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Accueil du site → Doctorat → Royaume-Uni → 2000 → Soil genesis and spatial variability in the semi-arid tropics : a critical appraisal of the catena concept in East Africa.

University of Newcastle upon Tyne (2000)

Soil genesis and spatial variability in the semi-arid tropics : a critical appraisal of the catena concept in East Africa.

Banda, Daniel Joseph

Titre : Soil genesis and spatial variability in the semi-arid tropics : a critical appraisal of the catena concept in East Africa.

Auteur : Banda, Daniel Joseph.

Université de soutenance  : University of Newcastle upon Tyne

Grade : Doctor of Philosophy (Ph.D.) : 2000

Résumé
The concept of the soil catena originated in the dry tropics but has proved a useful tool for analysing soil-landform systems on a much wider basis. Levels of integration of these processes across the catena are critically evaluated and the value of the catena concept for predicting soil spatial variability at different scales is assessed.Initial multivariate discrimant evaluations of the geomorphic definition of soil units over the entire catena showed that the catena concept was a highly effective tool for predicting soil variability at both the semi-detailed (1:50 000) and detailed (1:12 500) scales for soil survey. In the footslopes, Chi-square tests between the upper and lower footslopes, revealed very strong associations between position on the slope and the distribution of clay, total stand, Coefficient of Linear Extensibility (COLE), electrical conductivity (EC), exchangeable bases, and cation exchange capacity (CEC). These associations were repeated between slope sub-facets, suggesting equally strong associates, even at the micro-scale. Upper footslopes possessed a more variable micro-relief, related to termite mounds, and showed correspondingly higher coefficients of variation. Regression analysis showed a systematic increase in clay content, CEC, exchange Ca, K, and Na, and EC from the upper to the lower footslopes. Total sand content, however, showed a systematic decrease downslope. This suggests that although these properties may initially have been uniformly distributed in the lacustrine deposits, they have subsequently been pedogenetically re-worked and re-distributed, resulting in strong soil-slope associations across the entire footslope. Thus although soil development is more complex in the footslopes, soil-landform processes are still significantly integrated. Therefore the catena concept proved a valuable tool for predicting soil variability at different scales.

Mots clés : Landform ; Hillslope sediment Soil science Geology Mineralogy Sedimentology Soil science Geology

Annonce : EThOS (UK)

Accès au document : Proquest Dissertations & Theses

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