Thesis (M.S.)--Northern Michigan University, 2009. / Bibliography: leaves 30-33.

Thesis (M.S.)--Oregon State University, 2000. / Typescript (photocopy). Includes bibliographical references (leaves 48-52). Also available on the World Wide Web.

Thesis (M.S.)--Northern Michigan University, 2007. / Bibliography: leaves 44-48.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Norma L. Fowler and Marcy E. Litvak. Vita. Includes bibliographical references. Available also from UMI company.

Thesis (M.S.)--Brigham Young University. Dept. of Plant and Animal Sciences, 2006. / Includes bibliographical references.

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Arbuscular mycorrhizal fungi (AMF) provide numerous services to their plant symbionts. Understanding the effects of climate change on AMF, and the resulting plant responses, is a crucial factor in predicting ecosystem responses on a global scale. We used a manipulative climate change experiment embedded within a natural climate gradient in Oregon and Washington to examine how the effects of future climate change on AMF-plant symbioses are mediated by soil water availability, soil nutrient availability, and vegetation dynamics. Using structural equation modeling, we found that the direct effect of increasing temperatures was to decrease AMF colonization. Indirect effects of temperature, mediated through other variables, canceled each other out. However, future shifts in these relationships could either exacerbate or mitigate the negative direct effect of temperature. As ecosystems in Mediterranean climates experience more intense droughts and heavier rains, decreases in AMF colonization could have substantial consequences for plant communities and ecosystem function.

Thesis (Ph. D.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 193 p. : ill. Vita. Includes abstract. Includes bibliographical references.

To determine how Pacific Northwest prairies are influenced by local site factors versus. regional climate, we studied the reproduction, plant size, and density of sixteen natural populations of four perennial forb species native to Pacific Northwest prairies: Ranunculus austro-oreganus, Sidalcea malviflora spp. virgata, Microseris laciniata, and Eriophyllum lanatum. These populations were distributed along a 700 kilometer latitudinal gradient from southern Oregon to Whidbey Island, Washington. We found significant differences in plant size and reproduction among populations for all species, but correlations among edaphic and climate variables and plant size and reproduction were weak. Instead, density was more strongly correlated with both edaphic and climate variables, suggesting that this is a better indicator of long-term demographic processes. Although a few factors are important across species (e.g., nutrient availability and minimum temperature), response is idiosyncratic at the individual species level in Pacific Northwest prairies.

Concern for the severe loss of biodiversity of grassland species is often voiced. Plantation forestry is known to cause extensive and long lasting disturbance of the natural environment in particular in areas such as the mountain grassland of the Drakensberg escarpment. The survey was conducted in the Graskop area on sites within pine plantations along the Treur River bordering the Blyde River Nature Reserve. The results showed that restoration of plant species biodiversity through natural succession, on cleared plantation sites, required periods longer than seven years and that the regeneration of a great many of the indigenous forb species remained uncertain. Two survey areas were selected and within each survey area, sampling sites were selected to represent three categories of vegetation namely, undisturbed grassland and sites where pine trees had been removed three and seven years previously. Samples of plants were collected from each of these sampling sites. Analysis by means of a classification technique determined the species composition of the disturbed sites in relation to that of the intact grassland. Wheel point surveys were also carried out on these sites to provided information on the vegetation cover, as well as the degree of species regeneration on each site. The variation in vegetation composition of the various plots was ana lysed by means of Detrended Correspondence Analysis (DCA) and Two-Way Indicator Species Analysis (TWINSPAN). The results showed three distinct species assemblages which corresponded with the three categories of sampling sites. Also that the indigenous forbs species comprised 68% of all the sampled species most of which had failed to regenerate in either the three or seven year cleared plots. The most successful grass species in establishing and persisting in all sites were, Eragrostis curvula and Loudetia simplex. The fern, Pteridium aquilinum had a high prevalence on the disturbed grassland plots and the threat of its invasion of these habitats is compounded by the physical disturbance which eradication methods cause. Planning for grassland restoration involves cognizance of the complexity of grassland ecology, the influence of a multiplicity of environmental factors and the proximity of donor sites to the disturbed areas. Applying international restoration techniques used in grasslands of different origins to those of South African landscapes could result in disappointing and costly efforts. At best any attempt at managing grassland diversity should be preceded by an holistic investigation into the environmental conditions particular to the specific terrain and thereafter maintaining a conservative approach of allowing natural succession. The threat of invasive exotic species should be integral to conserving the integrity of the remaining intact natural grasslands in South Africa. It is acknowledged that in this study regeneration of grassland species on plantation sites cleared of pine trees three and seven years previously does not include a long time span such as needed for succession to take place but is useful in showing a trend in species re-colonization to resemble the vegetation of intact grassland, as well as highlighting the absence of a great number of indigenous forb species. Copyright / Dissertation (MInstAgrar)--University of Pretoria, 2012. / Geography, Geoinformatics and Meteorology / Unrestricted