Browsing by Subject "vegetation"
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- ItemOpen AccessDescription and Gradient analysis of the Coastal band Vegetation in the Groen River mouth area (Namaqualand Strandveld)(1998) Raiomondo, Domitilla; Cowling, R MStrandveld 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.
- ItemOpen AccessInterannual memory effects for spring NDVI in semi-arid South Africa(2008) Richard, Yves; Martiny, Nadège; Fauchereau, Nicolas; Reason, Chris; Rouault, Mathieu; Vigaud, Nicolas; Tracol, YannAlmost 20 years of Normalized Difference Vegetative Index (NDVI) and precipitation (PPT) data are analysed to better understand the interannual memory effects on vegetation dynamics observed at regional scales in Southern Africa (SA). The study focuses on a semi-arid region (25°S–31°S; 21°E–26°E) during the austral early summer (September–December). The memory effects are examined using simple statistical approaches (linear correlations and regressions) which require the definition of an early summer vegetation predictand (December NDVI minus September NDVI) and a consistent set of potential predictors (rainfall amount, number of rainy days, rainfall intensity, NDVI and Rain-Use-Efficiency) considered with 4 to 15-month time-lag. An analysis over six SA sub-regions, corresponding to the six major land-cover types of the area reveals two distinct memory effects. A “negative” memory effect (with both rainfall and vegetation) is detected at 7 to 10-month time-lag while a “positive” memory effect (with vegetation only) is observed at 12 to 14-month time-lag. These results suggest that interannual memory effects in early summer vegetation dynamics of semi-arid South Africa may preferably be driven by biological rather than hydrological mechanisms.
- ItemOpen AccessLand degradation in South Africa(2014-09-17) Hoffmann, Timm; Todd, Simon; Ntshona, Zolile; Turner, StephenSouth Africa has a long history of desertification research which stretches back to the last century. These resources contain literature on water, soil and veld degradation in both commercial and communal areas of South Africa. Also, the most important socio-economic reasons for land degradation are discussed. This resource contains various chapters and factsheets on land degradation in South Africa. A vast amount of data which was generated during the national review of land degradation in South Africa is also available in both GIS and Excel format.