There is little specific information currently available about the biology and ecology of the South East Coastal Plain Grassland ecological community. Some general information about habitat requirements is provided in Frood (1993), Davies et al. (2002), DSE (2004) and Yugovic (2011).
Land use history
Occurrences of the ecological community in the Yarram region are largely limited to a few sites on public land. The surrounding matrix in which they occur comprises highly modified agricultural landscapes. The original natural vegetation of the region was a mix of grassy woodland and swamp scrub. Small pockets of grassland and grassy wetland may have been interspersed within these types of vegetation.
With regard to the occurrences around Koo-Wee-Rup, Yugovic (2011) cites evidence of extensive grassland or open woodland on floodplains prior to European colonisation of the area. These occurred around Yallock Creek between the Koo-Wee-Rup and Tobin Yallock Swamps, as well as an open grassy plain adjacent to the western side of The Great Swamp that existed at the time (consisting of the combined Koo-Wee-Rup and Dalmore Swamps), where Cardinia Creek entered the swamp, and another open grassy plain north of Tooradin about 5 x 2–3 km in size. He further notes that grassland and Acacia woodland, essentially the same ecological community, were locally extensive on alluvial plains outside the Melaleuca scrub edges of The Great Swamp and the Tobin Yallock Swamp. Poa labillardierei (common tussock grass) dominated on non-saline and brackish sites with Themeda triandra (kangaroo grass) also present on slightly drier sites, while more saline sites were dominated by Poa poiformis (coast tussock grass). Acacia melanoxylon (blackwood) and to a lesser extent Eucalyptus ovata (swamp gum) were the dominant trees, being resilient to flood, drought and fire. Since Melaleuca now tends to occupy former grassland sites and is encroaching on some remnants, it is probable that the Indigenous inhabitants burnt back the edge of the swamp to facilitate access and food gathering/hunting (Yugovic, 2011). Yugovic details anecdotal evidence of frequent burning, and that neighbouring country where burning had ceased had become scrubby.
Ecological communities are a convenient way to classify complex and variable natural systems. Australia, and each State/Territory jurisdiction, applies its own system to classify ecological communities; this can cause problems when cross-referring amongst systems that may vary in on-ground accuracy. Any reference to vegetation and mapping units as equivalent to a national ecological community at the time of listing should be taken as indicative, rather than definitive. A unit that is generally equivalent may include some elements that do not meet the description. Conversely, some areas mapped or described as other units (not identified here) may sometimes meet the description. Judgement of whether an EPBC-protected ecological community is present at a particular site should focus on how an area meets the description and condition thresholds of the national ecological community, rather than on any other classification system.
Under the National Vegetation Information System (NVIS), the ecological community falls within Major Vegetation Group (MVG) 19 ‘Tussock grasslands’.
Victoria classifies its vegetation using a system of Ecological Vegetation Classes (EVCs). An EVC may be further subdivided into Floristic Communities. The EVC system includes complexes, mosaic and aggregate units for situations where specific EVCs cannot be identified at a site at the spatial scale used for vegetation mapping. Victoria has established bioregionally-based benchmarks for each EVC so condition assessments can be made with respect to a reference patch of a particular vegetation type. Benchmarks are not a comprehensive description of an EVC, but do provide an accessible summary of its main features and ecology.
The South East Coastal Plain Grassland ecological community generally corresponds to EVC 132 Plains Grassland, as benchmarked in the Victorian Gippsland Plain and Otway Plain Bioegions (DEPI, 2014), which are broadly equivalent to the IBRA subregions of the same name. However, as EVCs are broadly defined, the national ecological community represents the damper expressions of EVC 132. The benchmark for EVC 132 in the Gippsland Plains bioregion identifies two specific floristic communities, only one of which is equivalent to the South East Coastal Plain Grassland: EVC 132_62 South Gippsland Plains Grassland. However, no floristic communities are specified for grassland EVCs in the Otway Plain.
Differences from similar or intergrading ecological communities and adjacent vegetation communities
Four other nationally threatened grassy ecological communities also occur in the South East Coastal Plains bioregion. They may be distinguished from the South East Coastal Plain Grassland as follows.
