Lowland Grassy Woodland in the South East Corner Bioregion - Determination to make a minor amendment to Part 3 of Schedule 1 of the Threatened Species Conservation Act

The Scientific Committee is of the opinion that the amendment is necessary or desirable to correct minor errors or omissions in the Determination in relation to the Thackway and Cresswell (1995) reference.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Lowland Grassy Woodland in the South East Corner bioregion is the name given to the ecological community associated with rainshadow areas of the south coast and hinterland of New South Wales. These rainshadow areas receive less rainfall than more elevated terrain that partially surrounds them, with mean annual rainfall typically in the range of 700-1100 mm. The community typically occurs in undulating terrain up to 500m elevation on granitic substrates (e.g. adamellites, granites, granodiorites, gabbros, etc.) but may also occur on locally steep sites and on acid volcanic, alluvial and fine-grained sedimentary substrates. Lowland Grassy Woodland in the South East Corner bioregion is characterised by the assemblage of species listed in paragraph 2 and typically comprises an open tree canopy, a near-continuous groundcover dominated by grasses and herbs, sometimes with layers of shrubs and/or small trees. Undisturbed stands of the community may have a woodland or forest structure. Small trees or saplings may dominate the community in relatively high densities after partial or total clearing. The community also includes ‘derived’ native grasslands which result from removal of the woody strata from the woodlands and forests.

2. Lowland Grassy Woodland in the South East Corner bioregion is characterised by the following assemblage of species:

3. The total species list of the community is larger than that given above, with many species present in only one or two sites or in low abundance. The species composition of a site will be influenced by the size of the site, recent rainfall or drought conditions and by its disturbance history (including grazing, land clearing and fire). The number and relative abundance of species will change with time since fire, and may also change in response to changes in fire frequency or grazing regime. At any one time, above-ground individuals of some species may be absent, but the species may be represented below ground in soil seed banks or as dormant structures such as bulbs, corms, rhizomes, rootstocks or lignotubers. The list of species given above is mainly of vascular plant species, however the community also includes micro-organisms, fungi, cryptogamic plants and a diverse fauna, both vertebrate and invertebrate. The mammalian and avian components of the fauna have been described by Lunney and Leary (1990) and Miles (2005). Other components of the community are poorly documented.

4. Lowland Grassy Woodland in the South East Corner bioregion is characterised by an overstorey that is usually dominated by Eucalyptus tereticornis (Forest Red Gum), often with Eucalyptus globoidea (White Stringybark) and/or Angophora floribunda (Rough-barked Apple) and other eucalypts at some sites. For example, Eucalyptus melliodora (Yellow Box) and E.pauciflora (White Sally) may be locally common within the community. These are important components of this community because they are comparatively rare on the south coast lowlands, even though both species are more widespread in other communities on the tablelands. Other tree species include E.baueriana (Blue Box), E.bosistoana (Coastal Grey Box) and E.maidenii (Maiden’s Blue Gum), which may occur in transitional stands with adjacent communities in which they are more common, and E.viminalis (Ribbon Gum) associated with lower slopes adjacent to major streamlines. The understorey often includes an open stratum of small trees dominated by Acacia mearnsii (Black Wattle), A.implexa (Hickory Wattle) or Exocarpos cupressiformis (Native Cherry) and an open shrub stratum that commonly includes Bursaria spinosa, Cassinia spp. and/or Ozothamnus diosmifolius. Shrubs may attain high densities in localised areas in response to changes in grazing or fire regimes. The grassy ground cover is dominated by Themeda australis (Kangaroo Grass), Microlaena stipoides (Weeping Grass), Eragrostis leptostachya (Paddock Lovegrass) and Echinopogon ovatus (Forest Hedgehog Grass) with forbs such as Dichondra repens (Kidney Weed), Desmodium varians (Slender Tick Trefoil), Hydrocotyle laxiflora (Stinking Pennywort), Hypericum gramineum (Small St John’s Wort), Glycine clandestina and the fern Cheilanthes sieberi (Poison Rock Fern). The structure of the community varies depending on past and current disturbances, particularly clearing and grazing. Contemporary tree-dominated stands of the community are largely relics or regrowth of originally taller forests and woodlands, which are likely to have had scattered shrubs and a largely continuous grassy groundcover. At some sites, mature trees may exceed 40m, although regrowth stands may be shorter than 10m. After total or partial clearing, the tree canopy may remain sparse or may regrow to form dense stands of saplings and small trees, which are typically associated with a ground layer of reduced cover and diversity. Either or both of the overstorey and mid-stratum may be absent from the community. Native grasslands derived from clearing of the woodland and forest are also part of this community if they contain characteristic non-woody species listed in paragraph 2.

