G.N. Smit

University of the Free State | ufs · Department of Animal, Wildlife and Grassland Sciences

The diurnal activity budgets of giraffes were effectively studied from June 2012 until August 2013, in the Kalahari Region of southern Africa. Direct field observations identified how the daily activity budgets varied amongst the different subgroups of giraffes and the effects of seasonal changes and the time of the day. Feeding was the highest‐per...

To the modern‐day conservationist, knowledge on giraffe ( Giraffa camelopardalis ) movement patterns is crucial for the effective management of this increasingly threatened species. The aim of this study was to determine the seasonal distances travelled by giraffes in a highly seasonal semi‐arid savanna area and to investigate how specific climatic...

Diet selection concerning browse availability of giraffes (Giraffa camelopardalis) was studied over 15 months in an arid environment in South Africa. A global positioning system collar was fitted to a giraffe individual to assess the specific areas, consisting of different vegetation types, that the population utilised during different seasons. Res...

The concept of game ranching has developed over the last two decades, and many former domestic livestock farms have now been converted to game ranches. In the Molopo area of the North West Province, it is estimated that there are approximately 177 game ranches extending over an area of 160 000 hectares. Game ranch management should be based upon fa...

The Lets’eng-la-Letsie wetland is an official Ramsar site, but the wetland and upland catchment areas suffer from overgrazing, erosion and over exploitation. Chrysocoma ciliata has a reputation as an unpalatable invader and is particularly common on the drier northern slopes. The objectives of the study were to quantify the phytomass of this shrub...

A practical measure of assessing periods of potential nutritional stress of game species is needed in the management of these species in the Acacia karroo Riparian Thicket of the central Free State. The objectives of the study were to determine Nf concentration of four game species (browsers and mixed feeders) during different seasons, compare Nf w...

An online decision support system derived from research and expert knowledge was developed for arid rangeland management in central Namibia. The expert system emphasises the control of bush thickening and is divided into three forms of decisions: adaptive, reactive and ongoing good management. Adaptive decisions are mostly related to periods of pro...

In the Mopane Bushveld, Colophospermum mopane is viewed as a threat due to its ability to suppress the herbaceous layer. The objective of this study was to investigate the re-establishment of C. mopane over a 19-year period on seven plots thinned to different tree densities. Thinning was completed during 1989 and measurements done annually from 199...

A quantitative description of woody plant communities that aimed at aiding studies on grass–tree competition interactions, bush encroachment and estimation of food to browser herbivore species, was proposed during 1989. It evolved as the BECVOL-model and differs from other methods by being able to provide estimates for both complete plants and plan...

Seed production and seedling survival are under-researched in savannas. We investigated these in a population of a major thickening species, Acacia mellifera, in an arid Namibian savanna over a nine year period (late 1998–early 2007) We asked the following questions: (i) How does viable seed production vary with rainfall and tree size, (ii) when do...

We investigated the role of fire in controlling bush thickening in arid savannas. Three controlled fires were initiated to investigate the responses of planted seedlings, saplings and mature shrubs. The stem diameters of seedlings, saplings and mature shrubs prior to the fire were measured. Other dimensions of the saplings and mature shrubs such as...

The effects of pasture management, season and soil nutrient status on crude protein (CP) and macro mineral concentration of native pasture was studied in the Vertisol areas of the central Ethiopian highland. Soil and herbage samples from 18 continuously grazed (CG) and 12 seasonally grazed (SG) pasture sites were analyzed for N, P, Ca, Mg, K and Na...

The study area was located in the central Free State Grassland biome, but the vegetation partially represented riparian thicket. Leaf carriage patterns of deciduous species were determined from September 2004 to August 2008. Similarities existed between Acacia karroo and Diospyros lycioides – mature leaves were present from October to April, with s...

The investigation was conducted on an area covered by a dense stand of Colophospermum mopane. Seven plots (65 m × 180 m) were subjected to different intensities of tree thinning, ranging from a totaly cleared plot (0%) to plots thinned to the equivalent of 10%, 20%, 35%, 50% and 75% of the leaf biomass of a control plot (100%) with a tree density o...

The investigation was conducted in the Limpopo Province of South Africa. Twenty single stemmed trees of both Acacia erubescens and Combretum apiculatum subsp. apiculatum were randomly selected and five trees of each species were cut at heights of 5cm, 15cm, 30cm and 45cm above ground level. At the end of the following five growing seasons leaf dry...

