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University of the Witwatersrand (1983)

Factors associated with the encroachment of bush into semi-arid savanna grazing lands in Southern Africa

Dyer, Colin

Titre : Factors associated with the encroachment of bush into semi-arid savanna grazing lands in Southern Africa

Auteur : Dyer, Colin

Université de soutenance : University of the Witwatersrand

Grade : Master of Science (1983)

Résumé
A study was carried out in the semi-arid and arid savanna regions of South Africa to determine which environmental factors are associated with the process of bush encroachment. It was found, using discriminant analysis, that no single variable, or group of variables, was responsible for separating the degrees of woody density. Some soil textural factors showed associations with increased woody density. The highest woody densities were recorded on deep, sandy soils with a low annual rainfall. Several site variaoles change as a result of a change in the bush-grass community. The most prominent of t ese is a change in the distribution pattern of some soil cations (calcium, magnesium and sodium), which expands the two layered, water linked hypothesis of Walter (1971) on savanna dynamics, to include the leaching of nutrients. Bush clearing is not feasible in the arid regions on sandy s o ils , where the competitive effect of trees on grasses is strony, but the reverse Is weak. On fine textured s o ils , however, th" competition between these components is great in both directions, and control of woody thickening may be economically feasible.

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Page publiée le 13 février 2016, mise à jour le 3 janvier 2019