Aspects of the structure and functioning of the vegetation of the Hlatikulu Vlei.

Abstract

Hlatikulu Vlei, situated in the foothills of the Natal Drakensberg, is one of the priority wetlands in KwaZulu-Natal, occupying an area of 733 Hectares. The importance of Hlatikulu Vlei lies in its functions to store water, regulate stream flow and attenuate floods, as well as to provide suitable habitat for wildlife and grazing for livestock. Hlatikulu Vlei is a threatened system and has suffered the effects of human mismanagement. Forty-nine percent of the vlei has been classified as disturbed or destroyed, mainly due to the construction of two large dams and past drainage of vlei to facilitate pasture planting. The effects of grazing and fire on the plant communities has been considerably less. Vegetation communities at Hlatikulu Vlei have similarities with those at Ntabamhlope Vlei. The main plant communities present at Hlatikulu Vlei are: vlei grassland, sege-meadows, bulrushes and reedswamp. Species compositions of the mixed sedge and grass sedge-meadow community have a notably higher species diversity than similar communities sampled at Ntabamhlope Vlei and the mires at Highmoor. Soil type and moisture content are shown to be the most significant environmental factors determining the distribution of plant communities and species within the vlei. A wetland re-establishment and rehabilitation programme in the Hlatikulu Crane and Wetland Sanctuary has been effective in allowing many wetland plants to become reestablished. The sanctuary communities bear greater similarity to the sedge and rush sedge-meadow community, than the mixed sedge and grass sedge-meadow communities that were originally present. This is also reflected in the seed bank. All three Southern African crane species (Blue, Wattled and Crowned Crane) and fourteen species of waterfowl have been recorded in the Hlatikulu Crane and Wetland Sanctuary since the wetland rehabilitation programme. The waterfowl play a role in the dispersal of seeds into the sanctuary, particularly those of Schoenoplectus decipiens and Eleocharis dregeana and are in part responsible for the return of certain wetland plants to the sanctuary. The flooding of soils, the fluctuating water level and the soil type related to hummocks and to channels are shown to be responsible for the location of Cyperus denudatus, Arundinella nepalensis and Aristida junciformis in differing positions in the channels and on the hummocks and are also responsible for the maintenance and functioning of the hummocks and channels. Seed banks on the hummocks are similar to seed banks in the channels, however the extant vegetation on the hummocks is distinctly different to that in the channels. Certain species represented in the channel seed bank are being excluded from surviving to maturity.