Southern Sydney sheltered forest on transitional sandstone soils in the Sydney Basin Bioregion - 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 Southern Sydney sheltered forest on transitional sandstone soils in the Sydney Basin Bioregion (as described in the determination of the Scientific Committee under Division 5 Part 2) and as a consequence to omit reference to the Southern Sydney sheltered forest on transitional sandstone soils in the Sydney Basin Bioregion (as described in the final determination to list the ecological community) which was published on pages 6945 to 6952 in the NSW Government Gazette No. 116 dated 7 September 2007. 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. Southern Sydney sheltered forest on transitional sandstone soils in the Sydney Basin Bioregion is the name given to the ecological community characterised by the species assemblage listed in paragraph 2. The community typically has an open forest structure, although disturbance may result in local manifestations as woodland or scrub. The community is typically associated with sheltered heads and upper slopes of gullies on transitional zones where sandstone outcrops may exist, but where soils are influenced by lateral movement of moisture, nutrients and sediment from more fertile substrates, such as shale/ironstone caps or dolerite dykes, in adjacent areas.

2. Southern Sydney sheltered forest on transitional sandstone soils is characterised by the following assemblage of species:

3. The total species list of the community is considerably 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 not well documented.

4. Southern Sydney sheltered forest on transitional sandstone soils is an open forest dominated by eucalypts with scattered subcanopy trees, a diverse shrub layer and well-developed groundcover of ferns, forbs, grasses and graminoids. Some stands may take on structural forms of woodland or scrub, as disturbance associated with past clearing has resulted in reduced density and/or dense regrowth of the tree stratum. The dominant trees include Angophora costata, Eucalyptus piperita and occasionally  E. pilularis, particularly around Helensburgh.  Corymbia gummifera occurs frequently within the community, although generally at lower abundance than the other eucalypts. An open subcanopy includes  Allocasuarina littoralis,  Ceratopetalum gummiferum and occasionally  Elaeocarpus reticulatus and  Pittosporum undulatum. The understorey includes an open, diverse shrub stratum with species of  Acacia,  Banksia, Persoonia and several other genera.  Leptospermum polygalifolium, Leucopogon lanceolatus and  Lomatia silaifolia are frequently occurring shrubs, as are  Allocasuarina littoralis and some of the other subcanopy tree species.  Smilax glyciphylla and several other scramblers frequently occur in the shrub and ground strata. The prominent ground stratum comprises ferns ( Calochlaena, Pteridium, Gleichenia, Lindsaea), large emergent tussocks of  Doryanthes excelsa and  Gahnia sieberiana, and a range of grasses and graminoids including  Lomandra  longifolia, Entolasia stricta, Imperata cylindrica, Lepidosperma laterale and  Lepyrodia scariosa. Herbs,  Gonocarpus teucrioides and  Dianella caerulea, are also frequent components of the groundcover. There is considerable variation in species composition, richness and structure within the community in response to local edaphic gradients and geographic gradients across the range.

5. Southern Sydney sheltered forest on transitional sandstone soils is primarily associated with the heads and upper slopes of sandstone gullies, which are downslope from residual shale or ironstone caps. This is mainly gentle terrain, with slopes not often exceeding 10°, and sandstone outcrops occur infrequently, relative to sites within well-developed, steeper gullies. The associated shale caps may be weathered to varying degrees, and are sometimes represented only by outcropping ironstone on the adjacent ridges (indicating heavy weathering). Many of these shale and ironstone caps were mapped by Walker (1960) as the Woronora and Hammondville soil groups, although some locations of these soils were apparently overlooked at Walker’s (1960) coarse scale of mapping. In some cases, the transitional edaphic habitat may occur where sandstone overlies shale (e.g. Garrawarra Ridge). The community also occurs on sandstone sites associated with substrates other than shales and ironstones. For example, on the lower alluvial flats of the Hacking River near Audley, colluvial input from steep adjacent sandstone slopes mixes with loamy riverine deposits to create an enriched sandy loam supporting an unusual variant of the community. Another unusual occurrence is associated with a small dolerite dyke in Royal National Park, where lateral movement of sandstone-derived soils mix with more fertile loams derived from the dolerite.

