Legacy Effects in Prairie Restoration: a 73-Year Spatial History

Black Earth Rettenmund Prairie State Natural Area, one of the highest quality prairie remnants in southern Wiscon- sin's Driftless Area, has been the target of extensive restoration efforts since it was acquired by The Nature Conservancy (TNC) in 1986. In the present work, I analyzed the spatial history of this prairie using a Geographical Information System (GIS) and an extended series of air photos, on-the-ground surveys, early maps, and land-use records. In 1937, when the first air photo was taken, the site was nearly devoid of trees and shrubs. In subsequent years, the site became progressively woody until at the time of purchase by TNC, it was over half covered by shrubs and trees. Maps and field notes made by TNC and the Wisconsin Department of Natural Resources (DNR) provided detailed information on the woody taxa at the time of acquisition. Quaking aspen (Popu- lus tremuloides), eastern cottonwood (P. deltoides), and sumac (Rhus glabra) were the dominant woody species. Stewardship files during more than 25 years of restoration work provided data on the effort expended. Tree and shrub removal and frequent prescribed burns were used to restore the prairie. Although these efforts led to substantial success, a legacy of the woody vegeta- tion remained, complicating restoration efforts. Sumac and gray dogwood (Cornus racemosa) are particularly troublesome, but brambles (Rubus sp.) and grape (Vitis sp.) also present problems. I used a Global Positioning System (GPS) to define boundaries of current woody areas and I found that they corresponded closely to the areas previously dominated by trees and shrubs.