Vegetation and Soil Parameters at an Island Bridge Crossing

摘要

Roadsides are often planted with nonnative, disturbance-tolerant, herbaceous vegetation to enhance plant survival under highly disturbed soil conditions. We investigated vegetation and soils along the Ohio River, West Virginia, USA, at a new bridge crossing (Blennerhassett Island), a bridge crossing 45 yr old (Buckley Island), and an island with no bridge crossing (Muskingum Island) and at three distances from the bridge or center point at each site (0 m [under the bridge], 100 m away, 300 m away). Overall, 170 species (131 herbaceous, 10 shrubs, and 29 trees) were observed. Percent herbaceous cover and basal area of trees were lower at quadrats under the bridges (p 0.05). Species composition differed at quadrats under the bridges in comparison to distant quadrats (p 0.05) with exotics such as Japanese millet (Echinochloa crus-galli var. frumentacea P. Beauv.), and Italian perennial rye grass (Lolium perenne L.) prevalent under the new bridge. Numerous soil properties had highly altered levels at quadrats under bridges (p 0.05). We found bridges influence vegetation directly beneath them by creating an environment with nonnative, disturbance-tolerant, herbaceous vegetation with low percent cover and basal area. Differing vegetative parameters between sites were due to natural vegetative communities, while the presence of a bridge was responsible for differences between distances. The bridge was also found to alter soil chemistry and physical properties in the soil likely due to the application of fertilizer and road salts and disturbance during construction.