Seed dispersal and forest regeneration in a tropical lowland biocoenosis : Shimba Hills, Kenya / Thomas R. Engel.

Tese (Ph.D.) - University of Bayreuth, 2000

The plant seed dispersal by animals is a central process for the self-maintenance and dynamics of tropical forests. This is also true for the Shimba Hills National Reserve in south-eastern Kenya, the object of this study. This work compares local endozoochory, seed predation, the disperser spectra of plants and the (diaspore) food spectra of dispersers respectively, the duration of dispersal and resulting distribution patterns, as well as the temporal fruit availability and its utilisation. Following the life-cycle of plants, the early stages in plant recruitment and their complex biocoenotic connexes are investigated. Research on post-dispersal stages includes the role and establishment of the soil seed bank, natural germination responses of seeds, and various aspects concerning safe sites of seedlings and samplings. In addition, contributions are made to the occurrence and some synecological impacts on plant maintenance of animal species, for some of which relatively little relevant information was available. Furthermore, the relevant theories and methods of the mentioned topics are critically discussed. The project is part of the research program 'mechanisms for the maintenance of tropical diversity' of the German Research Foundation. Attention will be paid to the fundamental ecological questions of this program, i.e. some stochastic versus deterministic processes, mechanisms and causalities will be uncovered. However, the main emphasis of this work is focused on seed dispersal (sensu lato), natural forest regeneration and an improved understanding of the function and maintenance of the local biocoenosis. The knowledge gained is provided in order to benefit the conservation of the Reserve. The various screenings of this study are also meant to help fill the East African gap in the global map of rarely known seed dispersal spectra in species-rich communities. The Shimba Hills National Reserve represents a coastal lowland refuge of about 220 km for over 1000 angiospermous plant species and an as of yet unknown large number of animal species. The main vegetation pattern is a mosaic of seasonal evergreen forests, forests in either stages of progress or regression as well as anthropogenic grassslands and pine plantations.