title: Soil and groundwater nitrogen response to invasion by an exotic nitrogen-fixing shrub.
abstract: Autumn-olive (Elaeagnus umbellata Thunb.) is an invasive, exotic shrub that has become naturalized in the eastern United States and can fix nitrogen (N) via a symbiotic relationship with the actinomycete Frankia. Fixed N could potentially influence nutrient cycling rates and N leaching into soil water and groundwater. In situ net N mineralization, net nitrification, and net ammonification rates, as well as soil water and groundwater nitrate N (NO(3)-N) and ammonium N (NH(4)-N) concentrations, were measured under autumn-olive-dominated and herbaceous open field areas in southern Illinois. Soil net N mineralization and net nitrification rates were higher under autumn-olive compared with open field (p < 0.05) and could be driven, in part, by the relatively low C/N ratio (11.41 +/- 0.29) of autumn-olive foliage and subsequent litter. Autumn-olive stands also had greater soil water NO(3)-N (p = 0.003), but soil water NH(4)-N concentrations were similar between autumn-olive and open field. Groundwater NO(3)-N and NH(4)-N concentrations were similar beneath both types of vegetation. Groundwater NO(3)-N concentrations did not reflect patterns in soil N mineralization and soil water NO(3)-N most likely due to a weak hydrologic connection between soil water and groundwater. The increased N levels in soil and soil water indicate that abandoned agroecosystems invaded by autumn-olive may be net sources of N to adjacent terrestrial and aquatic systems rather than net sinks.
authors.affiliation: Dep. of Forestry, Southern Illinois University, Carbondale, IL 62901, USA.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Goldstein
authors.forename: Karl W J
authors.initials: KW
authors.lastname: Williard
authors.forename: Jon E
authors.initials: JE
authors.lastname: Schoonover
authors.forename: Sara G
authors.initials: SG
authors.lastname: Baer
authors.forename: John W
authors.initials: JW
authors.lastname: Groninger
authors.forename: Jennie M
authors.initials: JM
authors.lastname: Snyder
mesh_terms: D003247:Conservation of Natural Resources; D031263:Elaeagnaceae / Q000378:metabolism* / Q000382:microbiology; D004784:Environmental Monitoring; D040161:Frankia / Q000502:physiology; D009584:Nitrogen / Q000737:chemistry* / Q000378:metabolism*; D012987:Soil / Q000032:analysis*; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D012987:Soil; D014867:Water; D009584:Nitrogen