Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion - critically endangered ecological community listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion, as a CRITICALLY ENDANGERED ECOLOGICAL COMMUNITY in Part 2 of Schedule 1A of the Act. Listing of Critically Endangered Ecological Communities is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion is the name given to the ecological community characterised by the species assemblage listed in paragraphs 2 and 5. In NSW all sites are within the NSW South Western Slopes Bioregion (sensu Thackway & Creswell 1995).

 

2. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion is characterised by the following assemblage of species:

 

Acacia hakeoides

Acacia difformis

Acacia doratoxylon

Acacia havilandiorum

Acacia homalophylla

Acacia implexa

Acacia lineata

Acacia oswaldii

Acacia paradoxa

Acacia rhigiophylla

Acacia rigens

Acacia tetragonophylla

Acacia trineura

Alectryon oleifolius subsp. canescens

Atriplex semibaccata

Atriplex spinibractea

Austrodanthonia setacea

Austrostipa densiflora

Austrostipa elegantissima

Austrostipa scabra subsp. falcata

Austrostipa scabra subsp. scabra

Austrostipa verticillata

Baeckea crassifolia

Bertya cunninghamii

Brachychiton populneus subsp. trilobus

Bracteantha viscosa

Bulbine semibarbata

Calocephalus sonderi

Callitris glaucophylla

Callitris endlicheri

Calotis cuneifolia

Calotis lappulacea

Cassinia laevis

Cassytha melantha

Casuarina cristata

Chamaesyce drummondii

Cheilanthes austrotenuifolia

Cheilanthes sieberi subsp. sieberi

Chenopodium desertorum subsp. microphyllum

Chenopodium desertorum subsp. aniodiophyllum

Chenopodium pumilio

Joycea pallida

Chloris truncata

Daucus glochidiatus

Daviesia genistifolia

Dianella revoluta var. revoluta

Dodonaea viscosa subsp. cuneata

Elymus scaber

Einadia hastata

Einadia nutans subsp. nutans

Einadia polygonoides

Enchylaena tomentosa

Enteropogon acicularis

Eragrostis sp.

Eremophila deserti

Eremophila longifolia

Eremophila sturtii

Eucalyptus albens

Eucalyptus behriana

Eucalyptus dumosa

Eucalyptus microcarpa

Eucalyptus polybractea

Eucalyptus sideroxylon subsp. sideroxylon

Eucalyptus socialis

Eucalyptus viridis

Eutaxia diffusa

Exocarpos cupressiformis

Lachnagrostis filiformis

Leptospermum sp.

Maireana aphylla

Maireana enchylaenoides

Maireana microphylla

Melaleuca lanceolata subsp. lanceolata

Melaleuca uncinata

Myoporum montanum

Olearia ramulosa

Oxalis perennans

Ozothamnus tuckeri

Phebalium glandulosum subsp. glandulosum

Pittosporum angustifolium

Portulaca oleracea

Prostanthera aspalathoides

Pycnosorus thompsonianus

Rhagodia spinescens

Rumex brownii

Salsola kali

Santalum acuminatum

Sclerolaena muricata var. muricata

Senna form taxon 'zygophylla'

Sida corrugata

Thyridolepis mitchelliana

Vittadinia cuneata

Vittadinia pterochaeta

Wahlenbergia communis

Xerochrysum viscosum

Zygophyllum glaucum

 

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 condition and by its disturbance (including fire) history. The number of species, and the above-ground relative abundance of species, will change with time since fire, and may also change in response to changes in fire regime (including changes in fire frequency). At any one time, above ground individuals of some species may be absent, but the species may be represented below ground in the soil seed banks or as dormant structures such as bulbs, corms, rhizomes, rootstocks or lignotubers. The list of species given above is of vascular plant species, 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. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion varies in structure from tall mallee woodland with an open to mid-dense shrub layer and ground cover (sparseness perhaps an artifact of grazing history), to open or very dense mallee shrubland, with or without Broombush. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion varies between sites in the assemblage of species dominating the canopy layer. Three variants have been described (Benson 2008) as distinct communities, based largely on canopy composition and their tendency to occur on somewhat different landforms. These are 'ID 355: Bull Mallee-White Mallee tall mallee woodland on red sandy loam soils in the central western slopes of NSW'; 'ID 177: Blue Mallee-Bull Mallee-Green Mallee very tall mallee shrubland of the West Wyalong region, NSW South Western Slopes Bioregion', and 'ID 178: Broombush-Green Mallee-Blue Mallee very tall shrubland on stony rises in the NSW South Western Slopes Bioregion'. Benson noted however that these units do intergrade. Other data (D. Johnson 2004; S. Lewer 1998 data in litt.) suggests that the floristic composition of shrub layer and ground cover varies widely within, and overlaps between, the variants. Variability in the density and floristic composition of the shrub and ground layers may be partly a consequence of grazing history. The three Benson (2008) communities are all here regarded as variants included within, and as together comprising, Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion.

