Thesis (M.S.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Graduation date: 1996

Thesis (M.S.)--Oregon State University, 2008-01-15. / Printout. Includes bibliographical references (leaves 31-36). Also available on the World Wide Web.

Ranchers, farmers, land managers, and resource management agencies have been plagued with various types of invasive weeds for decades, ultimately affecting millions of acres of viable wildlife habitat, grazing, and recreational opportunities. Invasive weeds often have nutritional contexts that negatively affect animals in some way, increasing the incentive to avoid consuming it by various animal species and domestic livestock. With the current amount of land infested with this weed, and the limited knowledge of the reason for avoidance, the underlying causes of livestock avoidance require in-depth and fundamental understanding. In my MS program, I sought to explore the relationship of plant and herbivore interactions in regards to grazing, animal diet selection through the use of supplementation, along with understanding the chemical compounds that cause avoidance of medusahead by domestic animals. This research will help us better understand the reasoning behind grazing avoidance and preference, and provide further understanding and management approaches using livestock as an alternative management tool in hopes of creating sustainable ecosystems with complementary benefits for soils, plants, animals, and land managers.

Medusahead (Taeniatherum caput-medusae (L.) Nevski) is currently one of the biggest threats to rangelands and livestock operations in the Western US. High silica concentrations in medusahead contribute to its invasiveness. I developed a model to explain how silica is involved in the invasion process, and attempted to manipulate silica to increase use of the grass by livestock. Experiments were conducted to determine: 1) whether rotational grazing on established forages of improved nutritional quality would provide supplemental nutrients to increase cattle use of medusahead; 2) evaluate intake of and preference for medusahead treated with a glyphosate herbicide at different rates by sheep; and 3) evaluate intake and selection of medusahead by cattle by separating the effects of a glyphosate herbicide (Roundup®) from other chemicals in the formulation (salt, adjuvant). Additionally, experiments were conducted to 4) determine the nutritional value and digestibility of medusahead treated with Roundup® at different rates and at different plant particle sizes; and 5) determine if cattle grazing with trampling can increase seeding success on medusahead-invaded rangelands. Rotational grazing from supplemental pastures to medusahead-invaded pastures increased medusahead use by cattle during the second year of the study. Furthermore, glyphosate did not increase medusahead consumption in a choice between three glyphosate treatments, but did in a two-way choice test. Cattle grazed glyphosate-treated medusahead more than that of the non-treated grass and completely avoided the salt-treated grass. The active ingredient in a glyphosate herbicide increased consumption of medusahead while other ingredients in the herbicide (i.e., salt and adjuvant) had no influence on this choice. A smaller particle size increased the digestibility of medusahead compared to larger particle sizes. Glyphosate also increases digestibility, but not as much as particle size. Finally, cattle trampling did not help establish seeded plant species, and the seeding attempt was unsuccessful. Thus, grazing rotations between improved pastures and medusahead-infested rangeland, and the combined glyphosate application-grazing are new approaches for medusahead control, as they prepare a seed bed for revegetation and increase the nutritional quality of the grass for improved livestock nutrition.

Medusahead is a harmful weed that is invading public lands in the West. The invasion is a serious concern to the public because it can reduce forage for livestock and wildlife, increase fire frequency, alter important ecosystem cycles (like water), reduce recreational activities, and produce landscapes that are aesthetically unpleasing. Invasions can drive up costs that generally require taxpayer’s dollars. Medusahead seedlings typically spread to new areas by attaching itself to passing objects (e.g. vehicles, animals, clothing) where it can quickly begin to affect plants communities. To be effective, management plans need to be sustainable, informed, and considerate to invasion levels across large landscapes. Ecological remote sensing analysis is a method that uses airborne imagery, taken from drones, aircrafts, or satellites, to gather information about ecological systems. This Thesis strived to use remote sensing techniques to identify medusahead in the landscape and its changes through time. This was done for an extensive area of rangelands in the Channel Scabland region of eastern ashington. This Thesis provided results that would benefit land managers that include: 1) a dispersal map of medusahead, 2) a time line of medusahead cover through time, 3) “high risk’ dispersal areas, 4) climatic factors showing an influence on the time line of medusahead, 5) a strategy map that can be utilized by land managers to direct management needs. This Thesis shows how remote sensing applications can be used to detect medusahead in the landscape and understand its invasiveness through time. This information can help create sustainable and effective management plans so land managers can continue to protect and improve western public lands threatened by the invasion of medusahead.

