Document Type
Conference Proceeding
Publication Title
Shrubland Ecosystem Genetics and Biodiversity: Proceedings
Editors
E. Durant McArthur, Daniel J. Fairbanks
Abstract
Cheatgrass (Bromus tectorum) has recently displaced salt desert shrubland in many areas of the Great Basin. We studied the dynamics of cheatgrass invasion into an intact shadscale-gray molly community in Dugway Valley, Utah, by adding seeds and manipulating disturbance regime and resource availability. Shrub clipping or cryptobiotic crust trampling on large plots increased cheatgrass recruitment and biomass production slightly in a favorable moisture year (1997 to 1998), whereas in a less favorable moisture year (1998 to 1999) these disturbance treatments had a significant negative effect. In 1998 to 1999 small plot studies, recruitment was similar in intact shrub clumps and openings, but biomass and, therefore, seed production was three times greater in shrub clumps. Disturbance decreased recruitment but had no significant effect on biomass per plant. Added water had no effect in openings, but added N increased and reduced N decreased biomass. In shrub clumps, fertility manipulation had little effect, but added water increased biomass. Shrub simulation (water + N + shade) increased biomass per plant in openings, whether intact or disturbed. It had no effect in shrub clumps where shrubs were intact, but caused a large increase in both recruitment and biomass per plant where shrubs were removed. Shrub clumps provide foci of invasion because of their higher resource availability, but the shrubs have competitive as well as facilitative effects. In a dry year (1999 to 2000), there was no survival to reproduction in any treatment. There are no intrinsic obstacles to cheatgrass invasion at this site, but the process will be very slow because of low site productivity and the high probability of drought years. Disturbance is not a necessary precondition for invasion, but may facilitate the process in favorable years.
Pages
224-232
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Publisher
U.S. Department of Agriculture
Publication Date
2001
Disciplines
Biology
Recommended Citation
Meyer, Susan E.; Garvin, Susan C.; Beckstead, Julie. 2001. Factors mediating cheatgrass invasion of intact salt desert shrubland. In: McArthur, E. Durant; Fairbanks, Daniel J., comps. Shrubland ecosystem genetics and biodiversity: proceedings; 2000 June 13-15; Provo, UT. Proc. RMRS-P-21. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 224-232.
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Comments
This paper was presented at the 11th Wildland Shrub Symposium: Shrubland Ecosystem Genetics and Biodiversity held at the Brigham Young University Conference Center, Provo, UT, June 13-15, 2000.