 

5. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion typically has a canopy layer co-dominated by the mallee eucalypts Eucalyptus behriana (Bull Mallee) and E. dumosa (White Mallee), with either (on flat land) E. socialis (Red Mallee), or (on low rises) E. polybractea (Blue Mallee) and E. viridis (Green Mallee). More rarely, on higher rocky rises, the dominant species may be E. polybractea and either E. viridis or E. dwyeri with a tall shrub layer of Melaleuca uncinata (Broombush). Additional conspicuous tree species may include E. dwyeri (Dwyer's Red Gum), Casuarina cristata (Belah), Callistris glaucophylla (White Cypress Pine), and Callitris endlicheri (Black Cypress Pine). The shrub layer may vary strongly from site to site but typically includes Acacia species such as A. hakeoides (Hakea Wattle), A. havilandiorum (Havilands Wattle), A. rhigiophylla (Dagger-leaf Wattle), A. rigens (Nealie), A. tetragonophylla (Dead Finish) and A. homalophylla (Yarran); Eremophila species such as E. deserti (Turkeybush), E. longifolia (Berrigan, Emu Bush) and E. sturtii (Narrow-leaf Emu-bush, Turpentine Bush); Melaleuca uncinata (Broombush); Alectryon oleifolius subsp. canescens (Western Rosewood); Dodonaea viscosa subsp. cuneata (Wedge-leaf Hopbush); and Myoporum montanum (Western Boobialla). Ground cover is variable but includes daisies, small chenopods, Sida corrugata, Cheilanthes spp. (Rock Ferns) and a variety of other forb and grass species.

 

6. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion may intergrade to a limited extent with the adjacent communities Inland Grey Box - White Cypress Pine woodland (ID 80 of Benson 2008), Belah Woodlands (ID 55), Yarran Tall Shrubland (ID 77), Dwyers Red Gum - Black Cypress Pine mallee (ID 186), Mugga Ironbark - Inland Grey Box (ID 127), and may occur near Green Mallee - Black Cypress Pine mallee woodland (ID 256).

 

7. Parts of Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion (the Bull Mallee - White Mallee variant) have been included in the Red Mallee Complex in Mid-Lachlan Regional Vegetation Committee (1999), and some remnants of it around West Wyalong were included as a component of map unit P1 by Sivertsen & Metcalfe (1995). Some other occurrences, of the Blue Mallee - Bull Mallee - Green Mallee variant, were partly mapped as a component of map unit H2 by Sivertsen & Metcalfe (1995). Benson (2008, sub ID 177) lists numerous other references.

 

8. Some other vegetation types occurring in the South Western Slopes Bioregion (sensu Thackway & Creswell 1995) contain mallee eucalypts, but are not considered to be part of Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion. These excluded vegetation types are those described by Benson (2008) as: 'ID 243: Mugga Ironbark - White Cypress Pine woodland on low rises mainly in the Cobar Peneplain Bioregion', in which White Mallee (Eucalyptus dumosa) and the mallee form of Dwyers Red Gum (E. dwyeri) are only a minor element; 'ID 217: Mugga Ironbark - Inland Grey Box - cypress pine tall woodland on footslopes of low hills in the NSW South Western Slopes Bioregion', in which Green Mallee (Eucalyptus viridis) and the mallee form of Dwyers Red Gum (E. dwyeri) are only a minor element; 'ID 173: Sandplain mallee of central NSW', which occurs on sandy soils and has Porcupine Grass (Triodia scariosa) in the ground layer; 'ID 193: Red Mallee - White Mallee extremely tall "tree mallee" on silty-loam-clay soils of central South Western NSW' in which Red Mallee (Eucalyptus socialis) is a major element and in which Bimbil Box (Eucalyptus populnea subsp. bimbil) and E. intertexta (Gum Coolibah) often occur; 'ID 186: Dwyers Red Gum - Black Cypress Pine - Currawang shrubby low woodland on rocky hills mainly in the NSW South Western Slopes Bioregion', in which Dwyers Red Gum (Eucalyptus dwyeri) and Black Cypress Pine (Callitris endlicheri) are co-dominant; and 'ID 176: Green Mallee - White Cypress Pine very tall mallee woodland on gravel rises mainly in the Cobar Peneplain Bioregion'. Benson (2008) also refers to 'ID 256: Green Mallee woodland on rises in sandstone forests of the southern Brigalow Belt South Bioregion' as occurring in the northern part of the NSW South Western Slopes Bioregion, but has subsequently advised (J. Benson pers. comm. Nov. 2009) that this reference is erroneous; the community in any case can be differentiated from Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion by the lack of mallee eucalypts other than Green Mallee (Eucalyptus viridis), the sandstone substrates, and a different suite of shrubs.

