The quantification of rangeland condition in a semi-arid grassland of southern Africa

The degradation gradient technique was used to quantify rangeland, condition in areas ranging from poor, trampled areas close to watering points to well managed areas in a semi-arid, sweet grassland of southern Africa. Ecological values were linked to species by means of their individual positions on the degradation gradient. These species were further classified according to ecological index values. Identification of indicator species for purposes of rangeland condition assessment was done by using the correlations between the relative composition and the rangeland condition value of a species. Index values and Gaussian distribution curves were used in calculations to determine rangeland condition. The accuracy of these methods was tested and the best results were obtained by using the species curves of Themeda triandra and other species which dominate at other positions along the gradient. The advantage of this technique lies in its simplicity and ease of use. Another advantage is the fact that only the most important indicator and dominant species in the study area are used to determine rangeland condition.     

A study of animal production under different grazing regimes in the False Upper Karoo at Grootfontein

Three systems of animal production on the fragile Karoo veld, i.e. multi-paddock rotational grazing, pauci-paddock rotational grazing and continuous grazing were studied. Of these systems, multi-paddock rotational grazing gave the best results with continuous stocking resulting in the worst. All three systems studied had long histories of both continuous stocking- and of pauci-paddock rotational grazing. The veld, under both these previous systems of management has stabilised, but at different seral stages. The continuously stocked range stabilised in the early developmental seral stage, consisting mainly of annual grasses. The veld under pauci-paddock rotational management stabilised in the early to mid-developmental seral stage, consisting mainly of perennial grasses. Experimentation on veld in a stable condition is a prerequisite if valid conclusions in respect of rotational grazing and continuous stocking are to be drawn. Rotational grazing on overgrazed veld will result in poor animal performance, while it is generally accepted that continuous stocking on pristine veld will result in excellent animal performance for a number of years. Multi-paddock rotational grazing outperformed both pauci-paddock rotational grazing as well as continuous stocking on both types of veld. This is surprising taking into account the mid-seral stage condition of the vegetation. This supports the argument that with improved veld management, an improved production potential is possible on veld even in a degraded or current condition.     

The relation between canopy spread cover and the aboveground available phytomass of Nama Karoo subshrubs and grasses

The canopy spread cover of Karoo bushes and grasses in the Nama Karoo was measured and related to the aboveground phytomass available to the grazing animal. A correlation coefficient of r = 0.7456, calculated for Karoo bushes, indicates that this method can be used to non-destructively estimate available phytomass. This in turn can be used for the prediction of current grazing capacity in areas where Karoo bushes are dominant in the vegetation. In the case of the Karoo grasses, a rather loose definition and interpretation of the canopy spread cover, led to a low correlation coefficient, r = 0.5662. This renders the present method largely unsuited for available phytomass estimations to be used in further predictions of grazing capacity in the mountainous areas where the studied grasses are dominant in the vegetation. In the more arid areas, however, the method can be used to advantage.     

Drafting a Conservation Blueprint: A Practitioner's Guide to Planning for Biodiversity — Craig R Groves 2003

Individual forage species were appraised in varying distances along transects radiating from the water points of the ranch and traditional cattle post management systems. Measurements of plant height were used to assess the degree of forage species utilisation by livestock around water points. Livestock use forage plants more heavily near water points and the degree of use is more pronounced in the traditional cattle post areas, compared to ranch grazing. Utilisation of annual plants occurring at the 0m zone from water was greater than that of the same plant species growing at further distances. Periodic closure of water points aimed at reducing grazing pressure has been indicated as a method to promote production of forage around water points. With the exception of Panicum maximum, the abundance of which was low or non-existent in both management systems, Digitaria eriantha was the most utilised grass by livestock, followed by Schmidtia pappophoroides and Eragrostis lehmanniana. Stipagrostis uniplumis, one of the dominant grasses in the Kalahari Sandveld, exhibited a weak tendency to decline as distance from water increased. It was observed that high forage utilisation rates coincide with drought periods, implying that correct stocking rate adjustments should always match the available forage. Forage utilisation from water points in the traditional cattle post areas extended beyond 4 000m, especially during the dry periods.     

Impacts of non-selective grazing on cover,composition, and productivity of Nama-karoo grassy shrubland

The non-selective rotational grazing system has undergone a long and controversial development. The merits of this grazing system, where relatively large numbers of livestock are herded into numerous small paddocks for short timespans with long rests between grazings, have not been formally evaluated in a long-term monitoring experiment in the Karoo. In this study we used exclosures (controls) on a 7 000 ha farm in the Central Lower Karoo, camped into approximately 50-ha paddocks, to evaluate the impact of this grazing system on certain vegetation parameters. We report on the first four years of monitoring, after each of four replicate paddocks had received four treatments (one treatment = 40 - 60 Large Stock Unit grazing days per hectare over a period of 2 - 16 days). Concentrated defoliation with concomitant trampling, dunging, and urinating did not influence the perennial species composition, and cover of this grassy, semi-arid shrubland. Changes over time in plant composition, and cover are explained by annual, and short-term (e.g. quarterly) rainfall rather than by grazing impacts. Ephemerals were not favoured by this grazing system, but litter was more abundant in the treatment than the control areas. The dominant grass, Eragrostis lebmanniana, and shrub, Pentzia incana, are resilient to this defoliation regime, and show signs of compensatory growth. As yet there is no evidence that non-selective grazing increases diversity, but the severe defoliation and trampling may enhance the biomass turnover rate, resulting in more vigorous, and productive plants in the grazed areas. Diversity is unlkely to change rapidly in response to grazing, largely because of the persistence of grazing-tolerant perennials. Concentrating mixed herds of livestock onto small areas with lengthy rests can be a useful tool for 'kick-starting' moribund karoo veld into greater productivity. Several of the impacts hold potential for restoring the rangeland quality of degraded areas, but this needs to be tested.     

