Leslie R. Brown

Worldwide evidence of a unimodal relationship between productivity and plant species richness

Grassland diversity and ecosystem productivity The relationship between plant species diversity and ecosystem productivity is controversial. The debate concerns whether diversity peaks at intermediate levels of productivity—the so-called humped-back model—or whether there is no clear predictable relationship. Fraser et al. used a large, standardized, and geographically diverse sample of grasslands from six continents to confirm the validity and generality of the humped-back model. Their findings pave the way for a more mechanistic understanding of the factors controlling species diversity. Science, this issue p. 302 The humped-back model of plant species diversity is confirmed by a global grassland survey. The search for predictions of species diversity across environmental gradients has challenged ecologists for decades. The humped-back model (HBM) suggests that plant diversity peaks at intermediate productivity; at low productivity few species can tolerate the environmental stresses, and at high productivity a few highly competitive species dominate. Over time the HBM has become increasingly controversial, and recent studies claim to have refuted it. Here, by using data from coordinated surveys conducted throughout grasslands worldwide and comprising a wide range of site productivities, we provide evidence in support of the HBM pattern at both global and regional extents. The relationships described here provide a foundation for further research into the local, landscape, and historical factors that maintain biodiversity.

Troop Size, Habitat Use, and Diet of Chacma Baboons (Papio hamadryas ursinus) in Commercial Pine Plantations: Implications for Management

Primates living outside protected areas frequently come into conflict with humans. While the focus of most research has been on the costs and consequences of crop raiding in relation to subsistence agriculture, large-scale commercial agriculture presents conservation challenges of its own. Baboons that occupy commercial pine plantations in southern Africa often damage young trees and, consequently, are shot in large numbers. We here aim to describe the population structure and resource and habitat use by baboons in such areas to provide the data needed for the formulation of viable long-term conservation policies. We used radio-collars to obtain estimates of home range size and habitat usage from 2 plantation troops and detailed observation of 1 of these to determine their diet. We compared these data, together with counts of troop size, to those from individuals in the same population that did not enter plantation. Although the mean troop size (42.2) of baboons in plantations was significantly higher than in adjoining natural areas (18.3), population density (2.8 individuals/km2) did not differ. Plantation baboons had a comparatively restricted diet in which a few indigenous species were disproportionately represented. Pine cambium was not an important dietary component and the baboons generally avoided compartments of pine trees to forage in small pockets of various natural plant communities. We argue that foresters should shift their policy from one of baboon extirpation to the long-term management of local populations, in the context of a proper and ongoing evaluation of the discounted cost of baboon damage.

Phytosociological synthesis of the vegetation of the Borakalalo Nature Reserve, North-West Province

After classifications and descriptions of the northern, southern and western sections of the Borakalalo Nature Reserve have been completed, it was necessary to compile a synecological synthesis of the vegetation of the Reserve to compare the existing classifications and to summarize the vegetation of the entire Reserve as an ecological basis for the compilation of a management plan. Using 350 releves a synoptic table was compiled representing 44 plant communities. A TWINSPAN classification was used complementary to Braun-Blanquet procedures and revealed seven major vegetation types. By using an ordination algorithm (DECORANA) the floristic relationships among the different vegetation types are indicated against a habitat gradient.

The effect of reseeding methods on secondary succession during cropland restoration in the Highveld region of South Africa

The Grassland biome is the most transformed biome in South Africa, with cultivation and other human impacts having the largest effect on pristine grasslands. Conversion of natural grassland to cropland agriculture destroys natural vegetation seed banks. When croplands on the South African Highveld are abandoned, secondary succession often leads to low diversity Hyparrhenia hirta dominated plant communities. To investigate the effect of reseeding on secondary succession and botanical diversity, various reseeding treatments of cropland restoration were established on a recently abandoned cropland at Suikerbosrand Nature Reserve. Plots combining two seed mixtures, two seeding rates and two sowing methods were monitored and evaluated. The sowing method (plough vs rip-line) had the largest influence on the suppression of relic weeds as well as possible establishment of local non-sown species. The rip-line plots, where more resources were available due to spaces between the rip-lines, initially experienced higher densities of relic weeds followed by an increase in local non-sown species densities. Hyparrhenia hirta was one of the non-sown perennials increasing in the rip-line plots. The growth of H. hirta and relic weeds was, however, controlled in the plough plots, where species densities and phytomass production of perennial sown-in species were the highest.