6. Southern Sydney sheltered forest on transitional sandstone soils intergrades with other plant assemblages on sandstone, shale and ironstone substrates. Features that distinguish Southern Sydney sheltered forest of transitional sandstone soils from vegetation more typical of sandstone gullies in the eastern Sydney basin include its occurrences of Eucalyptus pilularis, Acacia binervata, Elaeocarpus reticulatus, Pittosporum undulatum and its relatively dense groundcover of ferns, grasses, rushes, lilies and forbs. These elements are apparently a response to enrichment of sandstone-derived soils from sources of additional nutrients, such as shale/ironstone caps, or rarely dolerite dykes and riparian material, which result in deeper, less rocky, more fertile sandy loams than those typical of sandstone gullies. Forests that occur on shales in the vicinity of Southern Sydney sheltered forest on transitional sandstone soils typically have a greater component of mesophyllous species in their shrub and subcanopy stratum, and trees such as  Eucalyptus globoidea, E. resinifera, E. paniculata or  Syncarpia glomulifera, which are not common in this community. These latter forests are classified as ‘Sydney Shale-Ironstone Cap Forest’ (map unit p143) by Tindall  et al. (2004) and Tozer  et al. (2006). This regional-scale map unit includes Endangered Ecological Communities, including Duffys Forest Ecological Community in the Sydney Basin Bioregion and O’Hares Creek Shale Forest.

7. Southern Sydney sheltered forest on transitional sandstone soils includes ‘Tall Blackbutt-Apple Shale Forest’ (map unit 20 of NPWS (2002), map unit 16 of NPWS (2003)). However, the description of this map unit as occurring ‘on remnant shale caps’ (NPWS 2002, 2003) is inaccurate, as the community is associated primarily with transition zones between shale and sandstone (see paragraph 5 above, Orscheg et al. 2006). In the extensive regional vegetation surveys of Tindall  et al. (2004) and Tozer  et al. (2006), Southern Sydney sheltered forest on transitional sandstone soils is one of several plant assemblages classified within a broader map unit (p140), Coastal Sandstone Gully Forest (Orscheg  et al. 2006). Southern Sydney sheltered forest on transitional sandstone soils belongs to the Sydney Coastal Dry Sclerophyll Forests vegetation class of Keith (2004).

8. Southern Sydney sheltered forest on transitional sandstone soils has been recorded from the local government areas of Campbelltown, Hurstville, Kogarah, Sutherland, Wollondilly and Wollongong within the Sydney Basin Bioregion and may occur elsewhere in the Bioregion. Bioregions are defined in Thackway and Cresswell (1995).

9. Southern Sydney sheltered forest on transitional sandstone soils is found within an estimated total extent of occurrence of less than 45 000 ha, bounded approximately by Hurstville, Carss Park, Bundeena, Otford, Stanwell Tops, Darkes Forest, Punchbowl Creek and Menai. Within this range, the community is currently estimated to occupy an area of approximately 400 – 4 000 ha, (Orscheg et al. 2006). These estimates indicate that the geographic distribution of Southern Sydney sheltered forest on transitional sandstone soils is highly restricted.

10. Clearing of areas where suitable habitat exists for Southern Sydney sheltered forest on transitional sandstone soils has occurred within the local government areas of Hurstville, Kogarah and Sutherland, where the community persists as small fragments surrounded by urban development. The remaining area of the community is principally in the upper Hacking River catchment around Helensburgh and in Royal National Park, although considerable clearing of the community has also occurred around the Helensburgh-Otford-Stanwell Tops area. Clearing has resulted in a moderate to large reduction in the geographic distribution of the community. Some areas of the community continue to be threatened by small-scale clearing and fragmentation associated with urban and rural residential subdivision, development and maintenance of transport corridors and easements. Clearing of native vegetation is listed as a Key Threatening Process under the Threatened Species Conservation Act.

11. The juxtaposition of Southern Sydney sheltered forest on transitional sandstone soils with urban and other developed areas exposes the community to influx of weeds and stormwater, heavy recreational use, incidental disturbance and some wilful damage. These result in degradation of the community, reduction in its ecological function and ongoing management challenges that are typical of bushland remnants in urban landscapes (Benson and Howell 1990). Stands of the community located downslope from developed areas are predisposed to further degradation. Weed infestations are most severe on the interfaces between bushland and urban and industrial areas and along drainage lines that carry stormwater runoff from developed areas. Problematic weed species in the community include the following:

‘Invasion and establishment of exotic vines and creepers’, ‘Invasion of native plant communities by exotic perennial grasses’ and ‘Invasion, establishment and spread of Lantana (Lantana  camara L.  sens. lat.)’ are listed as Key Threatening Processes under the Threatened Species Conservation Act.

