Graduate Thesis Or Dissertation
 

Restoration of Annual Grass-invaded Landscapes in the Sagebrush Steppe using Perennial Grass Seed Technologies and Wyoming Big Sagebrush Transplanting

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/08612w639

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  • Within the sagebrush steppe ecosystem, invasive annual grasses are of growing management concern as they outcompete native vegetation, change the fundamental nutrient cycling processes, decrease biodiversity, and increase frequency of wildfires. The most widely used and effective management tool to decrease invasive annual grass abundance, is the use of pre-emergent herbicides like imazapic. Although this herbicide is effective at annual grass control, it can have negative effects on native or desired seedlings. Thus, land managers often wait a year or more to seed native vegetation following herbicide treatment. In that time, cheatgrass and other invasive annual grasses have the opportunity to re-establish, making the herbicide treatment ineffective. By seeding and herbicide-treating annual grasses simultaneously (i.e., a single-entry approach), land managers can save a year or more in restoration costs. However, the native or desired seed needs to be protected in some sort of coating to prevent negative herbicide effects. An herbicide protection coating containing activated carbon has shown to successfully protect desired seeds in the form of pellets, and pods. This thesis outlines a new method of coating individual native grass seed in an herbicide protection formula containing activated carbon to test its effectiveness in both greenhouse and field settings. In the greenhouse study, we used a randomized block factorial design to test the efficacy of activated carbon-based herbicide protection coatings applied to individual bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Love) seeds for protecting seedlings from injury associated with low and high rates of pre-emergent herbicide (imazapic) application. The emergence of coated seed averaged 57% ± 5% (mean ± SE) compared to bare seed which had 14% ± 10% emergence with herbicide application. Seedling height for coated seed averaged 7.56 ± 0.6 cm compared to 2.26 ± 0.4 cm in uncoated bare seed in the presence of herbicide. Coated seeds produced 87% more plant biomass than uncoated seeds. The field study, a randomized block factorial design, repeated in two years, however, had two consecutive low precipitation and high temperature years resulting in low emergence and low survival of bare and coated seeds. Further field studies with either an added irrigation treatment or in more favorable climate conditions are suggested to determine effectiveness of carbon-based seed coatings in protecting desired seedlings from herbicide damage. This thesis also discusses a method of restoring Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) following wildfire. Sagebrush transplants have a higher establishment rate than seeding in low to mid elevation sagebrush steppe sites, however, their success is widely variable. Chapter four of this thesis outlines how 1) different ages of transplant at time of planting, 2) different seasons of planting (fall and spring planting), and 3) competition with invasive annual grasses, affect the survival and vigor (measured by transplant volume) of sagebrush transplants over two years. This completely randomized factorial design, repeated over two years, used ten age classes of transplants at time of planting (6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 weeks of age). Age classes 10 weeks and older in the first planting year and 12 weeks and older in the second planting year had the highest survival. Spring-planted transplants had higher survival than fall-planted transplants in both years; however, fall-planted transplants had increased vigor (measured by transplant volume) in both years. Competition did not affect survival of transplants in either year but it did affect volume of transplants. Volume was 54-fold greater when not competing with annual grasses compared to transplants competing with annual grasses in the first year, and nine-fold greater in the second year. Overall, the second year of the study had much lower sagebrush survival compared to the first year. Transplants are typically grown in a greenhouse for 6 months to a year before being planted in the field. This study demonstrated that reducing greenhouse growing time to 12 weeks compared to the traditional 24+ weeks, would cut greenhouse growing costs in half making this method of restoration more cost effective and a more favorable alternative to traditional restoration methods.
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  • This work was supported by USDA Agricultural Research Service.
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