Soil and Groundwater Nitrogen Response to Invasion by an Exotic Nitrogen-Fixing Shrub
- Christine L. Goldsteinabcd,
- Karl W. J. Williard *a,
- Jon E. Schoonoverb,
- Sara G. Baerb,
- John W. Groningerc and
- Jennie M. Snyderb
- a Dep. of Forestry, Southern Illinois Univ. Carbondale, currently at 1040 2nd St., Columbus, IN 47201
b Dep. of Forestry and Center for Ecology, MC 4411, Southern Illinois Univ. Carbondale, Carbondale, IL 62901
c Dep. of Plant Biology and Center for Ecology, MC 6509, Southern Illinois Univ. Carbondale, Carbondale, IL 62901
d Frost Valley YMCA, 2000 Frost Valley Rd., Claryville, NY 12725. Assigned to Associate Editor Christopher Green
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 (NO3–N) and ammonium N (NH4–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 NO3–N (p = 0.003), but soil water NH4–N concentrations were similar between autumn-olive and open field. Groundwater NO3–N and NH4–N concentrations were similar beneath both types of vegetation. Groundwater NO3–N concentrations did not reflect patterns in soil N mineralization and soil water NO3–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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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