Sandhill Pine Woodland in the Riverina, Murray-Darling Depression and NSW South Western Slopes 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 Sandhill Pine Woodland in the Riverina, Murray-Darling Depression and NSW South Western Slopes bioregions (as described in the determination of the Scientific Committee under Division 5 Part 2) and as a consequence to omit reference to the Sandhill Pine Woodland in the Riverina, Murray-Darling Depression and NSW South Western Slopes bioregions (as described in the final determination to list the ecological community) which was published on pages 2509 to 2517 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. Sandhill Pine Woodland in the Riverina, Murray-Darling Depression and NSW South Western Slopes bioregions is the name given to the ecological community dominated by Callitris glaucophylla, that typically occupies red-brown loamy sands with alkaline sub-soils on the alluvial plain of the Murray River and its tributaries, and on parts of the sandplain in south-western NSW. In the Riverina bioregion and the far south-western portion of the NSW South Western Slopes bioregion, the community is typically associated with prior streams and aeolian source-bordering dunes, which are scattered within an extensive alluvial clay plain dominated by chenopod shrublands. In the Murray-Darling Depression bioregion, the community occurs as scattered patches on sandhills and lunettes within an extensive aeolian sandplain dominated by woodlands of mallee eucalypts or belah. Bioregions are defined in Thackway and Cresswell (1995). Sandhill Pine Woodland is characterised by the assemblage of species listed in paragraph 2 and typically comprises an open tree canopy with a sometimes sparse, but 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. Sandhill Pine 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. Sandhill Pine Woodland is characterised by an open tree stratum, which may be reduced to isolated individuals or may be absent as a result of past clearing. The tree layer is dominated by Callitris glaucophylla (White Cypress Pine), either in pure stands or with a range of other less abundant trees or tall shrubs. These may include  Acacia melvillei, A.oswaldii, Allocasuarina luehmannii (Buloke),  Callitris gracilis subsp . murrayensis (Slender Cypress Pine),  Hakea leucoptera (Needlewood) , H.tephrosperma (Hooked Needlewood) , Myoporum platycarpum (Sugarwood) and  Pittosporum angustifolium (Berrigan). A scattered shrub layer is sometimes present and may include  Dodonaea viscosa subsp . angustifolia, Enchylaena tomentosa (Ruby Saltbush),  Sclerolaena muricata (Black Rolypoly) and/or  Maireana enchylaenoides (bluebush). The groundcover is highly variable in structure and composition. It may be sparse or more continuous, depending on the history of disturbance, grazing and rainfall events. It comprises grasses, such as  Austrodanthonia caespitosa (Ringed Wallaby Grass),  A.setacea (Small-flowered Wallaby Grass),  Austrostipa nodosa (a speargrass),  A.scabra (Rough Speargrass) , Enteropogon acicularis (Curly Windmill Grass),  Panicum effusum and  Paspalidium constrictum; and forbs including  Atriplex semibaccata (Creeping Saltbush),  Einadia nutans (Climbing Saltbush),  Erodium crinatum (Blue Storksbill) , Oxalis perennans, Sida corrugata (Corrugated Sida) and  Wahlenbergia spp. (bluebells). The structure of the community varies depending on past and current disturbances, particularly clearing, logging, grazing and soil erosion.

