2005 BES Annual Meeting Presentation and Poster Abstracts
Historical land use and vegetation gradients along a rural to urban riparian zone
Grace S. Brush
Abstract: Trees, shrubs and herbs were identified and measured in 111 plots located along 45 randomly selected transects crossing floodplains of 1st, 2nd, 3rd and 4th order streams in the Gwynns Falls watershed, Baltimore. At each transect location, stream bank relative to stream channel elevations were measured. The ten most common trees at the 1 meter elevation contain only one species that favors a wet environment, whereas the most common species at elevations > 1 meter include most riparian species. However, at these higher elevations, most populations consist of one to a few large trees and very few small individuals. The Gwynns Falls watershed has changed from forest to agriculture to urbanization and suburbia over the last 250 years. The distribution of wetland and upland species reflects not only the influence of the more recent urbanization on stream incision, aggradation and flooding, but also the historical influence of agriculture on streams prior to urbanization. In general, trees occurring in areas bordering streams with steeper banks where flooding no longer occurs consist of large individuals of riparian species including sycamore, green ash, black walnut, and black willow, with very few small stems. This indicates that these areas represent former floodplains that no longer function as riparian areas. The occurrence of species that prefer dry habitats at the lower elevation suggests that modern floods which are of short duration and the possibility of a lowered water table has minimized the amount of available water required by riparian species.