 

9. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion mainly occurs on red loamy soils. The variant of the community dominated by Bull Mallee and White Mallee tends to occur on plains to the east and north of West Wyalong, on red earths including the aeolian soil known as parna. The variant dominated by Blue Mallee - Bull Mallee - Green Mallee tends to occur on low hills and rises in sandy loam soils over substrates including gravel ferricrete (ironstone) and mixed sedimentary, metamorphic and granitic substrates (Benson 2008). The third variant, Broombush - Green Mallee - Blue Mallee, occurs in loamy sands on rocky rises of sandstone and other sedimentary rock types, mainly to the south-west of West Wyalong (e.g. Buddigower Nature Reserve, The Charcoal Tank Nature Reserve).

 

10. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion has been recorded from the local government areas of Bland and Temora, within the NSW South Western Slopes Bioregion (sensu Thackway & Creswell 1995), but may occur elsewhere in the Bioregion.

 

11. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion occurs mainly on private lands and roadside easements, and is poorly represented in conservation reserves. The Bull Mallee-White Mallee variant (ID 355 of Benson 2008) is not represented in any reserves. The Blue Mallee-Bull Mallee-Green Mallee variant (ID 177) occurs (Benson 2008) in Buddigower Nature Reserve and in Blue Mallee Forest Reserve. A stand of Blue Mallee in Big Bush Nature Reserve (Fleetwood 1987) has been tentatively assigned to this variant (Benson 2008), although J. Brickhill (in litt. 2008) does not consider that it has the characteristics of either ID 177 or 178. The Broombush-Green Mallee-Blue Mallee variant (ID 178) is recorded (Benson 2008) for Buddigower Nature Reserve, Blue Mallee Forest Reserve, and The Charcoal Tank Nature Reserve.

 

12. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion has a very highly restricted distribution, with known occurrences falling with a region of less than 4000 km2 bounded by Lake Cowal - Temora - Ardlethan - Ungarie. Estimation of the extent of occurrence within this region is difficult due to the lack of detailed mapping, but is probably of the order of 1 200 km2. An area of occupancy estimate of between 1 630 ha and 2970 ha, with a best estimate of 2 300 ha, can be derived from Benson's (2008) figures for current extent (comprising 100 ha +/- 10% of ID 355, 2 000 ha +/- 30% of ID 177, and 200 ha +/- 30% of ID 178). Using IUCN (2008) guidelines for calculating area of occupancy for species via a 2 x 2 km grid, this would imply a highly restricted AOO of less than 500 km2. Benson (2008) estimates the decline since settlement of ID 355 as more than 70% from a pre-European extent of 2 000 ha +/- 10%, the decline of ID 177 as more than 70% from a pre-European extent of 15 000 ha +/- 30%, and the decline of ID 178 as 75% from a pre-European extent of 800 ha +/- 30%.

 

13. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion provides habitat for the following species listed under the Threatened Species Conservation Act 1995: Bush Stone-curlew (Burhinus grallarius) - Endangered; Malleefowl (Leipoa ocellata) - Endangered; Gilbert's Whistler (Pachycephala inornata) - Vulnerable; Shy Heathwren (Hylacola cauta) - Vulnerable; Southern Scrub-robin (Drymodes brunneopygia) - Vulnerable; and the herb Spiny Peppercress (Lepidium aschersonii) - Vulnerable. The Malleefowl is also listed as Vulnerable under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. Brickhill (in litt. 2008) reports that malleefowl have seriously declined in the variant of the community dominated by Broombush - Green Mallee - Blue Mallee, and relates reports from birdwatchers and bird-banders that the Shy Heathwren and Southern Scrub-robin are also in serious decline in the occurrence of this community in The Charcoal Tank Nature Reserve.

 

14. Current or potential threats to the Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion community include (Benson 2008; D. Johnston in litt. 2008; J. Brickhill in litt. 2008): clearing of remnants for agriculture and road and easement works, inappropriate fire regimes, deterioration of genetic health and loss of ecosystem function due to small patch size, weed invasion, grazing and browsing by domestic and feral herbivores, and (in the Broombush - Green Mallee - Blue Mallee variant) potential over-harvesting for eucalyptus oil production and cut broombush. D. Johnston (in litt. 2008) identifies additional threats at one roadside site, and potentially applying at others, as including rubbish dumping, firewood collection, changes in grazing management, continuous grazing, and herbicide spraying.

