G.J. Bredenkamp

On the origin of northern and southern hemisphere grasslands

The origin of the grassy habit during the Eocene and the development of C4 grasses during the Miocene/Pliocene boundary are discussed before the origin of primary and secondary grassland in Eurasia and North America are discussed. A comparison shows that both Northern and Southern hemisphere primary grassland originated due to climatic changes to drier conditions during the end of the Eocene, and that modern grassland vegetation types can be traced back to the Oligocene. The Eurasian steppes becomes more fragmented towards the west and south and relicts of primary grassland exists only in the most xerothermic localised habitats in central and western Europe. Secondary grassland clearly due to manmade deforestation, started with the spread of Neolithic husbandry. Southern African grasslands were however not only determined by droughty conditions, but cooler conditions at high altitudes are one of the major driving forces that prevent colonisation by trees of a generally tropical origin.

A reappraisal of Acocks’ Bankenveld: origin and diversity of vegetation types

The great variety of vegetation types found in the Bankenveld was assessed by randomly selecting 220 releves, representing the major vegetation types, from 23 phytosociological studies from data stored in the TURBOVEG database at the University of Pretoria. These releves were classified by using TWINSPAN and then refining the result in MEGATAB. The phytosociological table was reduced to 120 releves which represent 16 major vegetation types found in the Bankenveld. An assessment was made to relate the vegetation types to various phytochoria and it is concluded that the Bankenveld has definite floristic affinities to the grassland of the interior plateaux of South Africa, the savannas of the Sour Bushveld and Sourish Mixed Bushveld, the Drakensberg Afromontane vegetation and the Kalahari vegetation.

Phytosociology of the B land type in the Newcastle – Memel – Chelmsford Dam area

This study forms part of the Grassland Biome Project. The results of a numerical classification (T winspan ) of 74 releves compiled in the Bb and Bd land types of the Newcastle – Memel – Chelmsford Dam area, were refined by Braun-Blanquet procedures. The analyses revealed five major plant communities which may be divided into seventeen plant communities. A hierarchical classification, description and ecological interpretation of the plant communities are presented.

The phytosociology of the grasslands of the Ba and Ib land types in the Pretoria–Witbank–Heidelberg area

An analysis of the plant communities of the grasslands of the Pretoria–Witbank–Heidelberg area is presented. Releves were compiled in 148 stratified random sample plots. A TWINSPAN classification, refined by Braun-Blanquet procedures, revealed fourteen plant communities, and a hierarchical classification, description and ecological interpretation of these plant communities are presented. Each of these plant communities may be regarded as an entity with a unique species composition, and with specific environmental relationships and an inherent forage production potential. The identification, classification and description of these plant communities are not only important for management purposes, but also for the preservation of biotic diversity.

The Eucleo divinori - Acacietum nigricentis, a new association from the calcareous bottomland clays of the Manyeleti Game Reserve, Eastern Transvaal Lowveld, Gazankulu, South Africa

As part of a vegetation survey programme for nature conservation areas in South Africa, a survey of the plant communities of the mesic calcareous bottomland clays in the Manyeleti Game Reserve was undertaken. The Eucleo divinori — Acacietum nigricentis, a new association, is restricted to these soils. From a Braun-Blanquet analysis of the vegetation, two new subassociations, each with two variants, were identified and described. A quantitative assessment of the woody component of each syntaxon is presented. Ordinations based on the floristic and habitat data revealed the position of the syntaxa on an environmental gradient.

The vegetation syntaxa of the Ba land type in the western Transvaal Grassland, South Africa

Relatively little is known about the vegetation of the western Grassland Biome in South Africa. The classification of the vegetation of the Ba land type forms part of a research programme on the synthesis of the vegetation of the western Grassland Biome. The result of the numerical classification obtained by T winspan was refined by applying Braun-Blanquet procedures. The result is a phytosociological table where one new order, three new alliances, nine new associations and four new subassociations are recognized. The new syntaxa are ecologically interpreted as well as described.

The Sub-humid Warm Temperate Mountain Bushveld plant communities of the Pretoria-Witbank-Heidelberg area

An analysis of the plant communities of the Sub-humid Warm Temperate Mountain Bushveld of the PretoriaWitbank-Heidelberg area is presented. Releves were compiled in 44 stratified random sample plots. A T winspan classification, refined by Braun-Blanquet procedures, revealed six plant communities and four variations which can be regarded as distinct ecological units. A hierarchical classification, description and ecological interpretation of the six plant communities and variations are presented. Each of these plant communities may be regarded as a unique entity with its own species composition and specific environmental relationships. The identification, classification and description of these plant communities are not only important for vegetation management purposes but also as a scientific basis for the compilation of policies for the preservation of biotic diversity. ’n Analise van die plantgemeenskappe van die Sub-humiede Warm Gematigde Berg-Bosveld binne die Pretoria–Witbank–Heidelberg studiegebied, word aangebied. Releves is in 44 gestratifiseerde ewekansig gekose monsterpersele saamgestel. ’n T winspan klassifikasie is op die floristiese data uitgevoer, waarna die tabel deur middel van Braun-Blanquet prosedures verder verfyn is. Ses plantgemeenskappe en vier variasies met elk ’n eie floristiese samestelling en produksiepotensiaal is sodoende onderskei. Hierdie gemeenskappe toon elk verwantskappe met sekere omgewingsfaktore en kan dus as aparte ekologiese eenhede beskou word. ’n Hierargiese klassifikasie, beskrywing en ekologiese interpretasie van die plantgemeenskappe en variasies word verskaf. Die identifisering, klassifisering en beskrywing van hierdie plantgemeenskappe is nie net belangrik vir veldbestuursdoeleindes nie, maar ook as wetenskaplike basis vir die opstel van ’n beleid vir die bewaring van biologiese diversiteit.

The vegetation of old-fields in Transkei

The aim of this paper is to identify, classify and describe plant communities on abandoned, formerly cultivated, old fields in the former Transkei (Eastern Cape Province) and to derive hypothetical succession pathways. Forty two releves, made in representative areas with abundant old-field lots, were classified and ordinated using standard methods of numerical vegetation data analysis. Three new associations were recognised, namely the Richardio brasiliensis-Eragrostietum planae. the Trichoneuro grandiglumis-Anstidetum congestae and the Tageto minutae-Cynodontetum dactyli. Within the Tageto minutae-Cynodontetum dactyli, two new sub-associations were recognised, namely cyperetosum esculenti and typicum. The most important coenocline spanning the young Tageto minutae-Cynodontetum dactyli and the old Richardio brasiliensis-Eragrostietum planae, correlated with the age of old-fields. We postulate that this coenocline might represent the main succession trend within the mesic old fields in Transkei The Trichoneuro grandiglumis-Aristidetum congestae characteristic of dry sandy soils does not participate in this cline.

A Braun-Blanquet reclassification of the Bankenveld Grassland in the Lichtenburg area, south-western Transvaal

The Bankenveld Grassland in the Lichtenburg area was reclassified using T winspan classification and subsequently Braun-Blanquet procedures to refine these results. In two phytosociological tables, two Major Communities, six Communities and eight Variants are identified and described. This new classification can now be included in the comprehensive phytosociological and syntaxonomical synthesis of the western Transvaal Grassland.