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Old man saltbush shrubland in western NSW - proposed endangered ecological community

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Preliminary Determination to support a proposal to list the Old Man Saltbush Shrubland in western NSW as an ENDANGERED ECOLOGICAL COMMUNITY in Part 3 of Schedule 1 of the Act. Listing of Endangered Ecological Communities is provided for by Part 2 of the Act.

The Scientific Committee has found that:

1. Old Man Saltbush Shrubland in western NSW is the name given to the ecological community dominated by stands of Atriplex nummularia (Old Man Saltbush) up to 2.5 meters tall. Throughout its range Old Man Saltbush Shrubland is scattered across a range of soil types on level to depressed plains, low-lying areas and depressions (Cunningham et al.1992, Porteners 1993, Porteners et al. 1997), sometimes being associated with dry lakes (Fox 1991, Scott 1992, Horner et al. 2002, White et al. 2002). In north-west NSW it occurs on alluvial plains that are periodically flooded and on sandy rises adjacent to floodplains (Pickard and Norris 1994).

2. The community is characterised by the following assemblage of species:

Acacia pendulaAristida behriana
Atriplex lindleyiAtriplex nummularia
Atriplex pseudocampanulataAtriplex vesicaria
Austrodanthonia caespitosaAustrostipa elegantissima
Brachycome linearilobaBromus arenarius
Calandrinia eremaeaCalocephalus sonderi
Chenopodium curvispicatumChenopodium nitrariaceum
Crassula colorata var. acuminataCrassula sieberiana
Disphyma crassifoliumDissocarpus biflorus
Einadia nutansEnchylaena tomentosa
Eragrostis australasicaEucalyptus coolabah
Eucalyptus largiflorensGeococcus pusillus
Goodenia pusillifloraLeptorhynchos panaetioides
Maireana microcarpaMaireana pyramidata
Malacocera tricornisMinuria cunninghamii
Muehlenbeckia florulentaNitraria billardieri
Osteocarpum acropterum var. deminutaPodolepis muelleri
Pogonolepis muellerianaPratia concolor
Pycnosorus pleiocephalusRhagodia spinescens
Rhodanthe corymbifloraSalsola kali
Sclerolaena brachypteraSclerolaena divaricata
Sclerolaena muricataSclerolaena tricuspis
Sclerolaena ventricosaSclerostegia tenuis
Senecio runcinifolius


3. The total species list of the community is considerably larger than that given above, with many species present in only a few sites or in low abundance. The species composition, richness and the relative abundance of a site will be influenced by the size of the site, recent rainfall or drought conditions and by its disturbance history (including fire and grazing regimes). 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 of vascular plants; the community also includes micro-organisms, fungi, cryptogamic plants and a diverse fauna, both vertebrate and invertebrate. These components of the community are poorly documented.

4. Old Man Saltbush Shrubland in western NSW is found in the Broken Hill Complex, Channel Country, Cobar Peneplain, Darling Riverine Plains, Mulga Lands, Murray-Darling Depression, Riverina and Simpson-Strzelecki Dunefields Bioregions. Bioregions are defined in Thackway and Creswell (1995). Old Man Saltbush Shrubland in western NSW has been recorded from the Local Government Areas of Balranald, Bogan, Brewarrina, Carrathool, Central Darling, Conargo, Hay, Lachlan, Murrumbidgee, Narromine, Walgett, Warren, Wentworth and Wakool. Old Man Saltbush Shrubland may occur elsewhere in the above bioregions.