5. Sandhill Pine Woodland shares a number of species with another endangered ecological community listed under the Threatened Species Conservation Act 1995: Allocasuarina luehmannii Woodland in the Riverina and Murray-Darling Depression 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,  Callitris glaucophylla is the most abundant tree species in Sandhill Pine Woodland, whereas in  Allocasuarina luehmannii Woodland,  A.luehmannii is the most abundant tree species. 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 Sandhill Pine Woodland occurs. The community includes: ‘Callitris glaucophylla Woodland’ (Community 36) and ‘ Dodonaea viscosa -  Callitris preissii Shrubland’ (Community 37) of Smith and Smith (1990); ‘Mixed Woodland, Callitris Woodland’ (a subunit of map units 4 and 11) of Fox (1991); ‘ Callitris Mixed Woodland’ (map unit 16) of Scott (1992), Porteners (1993) and Porteners  et al. (1997): ‘Prior Stream Remnant Woodland’ (Map unit 27) of Porteners (1993); ‘ Callitris glaucophylla open-woodland’ (Community 1c) of Westbrooke and Miller (1995) and Westbrooke  et al. (1998), and ‘ Callitris glaucophylla low open-woodland’ (Community 4) of Morcom and Westbrooke (1990); ‘ Thyridolepis mitchelliana –  Themeda australis understorey remnants in open woodland’ (Community 2) of Benson  et al. (1997); ‘ Callitris Mixed Woodland’ (map units 1,2,3 & 6) of Stafford and Eldridge (2000); Callitris, Yellow Box, Western Grey Box, Needlewood, Buloke (map unit 53) and Callitris Mixed Woodland (map unit 55) of Roberts and Roberts (2001); Source Bordering Sands Woodland (Community 6) of White  et al. (2002);  Callitris glaucophylla ±  Allocasuarina luehmannii ±  Alectryon oleifolius Woodland on Sandy Rises (map unit ALP017) of Horner  et al. (2002); and ‘Pine-Oak Woodlands on Alluvial Dunes and Plains’ (map unit ALP017) and ‘Pine Woodlands on Dunes of the Murray Floodplain’ (Map Unit FLP008) of McNellie  et al. (2005). A review and classification of vegetation in western New South Wales (Benson  et al. 2006) described four communities referrable to Sandhill Pine Woodland of the Riverina, Murray-Darling Depression and NSW South Western Slopes bioregions: ‘ Cypress Pine woodland of source-bordering dunes mainly on the Murray River floodplain’ (Community 19); ‘Slender Cypress Pine - Sugarwood - Western Rosewood open woodland on sandy rises of the semi-arid (warm) and arid climate zones’ (Community 21); ‘White Cypress Pine open woodland of sand plains, prior streams and dunes mainly of the semi-arid (warm) climate zone’ (Community 28); and ‘White Cypress Pine-Drooping Sheoak grassy open woodland of the Riverine Plain’ (Community 48). Sandhill Pine Woodland belongs to the Riverine Sandhill Woodlands vegetation class of Keith (2004).

7. Sandhill Pine Woodland has been recorded in the far south-western portion of the NSW South Western Slopes bioregion near Urana, extending through the Riverina bioregion, from the Urana – Narranderra district in the east, into the southern part of the Murray-Darling Depression bioregion, as far west as the South Australian border. It is currently known from the Balranald, Berrigan, Carrathool, Central Darling, Conargo, Corowa, Deniliquin, Hay, Murray, Narranderra, Urana, Wakool and Wentworth Local Government Areas, but may occur elsewhere in the Riverina, Murray-Darling Depression and NSW South Western Slopes bioregions sensu Thackway and Cresswell (1995). Throughout its distribution, the community occurs in relatively small patches, typically on red-brown sandy loams. In the Riverina and NSW South Western Slopes bioregions, these soils are associated with the beds of prior streams or source-bordering dunes adjacent to streams and lake beds, which are restricted and distinctive landforms on the extensive riverine plain. Further west, in the Murray-Darling Depression Bioregion, the community occurs on lunettes associated with dry lake beds, and as patches within a mosaic of vegetation types on extensive sandplains.

8. Vegetation mapping studies cited in Paragraph 6 allow the remaining area of Sandhill Pine Woodland to be estimated in various parts of its geographic distribution. Mapping by botanists from the National Herbarium of NSW (Fox 1992, Scott 1993, Porteners 1993, Porteners et al. 1997) covers the majority of the geographic distribution of the community, which includes map units 16 and 27 (see paragraph 6). These maps show that map units 16 and 27 have a combined extant area of approximately 85000ha, with an additional 86000ha estimated to have been cleared or degraded to ‘highly disturbed’ open areas, and a further 35000ha mapped as ‘scattered trees’ (Porteners 1993). Additional areas of these vegetation types occur as unmapped patches within mosaics containing other vegetation types. There are also additional areas of Sandhill Pine Woodland to the east of the National Herbarium study area. Mapping by White  et al. (2002) shows approximately 10000ha of vegetation (Community 6) referable to Sandhill Pine Woodland in this area. The Deniliquin 1:250000 map sheet is within the total area surveyed by Fox (1992), Scott (1993), Porteners (1993) and Porteners  et al. (1997). The Deniliquin sheet includes approximately 28000ha of the total 85000 ha of map units 16 and 27, 11000ha of the total 35000ha of these units mapped as scattered trees and 68000ha of the total 86000ha of map units 16 and 27 estimated to have been cleared (Porteners 1993). More recent mapping on the Deniliquin 1:250000 map sheet (McNellie  et al. 2005) shows approximately 13000ha of map units referable to Sandhill Pine Woodland (ALP017 and FLP008). The smaller area of mapped vegetation referable to extant Sandhill Pine Woodland by McNellie  et al. (2005) than by Porteners (1993) may be partly due to a more narrow interpretation of pine-dominated woodlands by the former authors, but may also reflect a decline in area of the community.