5. Lowland Grassy Woodland in the South East Corner bioregion includes: Bega Dry Grass Forest (map unit 20) and Candelo Dry Grass Forest (map unit 21) of Keith and Bedward (1999), which are listed as Endangered Ecological Communities under the Threatened Species Conservation Act 1995; those parts of South Coast Grassy Woodland (map unit 34) of Tindall et al. (2004) in the South East Corner bioregion; Bega Valley Shrub/Grass Forest (Vegetation Group 52), and those parts of Southern Escarpment Herb/Grass Dry Forest (forest ecosystem 50) and Far South Coast Forest Red Gum Grass/Herb Dry Forest/Woodland (Vegetation Group 54) that occur within the South East Corner bioregion (all as in Thomas et al. 2000 and Gellie 2005); and Far South Coast Grassy Woodland of Tozer et al. (2006). Lowland Grassy Woodland, in the South East Corner bioregion belongs to the Coastal Valley Grassy Woodlands vegetation class (Keith 2004) and may usually be distinguished from other assemblages in the South East Corner bioregion by the current or former dominance of Eucalyptus tereticornis, a grassy ground cover dominated by Themeda australis with Microlaena stipoides, and other species listed in paragraph 2. However, E.tereticornis is absent from some stands of the community which may include Angophora floribunda, E. melliodora, E. pauciflora or lack trees altogether.

6. Lowland Grassy Woodland in the South East Corner bioregion is currently known to occur within the Bega Valley, Eurobodalla and Palerang Local Government Areas, but may occur elsewhere in the bioregion. Bioregions are defined in Thackway and Cresswell (1995). Major occurrences are found to the west of Batemans Bay, around Moruya, in the Araluen valley, in the Cobargo - Bega – Candelo area, the Towamba Valley and near Tanja.

7. Since European settlement, and relative to the longevity of its dominant trees, which live for several hundred years, Lowland Grassy Woodland in the South East Corner bioregion has undergone a large reduction in geographic distribution due to clearing (Keith and Bedward 1999, Thomas et al. 2000, Tindall et al. 2004, Tozer et al. 2006). The total remaining area of Lowland Grassy Woodland in the South East Corner bioregion is estimated to be less than 15000 ha, representing approximately 20% of its projected area at the time of European settlement (Tozer et al. 2006). Clearing of the community has not been evenly distributed across its range. For example, Keith and Bedward (1999) estimated that less than 10% remains of Candelo Dry Grass Forest, a map unit occurring in the western parts of the Bega and Towamba valleys, which is included within Lowland Grassy Woodland. However, mapping carried out by Keith and Bedward (1999) was at coarser resolution than more recent mapping (Tozer et al. 2006), and omitted a number of smaller patches of the community in this region. Almost all of the remaining area of the community occurs on private land or on public easements, where its geographic distribution is undergoing a continuing decline due to small-scale clearing. ‘Clearing of native vegetation’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

8. Extensive clearing of Lowland Grassy Woodland, has resulted in fragmentation and loss of ecological connectivity. The remaining area of the community is severely fragmented, with more than 95% of mapped extant patches estimated to be less than 10ha (Tozer et al. 2006). The integrity and survival of small, isolated stands is impaired by the small population size of many species, enhanced risks from environmental stochasticity, disruption to pollination and dispersal of fruits or seeds, and likely reductions in the genetic diversity of isolated populations (Young et al. 1996, Young and Clarke 2000). Fragmentation also results in altered fire frequencies within some patches, which may reduce the viability of some native plant populations (Clarke 2000). Fragmentation of habitat and disruption of these ecological processes contribute to a large reduction in the ecological function of the community.

9. Almost all of the remaining area of Lowland Grassy Woodland is regrowth forest and woodland from past clearing activities (Miles 2005). Some of the area of the community that is now devoid of woody plant species retains a substantial suite of native grasses and herbs in the ground layer. These changes in structure and species composition contribute to a large reduction in the ecological function of the community.

10. Weed invasion also poses a major threat to Lowland Grassy Woodland, with introduced perennial grasses having particularly serious impacts (Miles 2002). Principal weed species include:

Several of these exotic species, particularly grasses, form a dense ground layer capable of smothering indigenous plants, reducing both reproduction and survival. The invasion and establishment of exotic species in Lowland Grassy Woodland, results in a large reduction in the ecological function of the community. ‘Invasion of native plant communities by exotic perennial grasses’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

11. Moderate to heavy grazing of Lowland Grassy Woodland, by livestock and introduced rabbits results in the decline and disappearance of palatable plant species, including shrubs and herbs, and compaction and erosion of topsoil, making it difficult for a diverse native understorey to re-establish. The effects of such overgrazing may be exacerbated under drought conditions. ‘Competition and grazing by the feral European Rabbit, Oryctolagus cuniculus’ is listed as Key Threatening Processes under the Threatened Species Conservation Act 1995. Habitat degradation associated with overgrazing and erosion contributes to a large reduction in ecological function of the community.

