n Plantekologiese Studie van die Manyeleti-Wildtuin

Abstract

The need for a scientifically based wildlife management programme for the Manyeleti Game Reserve, and the need for botanical surveys in conserved areas, which are also compatible with the broad classification of the vegetation of South Africa, led to the plant ecological investigation of the Manyeleti Game Reserve. The main objective of the study was to classify the vegetation of the study area according to the Braun-Blanquet technique on the basis of floristic composition. In this way it was also possible to identify, characterize, interpret ecologically, and describe the plant communities. The study area is situated in the Transvaal Lowveld, is the only proclaimed nature reserve in the Gazankulu homeland and covers approximately 22 700 ha. Archaian granite covers the greater part of the study area, but a broad dolerite dyke intersects the western part. The Reserve is on an undulating plain with a slight fall to the east, is situated at an altitude of 350 to 450 m and is intersected by numerous dry river beds. According to the Koppen classification, the area has an arid, warm climate, with the dry season in winter. Climatic data were obtained largely from nearby weather stations. The average temperature just exceeds 20°c, and the average rainfall is 614 mm per annum. By using aerial photographs, the study area was divided into nine fairly homogeneous physiographic/physiognomic units in which 264 sample plots were distributed in a stratified random manner. A complete floristicsurvey, a structural survey of the woody vegetation and a habitat survey, the latter including a number of quantitative physical and chemical properties of the soil were done in each sample plot. From these data a hierarchical classification of the vegetation was synthesized, using the Braun-Blanquet technique. Seven associations, 14 sub associations, 24 variants and three other plant communities, without syntaxonomical rank, were identified. They were characterized floristically and structurally, and interpreted ecologically, by means of the vegetation and habitat data. This classification was supported by the results of a numerical Cluster Analysis and a Principal Components Analysis on floristic data. However, the results of the ordination also elucidated the relationships and transitions between the plant communities and indicated that the vegetation in fact represented a broad continuous gradient. The discussion of the relationships between the plant communities and the habitat was, in addition to the Braun-Blanquet analysis, supplemented by results from a numerical Cluster Analysis and Principal Components Analysis of quantitative habitat data. The woody structure of each plant continuity was analysed and described by means of canopy cover per height class, density per height class and canopy-spread cover per height level. In an independent structural classification, by means of Cluster and Principal Components Analyses of the performance values of the height classes, a relative value calculated from cover and density values, the vegetation was divided into six structural veld types. The reactions of the individual species in relation to 27 quantitative soil characteristics were analysed according to the Ecological Profiles technique. A list of all species collected in the study area is included. This study resulted in an efficient classification of the vegetation, linked with a reliable ecological interpretation. The results may serve as a basis for the compilation of a wildlife management programme