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Herbaceous Layer Contrast and Alien Plant Occurrence in Utility Corridors and Riparian Forests of the Allegheny High Plateau

Darrin L. Rubino, Charles E. Williams and William J. Moriarity
The Journal of the Torrey Botanical Society
Vol. 129, No. 2 (Apr. - Jun., 2002), pp. 125-135
Published by: Torrey Botanical Society
DOI: 10.2307/3088726
Stable URL: http://www.jstor.org/stable/3088726
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Herbaceous Layer Contrast and Alien Plant Occurrence in Utility Corridors and Riparian Forests of the Allegheny High Plateau
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Abstract

Electric and petroleum utility corridors are common components of human-dominated landscapes, vital for the distribution of electric power, natural gas, and oil over short and long distances. Despite their economic importance, construction and maintenance of utility corridors can have negative impacts on the natural ecosystems that they traverse. For example, utility corridors can serve as foci for invasion of native plant communities by alien plant species that can adversely affect community structure and function. To determine how corridor establishment influences riparian vegetation of the Allegheny High Plateau of northwestern Pennsylvania, we compared the species composition and richness of the herbaceous layer (all vascular plants ≤ 1 m tall) of utility corridors and adjacent headwater riparian forests, and tested the hypothesis that utility corridors serve as foci for the invasion of adjacent riparian forest by alien vascular plants. We contrasted plant species richness and vegetative cover, cover by growth form, species richness and cover of alien plants and cover of microhabitat components (open soil, rock, leaf litter, log, bryophyte) in utility corridors and adjacent riparian forest at 17 sites. Cluster analysis revealed that herbaceous layer species assemblages in corridors and riparian forest were compositionally distinct. Herbaceous layer cover and species richness were significantly (P ≤ 0.05) greater in corridors than in riparian forest. Fern, graminoid, and forb species co-dominated herbaceous layer cover in corridors; fern cover dominated riparian forests. Cover of alien plants was significantly greater in corridors than in riparian forest. Alien plant species richness and cover were significantly and positively correlated with open soil, floodplain width, and active channel width in corridors but were significantly and negatively correlated with litter cover in riparian forest. Given that the majority of alien plant species we found in corridors were shade-intolerant and absent from riparian forests, we conclude that open utility corridors primarily serve as habitat refugia, rather than as invasion foci, for alien plant species in riparian forests of the Allegheny High Plateau.

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