Président du jury Visser, Marjolein
Promoteur Polygenis, Marie-José
;Bogaert, Jan ;De Cannière, Charles Publication Non publié, 2012-09-14
| Résumé : | This study focuses on the vegetation of the African city of Bujumbura, Burundi. Urban flora is detailed according to the origin of the species (native or introduced), their life form, the use of these species by the local population and their behaviour (invasive or not). The correlation between different natural and anthropogenic environmental factors and the composition of plant communities has been demonstrated through the analysis of vegetation plots. Three types of green areas were studied: spontaneous vegetation on terra firma, wetlands and domestic gardens. The main ecological factor correlated to the composition of the spontaneous vegetation of terra firma is the degree of urbanization. From the suburb to the city centre, savannah species typical for the region are replaced by alien invasive species, mostly ruderals. The latter generally have a large distribution, often on several continents. The physiognomy of the vegetation also changes, with hemicryptophytes and phanerophytes in the outskirts and the dominance of therophytes and chamaephytes in the city centre. In most of wetlands, a large proportion of the plant species are natives, but some wetlands are almost totally invaded by alien species. Soil type is the main environmental factor correlated with the variability of the vegetation. The flora of domestic gardens is mainly composed of introduced species used as ornamental, food or medicinal plants. The socio-economical status of the neighbourhood is the main factor correlated with the variability of the garden flora. In high standing neighbourhoods, most species are onamental, with many trees and shrubs. In popular neighbourhoods, the flora is mainly utilitarian (vegetables and fruits), with a significant proportion of native species, and composed mainly of annual species. A small proportion of the alien species cultivated in gardens has become invasive in the semi-natural vegetation of the city and its surroundings. Many other species cultivated in the gardens could become invasive, based on their ecology and their invasive behaviour in other regions with a climate similar to that of Bujumbura. Overall, the city of Bujumbura has a diverse flora, with many useful species (vegetables and fruits, traditional medicine, construction of fences and roofs, material for mats and art objects...). The vegetation also hosts wildlife: birds, fishes, hippos, crocodiles etc… In conclusion, the vegetation of Bujumbura contributes to biodiversity conservation and provides services to the urban population, but the expansion of alien invasive species and the consequent homogenization of the vegetation is a challenge for the future. |