5. Old Man Saltbush Shrubland in western NSW contains Atriplex nummularia as the dominant characteristic species. This community can form dense monospecific stands (Cunningham et al. 1992), crowding other species and resulting in low species richness (Beadle 1948). Scattered or isolated tree species including Eucalyptus spp. or Acacia spp. may be present in Old Man Saltbush Shrubland but do not define the community. In the far north-west of NSW the community has an open shrubland structure (Pickard and Norris 1994, Westbrooke et al. 2003). Associated species east of Peery Lake include Maireana pyramidata (Black Bluebush), Sclerolaena intricata (Poverty Bush), Sida intricata (Twiggy Sida) and Daucus glochidiatus (Native Carrot) (Westbrooke et al. 2003). In the floodplain of the Darling River close to the junction with the Paroo River, and in the southernmost sections of the Paroo River, the canopy species include Eragrostis australasica (Cane Grass), Muehlenbeckia florulenta (Lignum) and Chenopodium nitrariaceum (Nitre Goosefoot), with a lower shrub layer composed of Sclerolaena spp. (Copperburrs) (Pickard and Norris 1994). Along drainage lines and depressions Old Man Saltbush Shrublands form localised stands within larger areas of Atriplex vesicaria (Bladder Saltbush) shrublands (Pickard and Norris 1994). Atriplex vesicaria, Enchylaena tomentosa (Ruby Saltbush) and Rhagodia spinescens (Spiny Saltbush) are associated shrub species in the Darling Riverine Plain Bioregion (L. Forward, unpublished). In addition to these associated species, in and around the Riverina other species such as Einadia nutans (Climbing Saltbush) (Porteners 1993), Sclerolaena spp. (Copperburr) and Atriplex spp. (Saltbush) (Scott 1992) become more frequent. Further west around Pooncarie Maireana pyramidata, Rhagodia spinescens, Atriplex lindleyi and Osteocarpum acropterum var. deminuta (Porteners et al. 1997) become more common. Species associated with Old Man Saltbush Shrubland in Kinchega National Park include Chenopodium nitrariaceum and Sclerolaena divaricata (Tangled Copperburr); the community grades into Maireana pyramidata shrublands away from the Darling River and Darling Anabranch (Fox 1991).

6. As a species, Old Man Saltbush also occurs as a dominant substratum in other vegetation communities in the western NSW. These other communities can include but are not restricted to woodlands with an overstorey dominated by Acacia pendula (Weeping Myall or Boree), Eucalyptus largiflorens (Black Box) and Eucalyptus coolabah (Coolibah). These woodland communities are not part of the current determination, although isolated trees or stunted forms of these species may occur within the Old Man Saltbush Shrubland. Plantings of Atriplex nummularia alone are also not included in this determination.

7. A number of vegetation surveys and mapping studies have been conducted across the range of Old Man Saltbush Shrubland in western NSW with the following shrublands considered to be part of the nominated Endangered Ecological Community. Beadle's (1948: 223) description of 'Saltbush Formation 1 Atriplex vesicarium [sic] association' in western NSW included 'Type 3 Atriplex nummularium [sic]', which was "most frequent on the Hay Plains and less common along the Darling, Bogan and Macquarie rivers." Beadle noted that the species had not been recorded on the Gibber Plains in any quantity but was possibly more abundant prior to the introduction of stock. Fox (1991) described Old Man Saltbush Tall Shrubland from the Ana Branch 1:250000 and the NSW portion of the Mildura 1:250000 map sheets but found its occurrence too small to map. The Royal Botanic Gardens vegetation mapping of the Riverina Bioregion described 'Map Unit/Vegetation Community 19 Old Man Saltbush open shrubland' (Scott 1992, Porteners 1993, Porteners et al. 1997). Pickard and Norris (1994) mapped the vegetation of north-western NSW including 'Atriplex nummularia shrubland'. 'Bladder Saltbush and Old Man Saltbush shrubland' was identified in the Darling Riverine Plains during bioregional surveys (L. Forward, unpublished). Horner et al. (2002) described 'Map Group No. 13 Tall Open Atriplex nummularia Chenopod Shrubland' on the Dry Lake, Oxley, Hay, One Tree, Moggumbill and Gunbar 1:100000 map sheets. Plains Wanderer (Pedionomus torquatus) habitat mapping on the Hay Plain (Roberts and Roberts 2001) described vegetation type '13 Saltbush Shrubland, Old Man Saltbush shrubland'. 'Atriplex nummularia low open-shrubland' was mapped in Kinchega National Park by Westbrooke et al. (2001). In Nearie Lake Nature Reserve, Westbrooke et al. (1997) identified 'Atriplex nummularia low open shrubland'. White et al. (2002) reconstructed the distribution of pre-1750 vegetation types in the Riverina Bioregion and described the broad vegetation type 'Old Man Saltbush Shrubland'. J. Benson (unpublished) described two Old Man Saltbush communities across NSW: 'Old Man Saltbush shrubland in the semi-arid climatic zone in the southwestern NSW' and 'Old Man Saltbush shrubland in the semi-arid hot and arid climate zones in north-western NSW'. The community belongs to the Riverine Chenopod Shrubland vegetation class of Keith (2004).

