Medium-term changes in grass composition and diversity of Highland Sourveld grassland in the southern Drakensberg in response to fire and grazing management

Short, Alan; O’Connor, T.G.; Hurt, C.R.

doi:10.2989/10220110309485792

Cited by 19 publications

(10 citation statements)

References 8 publications

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“…Other South African grassland studies also found shifts in assemblage composition, loss of plant species and lower dominance in response to heavy grazing (Short et al. ; O'Connor ; Scott‐Shaw & Morris ). This indicates that only a small number of species were adapted to this level of disturbance, as could be expected since sustained heavy grazing is not prevalent in the evolutionary grazing history of these grasslands (Cingolani et al.…”

Section: Discussionmentioning

confidence: 83%

“…The grazing regime inside the ecological networks was complex, with cattle density limited to 2.5−3.0 ha·Large Animal Unit (LAU) −1 or 0.33−0.4 LAU −1 ha −1 (following the definition of Short et al. ), which concurred with recommended stocking density for the region, although the actual number of cattle (228 cows) was 17% more than recommendations (Appendix ), excluding 82 calves and an unknown number of un‐herded, free‐ranging cattle on adjacent communal land, and in connecting road reserves that enter and leave ecological networks with little constraint. Therefore, the grazing regime was similar to communal grazing, i.e.…”

Section: Methodsmentioning

confidence: 87%

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Moderate grazing sustains plant diversity in Afromontane grassland

Joubert

Pryke

Samways

2017

Applied Vegetation Science

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Abbreviations DBERG = Drakensberg Foothill Moist Grassland; DEM = Dynamic Equilibrium Model; IDH = Intermediate Disturbance Hypothesis; KZN = KwaZulu-Natal; MBELT = Midlands Mistbelt Grassland; RB = recently burned i.e. burned <12 months prior to sampling; UB = unburned i.e. not burned <12 months prior to sampling. Nomenclature Mucina et al. (2006) for grassland types; Plants of southern Africa (http://posa.sanbi.org/) for vascular plants AbstractAims: Natural disturbances drive plant assemblages in Afromontane grassland.Our aim is to assess how intensity of cattle grazing and time since last fire influence plant species richness, dominance and assemblage composition.Location: Central Midlands, KwaZulu-Natal province, South Africa.Methods: Sites differed in grazing intensity (light, moderate and heavy) and time since last fire: recently burned (RB) vs unburned (UB). We sampled plants in 24 vegetation quadrats (1-m 2 ) randomly located within each site (~1000 m 2 ). We used linear regression models for species richness and dominance, IndVal to identify indicator species and CCA for assemblage composition. All analyses were conducted at quadrat and site level.Results: Species richness was significantly influenced by time since last fire (RB > UB), grazing intensity (light < moderate > heavy) and the fire-grazing interaction at quadrat level. Dominance reciprocated the response of species richness to time since last fire (UB > RB), but did not respond consistently to grazing intensity (light > moderate > or < heavy). Plant assemblage composition was significantly influenced by time since last fire, grazing intensity and vegetation structure (live vegetation cover and vegetation height). Indicator species of species-poor, heavily grazed sites included alien species, such as Cirsium vulgare and Conyza bonariensis.Conclusion: Response of species richness to grazing intensity conforms to the predictions of the intermediate disturbance hypothesis. Burning and moderate grazing should be part of grassland management. To prevent species loss and influx of alien species, heavy grazing should be minimized. As development of grassland ecological networks in a timber matrix is being pioneered in South Africa, these findings indicate a way forward for the management of similar systems elsewhere in the world.

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Section: Discussionmentioning

confidence: 83%

Section: Methodsmentioning

confidence: 87%

Moderate grazing sustains plant diversity in Afromontane grassland

Joubert

Pryke

Samways

2017

Applied Vegetation Science

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“…Small populations of common reedbuck Redunca arundinum Boddaert, mountain reedbuck Redunca fulvorufula Afzelius, oribi Ourebia ourebi Zimmerman and grey rhebuck Pelea capreolus Forster occur. Mean stocking density over the past 15 years has been 0·07 animal units (AU) ha −1 (AU is the metabolic mass equivalent of a 455‐kg steer; Short, O'Connor & Hurt 2003).…”

Section: Study Area and Land Usesmentioning

confidence: 99%

Influence of land use on plant community composition and diversity in Highland Sourveld grassland in the southern Drakensberg, South Africa

