Clay Creek, southeastern Pennsylvania, USA

Beginning in the seventeenth century, colonial activities such as land clearing, agriculture, and milldam construction significantly altered the landscapes, vegetation, and hydrogeomorphology of the northeastern Piedmont region, modern-day USA. Presently, weedy and non-native vegetation dominate the altered riparian zones and hill slopes where old-growth, hardwood forests once prevailed. Various studies have identified pre-settlement herbaceous wetland floras based on fruits and seeds. However, only one report provided evidence of the dominant pre-settlement woody species by using the localized signal available from subfossil leaves; that work reconstructed Maple-Ash floodplain swamp forests along valley-margins and Oak-Beech mixed forests on upper-slopes at a site in Lancaster County, southeastern Pennsylvania. Here, we investigate subfossil leaves recovered from the buried wetland soils of White Clay Creek in neighboring Chester County, Pennsylvania, providing significant new spatial data to our understanding of regional old-growth forests. The leaf assemblage, radiocarbon dated to ca. 1650, is composed of woody species with a diverse range of wetland affinities, indicating sources in both the riparian zone and surrounding lower hill slopes. Obligate and facultative-wetland species include willow (Salix spp.) and Hazel Alder (Alnus serrulata). Box Elder (Acer negundo) is the only facultative species present, while American Beech (Fagus grandifolia), the white and red oak groups (Quercus Section Quercus and Q. Section Lobatae, respectively), and Tulip Tree (Liriodendron tulipifera) comprise the identified facultative-upland taxa. These results complement and corroborate previous work and allow for greater confidence in understanding the pre-European landscape, potentially increasing the effectiveness of regional environmental restoration projects. Sara J. Elliott. Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA; Bureau of Economic Geology, University of Texas, Austin, TX 78758, USA. sara.elliott@beg.utexas. edu (corresponding author) Christen L. Grettenberger. Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA. Elliott, Sara J., Grettenberger, Christen L. , Donovan, Michael P., Wilf, Peter, Walter, Robert C. , and Merritts, Dorothy J. 2016. Riparian and valley-margin hardwood species of pre-colonial Piedmont forests: A preliminary study of subfossil leaves from White Clay Creek, southeastern Pennsylvania, USA. Palaeontologia Electronica 19.1. 2A: 1-26 palaeo-electronica.org/content/2016/1379-pre-colonial-piedmont-forests Copyright Paleontological Society, January 2016 ELLIOTT ET AL.: PRE-COLONIAL PIEDMONT FORESTS Michael P. Donovan. Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA. Peter Wilf. Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA. Robert C. Walter. Department of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17604, USA. Dorothy J. Merritts. Department of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17604, USA.