Gippsland Red Gum (Eucalyptus tereticornis subsp. mediana) Grassy Woodland and Associated Native Grassland. This ecological community concerns grassy woodlands typically dominated by Eucalyptus tereticornis (Gippsland red gum) plus patches cleared of trees that are managed as native grassland. While it includes many grassy sites dominated by Themeda, it is associated with drier sites on the Central Gippsland Plain and lacks an abundance of species associated with damp sites. Eucalyptus tereticornis is a distinctive component of this ecological community but its distribution does not extend into the South Gippsland Plain around Yarram or west of the Strzelecki Ranges, where the South East Coastal Plain Grassland occurs. Therefore, the two ecological communities are regionally disjunct. The Gippsland Red Gum Grassy Woodland ecological community also corresponds to different Victorian Ecological Vegetation Classes/Floristic Communities, being a mix of EVCs 55-03 Gippsland Plains Grassy Woodland; 132_61 LaTrobe Valley Plains Grassland; and mosaic units with these EVCs that occur on the Gippsland Plain (Victorian) bioregion.
The Seasonal Herbaceous Wetlands (Freshwater) of the Temperate Lowland Plains occur on wetter sites than South East Coastal Plain Grassland, primarily localised drainage lines and depressions that become seasonally inundated during winter and spring rainfall events. They are dominated by grass and sedge species tolerant of wet conditions (typically Amphibromus spp., Carex tereticaulis, Deyeuxia spp., Glyceria spp., Lachnagrostis spp., Poa labillardieri or Rytidosperma duttonianum), and include a suite of forbs associated with wetlands that are absent, or not abundant, in sites that are damp to dry (for instance: Allittia spp. (swamp daisies), Ornduffia spp. (marshflowers), Ottelia spp. (swamp lilies) and Triglochin spp. (water ribbons)). The Seasonal Herbaceous Wetlands ecological community also corresponds to different, wetland Victorian Ecological Vegetation Classes, primarily EVC 125 Plains Grassy Wetland and EVC 647 Plains Sedgy Wetland and associated mosaic/complex units.
The Natural Temperate Grassland of the Victorian Volcanic Plain is a dryland grassland community that primarily occurs within the Victorian Volcanic Plain bioregion but may extend into adjacent parts of the Otway Plain. It is mostly associated with, but not limited to, Quaternary basalt soils. While Themeda triandra and Poa labillardierei are typical dominant species for both grassland communities, the Natural Temperate Grassland of the Victorian Volcanic Plain has a larger diversity and abundance of dryland grassland species, for instance Chrysocephalum apiculatum and Eryngium ovinum, and generally lacks species tolerant of damp sites, for instance Hemarthria uncinata (mat grass), Pratia spp. (pratia) or Pycnosorus spp. (billy buttons). The Natural Temperate Grassland of the Victorian Volcanic Plain ecological community corresponds to different Victorian Ecological Vegetation Classes. These are: EVC 132 Plains Grassland (covering two floristic communities for the Victorian Volcanic Plain: 132_61 Heavier-soils Plains Grassland; and 132_63 Low-rainfall Plains Grassland); EVC 654 Creekline Tussock Grassland; and EVC 897 Plains Grassland/Plains Grassy Woodland Mosaic.
Subtropical and Temperate Coastal Saltmarsh is a community of herbs and low shrubs on estuaries and tidal flats. Consequently, it can be distinguished from the South East Coastal Plain Grassland by its maritime location and the strong presence of halophytic species adapted to these conditions.
Davies et al. (2002) noted the grassland is closely related to EVC 3 Gippsland Lakes Damp Sands Herb-rich Woodland. The woodland occupies better drained sites with sandier topsoils. It can be distinguished from the grassland by its more extensive tree canopy and a higher cover of Pteridium esculentum (Austral bracken) and Lomandra longifolia (spiny-headed mat-rush) in the understorey. There also are other kinds of grassland in the region associated with saline, brackish or coastal sites, which can be distinguished by a greater presence of halophytic species, coastal species or proximity to the coast.
Level of protection in reserves
Most of the known sites for South East Coastal Plain Grassland occur on public land but only three sites are protected in conservation reserves. The Darriman Bushland Reserve covers about 20 hectares of mixed grassland, shrubland and woodland, situated within a matrix of rural land uses. The Pakenham Grassland Reserve is smaller, about 5 hectares in extent. It was formerly part of Pakenham airfield and the restricted access conferred some protection to the grassland. However, the airfield was decommissioned and developed for suburban housing, which now entirely surrounds the site. The Barwon River site is within the Connewarre Wildlife Reserve, which is approximately 3,700 ha in size, predominantly wetland but also including significant occurrences of remnant herbland and grassland. The grasslands at all three reserves are recognised for their natural values and managed accordingly.