8. Old Man Saltbush Shrubland in western NSW has undergone a large reduction in geographic distribution and has been extensively modified since European settlement. The reconstructed vegetation types of White et al. (2002) showed Old Man Saltbush Shrubland to have existed throughout the centre and west of the Riverina Bioregion, and estimated the reconstructed areal extent to be more than 87 000 hectares. In the Riverina Bioregion, Todd (2003) combined maps of extant vegetation and estimated the current areal extent of Old Man Saltbush Shrubland to be 27 500 hectares. This represents a decline in the distribution of the community of approximately 70 per cent in that region. In the Riverina, Old Man Saltbush Shrubland is now largely restricted to the north and central north-west of the bioregion (White et al. 2002); its current distribution is patchy and ranges from small clumps to scattered isolated individuals of Atriplex nummularia (Scott 1993, Porteners 1993, Porteners et al. 1997). Fox (1991) found that only small relict stands remain of what were extensive stands in the south-west corner of NSW from the Ana Branch and Mildura 1:250000 map sheets. The community, although not highly disturbed, is now very rare in the Pooncarie 1:250000 map sheet area (Porteners et al. 1997). Across the Hay Plain, Porteners (1993) found Old Man Saltbush to be largely cleared and showed little regeneration due to moderate to heavy grazing. Cunningham et al. (1992) described the occurrence of Atriplex nummularia throughout western NSW as becoming less frequent to the north and west. "Generally, only small relict areas remain of what were once extensive stands; many of these areas are found near property homesteads, in small paddocks formerly used for the maintenance of the station horses" (Cunningham et al. 1992). These changes represent a large reduction in the geographic distribution of the community. Clearing may affect areas of the nominated community. 'Clearing of native vegetation' is listed as a Key Threatening Process under Threatened Species Conservation Act.

9. In NSW only small areas of Old Man Saltbush Shrubland are currently known to occur within conservation reserves. In the Murray Darling Depression the community occurs in Nearie Lake Nature Reserve, in the Riverina from Kalyarr National Park, from Paroo-Darling National Park in the Mulga Lands and in the Darling Riverine Plain from Kinchega National Park. Westbrooke and Miller (1995) identified localised sites of 'Atriplex nummularia low open-shrubland (4d) community' in Mungo National Park that occupied less than one percent of the Park area. Atriplex nummularia, the species, is also known to occur in Kemendok Nature Reserve. J. Benson (unpublished) also cites the presence of Old Man Saltbush shrubland at Pindera Downs Aboriginal Area, Yanga Nature Reserve and Willandra National Park.

10. Old Man Saltbush Shrubland in western NSW is threatened by grazing from domestic and feral herbivores. Atriplex nummularia is palatable to stock, goats, kangaroos and rabbits (Porteners 1993, Porteners et al. 1997) and has long been considered an important fodder plant (Beadle 1948). Heavy grazing in this community thins overstorey shrubs and prevents regeneration (Porteners et al. 1997), while trampling by hard-hooved herbivores including cattle, sheep and goats directly affects understorey species, degrades soil structure and facilitates the invasion and establishment of exotic species. Fox (1991) also noted that much of the reduction in Atriplex nummularia is due to clearing to remove cover for rabbits. The species does not recover well from continual defoliation under heavy grazing pressure (Fox 1991, Cunningham et al. 1992, White et al. 2002) and this has contributed to a significant reduction in the geographic distribution and ecological function of the Old Man Saltbush Shrubland community. 'Competition and grazing by the feral European Rabbit Oryctolagus cuniculus' and 'Competition and habitat degradation by Feral Goats Capra hircus' are each listed as a Key Threatening Process under the Threatened Species Conservation Act, and may affect areas of the nominated community. Recovery is possible under appropriate management and in the Riverina Atriplex nummularia was observed to regenerate well in open grassland areas at Kulyarr National Park following removal of stock grazing (J. Brickhill, pers. comm.).

