Department of Forest and Wood Science

Permanent URI for this community

https://scholar.sun.ac.za/handle/10019.1/20

Browse

Browsing Department of Forest and Wood Science by browse.metadata.advisor "Boucher, C."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The ecological effect of Acacia saligna in a sand plain fynbos ecosystem of the Western Cape, South Africa
    (Stellenbosch : Stellenbosch University, 2002-12) Van den Berckt, Tom; Boucher, C.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science .
    ENGLISH ABSTRACT: The invasive Australian acacia, A. sa ligna, is widespread in the Western Cape, South Africa, and is widely used by local communities. Not surprisingly, the introduction of the biological control agent, the fungus Uromycladium tepperianum in 1987 was received with mixed emotions. In an effort to determine the socio-economical and ecological impact of the fungus, the Department of Water Affairs and Forestry has commissioned a study, of which this thesis forms part. For this thesis, a number of parameters, environmental as well as biological, were sampled, analyzed and compared with existing data from previous studies. The goal was to obtain a comprehensive estimation of the effect of A. saligna on a Sand Plain Fynbos community near Atlantis and to assess whether or not, the detrimental effect A. saligna has on plant biodiversity, has reached the stage where it has become irreversible. The floristic data confirmed results from earlier studies, that invasion of A. saligna in Fynbos communities induces a decline in plant diversity, especially in dense acacia thickets. This study mainly revealed structural changes rather than community shifts. The enrichment of the soil as noted by others authors was also confirmed for the study area. However, it was outside the scope of this study to determine the long-term effects of this enrichment on the Sand Plain Fynbos communities. Soil moisture content was sampled on three different occasions, in densely invaded and uninvaded study plots. The aim was to see if A. saligna had any influence on the availability of water in the upper soil. Contrary to expectations, moisture content under acacia stands was higher in spring and early summer in the top soil than in pristine fynbos. Pitfall traps were used to sample the arthropods that dwell the surface of the study area. For arthropods in general, the survey did not produce conclusive data, but spider species seem to be positively affected by the presence of A. saligna, probably due to the structural diversity they add to the fynbos. This study revealed that the full ecological impact of A. saligna on its environment is far from understood, mainly due to the richness and complexity of the fynbos communities and a lack of research about faunal aspect of the Fynbos ecosystem.
  • Thumbnail Image
    Item
    Reproductive biology and utilisation of Berchemia discolor (Klotzsch) Hemsley (Rhamnaceae)
    (Stellenbosch : Stellenbosch University, 1999-12) Lusepani, Nakwezi Esther; Boucher, C.; Marais, E. M.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest & Wood Science.
    ENGLISH SUMMARY: Berchemia discolor is an indigenous African fruit tree species with potential in terms of commercialisation and domestication. Indigenous fruit tree species play a role in the socioeconomic well being of small-scale farmers and rural communities. To facilitate the process of domestication and commercialisation of B. discolor, it is important to learn more about the biology of the species, nutritional value of the fruit, and if potential markets exist for the fruit. Fieldwork was carried out in Caprivi and Omusati in northern Namibia in order to study the reproductive phenology and the floral and pollination biology of the species. Analysis of the nutritional value of the fruit was carried out on the dry fruit pulp to assess the nutrients, minerals and vitamins contained in the fruit. In addition to this a socio-economic survey was carried out to assess the current trade in fruit and the utilisation of the tree and its products. The length of the reproductive phase during the 1996-97 season extended from mid October to end of March in Caprivi and from beginning of November to early April in Omusati. Vegetative growth and flower bud formation in Omusati occurred just after the onset of the first rain whereas in Caprivi it occurred two weeks prior to the onset of the rain. The flowers of B. discolor are dichogamous and protandrous. Pollinators are probably attracted to the flowers by olfactory stimuli, however visual stimuli also play a role as the flowers are greenish-yellowish in colour and several flowers are borne together in the inflorescence. Insect visitors to the flowers were identified as belonging to four different orders (Hymenoptera, Diptera, Coleoptera and Heterophera). Three of these orders have genera which may represent potential pollinators of B. discolor. Stigma receptivity probably occurred only after the elongation of the pistil subsequent to the presentation of pollen. The dry fruit pulp of B. ·discolor is rich in carbohydrates, calcium, sodium, iron, magnesium and potassium, but it is not a good source of phosphorus, fat, protein and ascorbic acid. The fruit trade is important for generating income, which is used to acquire other goods and services by the rural people. B. discolor could, subject to improvements on fruit quality and marketing become one of the commercial fruit in northern Namibia.