Thesis (Ph. D.)--Dept. of Soil and Water, Waite Agricultural Research Institute, University of Adelaide, 1994. / Includes bibliographical references (leaves 146-170).

Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1999. / Bibliography: leaves 135-156.

Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Soil and Land Systems, 2005? / "August, 2004" Title from t.p. on PDF file; viewed 29 June 2005. Includes bibliographical references. Also available in a print form.

Thesis (M.S.)--Oregon State University, 1992. / Includes mounted photographs. Typescript (photocopy). Includes bibliographical references (leaves 35-39). Also available on the World Wide Web.

Thesis (doctoral)--University of Tartu, 2004.

Thesis (M.S.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 48-56). Also available on the World Wide Web.

Bibliography: leaves 135-156. This study investigated the effects of the symbiotic association of plants with vesicular-arbuscular mycorrhizal fungi on the intensity of intraspecific competition and its consequences on popular structure. Four main glasshouse experiments were performed using the non-cultivated Rhodanthe chlorocephala ssp. Rosea, and the cultivated species Trifolium subterraneum grown at different plant densities, under different levels of phosphorus and light, and in environments with homogeneous and patchy distribution of phosphorus. Results emphasise that the main effects of mycorrhizas at the individual level may not by apparent at population level because of the influence of density-dependent processes. However, infected individuals with a strong response to the symbiosis would have an advantage in situations of competition.

No description available.

No description available.

Arbuscular mycorrhizal (AM) fungi form an obligate symbiosis with many wild and cultivated plants. The plant may benefit from improved nutrient uptake (particularly phosphorus) and resistance to drought, pests and disease. Compared to more natural habitats, arable systems support reduced diversity of AM fungi, with community structure shifted in favour of ruderal types. Physical disturbance is an important driver of these differences and reduced tillage systems might facilitate greater utilisation of the AM symbiosis as part of more sustainable production systems. In this study, the structure of root-associated AM fungal communities in barley grown under a range of tillage regimes was characterised, using high-throughput molecular methodology. AM fungal community structure was significantly influenced by tillage intensity, with soils subject to high tillage burden richest in ruderal types. These findings were consistent in both winter and spring barley cultivars. Significant temporal changes in AM fungal community structure suggested an important role for plant growth stage in determining AM fungal community dynamics. Functional differences can occur between fungal species and different fungus-plant combinations, and in the second part of this study the functional consequences of changes in community structure due to tillage were tested in a model system using intact field-soil cores. There were clear differences in AM fungal community structure due to differential physical disturbance. Although no functional effects were observed, this may have been due to the inherent limitations of recreating field conditions in microcosm experiments. The results of this comprehensive assessment of fine-scale spatial variation in AM fungal community structure in an arable system identify tillage as an important driver of AM fungal community dynamics, and plant growth stage is also a key factor which has rarely been addressed. Elucidating the functional significance of these changes remains essential in order to justify future changes to arable management practices.