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  1. Article: Response of three mesic South African perennial grassland forbs to defoliation and competition

    Chamane, Sindiso / Kirkman, Kevin P / Morris, Craig / O’Connor, Tim G

    African journal of range & forage science. 2019 Dec. 13, v. 36, no. 4

    2019  

    Abstract: The importance of maintaining biodiversity in natural grasslands under livestock production systems has been recognised. Forbs contribute more to species richness than grasses in South African grasslands. However, little is known about the impact of ... ...

    Abstract The importance of maintaining biodiversity in natural grasslands under livestock production systems has been recognised. Forbs contribute more to species richness than grasses in South African grasslands. However, little is known about the impact of grazing and grass competition on the population dynamics of forbs. The aim of this study was to determine the response of three mesic grassland perennial forb species to simulated intensive defoliation and interspecific competition from a neighbouring dominant grass, Themeda triandra, in a field experiment. Two of the selected forb species are sensitive to defoliation (Afroaster hispida and Gerbera ambigua) and one is potentially resistant to defoliation (Hypoxis hemerocallidea). Defoliation resulted in smaller plants of all three species following regrowth. Only A. hispida showed an interaction response to defoliation and competition. Thus, a competitive release was observed for A. hispida in that the height of defoliated plants was reduced by 45% compared with undefoliated plants under full competition, but there was no difference under partial or no competition. Gerbera ambigua was unaffected by competition. Hypoxis hemerocallidea was sensitive to competition irrespective of being defoliated or undefoliated. Findings of this study highlighted an individual response such that a general response cannot be predicted.
    Keywords Gerbera ; Hypoxis hemerocallidea ; Themeda triandra ; defoliation ; field experimentation ; forbs ; grasses ; grasslands ; grazing ; interspecific competition ; livestock production ; perennials ; population dynamics ; production technology ; regrowth ; species richness
    Language English
    Dates of publication 2019-1213
    Size p. 191-195.
    Publishing place Taylor & Francis
    Document type Article
    ZDB-ID 1160792-0
    ISSN 1727-9380 ; 1022-0119 ; 0256-6702
    ISSN (online) 1727-9380
    ISSN 1022-0119 ; 0256-6702
    DOI 10.2989/10220119.2019.1679884
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

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  2. Article: Fire effects on vegetation in a grassy dwarf shrubland at a site in the eastern Karoo, South Africa

    du Toit, Justin CO / van den Berg, Loraine / O'Connor, Tim G

    African journal of range & forage science. 2015 Jan. 2, v. 32, no. 1

    2015  

    Abstract: Fire is rare in semi-arid eastern Karoo dwarf shrublands, South Africa, and responses to fire are largely unknown. Recent increased grassiness, and hence fuel loads, at Grootfontein in the Eastern Cape allowed an accidental fire (24.3 ha) to carry, and ... ...

    Abstract Fire is rare in semi-arid eastern Karoo dwarf shrublands, South Africa, and responses to fire are largely unknown. Recent increased grassiness, and hence fuel loads, at Grootfontein in the Eastern Cape allowed an accidental fire (24.3 ha) to carry, and afforded the opportunity to examine compositional and structural effects of fire on a grassy dwarf shrubland. Sampling seven months after the fire, 108 species (102 perennial) were encountered, of which 74 were resprouters, six were fire sensitive (non-sprouters), and the remainder (rare, non-perennial or herbaceous) had an unknown response. The dominant pre-fire shrub, Eriocephalus ericoides , was extirpated by the fire, as was the unpalatable and sometimes invasive Ruschia intricata . All grass species resprouted, and grass became the dominant life-form after the fire, indicating a possible conferred competitive advantage. Resprouting shrubs grew to only a small fraction of their pre-burn size. The unpalatable, aromatic shrub Stachys rugosa was the dominant post-burn shrub. Extirpated species will need to regenerate from seeds, but no seedlings were found in the gaps where shrubs had stood. The widespread ability to resprout confers resilience on this vegetation, but fire does induce changes in structure, in the dominance of life forms, and it decreases canopy cover.
    Keywords Eriocephalus ; Stachys ; canopy ; fuel loading ; grasses ; seedlings ; seeds ; shrublands ; shrubs ; South Africa
    Language English
    Dates of publication 2015-0102
    Size p. 13-20.
    Publishing place Taylor & Francis
    Document type Article
    ZDB-ID 1160792-0
    ISSN 1727-9380 ; 1022-0119 ; 0256-6702
    ISSN (online) 1727-9380
    ISSN 1022-0119 ; 0256-6702
    DOI 10.2989/10220119.2014.913077
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

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  3. Article: Bush encroachment in southern Africa: changes and causes

    O'Connor, Tim G / Puttick, James R / Hoffman, M Timm

    African journal of range & forage science. 2014 May 4, v. 31, no. 2

    2014  

    Abstract: Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y ⁻¹. Encroachment was most rapid on small protected areas, ... ...

