The vegetation of the Roodeplaat Dam Nature Reserve. III. Phenological observations

The phenology of a number of phanerophytes, chamaephytes, hemi-cryptophytes, cryptophytes and therophytes was studied over a three-year period and it was found that certain phanerophytes exhibited activity as early as the second half of July. Most other species commence growing and/or flowering only in September, while the flowering phase of a number of species commences only in late summer or early winter

Neighbourhood analysis of competition between two Namaqualand ephemeral plant species

By using attributes of neighbours, such as number, size and distance, investigators have developed neighbourhood competition models that are able to predict plant performance of an individual in a plant population. A non-linear neighbourhood model proposed by SiLander & Pacala (1985) was applied to performance data (i.e. total above-ground dry mass) of Dimorphotheca sinuata and Ursinia cakilefolia, two Namaqualand ephemeral species. The best neighbourhood size was sought by varying the neighbourhood size and plotting an interference index against dry mass. The non-linear model was then fitted to the data and the r2 values determined for each neighbourhood. Correlations between performance (total above-ground dry mass) and different interference indices were much higher in mixtures than in monocultures for both species. Number of neighbours seemed to be the best predictor of performance for both D. sinuata and U. cakilefolia in mixtures. In monoculture, the best correlations were obtained when the distance of the neighbours was also taken into account, Even so, these correlations accounted for less than 50% of the variation in plant mass. Although these neighbourhood models may be useful in describing the inter-individual effects of interference on Namaqualand ephemeral species, it may be difficult to apply these results in the field

Ordination of the herbaceous stratum of savanna in the Nylsvley Nature Reserve, South Africa

The purpose of the study was to determine the ecological status of representative herbaceous species with respect to environmental factors and subhabitats of which the spatial and temporal pattern could be elucidated.The basal cover of the herbaceous vegetation was determined by means of the wheel-point method. Frequency data in each of 200 1 m2 contiguous quadrats were ordinated by means of detrended correspondence analysis (DECORANA).The distribution of the species along the first axis is a function of conditions representing an open habitat with full sunlight and somewhat drier conditions to the left and a denser and/or shrub habitat with more shade and wetter, more favourable conditions to the right. The gradient along the second axis is that of undisturbed conditions with more perennials at the lower end to disturbed conditions with more annuals at the upper end. From the scatter diagrams it can be concluded that the herbaceous layer is functionally homogeneous, that it represents a seral stage and that Eragrostis pallens and Digitaria eriantha, both with the highest basal cover in the study area, are representative of a seral stage rather than of the climax. The lack of pattern in the herbaceous layer can be attributed mainly to the large number of annual and perennial pioneer and disturbance-indicating species. In a similar study Whittaker et al. (in press) concluded that the woody vegetation dominates the pattern

Wetland plant communities of the Verlorenvalei Nature Reserve in the North-eastern Sandy Highveld, Transvaal

As part of the formulation of a management policy for the Verlorenvalei Nature Reserve, a phytosociological study of the wetlands was initiated. The classification, by means of the PHYTOTAB computer program, revealed two plant communities with one of the communities divided into seven vegetation zones. A classification description and ecological interpretation as well as a DECORANA ordination is presented

Fruit polymorphism in ephemeral species of Namaqualand. VI. Intermorphic competition among plants cultivated from dimorphic diaspores

Plants raised from disc and ray diaspores of Dimorphotheca sinuata, a polymorphic annual species from Namaqualand, were grown in replacement series. There were four plants per pot with disc to ray ratios of 4:0, 2:2 and 0:4. The plants were grown under different moisture and nutrient regimes. Disc plants were more aggressive than ray plants and thus the stronger competitors. Disc plants had a higher total dry matter in mixture than in monoculture under high moisture conditions. There was no difference in production between mixtures and monocultures of the ray plants. Ray plants were influenced more by disc plants than disc plants by ray plants. Both disc and ray plants were more successful when water and nutrients were freely available. Moisture was the main factor influencing intermorphic competition

