Cover changes and regeneration status of a peri-urban mangrove
Mohamed, M.O.S.; Neukermans, G.; Kairo, J.; Dahdouh-Guebas, F.; Koedam, N. (2008). Cover changes and regeneration status of a peri-urban mangrove, in: Mohamed, M.O.S. Are peri-urban mangrove forests viable? Effects of sewage pollution and wood exploitation on the structure and development of the mangroves of Mombasa (Kenya). pp. 102-127
In: Mohamed, M.O.S. (2008). Are peri-urban mangrove forests viable? Effects of sewage pollution and wood exploitation on the structure and development of the mangroves of Mombasa (Kenya). PhD Thesis. Free University Brussels. Laboratory of Plant Science and Nature Management: Brussel. 180 pp., more
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| Keywords |
Biological phenomena > Regeneration
Ecosystem disturbance
Mangroves
ISW, Kenya, Mombasa, Tudor Creek
Marine/Coastal |
| Abstract |
Stability of an ecosystem is determined by its resilience, regenerative capacity and numerous weak trophic links, amongst other natural and human induced factors. The Tudor creek mangroves, a typical peri-urban mangrove, are exposed to both episodic natural and recurrent human disturbances, including decades? long exposure to raw domestic sewage, sporadic unregulated-harvesting and episodic siltation. This study evaluates the regeneration patterns within extended gaps and the understorey. An evaluation on species mix and regeneration patterns is also done. Preliminary analysis of aerial photographs (1969 and 1992) and a satellite image (2005) indicate a 12.5% decline in closed canopy mangrove between 1969 and 1992, and a 55% decline between 1992 and 2005. Distribution of adult trees was variable, with mixed stands and large canopy openings in the mid intertidal range. Species composition of seedlings and saplings did not always reflect the overstorey species composition and varied with gap sizes. Gap sizes range between 10 - 50m² have higher or mostly adequate regeneration, while gaps smaller than 10m² and bigger than 60m² have lower regeneration levels. R. mucronata seedlings and saplings occurred in the understorey under all cover types and inundation regime, conferring advantages to this species under the current disturbance regime. This may favour its establishment in relation to other species. A. marina and C. tagal saplings and seedlings are restricted to the forest edges and gaps. The current status of the forest is reminiscent of a recovery phase, a multiphase succession stage, after a major disturbance event, accompanied by recurrent anthropogenic pressure. This study shows that species composition depends in part on the balance between natural large-scale and recurrent small-scale human disturbances. |
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