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Addis Ababa University (1998)

Root Growth Patterns and Plant Adaptability in Three Acacia Species

Haileselassie, Teklehaimanot

Titre : Root Growth Patterns and Plant Adaptability in Three Acacia Species

Auteur : Haileselassie, Teklehaimanot

Université de soutenance : Addis Ababa University

Grade : Master of Science in Biology 1998

Résumé
Trees and shmbs screened for desirable properties can play an important role in the rehabilitation of degraded lands. Indigenous species adapted to harsh conditions of degraded sites can reverse degradation processes by stabilizing soils, increasing organic matter and improvements of nutrient status etc. Studies have shown that Acacia species have a potential for use in agroforestry systems and rehabilitation of degraded lands. For proper evaluation of the use of Acacia species in rehabilitation schemes and for agroforestry systems, studies in the root growth patterns and adaptability are essential. The main objective of this study was, therefore, to assess the root growth patterns of some Acacia species namely, A.seyaf Del., A.senegal (L.) Willd. and A.tortilis (Forrsk) Hayne and see the relevance of the results in adaptation to aridity. The study was conducted in Abernosa Ranch and Abiyata Shalla National Park. To investigate rooting patterns of the selected Acacia species, young trees were carefully excavated exposing a representative portion of the root system and quantitative data taken on depth at which the first lateral root starts, radial spreading of lateral roots and the zone of most intense lateral roots. Saplings were completely uprooted and separated for shoot and root palis, and oven-dried for the determination of shoot-root ratio. To see the effect of the Acacia trees on their undergrowth, comparison of herbaceous root biomass was carried out with adjacent open grassland in Abernosa. There was some difference in root growth patterns between species, A.seyal characterized by few but very big lateral root in close proximity to the surface, A.senegal with very dense lateral roots near to the surface and A. tortilis with less prominent lateral roots as compared to the others. The length of the taproots and shootroot ratio of the saplings uprooted indicated that A.tortilis has greater depth penetration. There was no significant difference within species between the two sites for depth of first lateral root, zone of most intense lateral roots and for radius of lateral spread. Depth penetration and ramification of lateral roots seem to be a function of soil and bedrock conditions. The herbaceous root biomass under A.seyal was significantly higher than the adjacent open grassland indicating the influence in increasing productivity.

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