Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions - Determination to make a minor amendment to Part 3 of Schedule 1 of the Threatened Species Conservation Act

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Determination to make a minor amendment to Part 3 of Schedule 1 (Endangered ecological communities) of the Act by inserting the Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions (as described in the determination of the Scientific Committee under Division 5 Part 2) and as a consequence to omit reference to the Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions (as described in the final determination to list the ecological community) which was published on pages 2498 to 2504 in the NSW Government Gazette No. 37 dated 28 March 2008. Minor amendments to the Schedules are provided for by Division 5 of Part 2 of the 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. Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions is the name given to the ecological community dominated by Buloke ( Allocasuarina luehmannii), sometimes with co-occurring tree species, that typically occupies patches of red-brown loamy sands with alkaline sub-soils on the alluvial plain of the Murray River and its tributaries in south-western NSW.  Allocasuarina luehmannii Woodland is characterised by the assemblage of species listed in paragraph 2 and typically comprises an open tree canopy with a sparse and highly variable ground layer dominated by grasses and herbs, sometimes with scattered shrubs and/or small trees. The structure and species composition of the community varies depending on disturbance history and temporal variability in rainfall.

2. Allocasuarina luehmannii Woodland is characterised by the following assemblage of species:

A large number of infrequently recorded species also characterise the community. These include:

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 (including grazing, land clearing and fire) history. 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 both vertebrate and invertebrate faunas. These components of the community are poorly documented.

4. Allocasuarina luehmannii Woodland is characterised by an open tree stratum. The tree layer, dominated by  Allocasuarina luehmannii (Buloke) may also include  Callitris glaucophylla (White Cypress Pine) or  Melaleuca lanceolata (Moonbah), though usually in lower abundance than  A. luehmannii. Other tree species, including  Callitris gracilis (Slender Cypress Pine),  Eucalyptus  behriana (Bull Mallee) and  Eucalyptus largiflorens (Blackbox), may also occur at some sites within the community. A scattered shrub layer is sometimes present and may include  Sclerolaena  muricata (Black Rolypoly),  Enchylaena tomentosa (Ruby Saltbush),  Maireana spp. (bluebushes) and/or  Hakea  tephrosperma (Hooked Needlewood). The groundcover is highly variable in structure and composition. It is typically sparse, but may be more continuous within patches or following substantial rainfall events. It comprises grasses, including species such as  Austrodanthonia caespitosa (Ringed Wallaby Grass),  A. setacea (Small-flowered Wallaby Grass),  Austrostipa elegantissima (Feather Speargrass),  A. scabra (Rough Speargrass),  Enteropogon  acicularis (Curly Windmill Grass) and  Homopholis proluta; sedges including  Carex inversa and  Juncus subsecundus; and forbs including  Atriplex leptocarpa (Slender-fruit Saltbush),  Einadia  nutans (Climbing Saltbush),  Oxalis perennans,  Sida corrugata (Corrugated Sida) and  Vittadinia spp. The structure of the community varies depending on past and current disturbances, particularly clearing, grazing and erosion.

5. Allocasuarina luehmannii Woodland shares a number of species with another endangered ecological community listed under the Threatened Species Conservation Act 1995: Sandhill Pine Woodland in the Riverina, Murray-Darling Depression and NSW South Western Slopes bioregions. These two ecological communities inhabit similar soils and landforms and have similar geographic distributions. They may be distinguished on the basis of the relative abundance of their tree species and subtle differences in composition of their understorey. When tree abundance is assessed at hectare scales,  A.luehmannii is the most abundant tree species in  Allocasuarina luehmannii Woodland, whereas  Callitris glaucophylla is the most abundant tree species in Sandhill Pine Woodland. Differences in understorey composition are likely to be obscured as a result of the history of heavy disturbance throughout both communities. Vegetation with characteristics that are intermediate between Sandhill Pine Woodland and  Allocasuarina luehmannii Woodland are covered collectively under the two Determinations.

