Determining the current geographical extent of Gamba grass (Andropogon gayanus) infestations in Litchfield National Park and Coomalie Shire, NT using aerial survey

  • Isabella Amouzandeh

    Student thesis: Coursework Masters - CDU


    In northern Australia weed distribution n1apping is often inadequate, lirniting the ability of n1anagers to strategically respond to the threats posed by invasive plant species. This study developed and tested different lo\v resolution mapping techniques to provide Gan1ba grass (Andropogon gayanus) density and distribution data for both fire and weed n1anagcn1ent purposes. Aerial and ground-based surveys of gan1ba grass \Vcrc undertaken in Coon1alie Shire and Litchfield National Park (LNP), NT betvvccn the 9th April and 19th June 2008. Two different case studies were undertaken incorporating four different survey methods; reconnaissance, broad-scale transectbased, fine-scale transect-based, and ground-based. Data collected during surveys vas forn1atted and overlaid using a Geographical Inforn1ation Systctn (GIS) to create n1aps depicting the extent of gan1ba grass infestations in relation to the study area. Ninetyone percent of the properties surveyed in Coon1al ie Shire during the reconnaissance and transect-based aerial surveys were recorded with gan1ba grass, con1parcd to 11% of quadrats surveyed in the broad-scale transect based aerial survey of LNP. !v1aps reveal dense gan1ba grass infestations in Finniss Valley, Can1p Creek and Eva Valley in Cootnalie Shire, and in the cast and southernn1ost tip of LNP. Severall in1itations to the accuracy and reliability of survey results were identified including: the issues associated with scale; observer differences; environmental factors; usc of gamba grass in cattle grazing; lack of a prcdetennined flight path (in the reconnaissance survey); tin1e lag; and lin1ited ground-truthing. The n1ajor in1plications of results for fire and weed n1anagcrnent include the recalculation of the Grassland Fire Danger Index (GFDI) for Coon1alic Shire, and the prioritisation of control strategies in LNP within the outer lin1its of gmnba grass infestations.
    Date of AwardSep 2008
    Original languageEnglish
    SupervisorPiers Hugh Barrow (Supervisor), Keith Brian Ferdinands (Supervisor), Samantha Setterfield (Supervisor) & Penny Wurm (Supervisor)

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