Drivers of wildfire behaviour, severity and magnitude in the Limietberg conservation area : understanding the complexity of wildfire risk

Moir, Shaun Alexander (2014-12)

Thesis (MSc)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: The Western Cape Province in South Africa is home to one of the most diverse plant communities in the world, and has one of the highest concentrations of plants species in any temperate ecosystem in the world. The dominant vegetation is both fire-prone and fire-dependant (Van Wilgen & Scott 2001, Forsyth et al. 2010). The Western Cape in particular is emerging as a province that is increasingly prone to disaster events, particularly the threat of veld fires. The consequences of large wildfire disaster events are often devastating and far reaching (Van Wilgen & Scott 2001, Forsyth et al. 2010). This study was conducted in an attempt to investigate the drivers of wildfire behaviour, severity and magnitude in the Limietberg Conservation Area in order to gain a greater insight and understanding of the complexity of wildfire risk. Recognising the disaster prone character of the Western Cape and the increasing probabilities of future wildfire events in the province, this study aimed to strengthen the understanding of the drivers of wildland fire behaviour (i.e. wildland fire risk) in the Limietberg Conservation Area by analysing a number of fires to identify a range of drivers and patterns; examining the factors driving both fire danger and fire behaviour, including climate, topography, slope and fuel; examining the factors driving fire frequency and regime; and finally, determining possible ecological damage caused by the last 10 – 20 years of wildfire events in the Limietberg Conservation Area as measured by post-fire seedling ratios. This was achieved through the use of statistical techniques including multiple regression (McDonald 2009), ordination in the form of principal component analysis and non-metric multi-dimensional scaling (Clarke & Warwick 1994), and fieldwork in the form of post-fire regeneration (Proteaceae parent:seedling ratio) monitoring techniques (Bond et al. 1984; Vlok & Yeaton 2000; De Klerk et al. 2007). The results indicated that the interactions between factors driving fire danger and fire behaviour were indeed complex, being influenced mainly by meteorological variables (temperature, relative humidity, wind speed) but also quite strongly influenced by physical environmental factors (slope, topography). The use of ordination techniques in this sort of complex analysis was seen as extremely effective and its use in further fire research was strongly recommended.

AFRIKAANSE OPSOMMING: Die Wes-Kaap provinsie in Suid-Afrika is die tuiste van een van die mees diverse plant gemeenskappe in die wêreld, en het een van die hoogste konsentrasies van plantspesies in enige gematigde ekosisteem in die wêreld. Die dominante plantegroei is beide vuur geneig en vuurafhanklik (Van Wilgen & Scott 2001, Forsyth et al. 2010). Die Wes-Kaap in die besonder is opkomende as 'n provinsie wat toenemend geneig is tot ramp gebeure, veral die bedreiging van veldbrande. Die gevolge van groot veldbrand rampgebeure is dikwels verwoestend en verreikend (Van Wilgen & Scott 2001, Forsyth et al. 2010). Hierdie studie is uitgevoer in 'n poging om die oorsake van veldbrande, die gedrag, erns en omvang daarvan in die Limietberg Bewaringsgebied vir groter insig en begrip van die kompleksiteit van veldbrand risiko te ondersoek. Hierdie studie erken die rampgeneigdheid van die Wes-Kaap en die toenemende waarskynlikheid van toekomstige veldbrande in die provinsie. Dit het ten doel gehad om die oorsake van veldvuur gedrag (bv. brand risiko) in die Limietberg Bewaringsgebied deur die ontleding van 'n aantal brande se oorsake en patrone te identifiseer; die ondersoek van faktore wat beide brandgevaar en vuurgedrag, bepaal insluitend klimaat, topografie, helling en brandstof; die ondersoek van faktore wat vuur frekwensie en regime; en uiteindelik die bepaling van moontlike ekologiese skade veroorsaak deur die laaste 10 - 20 jaar van veldbrand gebeure in die Limietberg Bewaringsgebied, soos gemeet deur navuur saailing verhoudings. Die doel is bereik deur die gebruik van statistiese tegnieke waaronder meervoudige regressie (McDonald 2009), ordening in die vorm van hoofkomponent analise en multi-dimensionele skaling (Clarke & Warwick 1994), en veldwerk in die vorm van navuur herlewing (Proteaceae ouer:saailing verhouding) moniteringstegnieke (Bond et al. 1984; Vlok & Yeaton 2000; De Klerk et al. 2007). Die resultate dui daarop dat die interaksies tussen faktore wat brandgevaar en vuurgedrag inderdaad kompleks aandryf is en hoofsaaklik beïnvloed word deur meteorologiese veranderlikes (temperatuur, relatiewe humiditeit, windspoed), maar ook baie sterk beïnvloed word deur fisiese omgewingsfaktore (helling, topografie). Die gebruik van ordeningstegnieke vir hierdie komplekse tipe analise is bevind as uiters effektief en die gebruik daarvan in verdere vuur navorsing word sterk aanbeveel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/95810
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