The potential and regeneration capacity of soil seed banks in three eastern Ethiopian rangeland ecosystems (Asbuli grassland or arid grassland, Aydora open savanna or arid bush/grassland and Hurso closed savanna or arid bush land) were determined over a degradation gradient.Soil samples from 0.09 m2 blocks (100 mm deep) were spread evenly in plasti...

Namibian rangelands are encroached with Acacia mellifera, partially resulting from a poor understanding of vegetation dynamics. A conceptual state-and-transition model of vegetation dynamics in the semiarid Highland savanna in central Namibia, emphasising bush thickening by A. mellifera, is described. Two main states, a grassy and a bushy state, ar...

Arid and semi-arid rangelands that serve as the resource basis for the livestock production system known as the pastoral production system in Ethiopia are under enormous threat. These rangelands cover about 62% of the national land area and employs approximately 27% of the population. A survey was conducted in two pastoral weredas (districts; Erer...

Livestock grazing behaviour is poorly understood in the arid rangelands of Ethiopia, resulting in inadequate rangeland management and grazing systems, which are no improvement on the traditional practices by pastoralists. This study aimed at quantifying the influence of rangeland degradation on grazing behaviour of the livestock breeds in the Shini...

Effects of land use on soil nutrients and related soil parameters of Pellic Vertisols were assessed using soil samples collected from plots subjected to the cultivation of tef (Eragrostis tef) (TF) and grass pea (Lathyrus sativus) (GP) and native grassland subjected to year-round (continuous) grazing (CG) and seasonal grazing (SG). Soil under grass...

The distribution and compositional pattern of the grass layer, as well as soil quality of southern Ethiopian semi-arid rangelands were examined under three land-use systems (communal land, government ranch and a traditional grazing reserve enclosure) and along a distance gradient (near, middle and far) from water sources. In total, 49 grass species...

The condition of the semi-arid Borana rangeland in southern Ethiopia was assessed by studying different land-use systems (communal land, a government ranch and a traditional grazing reserve enclosure) and along a distance gradient (near, middle and far) from water sources. The assessment incorporated the soil, herbaceous and woody plant layers. Two...

The structure and advancement of woody vegetation was studied in a semi-arid rangeland of southern Ethiopia under three land-use systems (communal land, a government ranch and a traditional grazing reserve enclosure) and along a distance gradient (near, middle and far) from water sources. A total of 54 woody plant species were identified. Based on...

The objective of this study was to determine the condition and grazing capacity of commonly grazed rangeland of pastoralists living in the Kereyu-Fantale and Awash-Fantale districts of Ethiopia. In each of the districts, data on grass species composition, basal cover, bare ground, soil erosion and dry matter (DM) yield were collected. The most domi...

Although a few studies have reported an increase of woody plants in the rangelands of Ethiopia during the last few decades, most studies related to the importance of tree canopies have been conducted in lightly grazed areas that have suffered little disturbance. The woody vegetation composition, density, evapotranspiration tree equivalent (ETTE), b...

Two neighboring districts inhabited by pastoralists of different ethnic groups in the Middle Awash valley of Ethiopia were studied to make a preliminary investigation of the soil nutrient status and identifying the environmental factors most critical to grass production. Data were collected on soil nutrient status, grass yield (dry matter), percent...

A survey was conducted in the Borana pastoral areas of southern Ethiopia to assess current livestock production systems, rangeland management practices and the perceptions of the pastoralists towards rangeland degradation. This information is considered vital to future pastoral development planning and interventions. Data were collected from a tota...

The size and species composition of the soil seed bank of southern Ethiopia rangelands were examined under three land use systems (communal land, a government ranch and traditional grazing reserves) and along a distance gradient (near, middle and far) from water sources. Soil seed bank sampling was carried out at the end of the growing season from...

Pastoralism is the most dominant land use form in the arid rangelands of Sub-Saharan Africa, but this rangeland-based lifestyle is under threat. As a consequence a study was conducted in the Middle Awash Valley of Ethiopia with the main objectives of assessing and comparing the broad perceptions of two pastoral groups (the Oromo ethnic group living...