    Abstract Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y ⁻¹. Encroachment was most rapid on small protected areas, intermediate under commercial tenure, and slowest under communal tenure and large, natural environments with mega-herbivores present. Several drivers of bush encroachment, which interact and change over time, have been proposed. Fires, for example, were actively suppressed during the early twentieth century. However, rainfall interacts with fire and the rate of woody increase under fire exclusion is linearly related to mean annual rainfall. A reduction in browsing herbivores from the nineteenth century would have had a positive cumulative effect on woody cover whilst an increase in grazing herbivores would have reduced the competitive effect of grasses. Encroachment was most rapid during the high rainfall, mid-1970s, which followed the 1960s drought when cattle numbers were at their peak, and the grass layer was degraded. Increasing atmospheric [CO ₂] and climate change have emerged as important drivers in the recent literature. Bush encroachment depends on the interplay of history, environment, management and vegetation, recognition of which is essential for containing encroachment.
    Keywords browsing ; carbon dioxide ; cattle ; climate change ; conservation areas ; drought ; fires ; forage and feed science ; grasses ; grazing ; herbivores ; rain ; vegetation ; Southern Africa
    Language English
    Dates of publication 2014-0504
    Size p. 67-88.
    Publishing place Taylor & Francis
    Document type Article
    ZDB-ID 1160792-0
    ISSN 1727-9380 ; 1022-0119 ; 0256-6702
    ISSN (online) 1727-9380
    ISSN 1022-0119 ; 0256-6702
    DOI 10.2989/10220119.2014.939996
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

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  4. Article ; Online: Quantifying rehabilitation risks for surface-strip coal mines using a soil compaction Bayesian network in South Africa and Australia: To demonstrate the R

    Weyer, Vanessa D / de Waal, Alta / Lechner, Alex M / Unger, Corinne J / O'Connor, Tim G / Baumgartl, Thomas / Schulze, Roland / Truter, Wayne F

    Integrated environmental assessment and management

    2019  Volume 15, Issue 2, Page(s) 190–208

    Abstract: Environmental information is acquired and assessed during the environmental impact assessment process for surface-strip coal mine approval. However, integrating these data and quantifying rehabilitation risk using a holistic multidisciplinary approach is ...

    Abstract Environmental information is acquired and assessed during the environmental impact assessment process for surface-strip coal mine approval. However, integrating these data and quantifying rehabilitation risk using a holistic multidisciplinary approach is seldom undertaken. We present a rehabilitation risk assessment integrated network (R
    MeSH term(s) Australia ; Bayes Theorem ; Coal Mining ; Environmental Restoration and Remediation ; Risk Assessment ; Soil ; South Africa
    Chemical Substances Soil
    Language English
    Publishing date 2019-02-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2234931-5
    ISSN 1551-3793 ; 1551-3777
    ISSN (online) 1551-3793
    ISSN 1551-3777
    DOI 10.1002/ieam.4128
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Bonn / Germany

    Z 7647: Show issues

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  5. Article: Influence of Grazing Management on Plant Diversity of Highland Sourveld Grassland, KwaZulu-Natal, South Africa

    O'Connor, Tim G / Martindale, Greg / Morris, Craig D / Short, Alan / Witkowski, Ed T.F / Scott-Shaw, Rob

    Rangeland ecology & management. 2011 Mar., v. 64, no. 2

    2011  

    Abstract: Commercial livestock production offers one of the main opportunities for mainstreaming of biodiversity conservation in the grassland biome of South Africa. Grazing management is expected to influence success. With the uses of three long-term grazing ... ...

