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dc.contributor.authorStrydom, M.
dc.date.accessioned2016-01-21T09:54:50Z
dc.date.available2016-01-21T09:54:50Z
dc.date.created2015en
dc.date.issued2016-01-21T09:54:50Z
dc.identifier.urihttp://hdl.handle.net/123456789/1916
dc.description.abstractAustralian Acacia have become invasive in many parts of the world and are the most prominent invasive plants in South Africa. These nitrogen-fixing woody species change ecosystem structure and functioning, impacting on species richness and ecosystem services in their invaded ranges. These impacts cost economies billions of dollars annually. The environmental and economic effects have led to significant management efforts to control this invasion in South Africa. A large obstacle to the effective and sustainable management of invasive Australian Acacia, even in the presence of released biological control agents, is their ability to accumulate large seed banks. Despite the importance of seed banks for the successful management of these invasive plants and their relevance to monitoring management progress and success (e.g. biological control), there is a general lack of knowledge on their seed bank dynamics. Therefore, various aspects linked to the seed bank dynamics of four invasive Australian Acacia (A. longifolia, A. mearnsii, A. pycnantha and A. saligna) over space and time was studied. Through investigating this process it was aimed to assess the potential seeds that will have to be managed, whether the released biological control agents have an impact on the population dynamics of their invasive Australian Acacia hosts as well as when management should be conducted. Many seeds still resided in the seed banks of the studied species, regardless of the presence of the released biological control agents. These seed banks were not residual, i.e. the legacy of seed input from before biological control agents were released, but was shown to be the result of current seed accumulation over time. This seed bank accumulation suggested that seed production and survival remained high despite the impact of the biological control agents. Confirmation of this prediction was given through a study of seed production, which showed that many seeds are produced throughout the life-time of invasive Australian Acacia populations. Both the seed bank and seed production studies showed that irrespective of the seeds lost to biological control agents, these organisms have no impact on the population dynamics of invasive Australian Acacia, since more than enough seeds are produced to ensure population persistence. The development of the seed rain and seed bank over time indicated that the first few years of fruiting are important in determining seed bank size as well as the long-term persistence of seeds in the soil. Based on this finding a management strategy is proposed to control invasive Australian Acacia populations while they are still young, i.e. during the first few years post disturbance events. Focusing control efforts on the seedling stage will prevent the build-up of large seed banks, decrease the long-term persistence of seeds in the soil and will be more cost-effective, as removal of small plants requires fewer resources than large mature trees. Through investigating the seed bank dynamics of Australian Acacia, and establishing relationships between stand age (using tree size as a proxy), it was shown that seed banks can be used as an effective tool to monitor management effectiveness and progress.en
dc.description.statementofresponsibilityStrydom, Matthys
dc.format.extent4424718 bytes
dc.format.extent1254937 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypeapplication/vnd.ms-excel
dc.languageEnglishen
dc.language.isoen_US
dc.rightscopyrighten
dc.subjectAustralian Acaciaen
dc.subjectseed banksen
dc.subjectbiological controlen
dc.subjectseed productionen
dc.titleThe seed bank dynamics of invasive Australian Acacia in the presence of biological control agentsen
dc.mdidentification.purposeData of different phases in the seed bank dynamics process was collected in order to understand when management (mechanical, chemical or biological) should be conducted in order to potentially manage the lowest number of seeds over time. These data were also collected to understand the current impact of the released seed reducing biological control agents (more specifically the gall forming agents).en
dc.mdidentification.organizationnameCentre of Excellence for Invasion Biologyen
dc.mdidentification.deliverypointFaculty of Science, Natural Sciences Building, Private Bag X1, Stellenbosch University, Matielanden
dc.mdidentification.postalcode7602en
dc.mdidentification.phone0218082832en
dc.mdidentification.electronicmailaddresskcd@sun.ac.zaen
dc.mddataidentification.languageEnglishen
dc.mdusage.specificusageUnderstand seed bank dynamics of invasive speciesen
dc.mdusage.usagedatetime2020-01-01
dc.mdlegalconstraints.accessconstraintscopyrighten
dc.lilineage.statementAll data was collected by the author (Matthys Strydom).en
dc.dqcompletenessomission.valueunitPercentageen
dc.dqcompletenessomission.valueattributedata100en
dc.mdmaintenanceinformation.maintenanceandupdatefrequencyUnknownen
dc.mdfeaturecataloguedescription.cataloguedate2016-01-19
dc.mddistributor.distributorcontactCentre for Invsion Biologyen
dc.mdformat.nameMS Excelen
dc.mdformat.version2010en
dc.exgeographicboundingbox.westboundlongitude18.430201en
dc.exgeographicboundingbox.eastboundlongitude20.055042en
dc.exgeographicboundingbox.northboundlattitude-33.294985en
dc.exgeographicboundingbox.southboundlattitude-34.840293en
dc.exverticalextent.minimumvaluesea levelen
dc.exverticalextent.maximumvalue450en
dc.exverticalextent.unitofmeasuremetersen
dc.cibprojectDeterminants of invasion and scenarios of changeen


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