Mangrove trees have ecologic and economic importance. Ecologically, they are very important because they offer protection to the coast and sea and harbor a unique fauna and flora. Mangroves protect the coastline against erosion and strong waves caused by storms. At certain places, such as Florida, Sri Lanka and Hawai mangroves are planted to protect the coastal railways, coastal highways and the coastline itself (Teas 1977, Linden & Jemelov 1980). Mangrove trees also have economic importance. Firstly, there is the wood production. Since hundreds of years mangroves have been chopped for wood which can be used as fire wood, poles, wood to build furniture and houses, etc where certain mangrove species are favored ( loc. cit.). In particular Rhizophora, Ceriops and Bruguiera are being exploited for the construction of houses. Rhizophora and Bruguiera are being used in Gazi for the walls of the houses, while Ceriops is preferred to build the roofs. These species also appear to be the most important in Sri Lanka. Mangrove forests are also indirectly a major source for food for the coastal populations: as mentioned earlier the mangroves are nurseries and food sources for many fish species and other marine organisms (Teas 1977, Linden & Jernelov 1980, Kokwaro 1985). A new aspect of the use of mangrove vegetation is oyster culturing. The past years intensive research has been conducted by the Kenya Belgium Project (KBP) to achieve oyster culturing in the mangroves followed by commercialization. The relations between oysters, mangroves and coral reefs demonstrate the importance of each partners, the reef offers protection to the mangroves of heavy waves, and the mangrove roots are the ideal places for oyster fixation. Degradation of mangroves is a direct result of human activities. A good example of this is the coastal area of Florida, where vast areas of mangroves have disappeared through the construction of a harbor and the expansion of cities. All these reasons show the importance of the conservation and reforestation of mangroves. Therefore, it is also crucial to investigate the regeneration of mangrove trees. The KBP also provided research connected to the reforestation of mangroves. In 1992, under guidance of Van Speybroeck (then University of Nairobi), research had been done into the regeneration strategies of mangroves along the Kenyan coast. His conclusions were that the mangrove vegetation is clearly zonated and that also the juveniles follow this zonation pattern. Preliminary investigations also showed that fauna could play an important role in the formation of this zonation and in the regeneration of mangroves. The present research is connected to the latter finding: if one learns more about the faunistic factors influencing the regeneration, one will be able to go more efficiently about the reforestation of the mangroves. The goals of this thesis are three-fold: firstly, the the zonation of the mangrove vegetation is described, secondly, the predation of fauna on the juveniles that were planted, and thirdly, explanations are searched using additional and preliminary experiment for the possible preferences of consumption of propagules. |
