Fire in Southern Australia - Fire in Mediterranean Ecosystems - page 208

a variety of southeastern Australian studies, spanning spatial scales from local
to subcontinental, coastal to alpine environments, and differing methodologies
(e.g. charcoal counts, tree rings) indicate that fire activity increased substantially
during the early European era (nineteenth to early twentieth century; Banks 1989 ;
Mooney et al. 2001 ; Kershaw et al. 2002 ; Mooney & Maltby 2006 ; Zylstra 2006 ).
Colonial exploitation involved laissez-faire use of fire (Pyne 1991 ; Collins 2006 )
and is observed in other MTC regions upon European colonization. Some studies
indicate a decline in fire activity in the later twentieth century, due in part to
increasingly effective fire suppression, to levels similar to the pre-European era
(Kershaw et al. 2002 ).
A unique technique for reconstructing fire history is based on growth bands in
the arborescent monocot known as grasstrees Xanthorrhoea preissi ( Fig. 8.2b )
(Ward et al. 2001 ) and has been applied in southwestern Australia. It indicates a
very high fire frequency (3-4 fires per decade at a point scale) prior to European
colonization and a reduction in fire activity following colonization. Fluctuations
in putative European-era fire activity measured by this technique correspond with
differing eras of fire and land management policy (Ward et al. 2001 ; Lamont et al.
2003 ). Recent attempts at validation of the technique in kwongan heathlands,
however, have indicated major anomalies (Enright et al. 2005 ; Miller et al. 2007 ;
Enright & Thomas 2008 ) that limit the ability of this method to reconstruct fire
history prior to the early twentieth century. In all likelihood aboriginal burning
was very patchy and potentially not representative of regional fire regimes
(Enright & Thomas 2008 ).
The fire regimes of contemporary MTV communities vary widely according to
local climate and ignition patterns ( Table 8.1 ; Bradstock et al. 2002 ). Generally,
the point fire return interval in Australian MTVs is decadal to multidecadal (once
every few decades or more) (Burrows & Friend 1998 ; Gill & Catling 2002 ; Hobbs
2002 ; Keith et al. 2002 ; Enright & Thomas 2008 ), though important variations
occur above and below this range ( Table 8.1 ). Gill and Moore ( 1997 ) and Boer
et al. ( 2009 ) documented recent fire regimes in southwestern Australia open forests
(predominantly Eucalyptus marginata dominated jarrah forest). They found that
under the influence of extensive prescribed burning the average fire return interval
was 5-10 yrs. Fire activity is related to rainfall (Clarke 2002a ; Pausas & Bradstock
2007 ; Burrows 2008 ) with average fire frequency declining toward the drier end of
the rainfall gradient due to fuel constraints. In contrast, other MTV such as some
forests and wet heaths in high-rainfall areas ( 1000 mm) may have fire activity

limited by high fuel moisture and dependent on anomalously dry years, leading to
longer multidecadal fire intervals.
Impacts of European land use on fire regimes are varied. Vast areas of shrub-
land and woodland have been cleared for cereal cropping or utilized for rangeland
grazing in drier regions (McIvor & McIntyre 2005 ). This has resulted in a decline
in fire, among other changes to ecosystem functions (Hobbs 2002 ). There is an
emerging role for active restoration of fire in remnant vegetation of this kind for
biodiversity conservation purposes (Hobbs 2005 ; Prober et al. 2007 ). Large areas

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