The evaluation of the state of grass species composition was conducted as an attempt to confirm the survey conducted by the United Nations Convention to Combat Desertification (UNCCD), where the Zeerust District was identified as an area with serious degradation problems. Quantitative data was obtained through botanical surveys (April 2001-February 2002) and verified by household surveys (March 2001-April 2002). Study sites included Braklaagte, Dinokana, Doomlaagte, Serake and Supingstad, with benchmark sites in Madikwe Grune Reserve. Between 6-12 survey points per site were selected after consultation with local Agricultural Extension Officers and communities. Survey points included the range of veld condition between bush encroached and severely denuded and eroded areas. The results indicate 12.3 % to 45.1 % loss of vegetal cover. Resistance above 2 000 ohms, base saturation exceeding 100 % and pH values below 5.5 are evidence of soil degradation. The general profile of the fanning household is that of an aging adult community, with however, a relatively good knowledge of fanning practices. 52 % of the respondents depend on the government pension fund as a source of income. 60 % of the respondents use crop fanning products strictly for household purposes. Poor economic return from fanning activities has resulted in overutilization of the herbaceous layer with consequent changes of grass species composition towards retrogression and the establishment of woody species. This environmental degradation is a serious risk to long-term sustainable development. It is therefore, recommended that environmental education programmes and ecological restoration projects be started in degraded areas. The government should set up and enforce land-use policies. Community participation should be encouraged in all land care activities. Land degradation is a real social problem that must be tackled before many people's aspirations of a better life are met. / Thesis (M.Sc. (Biology) North-West University, Mafikeng Campus, 2003

A thesis report submitted in partial fulfilment of the requirements for the degree in Master of Science in GIS and Remote Sensing Faculty of Science University of the Witwatersrand. March 2017 Johannesburg, South Africa / Grass nitrogen is the main indicator of forage conditions in a rangeland environment. The main objectives of the research were to map the quality and quantity of common grass communities and to predict Nitrogen (N) content across different grass communities. A machine-learning algorithm of Support Vector Machines (SVM) was tested in the mapping of grass quality and quantity. An overall accuracy of 72.68% was achieved for the mapping analysis which demonstrated the capability of the Sentinel-2 10m resolution in discriminating the spectral properties of different grass communities. The foliar nitrogen was predicted using univariate regression, stepwise multiple linear regression (SMLR), multivariable regression methods, partial least square regression (PLSR) and random forest (RF). Foliar N was predicted using multivariate regression models; the best model was selected based on the highest coefficient of determination (R2) value, and the low root mean square error (RMSE). The best RF model for foliar N estimation was based on the simple ratio (SR) index because the model attained the highest prediction accuracy of 35%. The study demonstrates the applicability of Sentinel-2 MSI utility in mapping and estimation of leaf N at a landscape scale .The results of both regression models (univariate and multivariate) such as random forest and partial least squares indicated that the inclusion of the Sentinel-2 MSI red edge bands provides an opportunity to accurately map and estimate leaf bio-chemical composition using remote sensing techniques. / MT 2017

Increased functional diversity has been linked to an increase in ecosystem level processes (ELPs), such as productivity, ecosystem reliability and invasion resistance. However, there has been no exact definition of functional diversity and it is not known which indices are appropriate for its measurement. Consequently, continuous indices have rarely been applied in examination of relationships between functional diversity and ELPs and little is known of the mechanisms linking functional diversity to ELPs. This thesis begins by providing an exact definition of functional diversity, identifying its primary components and devising appropriate continuous indices for the measurement of these components. These indices are used to examine relationships between functional diversity and three ELPs - biomass production, the reliability of biomass production and invasion resistance. Initially these examinations are conducted using a mechanistic community assembly and dynamic model. This model is based on physiological and morphological character data for species occurring in the short-tussock grassland communities of the Luggate field experiment, in the southern South Island, New Zealand. Finally, relationships between functional diversity, mean annual community cover and the reliability of cover are examined in the Luggate field experiment. Functional composition (i.e. the actual functional characters of the species within a community) appeared to exercise the greatest influence on ecosystem reliability in the community assembly and dynamic model. However, there was evidence that functional diversity increased the reliability of productivity via the co-variance effect. Functional composition also exercised the greatest influence over mean annual productivity in the model, almost completely accounting for the negative relationship between functional diversity and mean annual productivity. These results are respectively analogous to the positive and negative selection effects seen in species richness / ELP relationships. Both functional diversity and functional composition influenced community invasion resistance in the model. Here, increased functional diversity acted to increase community resistance to invasion. In the Luggate field experiment, neither functional diversity nor functional composition was related to mean annual cover, though species richness was positively related to it. Increased functional diversity acted to increase the reliability of cover. However, this did not appear to occur via the co-variance effect, but as a result of increased functional diversity increasing consistency in the species composition of experimental plots through time. These results demonstrate that studies examining functional diversity must account for the effects of species identity. A framework is proposed to accommodate selection effects associated with functional diversity / ELP relationships. The usefulness of the co-variance effect as a testable mechanism linking functional diversity to ecosystem reliability in the field is questionable, as there is no objective way of measuring it.

