A comparative study of the plant ecology of three estuaries : Mgeni, Mhlanga and Mdloti.
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Date
1986
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Abstract
The vegetation of the Mgeni Estuary, Mhlanga Estuary and Mdloti Estuary
was analysed according to the Braun-Blanquet phytosociological method
using quadrats of 4m2 and 25m2 in area placed subjectively and the
Point-Centred Quarter method with points chosen whilst traversing. A
classification of plant communities is given. These are described
floristically and related to habitat variables. Indicator species of
the climatic climax of coast forest occur within the study area. The
absence of coast forest is ascribed to low altitude, tidal inundation
and the consequent effect of salinity, basal inundation resulting in a
high water-table and the influence of man. The floodplain of the Mgeni
Estuary is dominated by mangrove vegetation comprising mainly Bruguiera
gymnorrhiza and Avicennia marina whereas vegetation established on
Athlone Island is dominated by mesophytic thicket comprising mainly
Schinus terebinthifolius, Lantana camara, Chromolaena odorata and
Cardiospermum grandiflorum. The floodplain of the Mhlanga Estuary is
dominated by Phragmites australis. The shores of the Mdloti Estuary are
dominated by Barringtonia racemosa, Phragmites australis and Echinochloa
pyramidalis. Major differences in vegetation patterns of the three
systems are related primarily to the differences in the open nature of
the river mouths. This is controlled mainly by river flow and longshore
drift. Differences in vegetation patterns within an estuary are
dependent on differences in tolerances to salinity, basal inundation and
shade, together with variations in altitude and edaphic factors and
competition between species. Generally soils of Mgeni Estuary had higher
contents of small sized fractions, bulk densities, reserve acidities, organic matter, salts and exchangeable bases and lower pH than soils at
Mhlanga Estuary and Mdloti Estuary. Differences exist between mangrove
and non-mangrove soils at Mgeni Estuary and differences between the non-
mangrove soils at the three study sites. Major differences in soil characteristics are as a result of differences in tidal inundation,
geogenetic parameters and biotic factors. Information on topography,
hydrology, geology, climatic factors, biotic factors and historical
background of the area is given. A check-list of vascular plants is included. The work is illustrated by 44 figures.
Description
Thesis (M.Sc.)-University of Durban-Westville, 1986.
Keywords
Theses--Botany., Plant ecology--KwaZulu-Natal., Coastal ecology--KwaZulu-Natal., Estuarine ecology--KwaZulu-Natal., Mangrove ecology--KwaZulu-Natal.