Dry matter yield and nutritional value of companion crops,intercropped with maize,for grazing purposes in northwestern KwaZulu-Natal

The northwestern part of KwaZulu-Natal (KZN) in South Africa is suitable for sheep farming as well as crop production. However, there are some constraints to animal production due to the low quality of natural vegetation during winter. Alternative winter feeding strategies have been suggested from research conducted in similar vegetation types in other parts of South Africa. Grazing maize is a potential alternative fodder source but its low crude protein might be a limitation to acceptable livestock production. This preliminary study investigated the potential of inter-cropping maize with high protein content crops for providing sheep with fodder of acceptable quality during winter in northwestern KZN.

Raphanus sativus (Japanese radish), Ornithopus sativus (serradella) and Vicia dasycarpa (grazing vetch) showed promising results in terms of dry matter yield and nutritional value. The production of Pennisetum glaucum (babala) and Avena sativa (oats) was relatively high. However, the nutritional value of both these species was marginal. Glycine max (soybeans) and Lablab purpureus (dolichos) showed good and above required nutritional properties, but dry matter yield was low.     

Precision and accuracy of sward height distributions

Double normal distributions can be used to resolve many sward height frequency distributions into two components representing the 'short' (patches) and 'tall' (non～patches) areas in the sward. The effect of sample size on the precision and accuracy of parameters of sward height distributions was examined by drawing sub-samples (n=10) of increasing sample size (50 to 1 000) from simulated height data (n=10 000) from three different, typical height distributions, viz. normal (ungrazed), bimodal (leniently grazed) and positively skewed (intensely grazed). The coefficient of variation of components of all three distributions decreased sharply with increasing sample size and CVs for all means were <15% with 200 height measures, and <10% for all means, with the exception of the 'tall' mean in the bimodal distribution, at a sample size of 100. At a given sample size, proportions in the two components were less-precisely measured than the means, especially when the components are equally represented in the population (i.e. bimodal), where 500 measurements are required for a precision of 15%. Accuracy also increased with sample size, and with 400 samples, deviations were within 10% of the true values for most parameters of the three distributions. A sample size of 200 is recommended for quantifying the mean height of 'short' and 'tall' components of the sward whereas 400-500 samples are required to precisely estimate their relative proportions.     

Influence on a North‐Eastern Sandy Highveld sward of winter utilization by sheep

North‐Eastern Sandy Highveld was utilized selectively by sheep grazing alone in winter with a supplementary lick. Winter utilization in four consecutive years had no detrimental effect on production, cover or seed production but care should be exercised in recommending this practice because of the tendency to start “winter” grazing in the critical autumn months and to continue grazing into spring.     

Patch grazing of Tall Grassveld by cattle after a spring burn

Patterns of herbage removal by rotationally stocked cattle (at a density of 4.85AUE ha^-1) on initially structurally homogenous Tall Grassveld were examined over a single season. Three unreplicated camps were stocked early (29 days), at the recommended '10-15cm' sward height (44 days), and late (80 days) after a spring burn. Temporal change in the spatial distribution of herbage in each treatment was described by intensive measurement of compressed sward height (CSH) with a disc pasture meter and analysed with parametric and spatial statistics. Grazing pressure at the start of the grazing was highest in the early graze, intermediate at the recommended, and least in the late graze treatment because of variation in initial herbage mass related to period of deferment after the burn. The early graze paddock was most spatially uniform and the late graze paddock the most uneven and patchy before grazing. Such initial conditions significantly affected subsequent herbage removal patterns: the greater the amount and spatial variability of herbage accumulated before grazing, the greater the chance for patches to develop through area-selective grazing. The early graze paddock was utilised non-selectively during the first two grazing periods but similar to other treatments, became patchier with time. Spatial pattern, a mosaic of short, intermediate and tall patches, peaked in late summer and was most pronounced in the late graze treatment. Intensive, early stocking after a burn is recommended for minimising intraseasonal development of patches and efficient use of high-quality forage available after a burn.     

The influence of tree density on the grass layer of three semi-arid savanna types of southern Africa

The influence of bush density on the grass component of the herbaceous layer was investigated for three savanna veld types (Molopo Thornveld, Mixed Vaalbos Thornveld, and the Eastern Grass and Bushveld) in the Northern Cape and North-West Province of South Africa. Relationships between bush density and the density, species composition and phytomass production of the grass component were determined over a four-year period. Bush encroachment had an adverse influence on the density and production of the grass component, but not on the species composition. Fluctuations in seasonal rainfall appeared to be the most important factor governing changes in the species composition of the grass component. Bush enchroachment (2 500 tree equivalents ha^?l) decreased the potential grazing capacity by as much as 331%, 149% and 58% in the Molopo Thornveld, the Mixed Vaalbos Thornveld and the Eastern Grass Bushveld, respectively, In comparison to sites with tree densities of less than 400 tree equivalents ha^?1. In the encroached condition grazing capacities of 15, 13 and 10 ha LSU^?1 are recommended for the Molopo Thornveld, the Mixed Vaalbos Thornveld and the Eastern Grass and Bushveld, respectively. The implementation of bush control measures in all problem areas is proposed in order to restore the productivity of these areas in the long term.