A novel method for estimating tree dimensions and calculating canopy volume using digital photography

Studies on plant phenology and browse capacity require effective methods to rapidly quantify plant dimensions such as tree height, height of maximum canopy diameter, height of first leaves, maximum canopy diameter, and diameter of trunk(s) at height of first leaves. Here we describe a method for estimating tree dimensions and calculating canopy volume using a measuring staff (for calibration), a digital camera and our VolCalc software. The method requires a photograph be taken of the measuring staff placed next to an object whose measurements are to be determined. The two objects must be adjacent to one another in the photograph. For rapid analysis, multiple photographs of different objects can be taken over a short period of time using the measuring staff. The method is not limited to plants and can be used to determine, for example, browser height, height at which browsers feed, and primate resource abundance. The method has been tested in the field and provides a fast and precise tree dimension parameter estimation option, where sampling time is of the essence. Test results compare well to alternative methods currently utilised, showing improved precision and faster field data collection times, which are important to researchers and ecologists.

Impact of Domestic Animals on Ecosystem Integrity of Lesotho High Altitude Peatlands

Wetlands are considered ecologically sensitive ecosystems with unique habitats for a great variety of plants species, birds, small mammals and other aquatic organisms. The term “wetland” is used to describe various habitats where the soil is wet for extended periods of the year but not necessarily permanently waterlogged (Collins, 2005). Wetlands are formed where surface water collects or where ground-water seeps to the surface for long-enough periods to sustain vegetation typically adapted or tolerant of hydric soil conditions. Thus wetlands comprise a large variety of waterlogged habitats such as bogs, estuaries, fens, floodplains, marshes, peatlands, playas (pans), seeps, springs, and swamps located on various altitudes and topographical locations. In his book on wetlands of southern Africa, Cowan (1995) used the definition of a wetland as it is stated in Article 1.1 of the Ramsar Convention where it has been defined as: “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”. The South African National Water Act (Act 36 of 1998) defines wetlands as “land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land periodically covered with shallow water, and which in normal circumstances support or would support vegetation typically adapted to life in saturated soil”. Peatlands are unique wetland ecosystems in terms of their species composition and age. The process of peat formation is very slow which means that some of these wetlands are ancient as they have a deep peat deposit of over two metres. Peat is organic soil material with a particularly high organic content which, depending on the definition, usually has at least 20% organic carbon by weight. Peatlands are wetlands in which peat (dead plant matter) accumulates due to slow decomposition (Cronk & Fennessy, 2001). These peatlands can be classified into two major types namely bogs and fens. The definition of a bog is, a peataccumulating wetland that has no significant water inflows or outflows and supports acidophilic mosses, particularly Sphagnum (usually acidic; pH 7)( Cronk & Fennessy, 2001; Mitch & Gosselink, 2000). According to these definitions, the high-altitude wetlands of Lesotho are therefore incorrectly classified as bogs by Grobbelaar & Stegman (1987), Herbst & Roberts

Resource Selection on Woody Plant Species by Vervet Monkeys (Chlorocebus pygerythrus) in Mixed-Broad Leaf Savanna

Understanding how vervet monkeys (Chlorocebus pygerythrus) select resources provides information for effectively managing them and the environments they live in, which may reduce conflict with humans. This study investigates resource selection on woody plant species by two vervet monkey (vervet) troops living in human-modified mixed-broadleaf savanna in South Africa. Our findings indicate that one troops home range was more diverse in terms of woody plant species than the other. No relationship between the frequency of occurrence of resource items in the diet and the availability of those items was found for either troop, suggesting that food selection is not based on availability. However, resource items were selected in proportion to their energy content, indicating that vervets are potentially energy maximizers (species that select resource items based on energy content). This was noticeable for the vervets living in the more diverse home range. Vervets in the less diverse home range displayed less clear preference for higher energy food items. Despite this disparity between the troops, our findings suggest that both troops used whatever resource items were available to them, and that it is important to maximize the tree diversity in vervet habitats to ensure population persistence and reduce conflict with humans.