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Soil erosion and vegetation destruction have reached serious proportions in disturbed areas of the montane grasslands of the Natal Drakensberg. Little is known of the inherent ability of indigenous grasses to produce viable seed and establish seedlings for rehabilitation programmes. This study examined the effects of fire and small-scale disturbance on the seedling dynamics of the dominant grass, Themeda triandra Forssk. Annual seed production of T. triandra increased with length of burning rotation, ranging from 21 seeds m⁻² in the annual winter burn to 485 seeds m⁻² in the five-year burn. High predation of seeds (70-98%) and low viability (37% in 15 month-old seeds) contributed to the poor representation of T. triandra in the seed bank when compared to the aboveground vegetation. Seedling densities and survival were monitored by mapping quadrats at six-weekly intervals from November 1986 to September 1989. Highest establishment of T. triandra was recorded in the biennial spring burn treatment (< 184 seedlings m⁻²). Microclimatic studies of the seedling environment demonstrated that increases in photosynthetically active radiation following burning, and high soil moisture associated with accumulation of litter, favour seedling establishment. The main constraint to seedling establishment was high mortality in winter which resulted in a 1% survival of seedlings of T. triandra during the three-year study. This indicates that in the fire-climax grasslands of the study, seedlings contribute little to the population structure. The most significant factor contributing to low survivorship is intraspecific competition between seedlings. Spacing of seedlings in rehabilitation programmes is therefore a critical factor in optimizing seedling establishment. Analysis of the fate of seeds of T. triandra between their production and establishment, showed that the main constraints for seedling establishment were predation, low viability and poor germination. A population model, based on transitions between seeds, seedlings and mature tufts, predicts that a biennial spring burn is the optimal treatment for maximising both seedling establishment and vegetative growth. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland by Peter Carlson Chairperson of the Supervisory Committee: Professor Lawrence Flanagan Department of Biological Science Eddy covariance measurements were carried out to document the seasonal and inter-annual variation in CO2 flux in a mixed prairie grassland. There was very different net ecosystem carbon exchange between the two years of study. In 1998 the maximum net ecosystem carbon exchange was 4.95 g C m-2d-1, compared to 2.50 g C m-2d-1 in 1999. The most important environment control on CO2 uptake was volumetric soil moisture content through its affect on leaf area index. There was evidence of stomatal limitation of CO2 uptake, during periods of atmospheric drought. The total seasonal net ecosystem carbon gain for 1998 was 190.0 g C m-2, compared with 46.8 g C m-2 in 1999. This grassland is a large carbon sink in a growing season of above normal precipitation. In a year of normal summer precipitation, this grassland is a small carbon sink, replacing slightly more carbon than is lost through winter respiration. / xi, 99 leaves : ill. ; 28 cm.

Although controlled burning has been used to manage Highland Sourveld grasslands, little was known of its effects on the vegetation. This study examined the effects of past fire treatments on veld condition, species composition, dry matter production, quality and canopy recovery growth rates of these grasslands. Also, six techniques of estimating the species composition of grasslands were compared in order to decide on a standard technique for monitoring these grasslands. From this work it was concluded that the wheel point method is the most satisfactory. Veld condition scores were significantly lower in grassland protected from fire than where veld had been burnt or burnt and grazed at regular intervals. Frequent defoliation was found to maintain the grassland composition largely unchanged over a period of 30 years. Individual species were, however, found to react strongly to defoliation frequency. Plant demographic studies were therefore carried out to explain this differential response to burning. Three Decreaser and two Increaser I species were studied. In all species examined, recruitment of secondary tillers was stimulated by regular burning, each species being well adapted to a regular fire regime. Differential responses to burning were best explained by the combined effects of the different reproductive capacities and mortality rates of tillers of these species. A biennial spring burning regime was shown to be most suitable for maintaining the most important grass species at their present levels of abundance. Annual winter and biennial spring burning did not result in significant differences in dry matter production. Maximum net productivity was approximately 230 g/m² in both treatments, placing them amongst the more productive areas of Southern Africa. Examination of canopy recovery growth rates showed that there is little difference in the percentage canopy cover at the end of the growing season when veld is burnt annually in winter or biennially in spring. However, differences in season of burn resulted in exposure to erosive forces at different times of the year. The results of this investigation have highlighted the importance of regular burning during the dormant period in the montane grasslands of Natal. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1985.