Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion - vulnerable ecological community listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion, as a VULNERABLE ECOLOGICAL COMMUNITY in Part 2 of Schedule 2 of the Act. Listing of Vulnerable Ecological Communities is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion is the name given to the ecological community characterised by the species assemblage listed in paragraph 2. In NSW all sites are within the Sydney Basin Bioregion (sensu Thackway & Cresswell 1995).

2. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion 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 poorly documented.

4. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion is dominated by Eucalyptus parramattensis subsp.  parramattensis, Angophora bakeri and  E.  sclerophylla. A small tree stratum of  Melaleuca decora is sometimes present, generally in areas with poorer drainage. It has a well-developed shrub stratum consisting of sclerophyllous species such as  Banksia spinulosa var.  spinulosa, M. nodosa, Hakea sericea and H. dactyloides (multi-stemmed form). The ground stratum consists of a diverse range of forbs including  Themeda australis, Entolasia stricta, Cyathochaeta diandra, Dianella revoluta subsp.  revoluta, Stylidium graminifolium, Platysace ericoides, Laxmannia gracilis and  Aristida warburgii (Tozer 2003).

5. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion occurs almost exclusively on soils derived from Tertiary alluvium, or on sites located on adjoining shale or Holocene alluvium (Tozer 2003). It is most often found on sandy soils and tends to occur on slightly higher ground than Castlereagh Ironbark Forest or Shale Gravel Transition Forest in the Sydney Basin Bioregion (Tozer 2003). The boundary between Castlereagh Scribbly Gum Woodland and Castlereagh Ironbark Forest or Shale Gravel Transition Forest in the Sydney Basin Bioregion appears to be a function of the interaction of localised drainage conditions and the thickness of the Tertiary alluvium mantle (Tozer 2003).

6. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion corresponds to the community of the same name described by Benson (1992) (Map Unit 14a), NSW NPWS (1997, 2002) and Tozer (2003) (Map Unit 6). It is similar to the Scribbly Gum woodlands found on perched sands in the Mellong Swamp area in Yengo and Wollemi National Parks, however there are distinct geological and floristic differences (James 1997).

7. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion occurs within the local government areas of Bankstown, Blacktown, Campbelltown, Hawkesbury, Liverpool and Penrith (James 1997), but may occur elsewhere within the Sydney Basin Bioregion.

8. The main occurrence of Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion is in the Castlereagh area of the Cumberland Plain, with small patches occurring at Kemps Creek and Longneck Lagoon. It is also present around Holsworthy, however the floristic composition in this area shows stronger similarities to Castlereagh Ironbark Forest than at other localities (Tozer 2003).

9. The estimated area of extent of Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion in 1997 (Tozer 2003) is mapped as 3083 ± 171 ha (upper and lower plausible bounds, sensu Keith  et al. 2009). This represents 52.7 ± 2.9% of its pre-1750 extent. Much of the community, with the exception of the Holsworthy remnant, is represented in small, isolated fragments. The area reserved within the National Parks estate in 2002 was 386 ha (NSW NPWS 2002). Castlereagh Scribbly Gum Woodland is found within the Castlereagh Nature Reserve, Scheyville National Park and Windsor Downs Nature Reserve.

10. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion is known to contain an Endangered population (Dillwynia tenuifolia, Kemps Creek) and threatened plant species including  Acacia bynoeana, Allocasuarina glareicola, Dillwynia tenuifolia, Grevillea juniperina subsp.  juniperina, Micromyrtus minutiflora, Persoonia  nutans and  Pultenaea parviflora (James 1997) and  Grevillea parviflora subsp.  parviflora (voucher at NSW Herbarium).

11. Threats to Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion include clearing for urban development, frequent fire due to arson and hazard reduction burning intended to reduce fire risk to surrounding development, invasion by exotic plants, climate change, impacts from recreational vehicle use on soil, vegetation and water courses, removal of timber from the ground for firewood, rubbish dumping, and infestation by the soil pathogen Phytophthora cinnamomi. Clearing of understorey vegetation and addition of fertilisers in areas zoned for rural use has degraded some remnant Castlereagh Scribbly Gum Woodland (J. Sanders  in litt. 2010). Exotic plants that threaten Castlereagh Scribbly Gum Woodland include  Acacia baileyana (Cootamundra wattle),  Andropogon virginicus (Whiskey grass),  Asparagus asparagoides (Bridal Creeper),  Araujia sericifera (Moth Vine),  Ehrharta erecta (Panic Veldgrass),  Eragrostis curvula (African Love Grass),  Hypochaeris  radicata (Flat Weed),  Olea europaea subsp.  cuspidata (African Olive) and  Pennisetum clandestinum (Kikuyu). Low seedling recruitment in Castlereagh Scribbly Gum Woodland is thought to be related to high frequency fires and extended dry periods, with extended dry periods being predicted to increase for the region with climate change (B. Summerell  in litt. 2010). The alluvial soil that Castlereagh Scribbly Gum Woodland occurs on is particularly susceptible to erosion in areas subject to vehicle use after rain, and also to stormwater erosion. There is an infestation of  Phytophthora cinnamomi in Kemps Creek Nature Reserve and it is likely that the moist soils and vegetation of Castlereagh Scribbly Gum Woodland makes this community susceptible to  Phytophthora cinnamomi (J. Sanders  in litt. 2010). 'Clearing of native vegetation', 'High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and composition', 'Invasion and establishment of exotic vines and scramblers', 'Invasion of native plant communities by exotic perennial grasses', 'Invasion by African Olive  Olea europaea subsp.  cuspidata', 'Anthropogenic climate change', 'Removal of dead wood and dead trees' and 'Infection of native plants by  Phytophthora cinnamomi are listed as Key Threatening Processes under the  Threatened Species Conservation Act 1995.

12. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion is not eligible to be listed as an Endangered or Critically Endangered Ecological Community.

13. Castlereagh Scribbly Gum Woodland in the Sydney Basin Bioregion is eligible to be listed as a Vulnerable Ecological Community as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future, as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2010:

Clause 17  Reduction in geographic distribution of ecological community 

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 moderate reduction in geographic distribution.

Clause 18  Restricted geographic distribution of ecological community 

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

(c) moderately 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 19  Reduction in ecological function of ecological community

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 moderate 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: 05/12/10
Exhibition period: 05/12/10 – 28/01/11

References:

Benson DH. (1992) The natural vegetation of the Penrith 1:100 000 map sheet. Cunninghamia 2, 541–596.

James T. (1997) 'Native flora of western Sydney. Urban bushland biodiversity survey, technical report'. NSW National Parks & Wildlife Service, Hurstville.

Keith DA, Orscheg C, Simpson CC, Clarke PJ, Hughes L, Kennelly SJ, Major RE, Soderquist TR, Wilson AL, Bedward M (2009) A new approach and case study for estimating extent and rates of habitat loss for ecological communities. Biological Conservation 142, 1469-1479.

NSW NPWS (1997) 'Native flora in western Sydney. Urban Bushland Biodiversity Survey Stage 1: western Sydney'. (NSW National Parks & Wildlife Service: Hurstville).

NSW NPWS (2002) 'Native vegetation maps of the Cumberland Plain, western Sydney. Interpretation guidelines, final edition'. (NSW National Parks & Wildlife Service, Hurstville).

Thackway R, Cresswell 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.)

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