The vegetation of the Kroonstad area: A description of the grassland communities

A phytosociological analysis of the grassland vegetation data from the Kroonstad area is presented. The data set (193 relevés) was initially classified by using Twinspan, and the results refined by applying Braun-Blanquet procedures. Ten communities, grouped into four major communities, were identified and described

The physical environment and major plant communities of the Heilbron–Lindley–Warden–Villiers area, northern Orange Free State

An analysis of the physical environment and associated major plant communities of the Heilbron–Lindley–Warden–Villiers area (northern Orange Free State) is presented. Relevés were compiled in 263 stratified random sample plots. Care was taken to avoid severely degraded areas. A Twinspan classification, refined by Braun-Blanquet procedures, revealed three distinct vegetation types. These vegetation types were subdivided into seven major plant communities. A hierarchical classification, description and ecological interpretation of the seven major plant communities are presented. The easily distinguishable major plant communities should be managed as separate ecological units in order to achieve optimal utilization and conservation of the vegetation of this part of the Grassland Biome

Biomass cycles, accumulation rates and nutritional characteristics of grass layer plants in canopied and uncanopied subhabitats of Burkea savanna.

Annual biomass cycles, accumulation rates and nutritional characteristics of forage and non-forage species groups were determined in the canopied and open, uncanopied subhabitats of the herbaceous layer in Burkea africana savanna. The total amount of biomass of all species over the season was significantly greater in the open than under Burkea africana trees and Ochna pulchra shrubs. However, the amount of biomass and in-vitro diigestible organic matter of forage species was of the same order of magnitude under Burkea africana and in the open, and the amount of crude protein was in fact greater under Burkea africana trees than in the open and under Ochna pulchra in the case of forage species. The amount of biomass, crude protein and in-vitro digestible organic matter of non-forage species was greatest in the open. Biomass accumulation rate of total biomass was greatest in the open, whilst that of forage species was greatest under Burkea africana.Keywords: burkea africana; burkea savanna; crude protein; forage; grasses; herbaceous layer; nylsvley nature reserve; ochna pulchra; organic matter; plants; savanna; shrubs; south africa; subhabitats; tree

The effect of fire, with and without subsequent defoliation on the herbaceous layer of Burkea africana savanna.

A back-fire applied to the herbaceous layer during September 1978 resulted in significantly less dry matter production over the following year, compared to an unburnt area. This was largely due to the significant reduction in dry matter and basal cover of the non-forage species group which had, prior to the fire, exhibited a notable accumulation of dead material. In contrast, basal cover and dry matter production of the leafier forage species group were not significantly affected by the back-fire. On plots where the burn was followed by an 8-weekly clipping treatment, a slower biomass accumulation rate of the sward as a whole was recorded than on burnt plots allowed unchecked post-fire regrowth. The lowest rate was recorded on unburnt plots allowed unchecked growth. The burn plus 8-weekly clipping reduced the biomass accumulation rate of the non-forage species compared with the same group on unburnt unclipped plots. In a similar comparison, the rate of accumulation of forage species biomass was, however, stimulated by the burn plus 8-weekly clipping.Keywords: basal cover; biomass; burkea africana; clipping; defoliation; dry matter production; effect of fire; fire; herbaceous layer; nylsvley nature reserve; production; regrowth; savanna; south afric

A classification of the vegetation of the western Transvaal dolomite and chert grassland, South Africa

Relatively little is known about the vegetation of the western Grassland Biome in South Africa. The classification of the dolomite and chert grassland in the western Transvaal (Fa land type) forms part of a research programme on the syntaxonomic and synecological synthesis of the vegetation of the western Grassland Biome. Using a numerical classification technique (Twinspan) as a first approximation, the classification was refined by applying Braun-Blanquet procedures. The result is a phytosociological table from which two new alliances, six new associations, two new sub-associations and two new communities without syntaxonomic rank are recognized. The new syntaxa are ecologically interpreted as well as described. Associated gradients in habitat were identified by using an ordination algorithm (Decorana). This study should contribute to the present knowledge and ecological understanding of the vegetation of the western Transvaal