Browsing by Author "Cowling, R M"

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    Description and Gradient analysis of the Coastal band Vegetation in the Groen River mouth area (Namaqualand Strandveld)
    (1998) Raiomondo, Domitilla; Cowling, R M
    Strandveld vegetation around the Groen river mouth was sampled using complementary ordination and classification techniques (DCA and TWINSP AN). Four communities can be recognised, although samples are primarily divided into inland and coastal plots. Two inland communities are: Stoebaria utilis-Salvia lanceolata community, characterised by tall vegetation(> 1m), on deep, loose soils; Hermannia spp-Leserlia diffusa community of short (<0.6m) vegetation on shallow soils with a hardpan dorbank layer. Two coastal Strandveld communities are: Vanzylia amulata-Limonium peregrinum community which has short vegetation ( <0.5m) on characteristic shallow soils with a calcrete layer at 50 cm deep; Ruschia hutchensonia-Sasola nolothensis community characterised by deep alkaline soils. Of the environmental variables sampled, soil resistance and the presence of calcium carbonate in the soil best explain the distribution of plots and species in ordination space. Communities classified in this study differ subtly from the Tall, Medium and Short Strandveld communities and Strand communities proposed by le Roux and Boucher, 1989 and 1993.
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    'Enough to be considered useful': John Acocks' contribution to South African botany
    (2003) Hoffman, M T; Cowling, R M
    John Acocks died in 1979 after working for nearly 50 years as a botanist in South Africa. His scientific contributions have had a profound influence on southern African ecology and this introductory article which includes a biographical sketch of his life, places his contribution in perspective. The 10 articles which appear in this issue have been prepared not only as a tribute to his contribution but also as an assessment of its current utility. Scientific thought is constantly changing and an attempt has been made to indicate where Acocks’ views are still supported by current evidence and where revision is necessary. His contribution lay in three main areas. Firstly, his description of the vegetation (or Veld Types) of South Africa remains a work of considerable importance and will probably never be repeated at the same level of scale, by a single individual, again. Three articles show that when assessed at a smaller scale his Veld Type concept is robust in some, but not all, cases. Differences between Acocks’ views and current treatments of the data are highlighted for the Bankenveld and for the vegetation of the Subtropical Thicket and Nama-karoo biomes. Acocks’ second important influence concerns his views on precolonial vegetation and the extent of human impact. He could not have presaged the explosion of palaeoenvironmental techniques which have arisen since his death and which have provided a somewhat different view of pre-colonial environments from the one he articulated, particularly with regard to the influence of fire on grasslands, savannas and forests. Although his views on the expansion of the eastern Karoo are not upheld in the light of recent findings there is good evidence for significant changes in the fauna and flora of the Karoo over the last 300 years. Acocks’ final contribution lay in the field of veld restoration and grazing management where he continues to have an influence on a small sector of the farming and range science community today. Not only has John Acocks provided a rich theoretical framework for scholars to test but he has also left a legacy of well-organised data for future generations. The final two papers in this special issue indicate the utility of his archives which will gain in value over the years. Challenges to Acocks’ views will continue apace and much of what he has written will undoubtedly be revised. This doesn’t detract from his contribution in any way but serves to highlight the importance of the foundation that he created during his lifetime and which we acknowledge in this special issue.
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    Thirty years of change in the fynbos vegetation of the Cape of Good Hope Nature Reserve, South Africa
    (2001) Privett, S D J; Cowling, R M; Taylor, H C
    This study used permanently marked 50 m: sites, surveyed at a 30 year interval, to provide a descriptive account of the temporal change in the fynbos vegetation of the Cape of Good Hope Nature Reserve. South Africa. Management records were used to examine the role of post-fire age. fire frequency and intensity, as well as biotic interactions (competition from overstorey proteoids and alien plants) in influencing vegetation composition over this time period. The mean similarity in species composition of sites between surveys was 62%, indicating an average of nearly 40% turnover in species over the 30 year period. The main causes of this change included differences resulting from different stages in the post-fire succession as well as the impact of differential fire regimes (especially frequency effects). Competition from serotinous Proteaceae. which proved highly mobile after fire, as well as invasive Australian acacias also impacted on the composition of the vegetation over time. The study demonstrated that fynbos communities are temporally dynamic and that the changes over time in species composition are caused by a variety of processes. The study also provided evidence for the role of temporal diversity in contributing to the high species diversity in fynbos systems.