12. Frequent fires and other fuel reduction measures may pose a threat to the community, particularly along urban interfaces, where it occurs within strategic fire management zones for asset protection. Royal National Park also has a history of frequent unplanned ignitions through arson and incidental causes (National Parks and Wildlife Service, fire history records). Frequent fires may interrupt life cycles of key plant species, resulting in changes to vegetation structure and fauna habitats (Catling 1991, Keith 1996). In combination with other disturbances, they may also accelerate weed invasion. ‘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. Conversely, small isolated vegetation remnants in long-established urban areas may experience very long intervals between fires, resulting in senescence and recruitment failure in some species whose populations depend on periodic fires for persistence.

13. The distribution of Southern Sydney sheltered forest on transitional sandstone soils occurs within an area that has been invaded by exotic Rusa deer (Moriarty 2002). Deer are generalist herbivores that browse and graze on a wide range of native and exotic plant species (Keith and Pellow 2004). This adversely affects survival and reproduction in some native plants. The effects of deer herbivory appear to be more severe in small, recently burnt areas, as the animals concentrate their foraging activities on these areas to obtain fresh plant growth. Deer populations reach very high densities in areas where Southern Sydney sheltered forest on transitional sandstone soils adjoins the urban interface, including areas such as Helensburgh and Grays Point. ‘Herbivory and environmental degradation caused by feral deer’ is listed as a Key Threatening Process under the Threatened Species Conservation Act.

14. Ongoing fragmentation, influx of stormwater, pollutants and nutrients, the invasion of weeds, changes in vegetation structure and continuing degradation associated with altered fire regimes and feral deer have collectively resulted in a large reduction in the ecological function of the community.

15. Southern Sydney sheltered forest on transitional sandstone soils in the Sydney Basin Bioregion is eligible to be listed as an endangered ecological community as, in the opinion of the Scientific Committee, it is facing a 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 26

The ecological community’s geographic distribution is estimated or inferred to be:

(b) highly restricted,

and the nature of its distribution makes it likely that the action of a threatening process could cause it to decline or degrade in extent or ecological function over a time span appropriate to the life cycle and habitat characteristics of the ecological community’s component species.

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.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 08/07/11
Exhibition period: 08/07/11 – 02/09/11

References

Benson DH, Howell, J (1990) The natural vegetation of the Penrith 1:100 000 map sheet. Cunninghamia 2, 541-596.

Catling PC (1991) Ecological effects of prescribed burning practices on the mammals of south-eastern Australia. In: ‘Conservation of Australia’s forest fauna’ (Ed. D Lunney), pp 353-363. (Surrey Beatty and Sons: Sydney)

Keith DA (1996) Fire-driven mechanisms of extinction in vascular plants: a review of empirical and theoretical evidence in Australian vegetation. Proceedings of the Linnean Society of New South Wales 116, 37-78.

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 DA, Pellow BJ (2005) Effects of Javan rusa deer (Cervus timorensis) on native plant species in the Jibbon-Bundeena area, Royal National Park, New South Wales. Proceedings of the  Linnean Society of New South Wales 126, 99-110.

Mills K (2005) ‘Supplementary vegetation assessment. Landcom project 12860/3. Frances Street, Helensburgh, City of Wollongong.’ Kevin Mills and Associates, Jamberoo.

Moriarty A (2004) The liberation, distribution, abundance and management of wild deer in Australia. Wildlife Research, 31, 291-299.

NPWS (2002) Bioregional assessment study. Part 1. The native vegetation of the Illawarra escarpment and coastal plain. (NSW National Parks and Wildlife Service: Hurstville).

NPWS (2003) The native vegetation of the Woronora, O’Hares and Metropolitan catchments. (NSW National Parks and Wildlife Service: Hurstville).

Orscheg C, Ooi M, Keith D (2006) The ecological relationships and conservation status of Tall Apple-Blackbutt Shale Forest. Report to the NSW Scientific Committee, Sydney.

Thackway R, Cresswell ID (1995) (eds) An interim biogeographic regionalisation of Australia: a framework for establishing the national system of reserves. (Version 4.0 Australian Nature Conservation Agency: Canberra)

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 (2003). The native vegetation of the Cumberland Plain, western Sydney: systematic classification and field identification of communities. Cunninghamia 8, 1-75.

Tozer MG, Turner K, Simpson C, Keith DA, Beukers P, Tindall D, Pennay C (2006) Native vegetation of southeast NSW: a revised classification and map for the coast and eastern tablelands. Version 1.0. (Department of Environment and Conservation and Department of Natural Resources: Sydney)

Walker PH (1960) A soil survey of the county of Cumberland, Sydney region. (New South Wales Government Printer: Sydney)