PARENT SESSION
Oral Session #41: Agroecology and Urban Ecology. Presiding: M. Liebman.
Wednesday, August 8, 2001. 8:00 AM to 12:15 PM. Hall of Ideas L&M.
Riparian vegetation along a rural-urban gradient.
BRUSH, GRACE1, ZIPPERER, WAYNE2, 1 2
ABSTRACT- The riparian corridor in the Gwynns Falls watershed, a NSF LTER urban site, follows a gradient from rural/suburban in the upper watershed to densely urban where the Gwynns Falls enters the Patapsco River (Baltimore Harbor). Before early to middle 19th century, the watershed was mixed forest and rural. Piedmont streams, which characterize most of this watershed, overflow their banks every two to three years. Consequently, growth and seed dispersal of plants in such areas are adapted to frequent, low magnitude floods. With the onset of urbanization, streams were modified to prevent overbank flooding, which resulted in incised streams with steep banks. Analysis of data collected in 110 plots show a shift from mainly wetland species to a mix of mainly upland and exotic species along the rural/suburban-urban gradient. As streams become incised, the land surfaces adjacent to the streams are no longer actively flooded. These conditions inhibit regeneration of riparian species, leaving only older populations represented by large floodplain trees and young regenerating populations of upland and exotic species, in many of the relic or historical floodplains. This trend is expected to continue in the upper watershed, as development continues into rural/suburban areas.
KEY WORDS: urban, riparian, exotic, flooding