Diss. (sammanfattning) Umeå : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Thesis(Ph.D.)--University of Western Australia, 2006.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 26, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Robert J. Kremer. Vita. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 59-67). Also available on the World Wide Web.

Thesis (M.Phil.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M.S.)--University of Pretoria, 2004. / Title from PDF t.p. (viewed Mar. 11 2005). Includes bibliographical references (p. 99-107).

The release of the seed eating beetle Sulcobruchus subsuturalis for biological control of Caesalpinia decapetala in South Africa has been ongoing since 2000. This is the first post release evaluation of the efficacy of the agent against the weed. The study assessed the phenology of C. decapetala and S. subsuturalis at two sites and included determining the establishment of the beetle on the target weed at 25 study sites. In addition, the effects of S. subsuturalis on seed densities as well as seed germination and seedling recruitment were examined. Furthermore predation by native ants and attacks by native parasitoids were also examined at two release sites. Mature filled pods were available on the tree from September (spring) to March (summer) when the beetle is expected to be reproductively active. The majority of beetle releases by Working for water took place in summer. However the proportion of beetle infested seeds, which were only recovered inside pods in the tree canopy at study sites, was low (0 to 15.5%). Consequently high seed densities and seedling recruitment were observed in the field. In the laboratory, S. subsuturalis did not lay eggs on buried seeds, however seed infestation levels were generally high. Only 8.3% of the seeds containing adults germinated and 6.3% emerged into seedlings. Of the seeds containing larvae, only 14.6% germinated and 2.1% emerged into seedlings. Thus far, S. subsuturalis has failed to maintain high populations on the target weed, possibly due to egg predation by native ants (Crematogaster species, Pheidole megacephala, Messor natalensis and Tetramorium avium) and attacks by native parasitoids. Egg predation reached 100% within 10 days. Egg parasitism by unknown parasitoids ranged between 80 and 93.1% in Limpopo. The parasitic wasp Dinarmus altifrons was recovered once developing inside a C. decapetala seed infested with S. subsuturalis. Further investigations regarding attacks by indigenous parasitoids on S. subsuturalis are required to determine the extent of this problem. Meanwhile releases of S. subsuturalis against C. decapetala should continue. However release efforts need to be improved by (a) using inundative rather than inoculative releases (b) Releasing every year between September and March (summer) and (c) involving land owners, farmers and nature reserve authorities in release activities. Ultimately an additional agent should be sought for release against C. decapetala as the weed may not be the preferred host for S. subsuturalis.

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.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 5 uppsatser.

Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 72-79). Also available in electronic format on the Internet.