The study was conducted in a semi-arid savanna of South Africa, dominated by an almost pure stand of Acacia mellifera subsp. detinens (Black Thorn). Due to its invasive habits and suppression of the herbaceous layer, this woody species is viewed by land owners as a serious threat. Clearing of all A. mellifera trees in order to restore the productio...

This study assessed the concentrations of crude protein (CP) and minerals in tef (Eragrostis tef) and grass pea (Lathyrus sativus) residues, noug seedcake (Guizotia abyssinica) and grass pea grain produced on Vertisols of the Ethiopian highland. Soil and feed N and minerals were determined from samples obtained from tef and grass pea crop fields as...

The investigation was conducted in a savanna area covered by what was considered an undesirably dense stand of Colophospermum mopane trees, mainly because such a dense stand of trees often results in the suppression of herbaceous plants. The objectives of this study were to determine the influence of intensity of tree thinning on the dry matter yie...

The objectives of the study, conducted during the 2000/01 growing season in the Middle Awash Valley of Ethiopia, were to quantify the effects of two dominant woody species (Acacia tortilis and Balanites aegyptica) on grass species composition, grass dry matter (DM) yield and soil under light, medium and heavy grazing. At each study site two sub-hab...

Due to bush encroachment the grazing capacity of large areas of the southern African savanna has declined, often to such an extent that many previously economic livestock properties are now no longer economically viable. Attempts at restoring encroached areas by the removal of some or all of the woody plants will normally result in an increase of g...

The southern African Mopane savanna is a water-limited ecosystem and an increase in woody plant abundance often results in the suppression of herbaceous plants. In an attempt to counter this effect, the thinning or even total clearing of all woody plants is a common practise in South Africa. Since the outcome of woody plant removal is determined by...

Faecal samples from eight confined kudu populations were collected from May 1999 to December 1999. Samples were analysed for nitrogen concentration. Faecal nitrogen concentration (N1) reached a low during the dry-hot season (August to the end of October) and peaked in November. N1 was negatively correlated with kudu density for samples collected du...

Despite the crucial role of mineral elements in animal production and health, their status in soil, native pasture and animal body tissues or fluids in the mid-altitude of Ethiopia has had little study. To determine the concentration of mineral elements in soil, native pasture and blood serum of Horro cattle (local zebu), samples were collected fro...

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...

The vegetative growth and browse production dynamics of Colophospermum mopane trees were studied over a period of three years on six plots where the trees were thinned to the approximate equivalents of 75, 50, 35, 20, and 10% of tree density of the control plot (2711 trees/ha). Thinning reduced inter-tree competition which resulted in significant i...

Germination dynamics of Acacia mellifera sub species detinens from trees along a tree density gradient in a semi-arid savanna. M. G. Hagos1 and G. N. Smit2 Department of Grassland Science, University of the Free State, P. O. Box 339, Bloemfontain, 9300 The influence of tree thinning on the germination potential, root length, coleoptile length, ro...

The investigation was conducted on an area covered by a dense stand of Hardwickia mopane (Leguminosae: Caesalpinioideae). Seven plots (65×180 m) were subjected to different intensities of tree thinning, ranging from a totally cleared plot (0%) to plots thinned to the equivalent of 10, 20, 35, 50, and 75% of the leaf biomass of a control plot (100%)...

On an area covered by dense stands of Colophospermum mopane with little or no grass cover, ten sites were randomly selected. In the centre of each site, a core (monolith) of soil (2.0 m x 0.5 m x 1.0 m deep)was excavated and removed in 5 layers of 200 min. Roots were washed from the soil and sorted into classes (0-1.0 mm, > 1.0-5.0 mm, > 5.0-10.0 m...

The reproduction dynamics of Colophospermum mopane, including flowering, fruit bearing, the germination potential of the seed and seedling establishment were studied over a period of three years on six plots where the trees were thinned to the approximate equivalents of 75%, 50%, 35%, 20% and 10% of the tree density of the control plot (2 711 trees...

This review deals with issues including the determinants of vegetative growth of woody plants (soil water availability, water stress, soil nutrient availability, carbohydrate reserves, plant hormones, atmospheric CO2 concentration, tree age, competition, defoliation and shoot pruning, fire, pathogens, soil and climatic conditions), reproduction (th...

