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
Variation in biotic crusts, shrubs, rainfall and resistance to cheatgrass invasion in the Great Basin.
D'ANTONIO, CARLA *,1, 2, HAUBENSAK, KAREN1, 1 EXOTIC AND INVASIVE WEEDS RESEARCH UNIT, RENO, NV, USA2 ENVIRONMENTAL STUDIES DEPARTMENT, SANTA BARBARA, CA, USA
ABSTRACT- Cheatgrass (Bromus tectorum) is a highly successful invader of habitats in the Great Basin, appearing to establish in most communities without difficulty. Its ability to establish in intershrub spaces is important in creating the continuous fine fuels that carry fire through sagebrush-dominated habitat. By contrast, in salt desert communities, we have observed a relative lack of cheatgrass in intershrub spaces. We hypothesized that biotic crusts, which dominate intershrub spaces, may provide resistance to germination or establishment of cheatgrass. We conducted a seeding experiment manipulating crust condition and presence or absence of shrubs at three sites in north central Nevada over two years. In the dry year, cheatgrass establishment was confined to microsites where shrubs were present or had been removed. There was no effect of crust disturbance because establishment was negligible away from shrubs. In the wet year that followed, however, establishment was high in all microsites. Disturbance had only a minor stimulatory effect on cheatgrass germination, despite large differences in microtopography and infiltration rates between disturbed and undisturbed plots. Our data suggest that in dry years abiotic resistance limits the microsites that cheatgrass occupies, while in wet years there is very little resistance to invasion in any microsite.
Key words: salt desert