Temporal delineation of wetlands on Gull point, Presque Isle, Pennsylvania

Presque Isle is a recurved sand spit on the south shore of Lake Erie near Erie, Pennsylvania. Sand eroded from lake side beaches and transported to the distal end of the peninsula (Gull Point) has resulted in the extension of Gull Point and concurrent formation of shallow wetlands. The objectives of this chapter are to (1) demonstrate the use of aerial photographs to document the temporal and spatial history of wetlands on Gull Point, (2) analyze the spatial and temporal dynamics of the wetlands, and (3) create a spatial and temporal framework within which hypotheses regarding the population dynamics of the biota in the wetlands on Gull Point could be generated and tested. A series of aerial photographs and image analysis techniques were used to determine the ages and initial shapes of wetlands on Gull Point, subsequent changes in the spatial configuration of the wetlands as they became vegetated, and the probability that a newly formed wetland would survive to become an established wetland. Of 17 wetlands established on Gull Point between 1946 and 1993,15 were formed after 1973. Most formed on the bay side of Gull Point as elongated lagoon wetlands that became isolated from the bay by sand deposition. As lagoon wetlands aged, they became subdivided into wetland "systems" in which encroachment by Phragmites reduced the area of open water and isolated individual wetlands. Wetlands formed on the lake side of Gull Point as beach wetlands behind sand berms created by wave action during storms. Beach wetlands tended to persist for less than five years prior to destruction by wave action.