Seed and seedling ecology of two co-occurring ericoid fynbos shrub species
Master Thesis
1991
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University of Cape Town
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Abstract
The seed and seedling ecology of the ericoid fynbos shrubs Passerina paleacea and Phylica ericoides were studied. These species co-occur in dune fynbos and are dependent on soil seed banks for regeneration after recurrent fynbos fires. Phylica was stimulated by the heat effect of fire. The precise germination cue for Passerina could not be determined, although circumstantial evidence pointed to the role of an indirect fire effect associated with the removal of vegetation. The seed banks of both species were seasonally persistent, and were not substantially depleted during the year following seed input. Fire appeared not to kill significant numbers of seeds, but seed banks were largely, although not completely depleted during the winter following fire. Phylica appeared to lose little seed after dispersal and most seed appeared to survive for at least several years in the soil. This allowed Phylica to build up seed banks larger than the seed input in one year. Passerina produced much larger amounts of smaller seeds, most of which were lost before incorporation into the soil seed bank. These large losses were not limiting on population recruitment of Passerina af.ter fire, which was apparently limited by seedling mortality during summer drought. The recruitment of Phylica, in contrast, appeared to be limited by poor seedling establishment during the first winter after fire. This was possible largely due to germination failure, which is probably affected by the intensity of fire. Recruitment in mature vegetation was severely limited for both species, although Phylica appeared to have more potential than Passerina for recruitment in this environment. The implications of results for burning of fynbos and for commercial flower harvesting of Phylica are discussed. Differences between the species are also used for suggesting possible means of non-equilibrium coexistence.
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Bibliography: pages 140-167.
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Kilian, D. 1991. Seed and seedling ecology of two co-occurring ericoid fynbos shrub species. University of Cape Town.