Date of Award:
Master of Science (MS)
Christopher A. Call
Crested wheatgrass (Agropyron cristatum [L.] Gaertn.) is one of the most commonly seeded exotic species in the western United States. Although many degraded Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) plant communities have been seeded with crested wheatgrass during rehabilitation efforts, seed banks of these communities have not been characterized. I sought to characterize and explain the variation among 33 seeded communities in the northeastern Great Basin. Hierarchical clustering and principal components analysis identified four possible seed bank categories in these communities. Seed bank categories varied from high to low crested wheatgrass dominance. The crested wheatgrass-dominated category is a particularly attractive setting to develop management strategies that reduce crested wheatgrass dominance and increase native plant diversity. It is also a common practice to seed crested wheatgrass in mixture with native species after a disturbance to increase diversity. Empirical estimates as to how the density of crested wheatgrass seed and seedlings interfere with native species establishment have not been defined. A greenhouse experiment was established using an addition series design to determine the influence of interference between crested wheatgrass and four important native species. The existence of seed bank categories of Wyoming big sagebrush communities seeded with crested wheatgrass agrees with the hypothesis that seed banks closely resemble floristic composition. In addition, these results support the hypothesis that seed bank composition has a strong influence on succession in these communities, and characterizing seed banks is necessary to develop ecologically based management strategies for seeded Wyoming big sagebrush communities. Interference from crested wheatgrass on many native species suggests that further management practices to enhance diversity in crested wheatgrass-dominated communities are necessary to reduce competition from crested wheatgrass in the seed bank as well as the aboveground vegetation. These results also suggest that the practice of simultaneously seeding native species with crested wheatgrass may likely result in poor native species persistence unless combined seed bank density and seeding rate of crested wheatgrass is sufficiently low.
Gunnell, Kevin L., "Seed Banks of Sagebrush Communities Seeded with Crested Wheatgrass" (2009). All Graduate Theses and Dissertations. 250.
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