Agriculture Reference
In-Depth Information
1994
) and from which they expand outwards in the rare absence of fires (Luger &
Moll
1993
).
Most fires are started by people, although lightning-ignited fires occur with
some frequency in the mountains (Horne
1981
; Manry & Knight
1986
) and
occasionally such fires can exceed 100 000 ha (Versfeld
et al
.
1992
). Strong winds,
known locally as berg winds, play a critical role in determining fire size, and the
highest winds are during the summer drought (
Box 1.3
). As in other MTC
regions, many fynbos species resprout from lignotubers and have dormant
seedbanks that are stimulated by fire, plus a very rich geophyte flora that
resprouts and flowers after fire. Unlike California, annuals represent a less
impressive part of the postfire flora. Components of fynbos vegetation persist
on low-nutrient soils to the east of the Western Cape Province, and outside the
MTC, and this MTV extends in patches into the summer-rain climate of eastern
South Africa.
Western Australia and South Australia have a well-developed MTC and
landscapes are dominated by evergreen sclerophyllous heathlands (
Fig. 1.6f
),
mallee shrublands and
Eucalyptus
woodlands and forests with an abundance of
geophytes and other herbaceous perennials. The highly weathered coarse-
grained oligotrophic substrates are similar to pockets of such soil in South
Africa (
Fig. 1.5
) and this is one factor accounting for both regions sharing
many plant families (
Table 1.2
). The very low nutrient soils in the southwestern
portion of Western Australia support a sclerophyllous heathland vegetation
known as
kwongan
that has many floristic and structural relationships with
South Africa's fynbos (Pate & Beard
1984
). As in South Africa these shrublands
are resilient to very high fire frequencies. On drier or sometimes more fertile
sites various species of
Eucalyptus
form mallee vegetation characterized by
extensive coppicing from large lignotubers after fires (Parsons
1981
).
A significant portion of the Southwestern Botanical Province includes closed-
canopy
Eucalyptus
forests that tower above the associated shrubland commu-
nities (Rundel
2004
). The MTC extends eastward into South Australia and
western Victoria, with landscapes dominated by complexes of heathlands,
mallee and woodland communities. Eucalypt forest with a heath understory is
widely distributed across southern Australia into the non-MTC southeast with
an aseasonal climate (
Box 1.2
).
Conclusions
A significant portion of terrestrial vegetation is fire-prone. Climate and geology
interact with fire to create the environmental template that determines plant
traits, community assembly and plant and animal distributions. Mediterranean-
type climates dominate five widely separate parts of the globe in temperate
latitudes on the western ocean-facing sides of continents in both the northern
and southern hemispheres. Early observations of the dominance of evergreen
