Presidential Address:Vegetation deterioration in southern Africa: a research and researcher problem.

Keywords: botany; grassland science; grassland society of southern africa; presidential address; research; southern africa; vegetation; vegetation deterioratio

A comparison of some range condition assessment techniques used in Southern African grasslands.

Techniques currently used to assess range condition in the grassland biome of Southern Africa are reviewed. These indices were then used to evaluate each method in terms of sensitivity, index interpretation and efficiency, bearing in mind the objectives of each technique. The weighted key species method and degradation gradient method were found to currently provide the best indices for assessing range condition, and in this article the shortcomings of the techniques are recognized and suggestions are made for the application of these methods in different vegetation types; Techniques currently used to assess range condition in the grassland biome of southern Africa are reviewed. The methods were used to calculate range condition indices from fire-climax and climatic-climax grassland data. These indices were then used to evaluate each method in terms of sensitivity (i.e. the detection of spatio-temporal differences in index), index interpretation and efficiency, bearing in mind the objectives of each technique. The Weighted Key Species Method and Degradation Gradient Method were found to currently provide the best indices for assessing range condition. Shortcomings of the techniques are recognized and suggestions are made for the application of these methods in different vegetation types.Language: EnglishKeywords: Degradation gradient method; Grasslands; Grazing gradients; Indicator species; Ordination; Range conditions; Species responses; Techniques; Vegetation; Weighted key species method; condition indices; degradation; grazing gradient; key species; range condition; range condition assessment; vegetation types; grassland; efficiency; grassland biome; southern africa; method; objectives; degradation gradient; vegetation type; botan

Appendix:Veld en aangeplante weidingsbestuurterminologie in suidelike Afrika.

Keywords: afrikaans; botany; ecology; grazing; pasture management; southern africa; terminology; veld; veld managemen

Influence of habitat differences on the ecological grouping of grass species on a grazing gradient.

The ecological grouping (Decreaser and Increaser groups) of individual species was determined on two topographical units in the Highland Sourveld of the Orange Free State. For this purpose gradients were selected, giving special attention to fence-line comparisons, vegetation at different distances from watering points and ungrazed vegetation. The ecological grouping (Decreaser and Increaser groups) of species on a grazing gradient differed not only for different topographical units, but also for sub-habitats within a certain unit. Broad standardized groupings of species into Decreaser and Increaser groups are therefore scientifically wrong and of little practical use.Keywords: botany; decreaser species; ecotypes; grazing gradient; highland sourveld; increaser species; orange free state; ordination; south africa; subhabitat; subhabitats; units; watering point

Ecological status of species on grazing gradients on the shallow soils of the western grassland biome in South Africa.

Grasses on the shallow soils of the western grassland biome of South Africa were classified on their ecological status on the basis of their reaction to grazing. Vegetation data were gathered in such a way that those of different successional stages could be identified. An ordination technique was used to define the grazing gradient. Species abundance curves were statistically fitted to the grazing gradient and used to classify the species into decreaser and increaser categories.Keywords: bc land type; degradation; ecological status; grasses; grassland; grassland biome; grazing; grazing gradients; ordination; south africa; species abundance; succession; technique; veld condition assessment; western transvaa

Veld and cultivated pasture management terminology in southern Africa.

Keywords: botany; ecology; grazing; grazing management; pasture management; pastures; southern africa; terminolog

The use of degradation gradients for the assessment and ecological interpretation of range condition.

Multivariate procedures were used to subdivide the Southern African climatic climax grasslands of the 700-800 mm rainfall zone into relatively homogeneous grazing areas. The Euclidean distances from the first axis were used to determine the appropriateness of the degradation gradients for the assessment of the condition of a particular site. Knowledge of species response to grazing, community dynamics and recovery potential obtained through the ordination and regression studies was used to interpret the condition assessmentsLanguage: EnglishKeywords: Degradation gradients; Euclidean distances; Grasslands; Grazing impact; Homogeneous grazing areas; Key species; Multivariate procedures; Ordination; Recovery potential; Vegetation dynamics; grazing; gradients; range condition; pca; recovery; regression; procedure; degradation gradient; south afric

Developing decision support tools for rangeland management by combining state and transition models and Bayesian belief networks

State and transition models provide a simple and versatile way of describing vegetation dynamics in rangelands. However, state and transition models are traditionally descriptive, which has limited their practical application to rangeland management decision support. This paper demonstrates an approach to rangeland management decision support that combines a state and transition model with a Bayesian belief network to provide a relatively simple and updatable rangeland dynamics model that can accommodate uncertainty and be used for scenario, diagnostic, and sensitivity analysis. A state and transition model, developed by the authors for subtropical grassland in south-east Queensland, Australia, is used as an example. From the state and transition model, an influence diagram was built to show the possible transitions among states and the factors influencing each transition. The influence diagram was populated with probabilities to produce a predictive model in the form of a Bayesian belief network. The behaviour of the model was tested using scenario and sensitivity analysis, revealing that selective grazing, grazing pressure, and soil nutrition were believed to influence most transitions, while fire frequency and the frequency of good wet seasons were also important in some transitions. Overall, the integration of a state and transition model with a Bayesian belief network provided a useful way to utilise the knowledge embedded in a state and transition model for predictive purposes. Using a Bayesian belief network in the modelling approach allowed uncertainty and variability to be explicitly accommodated in the modelling process, and expert knowledge to be utilised in model development. The methods used also supported learning from monitoring data, thereby supporting adaptive rangeland management.Rangeland management State and transition model Queensland Bayesian belief network Adaptive management Decision support

Ordination of land types in the Karoo Region into reasonably homogeneous farming areas based on vegetation and environmental factors.

The 291 preliminary land types in the Karoo Region formed the basis for the demarcation of the 144 Reasonably Homogeneous Farming Areas (RHFAs). The land types were firstly reduced to 23 Floristic Climatic Regions (FCRs) according to character species for certain macroclimatic conditions. The character species were identified by means of computer classification and ordination techniques (PHYTOTAB, TWINSPAN and DECORANA). About 22 soils forms and numerous soil series were found in the Karoo Region. Based on differences in the inherent veld production potential and erodibility of the different soils, as well as differences in slope nine Veld Soil Potential Classes (VSPCs) were synthesised. The land types in each of the FCRs were, lastly, consolidated according to their similarity in terms of macroclimate and dominant topographical units and VSPCs, into RHFAs.Language: EnglishKeywords: Character species; classification; Computer classification; decorana; Environment; environmental factors; FCRs; floristic climatic regions; Homogeneous farming areas; karoo; Karoo Region; land types; ordination; Ordination techniques; phytotab; production; production potential; Reasonably Homogeneous Farming Areas; RHFAs; slope; soil series; soils; south africa; technique; twinspan; vegetation; veld soil potential classes; VSPC