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Julie Beckstead: Associate Professor Phone: (509)-313-6688 Fax: (509)-313-5804 eMail: Office#: HU 211
Education
Publications
Undergraduate research assistants supervised
Previous ResearchINVASIVENESS AND IMPACT OF AMMOPHILA ARENARIA: RELEASE FROM SOIL-BORNE PATHOGENS?
THE INDIRECT EFFECTS OF INVADING CHEATGRASS ON ASSOCIATIONAL HERBIVORY PATTERNS
AN EXPERIMENTAL TEST OF RESISTANCE TO CHEATGRASS INVASION: THE ROLE OF LIMITING RESOURCES
In low density patches, a disturbance reducing soil compaction had the strongest positive effect, significantly increasing biomass by 250% and density by 104% in comparison to the controls. The second strongest effect was reducing neighbors (native grasses), which significantly increased cheatgrass biomass and density. These results indicate that resources are present in low patches, but they are unavailable without disturbance and/or are exploited by competitors. Nitrogen addition did increase cheatgrass biomass and density in comparison to controls, but effects were minimal in comparison to reduced compaction and reduced neighbor treatments. In high density patches, we found nitrogen availability is important in maintaining cheatgrass densities in these less resistant patches.
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My current research focuses on exploring the interactions between invasive plant species and their enemies. I am looking for two motivated students to work together on a lab-related ecology project. We will investigate a little-explored seed pathogen of a locally invasive species, cheatgrass (Bromus tectorum).
The first step of this project is to determine the virulence of the fungus; test Koch's postulates, that is, prove that the specific fungal species is responsible for the seed death of cheatgrass. In addition, we will investigate the susceptibility or the lack thereof for cheatgrass from a variety of invaded systems in the inland Northwest. This project has important economical applications for agricultural systems, rangelands, and disturbed and undisturbed natural systems and will provide a unique vantage point to explore enemy-related theories in invasion biology. The research work will involve basic microbiology skills (aseptic techniques, making various types of agars, isolation of fungus, and inoculation experiments) as well as fieldwork involving collection of seeds from different invaded sites in eastern Washington. Preference will be given to students who have completed 
A basic tenet of invasion biology is that successful invaders are free from their natural enemies. I have received funding from USDA-NRI to directly test this Natural Enemies Hypothesis in collaboration with Dr. Ingrid Parker at the University of California, Santa Cruz. European beachgrass (Ammophila arenaria) is currently invading coastal dunes from Canada to central California. European research on Ammophila in its native range has established that soil-borne pathogens reduce Ammophila's growth and competitive abilities. We are comparing these European results with parallel experimental studies conducted on Ammophila in its introduced range of central California. If soil-borne pathogens are found to negatively affect Ammophila in its introduced range, then soil-borne pathogens from California could be further explored as a biocontrol measure to manage the current Ammophila problem and to aid in restoration of the dune system. This investigation will make a substantial conceptual contribution to the field of invasion biology by providing a direct test of the Natural Enemies Hypothesis. It will also contribute to the developing field of plant/pathogen ecology, emphasizing the rarely studied topic of soil-borne pathogens in a community ecology context.
Often in invasion biology we focus on the direct effects of an invading species on the invaded system, but are there indirect effects and are they important? Along with Dr. Susan Meyer and Dr. Carol Augspurger, I investigated the indirect effects of an invading species on associational herbivory patterns within a natural system. We combine invasion biology theory with that of associational herbivore to produce testable hypotheses. To test these hypotheses we studied a Great Basin shadscale (Atriplex confertifolia)-bunchgrass community in western Utah dominated by native bunchgrasses, invaded by cheatgrass (Bromus tectorum), and home to large populations of grasshoppers. First, we found that cheatgrass is a highly utilized food source for the generalist grass-feeding grasshoppers. Second, native species varied in the amount of herbivory received, which corresponded with their relative nitrogen content and some physical traits. This relative preference among native species affected the associational herbivory outcomes. Within a mosaic of low and high density cheatgrass patches, we document associational susceptibility on Elymus elymoides (a highly preferred native grass) located in high vs. low density cheatgrass patches (91% reduction in reproductive structures in high vs. low patches). In contrast, Poa secunda (a less preferred native species) did not demonstrate any pattern of associational herbivory when located within low or high density cheatgrass patches. We find that associational herbivory patterns result from host shifting due to the phenological availability of cheatgrass and native grass species with respect to the life cycle of generalist grasshoppers. We show that an indirect interaction, such as associational herbivory, plays a significant role in community dynamics.
We investigated whether low and high density cheatgrass (Bromus tectorum) patches, within a shadscale-bunchgrass community of western Utah, represent variation in resistance to invasion as maintained by differences in resource availability. Two parallel field experiments were conducted: 1) increasing resources within low density cheatgrass patches and, conversely, 2) reducing resources within high density cheatgrass patches. Treatments were applied at three life stages separately and across all stages.
Herbivore (primarily Mormon crickets and grasshoppers) and pathogen (head smut) pressures were documented to affect cheatgrass but did not explain resistance patterns. Instead we found that differential resource availability explains the observed variation in natural resistance. To ensure that this shadscale-bunchgrass community continues to resist cheatgrass invasion, the native plants and soil compaction must be protected from additional disturbance that could eliminate these resistant forces.