 

Past clearing activities have severely fragmented the community, creating patches with large edge-to-area ratios and reducing movement of animals and plant pollen and propagules. Fire regime (frequency, intensity and seasonality) may have profound effects on mallee vegetation types, and particular sequences of fire and subsequent wet or dry seasons may drive structure and floristics of mallee assemblages in very different and long-lasting directions (Bradstock 1989; Noble 1989; Wellington 1989; Cohn & Bradstock 2000). High fire frequency is likely to eliminate resprouting canopy species, exhausting their lignotubers; conversely, absence of fire may exhaust the long-lived soil seed bank of shrub and ground-cover species. 'High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and composition' is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

 

Weed invasion may constitute a threat to the persistence of constituent species of the Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion community, and/or to elements of its ecological function. Benson (2008) reports low weed presence in the variant dominated by Blue Mallee - Bull Mallee - Green Mallee, which occurs on higher ground, although D. Johnston (in litt. 2008) reports occurrence, at one site of this variant, of a low incidence of the introduced annual grasses Aira caryophylla (Silvery Hairgrass), Vulpia muralis (Rats-tail Fescue), Lamarckia aurea (Golden-Top), and the introduced perennial grass Anthoxanthum odoratum (Sweet Vernal Grass). Lewer (in litt. 1998) reports Avena fatua (Wild Oats), Aira cupianna (Silvery Hairgrass), and Vulpia myuros (Rat's Tail Fescue) for another site probably including transition zones to other communities. Data in Benson (2008, sub ID 355) and C. Bower (in litt. undated.) suggest markedly greater presence and cover of weeds in the variant dominated by Bull Mallee - White Mallee, which tends to occur on flatter ground near roads and agricultural land - weed species in this latter variant include Lycium ferocissimum (African Boxthorn), Trifolium angustifolium (Narrow-leaved Clover), Trifolium campestre (Hop Clover), Lolium rigidum (Wimmera Ryegrass), Medicago polymorpha (Burr Medic), Kickxia elatine subsp. elatine (Woolly Toadflax), Spergularia rubra (Red Sand-spurrey), and Sonchus oleraceus (Common Sowthistle). Much of the remnant Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion occurs as small patches, including along road verges, and in such situations may be expected to be more exposed and vulnerable to weed invasion.

 

15. Mallee and Mallee-Broombush dominated woodland and shrubland, lacking Triodia, in the NSW South Western Slopes Bioregion is eligible to be listed as a Critically Endangered Ecological Community as, in the opinion of the Scientific Committee, it is facing an extremely high risk of extinction in New South Wales in the immediate future, as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

 

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:

(a)

A very 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: 24/09/10

Exhibition Period: 24/09/10 - 19/11/10

 

References:

 

Benson JS (2008) New South Wales vegetation Classification and Assessment: Part 2 Plant communities of the NSW South Western Slopes Bioregion and update of NSW Western Plains plant communities, version 2 of the NSWVCA database. Cunninghamia 10, 599-673.

 

Bradstock RA (1989) Dynamics of a perennial understorey. In JC Noble and RA Bradstock (eds), Mediterranean landscapes in Australia. CSIRO Publications, East Melbourne.

 

Cohn J. S. & Bradstock R. A. (2000) Factors affecting post-fire seedling establishment of selected mallee understorey species. Aust. J. Bot. 48, 59-70.

 

Fleetwood R (1987) The Charcoal Tank Nature Reserve Vegetation Abundance and Distribution Ratings. NSW National Parks and Wildlife Service, Griffith.

 

Johnston D (2004) Eucalyptus behriana (Bull Mallee) - Eucalyptus dumosa (White Mallee): Results of a Botanical Assessment. Unpublished survey report.

 

IUCN (2008) 'Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.' (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland). (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf).

 

Mid-Lachlan RVC (1999) Draft Mid-Lachlan Regional Vegetation Management Plan. Mid-Lachlan Regional Vegetation Committee: Forbes

 

Noble JC (1989) Fire regimes and their influence on herbage and mallee coppice dynamics. In JC Noble and RA Bradstock (eds), Mediterranean landscapes in Australia. CSIRO Publications, East Melbourne.

 

Sivertsen D and Metcalfe L (1995) Natural vegetation of the southern wheat-belt (Forbes and Cargelligo 1:250 000 map sheets). Cunninghamia 4, 103-128.

 

Thackway R, Creswell ID (1995) An interim biogeographic regionalisation for Australia: a framework for setting priorities in the National Reserve System Cooperative Program. (Version 4.0. ANCA: Canberra.)

 

Wellington AB (1989) Seedling regeneration and the population dynamics of eucalypts. In JC Noble and RA Bradstock (eds), Mediterranean landscapes in Australia. CSIRO Publications, East Melbourne.

Page last updated: 28 February 2011