9. Sandhill Pine Woodland has undergone a large reduction in its geographic distribution as a consequence of clearing for cropping and pasture improvement (Grant 1989, Smith and Smith 1990, Scott 1992, Porteners 1993, Benson et al. 2006). This has occurred within a time span appropriate to the life cycle of the dominant species of the community, with much of the clearing taking place between 1880 and 1910 (Grant 1989). Some clearing for cereals and irrigated agriculture has occurred later in the twentieth century (DEC  in litt.). A recent synthesis of available map data indicates that the distribution of this community has been reduced by 40 - 75 % (Mackenzie and Keith 2007a). 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.

10. Most of the stands of Sandhill Pine Woodland that have escaped broad-scale clearing have been maintained as sources of timber, either in state forests or on private land. Logging of cypress pines for construction of fences and buildings has resulted in significant changes in the structure of vegetation in these remnants, indicating a large reduction in the ecological function of Sandhill Pine Woodland. As a consequence, many contemporary stands lack large old trees and, where tree recruitment has been limited by grazing, trees in other size classes may have been reduced in density or may have been eliminated altogether. Conversely, abundant regeneration of C.glaucophylla has occurred after logging at some sites when there has been a temporary reduction in numbers of livestock, feral rabbits and goats. This results in relatively dense even-aged stands of trees that have yet to attain the mature structure of the community. The structure of these dense even-aged stands contrasts markedly with that of some remnants in pastures, in which large senescent trees are the only remaining size class of trees present, as a result of the continual removal of regeneration by grazing animals (Mackenzie and Keith 2007b).

11. Most of the remaining stands of Sandhill Pine Woodland are degraded by overgrazing, which has resulted in simplification of community structure, changes in species composition, invasion of weeds and soil erosion (Stafford and Eldridge 2000). 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 (Scott 1992, Porteners 1993, Benson et al. 2006). Consequently, senescent trees are not replaced with new individuals and there is a prolonged trend of stand degeneration. This is particularly evident in stands of Sandhill Pine Woodland in the western areas of its distribution in the Murray-Darling Depression bioregion (Scott 1992, Porteners  et al. 1997, Mackenzie and Keith 2007b). Overgrazing also reduces structural complexity, plant species diversity and habitat suitability for vertebrate fauna of the community. The sandy-textured soils of Sandhill Pine Woodland are particularly sensitive to erosion when de-stabilised as a result of trampling by hooved animals and burrowing by rabbits (Semple 1987, Eldridge 1998, Eldridge and Greene 1994). These impacts are exacerbated under drought conditions. Lunettes that support Sandhill Pine Woodland are particularly vulnerable to erosion after overgrazing because their relatively steep slopes predispose them to erosion by water during and after rainfall events, as well as by wind. Collectively, the processes associated with overgrazing have resulted in a large reduction in the ecological function of the community. ‘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 Sandhill Pine Woodland, which continues to threaten the ecological function of the community. Principal weed species include:

13. Examples of Sandhill Pine Woodland have been recorded from Kalyarr, Mallee Cliffs, Mungo, Oolambeyan and Willandra National Parks, and Tarawi Nature Reserve (Morcom and Westbrooke 1990, Westbrooke and Miller 1995, Roberts and Roberts 2001, Porteners 1998, Benson et al. 2006). However, some of these reserves contain only a few hectares of the community, and all exhibit signs of degradation associated with past land uses and the continuing impacts of feral herbivores. Examples of Sandhill Pine Woodland with a diverse and healthy understorey that retain its native shrub component and contain a low abundance and diversity of weed species, are extremely rare in the region (Stafford and Eldridge 2000, DEC  in litt.).

14. Sandhill Pine Woodland of the Riverina, Murray-Darling and NSW South Western Slopes bioregions is not eligible to be listed as a critically endangered ecological community.

15. Sandhill Pine Woodland of the Riverina, Murray-Darling Depression and NSW South Western Slopes 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:08/07/11
Exhibition period: 08/07/11 - 02/09/11

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