Impacts and control of alien Proteaceae invasion in the Western Cape Province, South Africa
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Date
2017
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University of the Western Cape
Abstract
Research focused on ecological impacts and control of invasive alien species (IAS) is gaining
attention worldwide. The eradication and control of invasive alien plants (IAP) is essential for
the restoration of native plant communities. Understanding ecological impacts and potential
invasive risks of IAP is important for their effective management, particularly for prioritisation.
Most studies concerning impacts on vegetation structure and plant-pollinator interactions have
measured few ecological metrics, resulting in a superficial understanding of plant species
invasion. Additionally, most studies related to the control of IAP have focused on major
invaders which have demonstrated severe impacts, with less focus on emerging invaders. This
study assessed ecological impacts, invasive risks and chemical control options for alien Hakea
drupacea and Banksia species in the Western Cape Province, South Africa. Multiple ecological
metrics data on vegetation, soil and plant-pollinator parameters were measured and compared
between invaded and uninvaded sites. The invasion risk of fourteen Banksia species which
have been introduced to South Africa was evaluated by conducting a weed risk assessment
(WRA). The herbicide efficacy of resprouting Banksia integrifolia and Banksia serrata was
determined by rating plants response to different treatments, with percentage, height and
resprout vigour as measures. Results revealed significant negative impacts of alien H. drupacea
and Banksia speciosa invasion on native plant species richness and diversity and on the
abundance of native pollinators. The study demonstrated that 79% of Banksia species have a
high risk of invading the Fynbos Biome. Chemical control with triclopyr+picloram mix
provided effective means of controlling resprouting Banksia species. The high invasive risk
of Banksia species and competitive effects of invasive alien B. speciosa and H. drupacea with
native plant species for biotic and abiotic resources represents a major threat to biodiversity
conservation in the Fynbos Biome. The removal of both naturalised and invasive alien H.
drupacea and Banksia populations is recommended in order to conserve native plant
communities in the Fynbos Biome.
Description
Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol)