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