Impact of an Invasive Exotic Species on Stream Nitrogen Levels in Southern Illinois1

Authors

  • Christine L. Goldstein,

    1. Respectively, Former Graduate Research Assistant, Associate Professor, Assistant Professor, Department of Forestry, Southern Illinois University Carbondale, 1205 Lincoln Drive, MC 4411, Carbondale, Illinois 62901.
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  • Karl W.J. Williard,

    1. Respectively, Former Graduate Research Assistant, Associate Professor, Assistant Professor, Department of Forestry, Southern Illinois University Carbondale, 1205 Lincoln Drive, MC 4411, Carbondale, Illinois 62901.
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  • Jon E. Schoonover

    1. Respectively, Former Graduate Research Assistant, Associate Professor, Assistant Professor, Department of Forestry, Southern Illinois University Carbondale, 1205 Lincoln Drive, MC 4411, Carbondale, Illinois 62901.
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  • 1

    Paper No. JAWRA-07-0176-P of the Journal of the American Water Resources Association (JAWRA).Discussions are open until December 1, 2009.

(E-Mail/Williard: williard@siu.edu)

Abstract

Abstract:  Autumn-olive (Elaeagnus umbellata Thunb.) is an invasive, exotic shrub that has become naturalized in the eastern United States. Autumn-olive fixes nitrogen (N) via a symbiotic relationship with the actinomycete Frankia. At the plot scale, the presence of autumn-olive has been related to elevated soil water nitrate-N (NO3-N) concentrations. This study examined the relationship between autumn-olive cover in a watershed and stream water quality. Stream water nitrate-N (NO3-N) and ammonium-N (NH4+-N) concentrations were measured in 12 first order ephemeral streams draining watersheds with mixed forest cover and a range of 0-35% autumn-olive cover. Percent autumn-olive cover was positively correlated with mean stream NO3-N concentrations, but was not correlated with mean stream NH4+-N concentrations. While other studies have demonstrated a significant relationship between native N-fixers and stream NO3-N, this is the first study to document a relationship for an invasive, exotic N-fixing species. Results suggest that this exotic species can be an additional source of NO3 in local and regional water bodies and demonstrates an additional negative ecosystem consequence of invasion beyond losses in biodiversity.

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