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Although the Alexandria coastal dunefield comprises over 80% bare sand, diverse biota are supported in a number of discrete vegetated habitats. The most important of these are the 277 bushpockets, which average about 1 ha in area. The bushpocket vegetation composition is related to the geomorphology of the pocket and maintained in an early successional stage by sand movement. The bird communities are a function of the size of the bushpockets. In contrast, the small mammal diversity is independent of the bushpocket size, but is a function of vegetation structure. Birds and mammals play key roles in the bushpockets, with the endemic dune gerbil contributing to elevated seed predation compared with that of vegetation inland of the dunes. Birds and mammals disperse seeds of 17 and 29 plant species, respectively, to the pockets, the bushpig and vervet monkey being the most important dispersers. These animals also transport significant amounts of nutrients. The birds and mammals dispersing seeds and nutrients are largely transient visitors to the dunefield from the hinterland. A number of alien plant species are also dispersed by this zoochory, potentially threatening the ecological integrity of the dunefield. The bushpocket plant communities are therefore dependent on the activities of the birds and mammals, and in order to maintain these communities it is necessary to ensure the activities of these key species in the dunefield, indicating that dunefield management should include management of the animals and plant communities adjacent to the dunefield. |
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