The threats to the South Gippsland Plain Grassland are noted briefly in key sources about this ecological community (FFG-SAC, 1994; Frood, 1994; Cook and Yugovic, 2003; DSE, 2004a and 2007). In its Victorian listing determination, FFG-SAC (1994) concluded that ‘the community is significantly prone to future threats which are likely to result in extinction’. The key threats identified are discussed below.
The key threat impacting on most known patches is weed invasion. Native grassland species can be displaced by introduced pasture species that spread from surrounding agricultural lands or disturbed sites. If left unmanaged, the invasion of major weeds can lead to declines in native species cover and diversity. The most invasive pasture species are the perennial grasses: phalaris or canary grass (Phalaris spp.), paspalum (Paspalum dilatatum), Yorkshire fog (Holcus lanatus) and sweet vernal grass (Anthoxanthum odoratum). Annual and seasonal weeds, such as quaking grass (Briza spp.), capeweed daisy (Arctotheca calendula) or onion grass (Romulearosea) also may be present at some sites and contribute to weed impacts.
Native shrub species from surrounding scrub communities are actively encroaching into grassland at certain sites. The native shrub species include: Kunzea ericoides (burgan), Leptospermumcontinentale (prickly tea-tree) and Melaleuca ericifolia (swamp paperbark) (Frood, 1994; FFG-SAC, 1994; DSE, 2004a). Although these shrubs may be naturally present within grassland sites, their densities are shifting from a typically sparse presence to a dense cover. The increased shade from denser shrub canopies and greater competition for water and nutrients discourages the growth and spread of grassland species in the proximity. Encroachment can eventually result in structural transitions from native grassland to native shrubland, if not managed. Shrub encroachment on the Gippsland Plain may be a response to naturally or artificially-induced processes such as fluctuating hydrology or altered fire regimes, whereby shrubs encroach during wet periods and recede in prolonged dry periods.
The spread of invasive weeds into grassland is also fostered by the inadequate management of grassland sites, as discussed below.
Inappropriate management of grassland biomass (slashing, mowing, grazing and burning)
Inappropriate regimes of slashing, mowing, grazing and burning to manage fuel loads threatens remnants of the ecological community (FFG-SAC, 1994; Frood, 1994; DSE, 2004a). These activities need to be applied appropriately with due regard to maintaining grassland biodiversity over the long-term. For example:
Actions that disturb the topsoil can promote invasion by exotic weed species.
Mowing or slashing grasslands at the wrong height or season can limit natural recruitment, e.g. if undertaken during peak flowering, when flowers and fruits are removed in the process. Burning at the inappropriate time, for instance peak flowering in spring, may have similar impacts upon native species recruitment.
Conversely, preventing biomass removal eventually results in the formation of a closed, dense native grass sward and accumulation of litter. Natural gaps in the grass sward are essential to allow native forbs and wildflowers to germinate and establish away from the competitive influences of a grass sward. Closed swards are considered senescent and require active management to promote the formation of natural gaps that allows the growth of a diverse suite of forbs.
Patches of the South East Coastal Plain Grassland occur on roadside verges along Stringybark Lane near Jack Smith Lake, and along the Bass Coast between Anderson and Wonthaggi. Patches also occur along the disused Clyde–Tooradin railway line and within the Alberton and Woodside cemeteries.
Road and infrastructure maintenance may threaten remnant grasslands where management works are not undertaken in a sensitive manner (DSE, 2004a). Unintentional damage may occur during maintenance works, such as extending grading from the road edge into intact grassland or parking machinery directly on remnants.
In cemeteries, the preparation of new burial plots or other works may result in dumping of soil onto grassland sites. Amenity plantings of exotic species also may cause weed problems or detract from the natural value of remnants.
Fertiliser residues may drift from improved soils on adjacent lands. As many native grassland species are sensitive to elevated nutrients and weeds often respond positively to higher nutrient loads, fertiliser drift could significantly impact upon the ecological community (FFG, 1994; DSE, 2004a) by discouraging the growth of native species and promoting weed establishment.
Earthworks in or near to grassland sites can disrupt the natural hydrology of the South East Coastal Plain Grassland. Since the grassland is associated with boggy soils and has a unique assemblage of dryland and moisture-loving native species, any long-term disruption to natural water flows may have impacts upon that assemblage.
The South East Coastal Plain Grassland appears to occur as a naturally fragmented ecological community and has a restricted distribution within each of its main disjunct occurrences. Although this appears to be its natural situation, the degree of fragmentation renders the ecological community susceptible to localised adverse environmental events. The small size of patches, with most being under 10 hectares in size with large perimeter to area ratios, means that weeds and other disturbances can more easily extend into the core of patches leading to progressive degradation of an entire patch.