Document: RYA-3-64-42

Nitrogen immobilization for the restoration of cheatgrass, Bromus tectorum, infested rangelands.

LUSTER, R.A.* and E.W.SCHUPP

Utah State University, Logan, UT, 84322-5230 USA ¹

Abstract:
The overall goal of this project is to determine the potential for using nitrogen immobilization as a means to decrease the competitive ability of the annual exotic cheatgrass in wildland systems. The objective of this experiment is to evaluate how nitrogen manipulation affects per individual competitive relationships between cheatgrass and squirreltail, Elymus elymoides, during seedling establishment and early growth in a controlled greenhouse environment. We use the state-and-transition model theory for community succession as the basis for this research. We used completely additive two-species mixed-density combinations in greenhouse pots with three soil nitrogen treatments (N-immobilization, high ammonium, and high nitrate). Aboveground biomass and tiller production were noted for each individual plant after four months of growth and analyzed as functions of the mixed densities and soil nitrogen treatments. Treatment effect was significant for cheatgrass and squirreltail biomass. Mean squirreltail tiller number and biomass were highest in the high-nitrate treatment and lowest in the N-immobilization treatment. Mean cheatgrass biomass and tiller number were lowest in the N-immobilization treatment, mean tiller number was highest in the high ammonium treatment while mean biomass was highest in the high nitrate treatment. The effect of cheatgrass density on squirreltail biomass significantly changed with treatment. The effect of squirreltail density on cheatgrass biomass significantly changed with treatment as well. There were significant intra- and inter-specific interactions affecting tiller number and biomass for both species. Manipulating soil nitrogen levels may be the key to controlling cheatgrass proliferation and restoring native vegetation communities in the Great Basin. Controlling cheatgrass density while restoring native perennial grass cover in Great Basin wildland communities may break the recurrent fire cycle associated with cheatgrass-dominated landscapes.

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This abstract is being presented at: 10:30 AM in session:
RESTORATION ECOLOGY AND INVASIONS