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

(Rosengren 1999). Approximately one third of Victoria (c. 8 million ha) was probably occupied by grassy ecosystems, including
grasslands and grassy woodlands, at the time of European occupation, of which less than 0.5% remains (Lunt 1991). All
Victorian native grasslands are severely depleted (DNRE 1997) and all are now listed as threatened communities (DSE 2009a),
that is Central Gipssland Plains Grassland Community, Northern Plains Grassland Community, Plains Grassland (South
Gippsland) Community and Western (Basalt) Plains Grassland Community.
“Plains Grassland” is one of 28 Broad Vegetation Types recognised in Victoria, occurring on fertile plains with 300-1000 mm
annual rainfall, on heavy clay soils of basaltic origin (Western Volcanic Plains), outwash clays (Sale Plains) and alluvial silts and
clays (Northern Plains, Wimmera and West Gippsland). The category does not include coastal grasslands of Austrostipa
stipoides, dune grasses and sedges. Pre-1750 this formation is estimated to have covered 1,882,411 ha or c. 8.2% of the State, of
which 8277 ha (0.44%) was considered to be extant in the early 1990s. Only 2504 ha (30%) was in conservation reserves, while
4938 ha (60%) was on private land (Traill and Porter 2001). These estimates are similar to those of DNRE (1997) (Table 11).
Ecological Vegetation Classes (EVCs) are a more accurate categorisation of actual vegetation types present in the State. The
grassland EVC on the Western Volcanic Plains is Western Plains Grassland, in Gippsland it is Gippsland Plains Grassland and in
the north is Northern Plains Grassland. In general, much higher proportions of these Plains Grasslands EVCs have been lost than
of other grassland formations (Table 12).
Table 11. Bioregional pre-European areal distribution of grassland complexes in Victoria and proportion remaining. Source:
DNRE (1997). ‘Area remaining’ derived by calculation from the ‘% remaining’.
Region Victorian Bioregion Pre-European
area (ha)
Area
remaining (ha)
% remaining
Victorian Mallee Murray Mallee 51,512 52 0.1
Wimmera 329,737 1319 0.4
Victorian Volcanic Plain Victorian Volcanic Plain 826,402 1652 0.2
Midlands Dundas Tablelands 79,694 80 0.1
Goldfields 4,601 0 0.0
Victorian Riverina Victorian Riverina 444,713 3113 0.7
Coastal Plains Gippsland Plain 133,547 1870 1.4
Total 1,870,206 8086 0.4
All Victorian grasslands are presumed to have lost significant biodiversity since European occupation. Native vegetation and
species disappeared locally and regionally in many areas before any detailed records were made (Mansergh et al. 2006a). Exotic
plants have been reported to comprise 29% of the Southern Victoria grassland vascular flora (Kirkpatrick et al. 1995).
Gippsland Grasslands
The West Gippsland plains consist largely of uplifted marine and fluviatile sediments and swamp deposits at Koo-wee-rup (Hills
1967). The largest areas of grasslands on the Gippsland Plains at the time of European settlement were between Stratford,
Rosedale and Sale, north of the Latrobe River with some onthe floodplains of the Latrobe and Macalister Rivers, in coastal South
Gippsland east of Yarram between Seaspray and Welshpool, and north of Westernport around Kooweerup Swamp (DNRE 1997,
Lunt et al. 1998, Rosegren 1999). The Central Gippsland grasslands occur on leached sandy soils in areas with perched
watertables and an abundance of swamps and small lakes (Rosegren 1999). In the Nambrok-Denison area, between the Latrobe
and Thomson Rivers, grassland occupied areas with heavy loam topsoil over heavy clay on flat, alluvial plains 3.5-7 m above the
floodplain of the Thomson, and were infrequently flooded (Kirkpatrick et al. 1995). Moore (1993) mapped the coastal plain from
Sale to Lakes Entrance as Temperate Shortgrass (Austrodanthonia- Austostipa-Enneapogon). To the north, in primarily forested
country he mapped a wide zone of Temperate Tallgrass (Themeda-Poa-Dichelachne) continuous up the east coast to north of
Sydney,west across Victoria to the Hamilton area and inland to Rutherglen and the ACT.
The historical extent and nature of Gippsland grasslands is very poorly known. Indeed, Gullan et al. (1985) did not recognise the
presence of any natural grassland community in South and Central Gippsland, and Moore (1993) mapped the whole of West and
South Gippsland except Wilsons Promontory (!) as an area without native grasslands. However many secondary grasslands
derived from grassy woodlands currently exist in the region (Lunt et al. 1998) and several remnant native grasslands have
recently been recognised.
Kirkpatrick et al. (1995) briefly described two Gippsland grassland communities: 1. South Gippsland Themeda Grassland, a
closed tussock formation, occasionally with significant amounts of Hemarthria uncinata R.Br. (Poaceae) and a variety of other
grasses and rushes, found in the Welshpool-Seaspray areas; and 2. Central Gippsland Themeda Grassland, also a closed tussock
formation, but with abundant Asteraceae, Liliaceae and Orchidaceae and scattered trees at some sites, found on alluvial plains
between Traralgon and Johnsonville and derived originally from woodland or open forest.
Substantially different grasslands have recently been identified in the Westernport and Mornington Peninsula regions. These
have been described and delineated by inspections of the very restricted remnants that remain, and by analysis of early survey
maps, plans, fragmentory historical records, aerial photographs and other sources (Cook and Yugovic 2003, Yugovic and
Mitchell 2006, Sinclair 2007). They include c. 12 km 2 north of Tooradin (Cook and Yugovic 2003) and small areas (< 6 km 2 ) at
Safety Beach (Sinclair 2007). Poa labillaredieri was the major grass, dominating the wetter areas, with T. triandra on drier sites
(Yugovic and Mitchell 2006). The Westernport grasslands were occasionally flooded, but aboriginal burning probably prevented
them being overrun by Melaleuca ericifolia Sm., which also may have been constrained by soil factors (Lunt et al. 1998,
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