Agriculture Reference
In-Depth Information
of intact dry shrublands remain in sparsely inhabited coastal regions of southern
Western Australia and South Australia, where lightning ignites occasional large
fires (McCaw
et al.
1992
) resulting in multidecadal fire regimes. Suppression
capacity and other management activities in these areas are often minimal.
Mosaics of open forests, woodlands and shrublands in higher-rainfall areas are
juxtaposed with densely populated urban centers and intensive rural industries
such as plantations, orchards, vineyards, etc. Considerable areas of eucalypt open
forest are managed for timber production, though recent, large-scale transfers of
such land into conservation reserves have occurred. In many states such reserves
now occupy a larger area than natural forests used for timber production. Fire
management in these regions has a strong emphasis on protection of urban and
rural assets, through active fire prevention involving surveillance or fuel reduction
and fire suppression. There is increasing emphasis on formal ecological manage-
ment of fire using appropriate information and planning systems (Keith
et al.
2002
; Bradstock & Kenny
2003
; Burrows
2008
; Gill & Allan
2008
). In these
reserves both human ignitions from accidents and arson, as well as lightning
ignitions, are important (Bradstock & Gill
2001
; McCaw & Hanstrum
2003
).
Major unplanned fires on the scale of 10
3
-10
5
ha occur regularly in southern
Australian ecosystems (Ellis
et al.
2004
; Esplin
et al.
2003
; Collins
2006
). There is
an apparent connection with El Nin˜ o generated droughts and major fire activity in
the southeast (e.g. Verdon
et al.
2004
; Hennessy
et al.
2006
) but these linkages
require more formal exploration. Major fires are driven by warm, dry air masses
generated by southern ocean cold fronts and/or tropical depressions in the south-
east, whereas in the southwest such air masses are generated by the eastward
passage of strong anticyclones (Luke & McArthur
1978
; McCaw & Hanstrum
2003
; Hennessy
et al.
2006
; Hasson
et al.
2009
). Global change factors may further
direct fire regimes toward extremes (Williams
et al.
2009
; Bradstock
2010
).
Diversity in MTV - Resources vs. Fire?
Contemporary MTV has origins in the Cretaceous with diversification throughout
the Tertiary and Quaternary (Hopper & Gioia
2004
; Hill
2004
), encompassing the
break-up of Gondwana, opening of the southern ocean, northern drift of the
continent and consequent onset of aridity (see
Chapter 10
). Australian vegetation
in the early Tertiary under a relatively warm, wet climate, despite a position of
high latitude, consisted of rainforests with gymnosperm and angiosperm domin-
ants. It is postulated that the ancestors of the diverse sclerophyll flora occupied
oligotrophic habitats on forest margins, such as shallow, periodically waterlogged
soils, that may have shaped the capacity to cope with infertile soils. Families of
plants attributed to these origins include Proteaceae (see
Box 7.1
), Fabaceae,
Casuarinaceae, Myrtaceae and Ericaceae. Sclerophyllous vegetation rose in prom-
inence throughout the late Tertiary and Quaternary in conjunction with increasing
aridity and evidence of fire (Hill
2004
).