Document: DUA-3-69-10

Responses of a low-diversity grassland to six years of experimental soil disturbance and nitrogen addition.

PELTZER, D.A.*, S.D.WILSON and H.A.HAGER

University of Regina, Regina, Saskatchewan, Canada ¹

Abstract:
Community stability is often thought to increase with species diversity, but despite recent theoretical and empirical work on diversity-stability phenomena, no consensus has emerged on the generality of this relationship. We examined community stability, productivity, and resource availability in a low-diversity grassland dominated by two introduced perennial grasses, Agropyron cristatum and Bromus inermis. Three levels of soil disturbance (no disturbance, 50% bare ground, 100% bare ground) and four levels of nitrogen (no N added, 5 g N/m²/yr added, 15 g N/m²/yr added, or sawdust added at a rate of 400 g/m²/yr to immobilize N) were applied in factorial combinations to 120, 5 by 15 m plots for six years. In the first year of the experiment, seeds of over 50 local native prairie species and seedlings of woody plants were added to all plots to increase the local species pool. Adding N had the expected results of increasing plant standing biomass and soil available N. Soil disturbance reduced plant standing biomass and increased soil available N. The community composition of this species-poor grassland was relatively stable along both N addition and soil disturbance gradients with A. cristatum and B. inermis dominating the community in all treatment combinations. In contrast to results from previous studies, our results suggest that low-diversity communities can be surprisingly stable in the face of environmental changes.

Keywords: disturbance, diversity, fertilization, grassland, productivity, stability, succession

This abstract is being presented at: 3:30 PM in session:
AGROECOLOGY