Thesis (MScFor)--Stellenbosch University, 2002. / 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. / AFRIKAANSE OPSOMMING: Die Australiese akasia, A. saligna, is wydverspreid in die Wes-Kaap, Suid-Afrika, en word
dikwels gebruik deur die plaaslike gemeenskap. Dit is dan nie verbasend dat die invoering van die
biologiese bestrydingsmiddel, die swam Uromycladium Tepperianum in 1987, met teenstrydige
emosies ontvang is nie. In 'n poging om die sosio-ekonomiese en ekologiese impak van die swam
te bepaal, het die Department van Waterwese en Bosboukunde 'n ondersoek aangevra waarvan
die tesis deel vorm. Vir die tesis word 'n aantal parameters, omgewings sowel as biologies,
geproef, geanaliseer en vergelyk met bestaande data van vroeër navorsing. Die doel van die studie
is om te bepaal watter effek A. saligna op 'n sandpleinfynbos gemeenskap naby Atlantis het en
om sodoende vas te stelof die nadelige effek van A. saligna op die biodiversiteit onomkeerbaar
is. Plantaardige data bevestig resultate uit vroeër studies dat A. saligna 'n afuame in plant
diversiteit, veral in digte akasiabosse, veroorsaak. In die studie word getoon dat die toename van
A. saligna strukturele veranderings in plaas van gemeenskaplike verskuiwings tot gevolg het. Die
verryking van die grond, deur ander navorsers genoteer, word ook in die studie bevestig. Dit is
egter buite die veld van studie om die lang termyn gevolge van die verryking van die grond op die
sandpleinfynbosgemeenskap te beslis. Op drie verskillende geleenthede word die watergehalte
van die grond getoets onder die akasiabosse en die fynbos. Die doel van die toetse is om vas te
stel hoe A. saligna die beskikbaarheid van water in die boonste grondlaag beïnvloed. In
teenstelling is hoër vogtigheidsvlakke in die boonste grondlaag onder die akasiabosse as onder
die fynbos gevind gedurende lente en vroeë somer. Lokvalle is gebruik om monsters te neem van
die antropodieë woonagtig op die oppervlak van die studiearea. Oor die algemeen is die opname
vir die antropodieë onvoldoende. Dit is egter insiggewend dat die spinnekopspesies voordeel trek
uit die aanwesigheid van A. saligna. Dit is waarskynlik omdat die akasia strukturele diversiteit
aan die fynbos verleen. Die studie onthul dat die volle ekologiese impak van A. saligna op sy
omgewing moeilik verstaanbaar is as gevolg van die diversiteit en kompleksiteit van fynbos
asook 'n gebrek aan navorsing.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53104 |
| Date | 12 1900 |
| Creators | Van den Berckt, Tom |
| Contributors | Boucher, C., Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science . |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 118 p. : ill. |
| Rights | Stellenbosch University |
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