Agriculture Reference
In-Depth Information
ecosystems, some fire prone, some with C
4
grasses (largely unknown in MTC
sclerophyll vegetation), and some with semi-succulent growth forms. As a conse-
quence the term MTV has a narrow definition that refers to the presence of
evergreen sclerophylls that are usually very fire prone but says very little about
the ecosystem, and for that reason the term mediterranean-type ecosystems needs
to be applied with care.
MTV contains prominent centers of high plant diversity, most notably the
kwongan shrub-dominated complexes in MTC southwestern Australia (Pate &
Beard
1984
; Hopper & Gioia
2004
). Species richness tends to be lower in structur-
ally similar vegetation in other MTC landscapes in southern and southeastern
Australia, particularly at higher levels of scale. Nonetheless, regions containing
large tracts of shrubby vegetation have significant diversity in the southeast
(Beadle
1981
; Rice and Westoby
1983
). MTV is nationally and internationally
important in this regard.
MTV is strongly associated with fire throughout most of its range. Fire is
potentially important in maintaining the composition and character of MTV
and its place in Australian landscapes.
Habitats
MTV commonly occurs on soils that are acidic and sandy, or else derived
in situ
from limestone or aeolian deposits of calcareous origin. The latter occur in and
around coastal regions in southwestern and southern Australia, plus the lower
Murray basin in southeastern Australia (Specht & Moll
1983
; Blackburn &
Wright
1989
). Parent materials are often ancient, particularly in the west (Hopper
2009
) and subject to deep
in situ
weathering, as illustrated by lateritic caps and
escarpments in the southwest, and with considerable redistribution of surface
material via wind occurring in southern dune and sandsheet environments
(Wasson
1989
). MTV occurs at greater elevations and in more rugged terrain in
much of southeastern Australia, where Tertiary and Quaternary (see
Fig. 9.1
)
uplifting has created habitats of steep terrain and skeletal soils, often in high
rainfall environments (Wasson
1982
). Tertiary volcanic activity in the east may
also have diversified soils, both
in situ
and through erosion and deposition across
the Murray-Darling basin (Beadle
1981
; Specht & Specht
1999
).
Many MTV soils are very infertile (low phosphorus and nitrogen) as a result
of their antiquity (Specht & Moll
1983
; Pate & Dell
1984
). A comparison of
MTC regions in
Fig. 1.5
shows that southern Australia overlaps with the
Cape region of South Africa; both are far more infertile than other MTC land-
scapes. Beadle (
1981
) invoked nutrients as a key determinant of community
distributions and diversity in Australian ecosystems. Specht and Moll (
1983
)
argued that demarcations between tree-dominated vs. treeless communities
are governed by interactions between moisture and degree of soil leaching,
which is indicative of nutrient availability. Beard (
1984
) noted a lack of
functional hypotheses involving nutrients that would explain distributions of