12. Lowland Grassy Woodland, has undergone a very substantial loss of native mammal fauna since European settlement. This is best documented in the Bega valley, where Lunney and Leary (1988) concluded, after an examination of historical and contemporary records, that at least six native mammal species had become locally extinct, including the Wallaroo (Macropus robustus), the Parma Wallaby (Macropus parma), the red-necked Pademelon (Thylogale thetis), the Tasmanian Bettong (Bettongia gaimardi), the Eastern Quoll (Dasyurus viverrinus) and the Brush-tailed Phascogale (Phascogale tapoatafa). The loss of habitat, invasion of feral predators and hunting activities were implicated as causes of these extinctions. The disruption of ecological processes associated with loss of key fauna contributes to a large reduction in ecological function of the community.

13. Tall trees approximating the stature of the community prior to European settlement remain principally as isolated individuals within paddocks. These and other remnant and regrowth trees suffer episodes of elevated mortality related to drought and recurring insect attack consistent with rural tree decline (Reid and Landsberg 2000). Loss of these large trees, which provide habitat resources for a range of fauna, contributes to a large reduction in ecological function of the community.

14. The Scientific Committee is of the opinion that Lowland Grassy Woodland in the South East Corner Bioregion is not eligible to be listed as a critically endangered ecological community.

15. Lowland Grassy Woodland in the South East Corner Bioregion is eligible to be listed as an endangered ecological community as, in the opinion of the Scientific Committee, it is facing a very high risk of extinction in New South Wales in the near future, as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

Clause 25

The ecological community has undergone, is observed, estimated, inferred or reasonably suspected to have undergone, or is likely to undergo within a time span appropriate to the life cycle and habitat characteristics of its component species:

(b) a large reduction in geographic distribution.

Clause 27

The ecological community has undergone, is observed, estimated, inferred or reasonably suspected to have undergone, or is likely to undergo within a time span appropriate to the life cycle and habitat characteristics of its component species:

(b) a large reduction in ecological function,

as indicated by any of the following:

(d) change in community structure

(e) change in species composition

(f) disruption of ecological processes

(g) invasion and establishment of exotic species

(h) degradation of habitat

(i) fragmentation of habitat

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 02/12/11
Exhibition period: 02/12/11 – 03/02/12

References

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Gellie NJH (2005) Native vegetation of the southern forests: South-east Highlands, Australian Alps, South-west Slopes and South-east Corner bioregions. Cunninghamia 9, 219-254.

Keith DA (2004) ‘Ocean shores to desert dunes: the native vegetation of New South Wales and the ACT.’ NSW Department of Environment and Conservation, Sydney.

Keith D, Bedward M (1999) Native Vegetation of the South East Forests Region, Eden, NSW. Cunninghamia 6, 1-218.

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Miles J (2002) Weeds of the NSW south coast. A guide to identification and control. Report to the Bega Valley and Eurobodalla Shire Councils, Shoalhaven City Council and Illawarra District Noxious Weeds Authority.

Miles J (2005) Recognition and management of Endangered Ecological Communities in the south east corner of NSW. Southern Rivers Catchment Management Authority, Bega.

Reid N, Landsberg J (2000) Tree decline in agricultural landscapes: what we stand to lose. Pp 127-166 in (Eds. RJ Hobbs, CJ Yates) Temperate eucalypt woodlands in Australia: biology, conservation, management and restoration (Surrey Beatty & Sons: Chipping Norton).

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Thomas V, Gellie N, Harrison T (2000) Forest Ecosystem Classification and Mapping for the Southern CRA Region. Report for the NSW CRA/RFA Steering Committee, Project No. NS 08EH. NSW National Parks and Wildlife Service, Queanbeyan.

Tindall D, Pennay C, Tozer MG, Turner K, Keith DA (2004) Native vegetation map report series. No. 4. Araluen, Batemans Bay, Braidwood, Burragorang, Goulburn, Jervis Bay, Katoomba, Kiama, Moss Vale, Penrith, Port Hacking, Sydney, Taralga, Ulladulla, Wollongong. NSW Department of Environment and Conservation and NSW Department of Infrastructure, Planning and Natural Resources, Sydney.

Tozer MG, Turner K, Keith DA, Simpson C, Beukers P, Mackenzie B, Tindall D, Pennay C, (2004) Native vegetation of southeast NSW: a revised classification and map for the coast and eastern tablelands. Version 1.0. NSW Department of Environment and Conservation and NSW Department of Natural Resources, Sydney.

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