Document: KEN-3-41-19

Forest clearance and plant cultivation by prehistoric people in southwestern Ohio.

MCLAUCHLAN, K.K.*

University of Minnesota, St. Paul, MN 55108, USA ¹

Abstract:
Despite archeological evidence that prehistoric people in North America modified the landscape through a variety of methods, including agriculture and earthworks, there is inconclusive paleoecological evidence for their impacts on local vegetation. In this study, I examined sediment cores from two small ponds constructed by the Hopewell culture as part of a 51 ha earthworks site in southwestern Ohio, USA (Fort Ancient). The 2000-year pollen record from these sediments shows that the Hopewell people dramatically modified local vegetation and maintained a deforested landscape. Sediment deposition in the ponds began at approximately 70 B.C. and 130 A.D., respectively, during Hopewell occupation of the site. During this period, both sediment cores have extremely low pollen accumulation rates, high sedimentation rates, and low organic matter content, indicating open vegetation structure with few nearby trees and high rates of erosion. Pollen assemblages during this time are characterized by over 50% pollen from herbaceous taxa, especially Ambrosia, an annual weed of open ground and agricultural fields, and known Hopewell cultigens: Chenopodiaceae, Polygonum erectum-type, and Iva annua-type. Analysis of pollen samples from modern forests, pastures, agricultural fields, floodplains, and ditches reveals no modern analog for these pollen assemblages. The absence of modern analogs and the presence of pollen of cultigens suggest that the herb-dominated assemblages during Hopewell times were a result of cultivation in addition to colonization of disturbed soil by weeds. This is the first time that any evidence for the location of Hopewell gardens has been found. After abandonment of the site by the Hopewell, arboreal pollen becomes more prevalent, especially oak and hickory, which are common in modern forests of the region. Hopewell activities, such as clearing trees, repeatedly disturbing the soil, causing erosion, and favoring or cultivating varieties of weedy plants, affected local vegetation at the Fort Ancient site for several hundred years. This record provides strong evidence for extensive and persistent prehistoric human impacts on vegetation assemblages in northeastern North America.

Keywords: paleoecology, pre-settlement vegetation, anthropogenic disturbance, archeology, deciduous forest, prehistory

This abstract is being presented at: 2:15 PM in session:
Oral Session #32: Paleoecology.