Literature review: Impact of Chilean needle grass ... - Weeds Australia

on basalt duplex soils had the highest probablity of destruction but also supported the largest number of grasslands. These are
more readily cultivated than stony and uniform soils and are relatively high in nutrients. In terms of the road class of the nearest
roads, grasslands on local roads had the highest probability of destruction, followed by patches on highways, possibly because
local roads are more likely to be grazed, illegally cropped or sprayed with herbicides. In terms of land tenure, grasslands on
Crown land were most likely to have been destroyed (mostly by weed invasion), those on private land were less likely to have
been destroyed than those on roadsides, and no railway line grasslands were lost. However the number of private grasslands in
1984 was severely underestimated, and it is likely that in reality large numbers were probably destroyed during the period.
Country Fire Authority brigades also had a major impact on destruction: those brigades area where management of grasslands
had changed from burning to managment using herbicides experienced the highest levels of destruction.
McDougall (1987) argued that management requirements for remnants needed to be site specific, depending on the particular
weed problems and specific conservation requirements, and that much remained to be learned. He acknowledged that the effects
of fire on the inter-tussock herbs was then largely unknown, but recommended burning at 3-5 year intervals between early
October and mid-December to reduce weeds and prevent overdominance by T. triandra, except at sites with spring-flowering
rare or endangered species, for which late summer or autumn fires were appropriate. The main management issues for these
grasslands currently include inadequate knowledge of threatened taxa, management of introduced grasses, prevention of new
weed incursions and generalised ecosystem degradation (Groves and Whalley 2002).
Loss of unreserved remnants continues through development for housing and agriculture. Degradation of ‘protected’ remnants
also continues, including decline in quality, loss of species etc., as a result of invasive species, pollution at the local and global
levels (e.g. N and CO 2 enrichment of the atmosphere), alteration of hydrological processes, other changed ecological processes,
and inappropriate or inadequate management.
South Australia
South Australia once had immense areas of temperate native grassland and grassy woodland in what is now the agricultural zone
(Davies 1997). The grassy vegetation in that State occurred mainly on plateaus and in broad valleys on lower slopes from the
Orroroo and Peterborough areas in the southern and western Flinders Ranges through the Mount Lofty Ranges to Peterborough
and Murray Bridge. Smaller areas occurred on the sub-coastal plain of the South East between Bordertown and the Victorian
border, on the southern Eyre Peninsula, the Yorke Peninsula, and on basalt soils near Mount Gambier (Lunt et al. 1998).
However their composition and previous distribution is unclear (Davies 1997). As in Victoria, recognition that grasslands existed
in some areas has been slow in coming. Lange (1983) failed to acknowledge the existence of grasslands in the South East. The
grasses there, he noted, “do not form savannah; usually they grow sparsely” (p. 99). In the mid 1990s half of the significant
South Australian remnants were on private land, one third on roadsides and one sixth on Crown land (Kirkpatrick et al. 1995).
Exotic plants have been reported to comprise 30% of the South Australian temperate grassland vascular flora (Kirkpatrick et al.
1995).
Moore (1993) mapped these grasslands as Temperate Shortgrass (Austrodanthonia-Austrostipa-Enneapogon) formations,
extending from south of Adelaide through the Mount Lofty Ranges to north of Port Augusta, and in parts of the South East.
Two extant temperate grassland communities are under threat or inadequately conserved: Lomandra effusa/Lomandra multiflora
subsp. dura (open) tussock grassland (co-dominant with Austrodanthonia and Austrostipa spp.), known as Mat-rush Grassland
(Scented Mat-rush and Stiff Mat-rush Lomandra dura according to Lunt et al. 1998), or Irongrass communities (Carter et al.
1993) and Austrodanthonia/Themeda tussock grassland. The former occurs on similar soil types and under similar ecological
conditions to other temperate grassland communities in Australia, so despite the dominants not being grasses, the formations are
considered in ecophysiological terms to be temperate grasslands (Carter et al. 1993). It is most common on skeletal soils in the
eastern Mount Lofty Ranges and the Mid North (Kirkpatrick et al. 1995). Both communities were mainly found in the Mid
North, in the Clare-Port Pirie-Peterborough region but have largely been destroyed by cropping and grazing. Grass dominated
communities may have occurred near Adelaide and more widely in the lower South East, but are extremely poorly conserved
(Lunt et al. 1998, Davies 1997).
Areas of T. triandra grassland are “suspected to have existed” in the lower South East, “primarily on basalt soils (e.g. around
Mount Schanck and Mount Gambier)”(Foulkes and Heard 2003 p. 48). These areas were described by early settlers as lighted
wooded with Acacia melanxoylon R.Br, and eucalypts.
A number of other grassland community types are present in South Australia, including Austrostipa grasslands and Murray
Lakes grasslands (Davies 1997). The Austrodanthonia caespitosa – Enchylaena tomentosa Marsh Margin Grassland occurred on
the margins of the Murray lakes, and “only survives in small roadside fragments” (Kirkpatrick et al. 1995). A Themeda-
Geranium retrorsum-Arthropodium strictum community occurs in the Mount Lofty Ranges in the Mid North (Kirkpatrick et al.
1995). Mathison (2004) stated that South Australian native grasslands are not climax communities but transitional states and can
radically change their nature when there is a change in the management regime. Stafford (1991) provided some descriptive
information on secondary grassland (transitional to woodland) developed in the East Torrens district after cessation of cropping
and grazing. This probably constituted ‘enriched grassland’ in the sense of McIntyre and Lavorel (2007).
Approximately half of the 20 most abundant vascular plant species in South Australian grasslands are exotic and annual grasses
including Avena spp. Bromus spp. and Vulpia spp. are amongst the most invasive (Lenz et al. 2003)
Tasmania
As in other areas of southern Australia, the natural grasslands of Tasmania were rapidly occupied by European settlers (Benson
and Redpath 1997), however they are better reserved than mainland grasslands (Kirkpatrick et al. 1995). Tasmanian non-alpine
grasslands occur mostly on valley bottoms, on heavy clays or alluvial soils and lower slopes on shallow rocky soils, mostly in
the drier Midlands” (Lunt et al. 1998). Moore (1993) mapped a narrow band of Temperate Shortgrass (Austrodanthonia-
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