Home range utilization by chacma baboon (Papio ursinus) troops on Suikerbosrand Nature Reserve, South Africa

Rapid urbanization coupled with decreasing areas of natural habitat are causing baboon populations to become scattered and isolated, often resulting in increased levels of human-baboon conflict. To implement baboon-human conflict management strategies, it is essential to formulate realistic conservation policies that deal with all stakeholder concerns and ensure the conservation of viable baboon populations. A study was initiated in response to complaints of perceived excessive baboon numbers and associated lack of food resources on Suikerbosrand Nature Reserve in South Africa. Data obtained from GPS tracking collars fitted to one baboon from each of 10 identified troops were analyzed to determine home range size and utilization. The spatial representation of home ranges generated from this study will allow reserve management to identify areas of potential high and low human-baboon conflict and will contribute to the development of a formal baboon management plan to reduce human-baboon conflict on and around the reserve. Home ranges were unevenly distributed and had a mean size of 26.72 km2 ± 13.91 SD in the cold/dry season and 26.54 km2 ± 12.76 SD in the warm/wet season. Troop home ranges overlapped to some degree and five troops utilized areas outside the reserve. Although no significant relationship between troop size and home range was found, there was a positive relationship between troop size and daily distance travelled. All troops had significantly longer mean daily distances during the warm/wet season than during the cold/dry season (P ≤ 0.02).

Engaging ODL Students with Biodiversity Issues: A South African Case Study on the Role of ESD

Biodiversity is regarded as a key asset in safeguarding the well-being of future generations. The threat to biodiversity through indiscretionary human activities is increasingly gaining attention, from local to global scales. Biodiversity forms part of the agenda for Education for Sustainable Development (ESD) through addressing inter-linkages between the various components and systems comprising the environment. This has been illustrated throughout the Decade of Education for Sustainable Development, which ended in 2014. As a result, significant progress has been made at various levels on the understanding of the impact of human consumption on biodiversity, together with the sensitization of students in terms of their potential roles to curb habitat and species loss as well as environmental degradation. This chapter utilises a case study approach to reflect on the way biodiversity is dealt with through the blended approach to ESD in the Diploma in Nature Conservation offered by the University of South Africa (UNISA). This blended approach is unique due to the combination of open distance learning (ODL), practical sessions, and work-integrated learning (WIL). A review of the flexibility of a blended approach to ODL, the challenges that were experienced, the means through which these were addressed and a future perspective, concludes this chapter.

The effects of fire-breaks on plant diversity and species composition in the grasslands of the Loskop Dam Nature Reserve, South Africa

There is a dearth of knowledge on the effects of annual burning of fire-breaks on species composition, plant diversity and soil properties. Whittakers plant diversity technique was used to gather data on species composition and diversity in four grassland communities on the Loskop Dam Nature Reserve (LDNR). The study demonstrated that fire-beaks did not have a negative effect on plant diversity and an increase was even noted in various diversity parameters in the grassland on abandoned cropland. Fire-breaks were changing the species composition, as three of the four communities illustrated a clear separation in species composition between fire-break and unburnt plots. There was not a strong association between specific species and the fire-break or unburnt plots, except for Themeda triandra and Tristachya leucothrix, known for their association with and without fire, respectively. The change in species composition was not negatively affecting range condition. Carbon and nitrogen concentrations were slightly lower in the fire-break than unburnt soils, but the reduced concentrations were unlikely to cause severe soil degradation in fire-break zones. From a management perspective, fire-breaks appear to be a sustainable management tool as they are not adversely affecting plant diversity or range condition in the grassland association on LDNR.