    Abstract Commercial livestock production offers one of the main opportunities for mainstreaming of biodiversity conservation in the grassland biome of South Africa. Grazing management is expected to influence success. With the uses of three long-term grazing trials, effects of stocking rate and cattle-to-sheep ratio on the plant composition and diversity of Highland Sourveld grassland in KwaZulu-Natal were examined. Plant diversity was sampled with the use of modified Whittaker plots. Canonical correspondence analysis was used to test the effects of treatments on compositional variation, and general linear models were used to test individual species' responses. In a biennial rotation, burned/grazed plots supported lower species richness of forbs and all plants than unburned/ungrazed plots, attributed to the impact of grazing during the season of occupation. A high stocking rate resulted in a long-term decrease of forb richness in one experiment, but an increase in another. An increasing proportion of sheep to cattle resulted in a long-term decrease of the richness of forbs and of total species richness. The three trials identified nongrass species that behaved as increasers or decreasers in response to an increase in stocking rate, and a set of species that behaved as decreasers in response to an increasing proportion of sheep to cattle. Constraints on using long-term trials for identifying the effects of livestock management on plant diversity include lack of baseline data, limited replication, pre-experimental impacts on the study site, and the difficulty of assessing uncommon species.
    Keywords cattle ; ecosystems ; forbs ; grasslands ; grazing ; grazing management ; linear models ; livestock production ; sheep ; species diversity ; stocking rate ; South Africa
    Language English
    Size p. 196-207.
    Publishing place Society for Range Management
    Document type Article
    Note Summary in Spanish.
    ZDB-ID 2180183-6
    ISSN 1551-5028 ; 1550-7424
    ISSN (online) 1551-5028
    ISSN 1550-7424
    DOI 10.2111/REM-D-10-00062.1
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Long-term response of an herbaceous sward to reduced grazing pressure and rainfall variability in a semi-arid South African savanna

    O'Connor, Tim G

    African journal of range & forage science

    Volume v. 32,, Issue no. 4

    Abstract: Reduced grazing pressure is expected to promote recovery of degraded semi-arid savanna. Transformation of degraded livestock ranches to a wildlife reserve in 1982 created a system with about one-third of the grazing pressure, which was maintained until ... ...

    Abstract Reduced grazing pressure is expected to promote recovery of degraded semi-arid savanna. Transformation of degraded livestock ranches to a wildlife reserve in 1982 created a system with about one-third of the grazing pressure, which was maintained until 2011. Herbaceous composition and condition were monitored on four occasions between 1982 and 2011. Baseline measurements were taken following eight years of above-average rainfall conditions. Palatable perennial grasses and sward condition deteriorated markedly in response to severe, sustained drought during the early 1990s. Perennial grasses did not respond to a single record high rainfall season (2000) but recovered following a sequence of four above-average years (2008–2011). This monitoring study illustrated that recovery of a degraded semi-arid savanna may require decades of reduced grazing pressure for some degree of recovery in the absence of intervention. An appropriate time frame for management of these systems is in the order of a century.
    Keywords grasses ; grazing intensity ; ranching ; monitoring ; management systems ; sward ; savannas ; conservation areas ; rain ; livestock ; drought
    Language English
    Document type Article
    ISSN 1727-9380
    Database AGRIS - International Information System for the Agricultural Sciences and Technology

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    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

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  7. Article: Bush encroachment in southern Africa: changes and causes

    O'Connor, Tim G / Puttick, James R / Hoffman, M Timm

    African journal of range & forage science

    Volume v. 31,, Issue no. 2

    Abstract: Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y ⁻¹. Encroachment was most rapid on small protected areas, ... ...

    Abstract Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y ⁻¹. Encroachment was most rapid on small protected areas, intermediate under commercial tenure, and slowest under communal tenure and large, natural environments with mega-herbivores present. Several drivers of bush encroachment, which interact and change over time, have been proposed. Fires, for example, were actively suppressed during the early twentieth century. However, rainfall interacts with fire and the rate of woody increase under fire exclusion is linearly related to mean annual rainfall. A reduction in browsing herbivores from the nineteenth century would have had a positive cumulative effect on woody cover whilst an increase in grazing herbivores would have reduced the competitive effect of grasses. Encroachment was most rapid during the high rainfall, mid-1970s, which followed the 1960s drought when cattle numbers were at their peak, and the grass layer was degraded. Increasing atmospheric [CO ₂] and climate change have emerged as important drivers in the recent literature. Bush encroachment depends on the interplay of history, environment, management and vegetation, recognition of which is essential for containing encroachment.
    Keywords herbivores ; grazing ; conservation areas ; cattle ; vegetation ; climate change ; carbon dioxide ; drought ; fires ; grasses ; forage and feed science ; browsing ; rain
    Language English
    Document type Article
    ISSN 1727-9380
    Database AGRIS - International Information System for the Agricultural Sciences and Technology

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    Kategorien

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