PARENT SESSION
Contributed Oral Session 11: Invasive Species: Arid Lands
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 520 A, Level 5, Palais des congrès de Montréal

Integrating weed control and restoration on western rangelands.

Allcock, Kimberly^*,1, Blank, Robert¹, Chambers, Jeanne^{2, 3}, Doescher, Paul³, Mazzola, Monica¹, Nowak, Robert¹, ¹ University of Nevada, Reno, Reno, Nevada, 89557² USFS Rocky Mountain Research Station, Reno, Nevada³ Oregon State University, Corvallis, Oregon, 97331

ABSTRACT- Efforts to control cheatgrass (Bromus tectorum ) need to focus on controlling its high competitive ability and reproductive capacity while simultaneously restoring native plants on Great Basin rangelands. Our goal is to identify ecological mechanisms by which to control the spreading dominance of cheatgrass on Great Basin rangelands. We have implemented a series of experiments to test techniques for controlling cheatgrass and other weeds, establishing native plant communities, and restoring ecosystem structure and function. One of these experiments tested the role of soil nitrogen in mediating competition between native species and cheatgrass, and to assess the effectiveness of a resource-efficient suite of native species in reducing soil nitrogen and cheatgrass production. We used a completely randomized split plot design at each site, with sucrose addition (to reduce available soil nitrogen) as a whole-plot factor, and native species or species mix and addition or removal of cheatgrass as the split plot factors. Initial data show that sucrose generally decreased soil nitrogen, (as well as affecting other soil nutrients), and in many sites resulted in reduced cheatgrass biomass and seed production. Effects of native species on cheatgrass density, and of cheatgrass on native species density, were not consistent across sites in the first year. Species responded differently to both sucrose addition and competition with cheatgrass, though sagebrush Artemisia tridentata and bluebunch wheatgrass Pseudoroegneria spicata performed consistently well. The experiments were repeated in 2004, and data collection on both iterations will continue into the future. Subsequent years of data will be vital for determining the competitive effects of established native species on cheatgrass performance and for assessing the effectiveness of the observed reductions in cheatgrass seed production with sucrose application. However, our initial results indicate that soil nitrogen could be an important mediator in interactions between native species and cheatgrass. We hope our research will provide an ecological understanding of why restoration techniques succeed or fail, and help us develop conceptual and economic bases for choosing appropriate management techniques.

Key words: bromus tectorum, competition, sagebrush steppe