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Author
Lang'at, J.K.S.Date
2008
Metadata
Show full item recordAlternative Title
MARG I Final ReportAbstract
Mangroves have a wide environmental tolerance, adapting to growth in different conditions. Different mangrove formations have been identified and are thought to be influenced by the environmental settings prevalent to sites in which these formations occur. It is thus important for mangrove management agents to incorporate site conditions in management plans. Mangrove forests in Kenya occur in six landscape types; sheltered bays and reef patches, drowned river valleys, bays, behind marine influenced barrier dunes, behind barrier dunes and abrasion (reef platforms). Preliminary studies in Kenya have shown that mangrove forests north and south of Tana River differ in structural attributes. Therefore, this study aimed at describing mangrove forest structural attributes in relation to the biophysical features along the Kenyan coast. Information on biophysical features and mangrove forest structure (for the north coast and some sites in the south) was reviewed from published peer-reviewed articles and other literature materials. Vegetation data for the mangroves of the Shirazi-Funzi and Majoreni in the south coast was generated by the standard sampling techniques. Plots (10 m x 10 m each) ranging from 22 to 44 were established in each site and within each plot tree height (m), diameter at breast height (DBH; cm) and canopy cover (%) were determined for all trees with ≥5.0 cm DBH. The mangroves of Lamu and Ungwana Bay showed superior structural features than most sites in the southcoast. Likewise, mangrove forests under riverine influence (Ungwana Bay and Ramisi) were more complex than other sites, except Lamu. Rhizophora mucronata Lam. was the overall principal species in most sites, however, most sites depicted mangrove species distribution typical of the Kenyan coast. Tudor creek (Mombasa) was the poorest in most forest structural attributes probably due to degradation associated with proximity to urban setting. In the Shirazi-Funzi and Vanga complex the overall stand density ranged from 1573 to 1839 stems/ha; with height and basal area ranging from 6.0 to 7.4 m and 17.7 to 30.3 m2/ha respectively. Ramisi mangrove forests were more structurally complex than the other site and consequently had significantly larger trees than those in other sites in the southcoast (p < 0.001). Funzi mangroves were significantly taller than most sites in the area (p = 0.001). As in other areas along the Kenyan coastline, R. mucronata had the highest Importance Value in this section (ranging from 110 to 194) while Bruguiera gymnorrhiza (L) Lamk. and Xylocarpus granatum Koenig were least important in most sites. Findings from this study have wide application in sustainable utilization and management of mangroves along the Kenyan coast. Management plans which take in to consideration the harvesting systems need to be applied to reduce the effects of selective harvesting in most sites. Critical areas such as seaward fringe and degraded areas need to be protected to avoid shoreline recession and to allow sufficient regeneration potential and maintain forest cover.Pages
26pp.Publisher or University
Kenya Marine and Fisheries Research InstituteCollections