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University of Namibia (2013)

The influence of Acacia Mellifera on soil fertility, herbage quality and composition and sandy soils in camel-thorn savannas of Namibia

Nzehengwa, James M.

Titre : The influence of Acacia Mellifera on soil fertility, herbage quality and composition and sandy soils in camel-thorn savannas of Namibia.

Auteur : Nzehengwa, James M. 

Université de soutenance : University of Namibia

Grade : Masters of Science in Rangeland Resources and Management. 2013

Résumé
Acacia mellifera is viewed negatively due to its invasive nature to the extent that farmers tend to remove it from their farms without really considering that it may have beneficial effects. Thus the study looked at the role it plays on soil fertility, herbage quality, and botanical composition with reference to N-fixation. Soil and grass samples were collected at Corsica Resettlement farm at 6 distances within three sub-habitats from bases of five A. mellifera trees outwards. The nutrient concentrations of soil (Total N, % of Organic, Ca, K, Cu) and that of herbaceous plants (N, Ca, P, K, Cu) were found to be significantly higher (p<0.01) under tree crown zone than other sub-habitats and decreased along a distance gradient from A. mellifera tree outwards. This is attributed to biological N fixation, shading, litter, ‘nutrient pump’ and decomposition of roots and nodules. Soil Mg and P and plant Mg, Mn and Zn concentration did not significantly differ among sub-habitats. Amounts of plant N, Ca, K increased with amounts of soil N, Ca, K. Herbaceous species composition varied significantly among sub-habitats, with at most 85% similarity between areas under trees and those outside the tree crowns. Perennial grasses (Stipagrostis uniplumis and Stipagrostis ciliata) were commonly found in all clusters, while forbs only occurred under the tree crown zone, leading to the observed differences. The study confirms that A. mellifera enriches the soil fertility and improves herbage quality through N-fixation, but this process is also interactively linked to the dynamics of other nutrients.

Mots clés : Sub-habitats — Herbaceous composition — soil enrichment — Herbaceous quality improvement —N-fixation — Range management — Acacia mellifera

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Page publiée le 17 août 2015, mise à jour le 16 février 2018