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Citation. Wedin, D. A.; Tilman, D. 1992. Nitrogen cycling, plant competition and the stability of tallgrass prairie. Pages 5-8 in D. D. Smith and C. A. Jacobs, Eds., Proceedings of the Twelfth North American Prairie Conference. University of Northern Iowa Press, Cedar Falls, IA. [1208 LTER]
Abstract. Five perennial grass species (Schizachyrium scoparium (Michx.) Nash. Andropogon gerardi Vitman., Poa pratensis L., Agropyron repens (L.) Beauv., and Agrostis scabra Willd.) were grown on an experimental soil nitrogen (N) gradient. In competition plots on low-N soils, the two prairie bunchgrasses. Andropogon and Schizachyrium, completely displaced the other three species within three years. However, displacement did not occur on high-N soils. In N-cycling studies using monocultures, the two prairie species reduced soil N supply rates compared to the other species by tying up N in their slowly decomposing litter. These species, therefore, create the low-N conditions for which they are superior competitors. This positive feedback between plant competition and N cycling may be a critical process in tallgrass prairie. Alteration of the N cycle can disrupt this feedback, however. High rates of atmospheric N deposition caused by air pollution may be sufficient in parts of the Midwest to seriously threaten the stability of tallgrass prairie remnants.