6. A number of vegetation surveys and mapping studies have been carried out in regions within which Allocasuarina luehmannii Woodland occurs (reviewed in Mackenzie and Keith 2007). Sluiter  et al. (1997) surveyed buloke and pine woodlands in Victoria and southern New South Wales, and identified 12 species groupings from an analysis of their survey data. The majority of these were confined to Victoria, however, ‘Semi-arid grassy pine – Buloke Woodland’ (Group 3), ‘Buloke Grassy Woodland’ (Group 9) and possibly ‘Semi-arid Northwest Plains Buloke Grassy Woodland’ (Group 8) are referrable to  Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions. The community also includes ‘ Eucalyptus largiflorens –  Melaleuca lanceolata –  Allocasuarina luehmannii Woodland’ described in Smith and Smith’s (1990) study of riparian vegetation in the Murray River valley. None of the available regional-scale vegetation mapping studies in the Riverina region (Scott 1992, Porteners 1993, Porteners  et al. 1997, Roberts and Roberts 2001, Horner et al. 2002, McNellie  et al. 2005) show the distribution of woodlands dominated by Buloke, ostensibly because stands of this vegetation were too small or too difficult to delineate at their respective mapping scales. However, locations of Buloke woodland surveyed by Sluiter  et al. (1997) show some spatial association with broader map units from these studies pertaining to mixed woodlands on sandy soils of the alluvial plain. A recent review and classification of vegetation in western New South Wales (Benson  et al. 2006) described ‘Buloke – Moonbah – Blackbox open woodland on sandy rises of semi arid (warm) climate zone’ (Community 20), which is referrable to  Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling-Depression bioregions. A second assemblage, ‘Semi-arid shrubby Buloke – Slender Cypress Pine woodland’ (Community 22) of Benson  et al. (2006), apparently represents an outlying form of  Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions. Community 22 contains a greater diversity of understorey shrubs and occurs further west than Community 20 (Benson  et al. 2006).  Allocasuarina luehmannii Woodland belongs to the Riverine Sandhill Woodlands vegetation class of Keith (2004).

7. Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions forms part of the broader ecological community listed on Schedule 2 of the  Environment  Protection and Biodiversity Conservation Act  1999, known by the similar name, ‘Buloke Woodlands of the Riverina and Murray Darling Depression Bioregions’. This broader community also occurs in Victoria and apparently has a larger distribution than that currently known for the community described in this Determination.

8. Allocasuarina luehmannii Woodland has been recorded in the southern part of the Riverina bioregion from near Urana and Mulwala in the east to the Barham district, and may extend as far west as Euston in the southern part of the Murray-Darling Depression bioregion. The community occurs in small patches within this range and is currently estimated to cover less than 500-1500 ha (Benson  et al. 2006). It is currently known from the Balranald, Berrigan, Conargo, Corowa, Deniliquin, Murray and Wakool Local Government Areas, but may occur elsewhere in the Riverina and Murray-Darling Depression bioregions. Bioregions are defined in Thackway and Cresswell (1995).

9. Approximately 6 ha of Allocasuarina luehmannii Woodland are estimated to occur within Lake Urana and Wiesners Swamp Nature Reserves (Benson  et al. 2006). The remainder of the community occurs on private land or on public easements. Sluiter  et al. (1997) identified incremental roadside clearing, travelling livestock (droving) and opportunistic livestock grazing on roadside reserves, land clearing on private and leasehold land, firebreak construction, herbicide application and fertiliser drift as the main threats affecting  Allocasuarina luehmannii Woodland in New South Wales.

10. Allocasuarina luehmannii Woodland has undergone a large reduction in its geographic distribution as a consequence of clearing for cropping and pasture improvement (Smith and Smith 1990, Sluiter  et al. 1997, Benson  et al. 2006). This has largely occurred within the past 170 years, a time span appropriate to the life cycle of the dominant species of the community. In many cases, remnants are confined to roadsides or other small fragments (Sluiter  et al. 1997), while some stands of the community have been reduced to a few isolated trees (Scott 1992). Fragmentation of the remaining stands is likely to have resulted in a large reduction in the ecological function of the community due to the small population sizes of many constituent 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 & Clarke 2000). The geographic distribution of the community continues to decline as a consequence of small-scale clearing (Sluiter  et al. 1997). ‘Clearing of native vegetation’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

