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University of the Witwatersrand (1991)

The distribution of vesicular-arbuscular mycorrhizal fungi in the savanna regions of Nylsvley Nature Reserve in relation to soil fertility factors

Dames, Joanna Felicity

Titre : The distribution of vesicular-arbuscular mycorrhizal fungi in the savanna regions of Nylsvley Nature Reserve in relation to soil fertility factors

Auteur : Dames, Joanna Felicity

Université de soutenance : University of the Witwatersrand

Grade : Master of Science (MS) 1991

Résumé
The vegetation of the Nylsvley Nature Reserve situated in the Northern Transvaal, South Africa, is a semi-arid savanna dominated by Burkea africana and Eragrostis pallens, interspersed with patches of Acacia spp. and E. lebamanniana. The Burkea savanna is established on soil which is naturally low in phosphorus while the Acacia savanna is established on soil with higher phosphorus levels. Spores of vesicular-arbuscular mycorrhizal (VAM) fungi were extracted from soil samples by wet sieving and sucrose centrifugation after which they were enumerated and identified. Thirteen VAM species were isolated from the savanna regions. The population was composed of three Glomus spp. , four Acaulospora spp., one Gigaspora sp., three Scutellispora spp. and two species of uncertain identity. Root samples were cleared and stained with acidic glycerol-trypan blue and assessed for mycorrhizal colonization. Significant positive correlations were indicated between spore densities and mycorrhizal root infection. The total spore population was negatively correlated with available P, organic C, K, Ca, Mg, and pH. Individual species differed markedly from the population as a whole in their interactions with soil factors, these were examined using linear regressions. The VAM root colonization as assessed by the mycorrhizal % was significantly negatively correlated with P while the frequency % was negatively correlated with P and K. The inter-relationships between the different VAM species and environmental factors were further explored using principal component analysis. The population structure and the factors affecting the population are discussed.

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