A large portion of the historical steppe and shrub-steppe habitats in eastern Washington have been altered through biotic and abiotic processes resulting in the annual grass medusahead (Taeniatherum caput-medusae (L.) Nevski) becoming a large component of the altered vegetation. Experiments were conducted to determine whether: 1) protein supplementation would help increase utilization of medusahead by cattle, 2) native and introduced grass cultivars could establish in the region, and 3) mechanical disturbance would aid in establishing Vavilov II Siberian wheatgrass (Agropyron fragile [Roth] P. Candargy) and Immigrant forage kochia (Bassia prostrata [L.] A.J. Scott). Cattle grazing medusahead-infested rangeland for 10-d periods during summer months increased consumption of medusahead due to a reduction in the quality of forage alternatives. Cattle supplemented with a protein concentrate increased consumption of medusahead during d 6 to 10 of the grazing periods resulting in a reduction of medusahead abundance over time. Introduced grass cultivars; Vavilov II, Hycrest IIcrested wheatgrass (Agropyron cristatum [L.] Gaertn.), and Bozoisky II Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), and a native grass mix; Sherman big bluegrass (Poa secunda J. Presl), Secar Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkworth), Bannock Thickspike wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.] Gould), and Recovery Western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve) were planted at three locations. Sherman big bluegrass was the only native species that established with 47 % initial establishment and persistence increasing to 65 % over the course of the study. Hycrest II had 64 % stand establishment but persistence decreased to 48 % and Vavilov II had 57 % initial establishment and decreased to 50 %. Sherman Big bluegrass had greater biomass production in May however, the later maturing Hycrest II and Vavilov II had similar biomass production to Sherman Big bluegrass in July. Bozoisky II had poor stand establishment and decreased over the course of the study. Mechanical disturbance from disking in the fall was successful in establishing Vavilov II and Immigrant forage kochia. In conclusion, cattle can be used to reduce medusahead abundance in rangelands and revegetation with Vavilov II, Hycrest II and Sherman big bluegrass was successful. Mechanical disturbance was successful in aiding in establishment of Vavilov II and Immigrant forage kochia.

Medusahead (Taeniatherum caput-medusae ssp. asperum (Simk.) Melderis) is a Eurasian annual grass that infests large areas of U.S. rangelands, dominating former bunchgrass/shrub sites. Squirreltail (Elymus elymoides (Raf.) Swezey) is a native perennial grass that has demonstrated the ability to establish in stands of medusahead. A study conducted on two sites near Burns, OR had the objectives of quantifying competition between medusahead and squirreltail, and determining the effect of moisture availability on competition. Two hundred plots were arranged in a factorial design. Measurements were taken of plant growth, seed production, soil moisture, and climate. Results for the two years are contrasting. The first year was very dry. Medusahead grew and reproduced well, producing a seed crop up to 10 times the amount planted; squirreltail grew poorly and did not reproduce. Samples of squirreltail seed retrieved from the plots in late summer were found to have remained dormant since seeding. The second year had above-average precipitation. Medusahead grew and reproduced well again. Squirreltail grew and reproduced abundantly on one of the sites, both on freshly-seeded plots and on plots containing dormant seeds and surviving plants from the previous year. In all cases, medusahead exhibited stronger interspecific and intraspecific competitive effects than did squirreltail seedlings. With adequate soil moisture, squirreltail reduced average weight and median seed production of individual medusahead plants, but did not reduce medusahead seed production per square meter. Medusahead succeeded in a drought year by utilizing deep soil moisture, and utilized shallower moisture in a wet year. During a wet year in plots containing mature squirreltail, medusahead utilized shallower moisture, while squirreltail strongly utilized much deeper moisture. Interspecific competitive interference by medusahead on squirreltail seedlings suggests the potential benefits of suppressing medusahead during the seeding year for squirreltail in a rehabilitation effort, especially if climatic conditions are conducive to squirreltail germination and establishment. / Graduation date: 1997