11. Many of the remaining stands of Allocasuarina luehmannii Woodland are degraded by overgrazing, which has resulted in simplification of community structure, changes in species composition, invasion of weeds and soil erosion. Overgrazing by domestic livestock and feral herbivores, including rabbits and goats, has resulted in a scarcity of woody understorey plants and a lack of regeneration of palatable trees and shrubs. Consequently, senescent trees are not replaced with new individuals and there is a prolonged trend of stand degeneration. Overgrazing also reduces structural complexity, plant species diversity and habitat suitability for vertebrate fauna of the community. The sandy-textured soils of  Allocasuarina luehmannii Woodland are sensitive to erosion as a result of trampling by hooved animals and burrowing by rabbits. These impacts are exacerbated under drought conditions. Collectively, these processes have resulted in a large reduction in the ecological function of the community (Sluiter  et al. 1997, Benson  et al. 2006). ‘Competition and grazing by the feral European Rabbit,  Oryctolagus cuniculus’ and ‘Competition and habitat degradation by Feral Goats,  Capra hircus’ are listed as Key Threatening Processes under the Threatened Species Conservation Act 1995.

12. Fragmentation, grazing and small-scale physical disturbance have resulted in weed invasion throughout the distribution of Allocasuarina luehmannii Woodland, which continues to threaten the ecological function of the community. Principal weed species include:

‘Invasion of native plant communities by exotic perennial grasses’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

13. Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions is not eligible to be listed as a critically endangered ecological community.

14. Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression bioregions 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

Benson JS, Allen CB, Togher C, Lemmon J (2006) New South Wales vegetation classification and assessment. Part 1 Plant communities of the NSW western plains. Cunninghamia9 , 383-450.

Horner G, McNellie M, Nott TA, Vanzella B, Scleibs M, Kordas GS, Turner B, Hudspith TJ (2002) Native vegetation map report series No. 2. Dry Lake, Oxley, Hay, One Tree, Moggumbill and Gunbar 1:100000 map sheets. NSW Department of Land and Water Conservation, Parramatta.

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.

Mackenzie B, Keith DA (2006) Assessment of Woodland Assemblages dominated by Buloke for listing as a threatened ecological community under the Threatened Species Conservation Act. Report to the NSW Scientific Committee

McNellie M, Horner G, Nott TA, Vanzella B, Scleibs M, Kordas GS, Turner B, Hudspith TJ (2005) Native vegetation map series. Deniliquin 1:250000 map sheet. NSW Department of Natural Resources, Parramatta.

Smith P, Smith J (1990) Riparian Vegetation of the River Murray. Report to the Murray-Darling Basin Commission, Canberra. Margules and Partners Pty Ltd and Department of Conservation Forests and Lands.

Porteners MF (1993) Natural vegetation of the Hay Plain: Booligal-Hay and Deniliquin-Bendigo 1:250 000 maps. Cunninghamia3 , 1-122.

Porteners MF, Ashby EM, Benson JS (1997) The natural vegetation of the Pooncarie 1:250 000 map. Cunninghamia5 , 139-231.

Roberts I, Roberts J (2001) Plains-wanderer (Pedionomus torquatus) Habitat Mapping including Woody Vegetation and other Landscape Features. Riverina Plains, NSW. Report to NSW National Parks and Wildlife Service, Sydney.

Scott JA (1992) The natural vegetation of the Balranald-Swan Hill area. Cunninghamia2 , 597-654.

Sluiter IRK, Minchin PR, Jaensch SC (1997) The Buloke and Pine Woodlands of semi-arid and dry sub-humid Victoria and nearby areas. Ogyris Ecological Research Report No. 97/02

Thackway R, Cresswell ID (1995) An interim biogeographic regionalisation for Australia: a framework for setting priorities in the National Reserves System Cooperative Program. (Version 4.0. Australian Nature Conservation Agency: Canberra.)

Young A, Boyle T, Brown A (1996) The population genetic consequences of habitat fragmentation for plants. Trends in Ecology and Evolution11 , 413-418.

Young A, Clarke G (2000) Genetics, demography and the viability of fragmented populations. (Cambridge University Press: Cambridge)