| Summary: | This study was conducted to determine if, and how, over storey
proteoid shrubs affect the species richness of a southern Cape
mountain fynbos community. Protea eximia, P. lorifolia and P.
repens were the dominant overstorey shrubs in the community
studied.
The percentage canopy cover and density of overstorey protea
shrubs before a fire were regressed against the a-diversity of
understorey species after a fire, for spatial scales ranging
from 1 - 100m². High canopy cover percentages (≥ 50%) and high
densities (≥ 30 plants per 100m²) of overstorey proteas before
a fire enriched the a-diversity levels of understorey species
after a fire. The spatial scale at which α-diversity was
measured affected results. The number of understorey species at
a site, where overstorey proteas were absent for several fire-cycles,
was compared with those where overstorey proteas
persisted. The number of understorey species was least where
the overstorey proteas were lacking for several fire-cycles,
but results also depended on the spatial scale at which α-diversity
was measured. The basal cover percentage and density
of sprouting understorey species of two sites, burned at
several short (6 year) fire-cycles and where overstorey proteas
were lacking, were compared with those of an adjacent site
which was not burned for 28 years and where the overstorey
proteas persisted. Where several short fire-cycles eliminated
the overstorey proteas, the basal cover percentage of
understorey sprouters was approximately 32% higher than where
the overstorey shrubs persisted. The number of understorey
species in dense clumps of understorey sprouters was contrasted
against those on 0.25m² quadrats located in the open and under
burned skeletons of overstorey protease In dense clumps of
sprouters the mean number of understorey species was less than
half of that for quadrats located in the open, or for quadrats
located under the burned protea skeletons. Species specific
competitive interactions amongst overstorey protea and
understorey sprouter species were examined for several pyric
successional stages. Competitive interactions between
overstorey proteas and understorey sprouters were evident in
all pyric successional stages.
Results indicate that the overstorey proteoid shrubs are
important to restrain the competitive ability of understorey
sprouters, to prevent homogeneity in post-fire regeneration
niches and to amplify within-community patchiness of
understorey species, which ultimately enhances the species
richness of fynbos communities. === Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.
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