Leaf dry mass (DM) at peak biomass was estimated for different plant communities in a semi‐arid savanna. These estimates included the total leaf DM, as well as estimates of the leaf DM at browsing heights of 1.5 m, 2.0 m and 5.0 m. The total leaf DM in the different plant communities ranged between 1 224 kg ha and 2 672 kg ha. The contribution of i...

Five plots on sandy soil were thinned to differing tree densities. Three subhabitats were distinguished, viz. under leguminous trees, under non‐leguminous trees, and between tree canopies. Soil under both leguminous and non‐leguminous trees was richer in nutrients (% total N, % organic C, Ca, K, Mg) than between tree canopies. Certain nutrients (K,...

Acacia tortilis, A. karroo and Dichrostachys cinerea subsp. africana trees were divided into nine height classes, with increments of 0.5 m. The abundance of P. maximum growing under their canopies was estimated by scoring on a scale of 0 (no P. maximum) to 3 (P. maximum predominates). Presence of P. maximum was mainly associated with larger trees o...

Four species viz. Tomoptema cryptotis, Ptychadena anchietae, Kassina senegalensis and Phrynomerus bifasciatus were studied during the 1987/88 breeding season. Observations included estimates of mating calls on an index scale of 0–4 and the recording of eggs and young tadpoles during subsequent days. Relations between calling and spawning and the co...

The relations between woody and herbaceous plants in southern African savannas are reviewed in the context of pastoral use. Current knowledge is summarised, important gaps are indicated and research priorities are suggested. Although all savannas consist of a grass and a woody component, the physical determinents, biological interactions and indivi...

Eight camps, grazed annually during different seasons by steers, were surveyed. Herbaceous species were grouped into Decreaser and Increaser categories according to their reaction to grazing. The Increaser IIa (light overgrazing) and IIb (moderate overgrazing) herbaceous species were the most abundant and were significantly negatively correlated. W...

Cold damage to woody plants in the Sourish Mixed Bushveld. An incident of damage to woody plants by cold in the Sourish Mixed Bushveld was investigated. Woody plants in eight paddocks which were subjected to long‐term grazing treatments and which gave rise to different tree densities, were examined. The most common form of damage was top kill, and...

Association of Cymbopogon plurinodis with the day content of soil in the Sourish Mixed Bushveld. In a camp, typical of the Sourish Mixed Bushveld, a marked decrease in the abundance of Cymbopogon plurinodis along a soil gradient from high to low clay content was found. The association appears to be independent of the grazing treatment over a 51‐yea...

Various descriptive units for woody plant communities are proposed. These are the Evapotranspiration Tree Equivalent (ETTE), Browse Tree Equivalent (BTE) and Canopied Subhabitat Index (CSI), which describe the status of a woody community in terms of potential moisture use, value of the trees as food for browsers and subhabitat suitability for grass...

Calculation procedures for various quantitative descriptive unit‐values are described. These procedures are divided into primary and secondary calculations. The former is then divided into the calculation of spatial tree volume and preliminary calculations regarding the complete quantitative description. The latter include the calculation of the Ev...

A simple, inexpensive method for estimating linear tree dimensions is described and tested. The method is based on a visual overlap of two images, namely, the tree to be estimated and a group of length scales incorporated on a colour slide. Additional advantages of the proposed method include accuracy, application by one person only and both vertic...

Die subhabitatvoorkeure van sewe grasspesies en die nie‐grasagtige kruide, tipies van die Suuragtige‐Gemengde Bosveld, is in agt kampe, wat verskillende langtermyn‐beweidingsbehandelings ontvang het, ondersoek. Twee subhabitatte is geidenti‐fiseer, nl. onder borne en tussen bome. Verskille in die subhabitatvoorkeure van die verskillende spesies is...

The term “problem tree” refers to a conceptual model used as a diagnostic tool to analyse a sequence of events that leads to a problem (such as bush encroachment in rangelands). A problem tree is useful because the consequences of different interventions can be visualised and understood more easily in diagrammatic form, thereby guiding management d...

Scientists can learn a great deal from innovative farmers who apply adaptive management principles based on experience gained over decades. This paper records 31 observations that a farmer, Jan Labuschagne, made on his farm to the south of Gobabis. The observations relate to aspects such as animal behaviour and performance, animal trampling, and ap...