El-Mahi, Yousif A. (1990) Aspects of vegetation resilience and change in relation to major environmental disturbances in the semi-arid parts of Kordofan region-Sudan. Doctoral thesis, Durham University.
The aim of this study has been to investigate the different responses of vegetation to the major environmental disturbances and discontinuities in Kordofan region of the Sudan. Data used have been obtained from fieldwork survey, aerial photographs and a landsat image in combination with existing maps and statistics on vegetation, climate, agriculture and population. Results obtained have shown that most plant species are neither randomly distributed nor indications of the postulated regularity of distribution were detected. Such a distributional pattern was explained through the pattern of surface properties. These have included rainfall, soil characteristics, micro-topography and the type of vegetation itself. The different types of vegetation identified were shown to reflect various succession stages following either excessive cultivation, grazing or both. Climatically conditioned natural vegetation is virtually absent as the effect is almost entirely masked by man's activities. Evidence presented showed that various types of woodland were formerly more extensive and that they have been replaced by secondary shrubland, bushland and grassland. Most plant communities have been explained by their history of cultivation and grazing pressure. These two were found to interpret the process of successional changes, to radically alter its dynamics and to set plant species on a wide variety of paths which is largely controlled by the pressure exerted. Achieved result indicated that vegetation in the area has persisted to exist and to re-establish itself after virtual elimination. This is shown to reflect a high degree of resilience in the system. Evidence were shown that if the vegetation is protected and the climatic and edaphic conditions were favourable, it will eventually be succeeded by a richer type of vegetation. It has not been possible to prove neither to reject the claim often found in literature that the vegetation zones in this region are constantly shifting southward as a result of overgrazing, overcultivation and accelerated soil erosion. However, it has been possible to recognise a process of successional changes which varies from one place to another in terms of nature and intensity depending largely on site characteristics.
|Doctor of Philosophy
|Copyright of this thesis is held by the author
|08 Feb 2013 13:41