11. Grazing pressure continues to act in concert with other threats including alterations to natural fire and water regimes (Porteners 1993, Porteners et al. 1997, White et al. 2002). As Atriplex species decline, they are replaced by less palatable species such as Sclerolaena muricata (Black Rolypoly), Sclerolaena tricuspis (Giant Redburr) and Maireana aphylla (Cotton Bush), as well as ephemeral herbs and grasses (Beadle 1948), resulting in a change to community structure and species composition. As a consequence of the above processes of degradation the community has undergone a large reduction in ecological function. 'High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and composition' and 'Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands' are each listed as a Key Threatening Process under the Threatened Species Conservation Act, and may affect areas of the nominated community.

12. The Old Man Saltbush Shrubland in western NSW 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 Amendment (Listing Criteria) Regulation 2005:

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:
(c) 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

Associate Professor Lesley Hughes
Chairperson
Scientific Committee

Proposed Gazettal date 17/03/06
Exhibition period: The exhibition period for comment on the Preliminary Determination for the Oldman Saltbush Shrubland in western NSW has been extended until Friday 12th June, 2006.

References

Beadle NCW (1948) 'The vegetation and pastures of western New South Wales with special reference to soil erosion.' Soil Conservation Service, Sydney.

Cunningham GM, Mulham WE, Milthorpe PL, Leigh JH (1992) 'Plants of western New South Wales.' (Inkata Press: Port Melbourne, Victoria)

Fox MD (1991) The natural vegetation of the Ana Branch - Mildura 1:250000 map sheet (New South Wales). Cunninghamia 2, 443-493.

Horner G, McNellie M, Nott TA, Vanzella B, Schliebs M, Kordas GS, Turner B, Hudspith TJ (2002) 'Native vegetation map report no. 2, abridged version: Dry Lake, Oxley, Hay, One Tree, Moggumbill and Gunbar 1:100000 Map Sheets.' NSW Department of Land and Water Conservation, Parramatta.

Keith D (2004) 'Ocean Shores to Desert Dunes: The Native Vegetation of New South Wales and the ACT.' (NSW Department of Environment and Conservation: Hurstville)

Pickard J, Norris EH (1994) The natural vegetation of north-western New South Wales: notes to accompany the 1:1000000 vegetation map sheet. Cunninghamia 3, 423-464.

Porteners MF (1993) The natural vegetation of the Hay Plain: Booligal-Hay and Deniliquin-Bendigo 1:250000 maps. Cunninghamia 3, 1-122.

Porteners MF, Ashby EM, Benson JS (1997) The natural vegetation of the Pooncarie 1:250000 map. Cunninghamia 5, 139-232.

Roberts I, Roberts J (2001) 'Plains Wanderer (Pedionomus torquatus) habitat mapping including woody vegetation and other landscape features, Riverina Plains - NSW.' NSW National Parks and Wildlife Service, Dubbo.

Scott J (1992) The natural vegetation of the Balranald-Swan Hill area. Cunninghamia 2, 597-652.

Thackway R, Creswell ID (1995) (Eds) 'An interim biogeographic regionalisation of Australia: a framework for establishing the national system of reserves.' Australian Nature Conservation Agency, Canberra.

Todd M (2003) 'Draft Riverina biodiversity project: acceleration of the outcomes of bioregional assessment projects - Riverina and Cobar Peneplain Bioregions.' NSW National Parks and Wildlife Service, Griffith.

Westbrooke ME, Miller JD (1995) The vegetation of Mungo National Park, western New South Wales. Cunninghamia 4, 63-80.

Westbrooke ME, Miller JD, and Kerr MK (1997) Vegetation and flora of Nearie Lake Nature Reserve. Cunninghamia 5, 129-138.

Westbrooke ME, Kerr MKC, Leversha J (2001) The vegetation of Kinchega National Park, western New South Wales. Cunninghamia 7, 1-26.

Westbrooke M, Leversha J, Gibson M, O'Keefe M, Milne R, Gowans S, Harding C, Callister K (2003) The vegetation of Peery Lake area, Paroo-Darling National Park, western New South Wales. Cunningamia 8, 111-128.

White MD, Muir AM, Webster R (2002) 'The reconstructed distribution of indigenous vegetation types across the NSW Riverina.' NSW National Parks and Wildlife Service, Hurstville.

 

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This document was on public exhibition from 17 March 2006 to 12 June 2006. All submissions received during this period will be taken into account as the Scientific Committee prepares its final determination.

Page last updated: 27 February 2011