O’Connor

2005

Journal of Applied Ecology

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Summary1. Biodiversity conservation of grasslands in the face of transformation and global climate change will depend mainly on rangelands because of insufficient conservation areas in regions suited to agriculture. Transformed vegetation (pastures, crops and plantations) is not expected to conserve much biodiversity. This study examined the impact of land use on the plant diversity and community composition of the southern Drakensberg grasslands in South Africa, which are threatened with complete transformation to pastures, crops and plantations. 2. The main land uses in this high rainfall region are: ranching or dairy production under private tenure using indigenous grassland, pastures ( Eragrostis curvula , kikuyu and ryegrass) and maize; plantation forestry; communal tenure (maize and rangelands); and conservation. 3. Plant diversity and composition were assessed using Whittaker plots. Transformed cover types were depauperate in species and ranged from kikuyu (1·4 species m − 2 ) and ryegrass (2·9), to pine plantation (3·1), E. curvula pasture (3·1), commercial maize (3·2) and communal maize (7·8). With the exception of pine plantations, these communities supported mostly exotic (50 of 70 species) or ruderal indigenous species and made little contribution to plant species conservation. Abandoned communal cropland reverted to an indigenous grassland almost devoid of exotic species within c. 20 years. 4. It was predicted that frequently cultivated sites (maize and ryegrass) would support less diversity than long-lived pastures (kikuyu and E. curvula ). This was contradicted by the relatively high species diversity of communal maize fields, which was attributed to a lack of herbicides, and the depauperate communities of kikuyu and of E. curvula pasture, which were attributed, respectively, to a dense growth form and a severe mowing regime. 5. Pine plantations harboured fourfold more indigenous species per plot (27) than other transformed types. Species were mostly shade-tolerant grassland relics that had persisted for 12 years since planting, and some forest colonizers. Indigenous species were unlikely to be maintained because of aggressive invasion by the exotic Rubus cuneifolius and severe disturbance associated with tree harvest and replanting. 6. The richness of indigenous grasslands was expected to differ in response to grazing pressure but they differed only in composition. Grasslands were dominated by grasses, despite the richness of herbaceous species. The dominance of Themeda triandra was reduced under livestock grazing in favour of more grazing-tolerant species. Exotic species were inconspicuous except for the dicotyledon Richardia brasiliensis , a subdominant under communal grazing. 7. Southern Drakensberg grasslands are probably now stocked with livestock six-to 35-fold higher than during pre-settlement times. A grassland protected for c. 50 years supported twofold greater richness (101 species plot 8. Synthesis and applications . Land acquisition is costly, thus conservation of plant diversity in ...

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“…Coleford Nature Reserve (CNR; 1272 ha) was acquired in 1958 for wildlife conservation, prior to which it was a private farm with cultivation practised on wetlands. Mean stocking density over the past 15 years was 0.07 (up to 0.12) animal units (AU) ha À1 (AU defined as the metabolic mass equivalent of a 455 kg steer) (Short et al 2003). Wetlands were extensively drained and cultivated whilst the property was used for agriculture, but wetlands were re-established in the mid-1980's by plugging canals (KZN Wildlife, unpublished reports).…”

Section: Conservation Propertiesmentioning

confidence: 99%

“…Communal areas differ from their commercial counterparts in that livestock stocking rates can be three-fold greater (Tapson 1993) and that cultivation has limited inputs of fertilizer and lacks mechanized harvesting. Public bodies are charged with administration of conservation lands, on which only light grazing by indigenous wildlife occurs (Short et al 2003). Differences between the types of land tenure thus result in differences in land use.…”

Section: Introductionmentioning

confidence: 99%

Impact of land use on vegetation composition, diversity, and selected soil properties of wetlands in the southern Drakensberg mountains, South Africa

Walters

Kotze

O’Connor

2006

Wetlands Ecol Manage

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Wetlands provide the ecosystem services of enhancing water quality, attenuating floods, sequestrating carbon and supporting biodiversity. In southern Africa, the pattern and intensity of land use is influenced by whether land tenure is public (state), private (individual ownership), or communal (shared agricultural and grazing resources). The influence of land tenure and its associated use on service provision was compared for communal tenure (grazing, maize production), wildlife conservation, and commercial agriculture (grazing, planted pastures) in the southern Drakensberg. Ordination analyses revealed that oxbow marshes, hill slope seepages and hygrophilous grasslands, the main hydro-geomorphic units, supported distinct plant communities that differed in their response to land use because of wetness or slope. Oxbows, uncultivated because of wetness, were inherently species poor with few exotics. Composition of hill slope seepages, uncultivated because of saturated slopes, varied among tenure types most likely in relation to grazing pressure. Seepages were threatened by the exotic invasive Rubus cuneifolius. Eighty-five percent of hygrophilous grassland had been cultivated by 1953, most of which was subsequently abandoned to secondary grassland. Primary hygrophilous grassland and hill slope seepages were the main repository for indigenous plant diversity, while communal maize fields supported a diverse mixture of mainly exotic species. Soil carbon concentrations decreased from oxbows to pastures, seepages, primary hygrophilous grassland, secondary grassland, and maize on former grassland (7.0, 4.1, 4.0, 3.5, 2.4, and 1.7%, respectively). The pattern for total soil nitrogen and sulphur were the same. Cultivation of hygrophilous grassland was estimated to have reduced soil carbon stocks to 69% of pre-settlement levels by 1953 ($150 years BP). Stocks then increased by 8% to 2001 following crop abandonment. Cultivation has impaired water quality enhancement and flood attenuation because of greater amounts of bare ground and shorter vegetation. Further improvement of ecosystem services will depend on the influence of socio-economic factors on communal cropping.

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Medium-term changes in grass composition and diversity of Highland Sourveld grassland in the southern Drakensberg in response to fire and grazing management

Cited by 19 publications

References 8 publications

Moderate grazing sustains plant diversity in Afromontane grassland

Moderate grazing sustains plant diversity in Afromontane grassland

Influence of land use on plant community composition and diversity in Highland Sourveld grassland in the southern Drakensberg, South Africa

Impact of land use on vegetation composition, diversity, and selected soil properties of wetlands in the southern Drakensberg mountains, South Africa

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