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Title: Human disturbances and vegetation dynamics in the Narok district of Kenya
Author: Ogutu, Zadoc A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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This thesis is an examination of human impact on plant species composition and vegetation structure of Narok District, Kenya. This is done by comparing the vegetation on disturbed and undisturbed sites. A literature review confirms the influence of administation, abiotic and biotic factors on vegetation dynamics. A macro-scale approach to the research, based on satellite imagery, confirms rapid expansion of cultivation. A subsequent micro-scale approach, based on field sampling, suggests that present human activities are becoming increasingly permanent and predominantly large-scale. This trend is accounted by increasingly human population and the change in Maasai lifestyles. The description of vegetation data using indices of similarity suggests that samples asociation is determined by proximity factors and human disturbance. Alpha diversity indices suggest that medium human disturbances increase species diversity. Examination of floristic and structural characteristics suggests that high human disturbances reduce the number of woody species and the volume of wood while low disturbances favour the predominance of woody species. On the contrary, medium human disturbances attract both successional and climax species. Also, climatic and soil factors by determining plant lifeforms and the height of plants, affect the amount of wood in the different site categories. An inhibition model is suggested for the change in species composition at different height categories. This is either due to the exclusion of seedling recruitment by resource monopolization in undisturbed sites or due to suppression of recruitment of plants to the next stage in disturbed sites. PCO ordination of floristic data based on species association shows samples pattern along axis 1 which varies with moisture gradient, organic carbon, nitrogen and zinc while the pattern along axis 2 suggests the influence of human disturbance, mainly between disturbed and undisturbed forest and bushland samples. Classification of vegetation data using both average linkage and furthest neighbour algorithms produce clusters on the basis of sample closeness suggesting a continuous, rather than a discrete, distribution of species. Lack of earlier fusing of samples of the same disturbance characteristics and from the same plant community is attributed to two factors. First, is the relatively recent human influence which has had little influence on plant composition. Second, is plant resilience which resists and/or reduces human impact on vegetation. In view of the findings, it is recommended that vegetation management should aim at reducing extreme disturbances. Low disturbances, it is postulated, reduce re-establishment potential of a site by promoting resource monopolization while high disturbances degrading site conditions for recolonization. A defined land use policy is suggested as a pre-requisite to implementation of the proposals offered.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available