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United States Department of Agriculture

Agricultural Research Service

Title: Effects of resource availability and propagule supply on native species recruitment in sagebrush ecosystems invaded by Bromus tectorum

Authors
item Mazzola, Monica -
item Chambers, Jeanne -
item BLANK, ROBERT
item Pyke, David -
item Schupp, Eugene -
item Allcock, Kimberly -
item Doescher, Paul -
item Nowak, Robert -

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 27, 2010
Publication Date: August 14, 2010
Citation: Mazzola, M.B., Chambers, J.C., Blank, R.R., Pyke, D.A., Schupp, E.W., Allcock, K.G., Doescher, P.S., Nowak, R.S. 2010. Effects of resource availability and propagule supply on native species recruitment in sagebrush ecosystems invaded by Bromus tectorum. Biological Invasions. 13:513-526.

Interpretive Summary: Nitrogen reduction through carbon additions can potentially immobilize soil N and reduce the competitiveness of annual invasive grasses such as cheatgrass relative to native perennial species that are more tolerant of resource limiting conditions. We tested whether nitrogen reduction via sucrose addition would negatively affect cheatgrass while creating an opportunity for establishment of native perennial propagules. Experimental plots in central Nevada, were seeded with different densities of both cheatgrass (0, 150, 300, 600, and 1200 viable seeds m-2) and native species (0, 150, 300, and 600 viable seeds m-2). Sucrose addition reduced soil available N and decreased cheatgrass density, biomass and seed production, but only for the first year. Native species establishment was not enhanced by sucrose addition. For sagebrush steppe ecosystems dominated by cheatgrass, long-term resource reduction and high propagule input of native perennial species may reduce cheatgrass dominance and facilitate reintroduction of natives.

Technical Abstract: Resource availability and propagule supply are major factors influencing establishment and persistence of both native and invasive species. Increased soil nitrogen availability and high propagule inputs contribute to the ability of annual invasive grasses to dominate disturbed ecosystems. Nitrogen reduction through carbon additions can potentially immobilize soil N and reduce the competitiveness of annual invasive grasses. Native perennial species are more tolerant of resource limiting conditions and may benefit if nitrogen reduction decreases the competitive advantage of annual invaders and if sufficient propagules are available for their establishment. Bromus tectorum, an exotic annual grass in the sagebrush steppe of western North America, is rapidly displacing native plant species and causing widespread changes in ecosystem processes. We tested whether nitrogen reduction would negatively affect B. tectorum while creating an opportunity for establishment of native perennial propagules. A carbon source, sucrose, was added to the soil, and plots were then seeded with different densities of both B. tectorum (0, 150, 300, 600, and 1200 viable seeds m-2)and native species (0, 150, 300, and 600 viable seeds m-2). In the first year, sucrose reduced soil available N and decreased B. tectorum density, biomass and seed production. However, the effect was short-term and, by the second year, there was a substantial increase in B. tectorum density. Native species establishment was not enhanced by sucrose addition. Increasing propagule availability increased both B. tectorum and native species establishment. Survival of native seedlings was low and recruitment is likely governed by the seedling stage. Increasing propagule supply of native species over the long-term could increase native seedling establishment and enhance native propagule availability after disturbances or in years when environmental conditions are more conducive to native species establishment. For sagebrush steppe ecosystems dominated by B. tectorum, long-term resource reduction and high propagule input of native perennial species may reduce B. tectorum dominance and facilitate reintroduction of natives.

Last Modified: 9/10/2014
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