Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Eucalyptus camaldulensis Dehnh., or River Red Gum, is a commercially valuable yet recognised
invasive alien plant (IAP) of riparian zones throughout South Africa. The invasive potential of E.
camaldulensis is widely recognised, with specific regulations aimed at the management of E.
camaldulensis. E. camaldulensis is known to use large amounts of water, reduce biodiversity,
change river morphology and impact hydrological regimes of rivers. In the native range throughout
Australia, E. camaldulensis displays a distinct relationship between rainfall, and flood events, for
seed dispersal, germination and establishment, and consequently spatial extent, yet little is known
about the relationships in the South African context. The aim of this project was to assess the
impact of high rainfall and flood events on the establishment and distribution of E. camaldulensis
along the Middle Breede River, between Worcester and Swellendam in the Western Cape, by
establishing the current spatial extent of E. camaldulensis along the river, identifying flood events
since 1950 and evaluating the impact rainfall and flood events had on the spatial extent thereof.
Aerial imagery, rainfall, discharge and river level data was obtained dating back to 1980, as well as
field data comprising of GPS-bounding of E. camaldulensis stands. Additionally, density
measurements were obtained and interviews conducted with land users. Spatial analysis of aerial
imagery, coupled with perimeter (GPS) data and density data were used to conduct spatio-temporal
analysis, employing GIS and conventional statistical approaches to address the various objectives.
Results indicated E. camaldulensis stands had a small overall increase in spatial extent since 1980.
Flooding and rainfall events coincided with an increase in occurrence of E. camaldulensis with
elevated river levels and frequent flooding, while spatial variation of this relationship was observed.
The hydrological regime of the Breede River coincides with a slow increase in spatial extent of E.
camaldulensis stands, but no affirmation of a positive real-world relationship was possible using the
available data. Results further suggested, based on the current age class composition, that existing
stands originated roughly during 1980, possibly due to commercial forestry related seeding into the
river. Reduced fragmentation between stakeholders, educational programmes and improved
reporting systems were recommended for improved IAP management within the area. / AFRIKAANSE OPSOMMING: Eucalyptus camaldulensis, of Rooibloekom (RB), is ‘n waardevolle kommersiële, maar erkende
indringer plantspesie (IP) wat veral oewersones in Suid-Afrika indring. Die indringerpotensiaal van
E. camaldulensis is welbekend, en spesifieke regulasies, gemik op die bestuur van RB en ander
spesies is reeds aangeneem. E. camaldulensis is veral bekend vir sy hoë watergebruik, sy
vermindering van biodiversiteit, sy vermoë om riviervorme te verander en sy algehele impak op die
hidrologiese patroon van riviere waarmee dit in aanraking kom. In sy oorspronklike
verspreidingsgebied in Australië toon E. camaldulensis ‘n bepaalde verhouding tussen reënval en
vloedgebeurtenisse vir saadverspreiding, ontkieming en vestiging en derhalwe die ruimtelike
verspreiding van die spesie; alhoewel hierdie verhouding in die Suid-Afrikaanse konteks steeds
redelik onverduidelik bly. Die doelwit van hierdie studie was dus om die impak van hoë reënval en
vloedgebeurtenisse op die ruimtelike verspreiding en vestiging van E. camaldulensis teenaan die
Middel Breëde Rivier, spesifiek tussen Worcester en Swellendam, te evalueer. Hierdie doelwit was
bereik deur die historiese ruimtelike verspreiding teenaan die rivier te meet, hoë reënval en
vloedgebeurtenisse vanaf 1980 te identifiseer, en die huidige verspreiding en omtrek met GPS te
meet. Digtheidafmetings, sowel as onderhoude met belanghebbendes teenaan die rivier was ook
opgeneem. Visuele interpretatasie van lugfotos, sowel as omtrek (GPS) en digtheid-data was
gebruik om ruimtelike analise uit te voer, deur die gebruik van GIS en konvensionele statistiese
metodes, ten einde die doelwitte te evalueer. Resultate dui aan dat E. camaldulensis areas ‘n klein
algemene groei getoon het sedert 1980. Hoë-reënval en gereëlde vloedgebeurtenisse het ook
gepaard gegaan met ‘n groei van E. camaldulensis oppervlak, alhoewel hierdie verhouding
ruimtelike variasie getoon het, met ‘n algemene groei patroon gemerk oor die volledige
studietydperk. Ook geen stimulerende verhouding kon vanuit die beskikbare data bevestig word nie.
Addisionele resultate het aangedui dat die verspreiding van E. camaldulensis ongeveer 1980
onstaan het, moontlik as gevolg van kommersiële bosbou-aanplanting en verwante saadverspreiding
in die rivier vanaf daardie tyd. Aanbevelings ten opsigte van verbeterde indringerbestuur sluit in die
beperking van huidige fragmentasie tussen belanghebbendes en betrokke verwyderingsorganisasies,
addisionele onderrigprogramme sowel as die verbetering van terugvoersisteme.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97021 |
| Date | 04 1900 |
| Creators | Raath, Gideon |
| Contributors | Poona, N. K., Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 187 pages : illustrations, maps |
| Rights | Stellenbosch University |
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