Department of Environment and Conservation (NSW), 2005
ISBN: 1 7412 2144 7
5 Distribution and Habitat
Populations are defined by the International Union for the Conservation of Nature and Natural Resources (IUCN 1994) as “geographically or otherwise distinct groups between which there is little [genetic] exchange, typically less than one migration per year”. A migration in the case of plant species is considered to be the movement of seed propagules or pollen between populations. A very low level of genetic exchange between sites is suspected for D. sp. C Illawarra because it appears to reproduce primarily by vegetative means. Consequently, in this recovery plan each site (as defined below) is considered to contain a discrete population.
For this recovery plan, sites are defined as discrete groups of D. sp. C Illawarra plants that are separated from other groups by an arbitrary distance of 200 metres or more. These sites have been labelled with the prefix Dc followed by a unique number for each site (eg. Dc1, Dc2 etc). Sites have been further divided into sub-sites (Dc1a, Dc1b etc) where discrete groups of plants at a site are separated from other groups within that site by an arbitrary distance of 50 metres or more.
A total of 41 sites comprising 52 sub-sites have been recorded for D. sp. C Illawarra.
D. sp. C Illawarra is endemic to the Illawarra region of NSW where it has been recorded from 41 sites within the local government areas (LGAs) of Wollongong, Shellharbour, Kiama and Shoalhaven. These sites are located within the Sydney Basin Bioregion, as defined in the Interim Biogeographic Regionalisation of Australia (Thackway & Cresswell 1995).
The main distribution of D. sp. C Illawarra extends from Avondale in Wollongong LGA to Toolijooa in Kiama LGA, a distance of 27 kilometres. An outlying site at Scarborough (northern Wollongong LGA) is located approximately 35 kilometres north of this main distribution. The species western distributional limit follows the upper slopes of the Illawarra escarpment.
- Download a large version of the Daphnandra sp. C 'Illawarra' Illawarra Socketwood Species Distribution Map - (daphnandramap1.pdf - 206 KB)
Table 1 describes the tenure and zoning of the 41 recorded D. sp. C Illawarra sites. Almost 90 per cent of sites occur on freehold land, with the zoning of these sites evenly divided between rural land uses and environmental protection.
Three sites (Dc17, Dc27 and Dc40) have been recorded in the Minnamurra Rainforest section of Budderoo National Park.
Shellharbour City Council
A site at Blackbutt (Dc15) occupies land that is managed by Shellharbour City Council. Although the land is presently zoned 1(c) Rural, council has agreed to rezone the relevant land parcel to 6(a) Public Open Space in the draft Urban LEP (Linda Madden, Shellharbour Council, pers. comm.).
Kiama Municipal Council
A site at Jerrara Dam (Dc35) occurs on community land that is managed by Kiama Municipal Council as a public reserve.
All five freehold sites within Wollongong LGA are zoned for environmental protection. The remnant vegetation at one of these sites (Dc3) is the subject of a Property Agreement under the Native Vegetation Conservation Act 1997.
Five sites within Shellharbour LGA are zoned for rural uses, while a further five sites are zoned for environmental protection.
Twelve sites within Kiama LGA occur on freehold land that is zoned for rural uses. One of these sites (Dc21) is the subject of a Voluntary Conservation Agreement with the DEC. A further eight sites within the LGA occur on land that is zoned for environmental protection.
One site occurs within Shoalhaven LGA on land that is zoned for environmental protection.
- 5.4.1 Landform
- 5.4.2 Soil Landscape
- 5.4.3 Geology
- 5.4 Habitat
- 5.4.4 Soils
- 5.4.5 Climate
- 5.4.6 Altitude
- 5.4.7 Associated vegetation
The following habitat details are based primarily on field observations of the 18 D. sp. C Illawarra sites (or 27 sub-sites) that were surveyed during the preparation of this plan. The soil landscape, geology and altitude sections however, incorporate data from a desktop assessment of all 41 recorded D. sp. C Illawarra sites (or 52 sub-sites).
D. sp. C Illawarra occupies the rocky hillsides and gully slopes of the Illawarra lowlands, occasionally extending onto the upper escarpment slopes. The species inhabits sites with sheltered aspects or in locations conducive to the development of moist closed forest vegetation.
*1=rural uses, 7=environmental protection, 8=national park
D. sp. C Illawarra sites are generally characterised by moderate to very steep slopes, with slope gradients ranging from 5 to 40°. Minimum distance to the nearest ephemeral water course at surveyed sub-sites ranges from 0 to 110 metres, although over 80% of these sub-sites are located at least partially within 30 metres of the nearest watercourse.
Table 2 shows the distribution of D. sp. C Illawarra sub-sites by soil landscape unit. The species has been recorded on seven soil landscape units but is most closely associated with the Bombo, Wattamolla Rd, and to a lesser extent, Cambewarra units. Appendix 1 contains descriptions of the soil landscape units that have been recorded in association with D. sp. C Illawarra.
|Soil Landscape Unit*||Sub-sites|
|Wattamolla Rd||18 (35%)|
|Illawarra Escarpment||1 (2%)|
*after Hazelton (1992) and Hazelton & Tille (1990)
Table 3 shows the distribution of D. sp. C Illawarra sub-sites by substrate. The species has been recorded on eight geological units although the vast majority of sub-sites occur on Budgong Sandstone or Bumbo Latite.
|Budgong Sandstone||25 (48%)|
|Bumbo Latite||20 (38%)|
|Illawarra Coal Measures||2 (4%)|
|Minnamurra Latite||1 (2%)|
|Cambewarra Latite||1 (2%)|
|Irwins Creek Breccia||1 (2%)|
|Narrabeen Group Sediments||1 (2%)|
|Quaternary Alluvium||1 (2%)|
*after Bowman 1974a, 1974b and 1974c)
The soils present at surveyed D. sp. C Illawarra sub-sites consist of loams and clay loams with varying amounts of unconsolidated and outcropping surface rock present. No surface soil was present at a small number of sub-sites where the species grows out of unconsolidated rock material.
The Illawarra area has a generally mild climate with extremes in temperature being moderated by coastal effects (Mills & Jakeman 1995). Average minimum and maximum temperatures are closely related to altitude and proximity to the coast (see Table 4).
|Station||Altitude||Distance inland||Average January Maximum||Average July Minimum||Average Annual maximum||Average annual minimum|
|Moss Vale||672 m||45 km||21.6||1.2||19.4||6.8|
|Wollongong||12 m||0.5 km||25.9||7.8||21.6||12.6|
*Source: Mills & Jakeman (1995)
Rainfall is very high compared with much of NSW. Average annual rainfall figures range from just below 1000 mm near Lake Illawarra to over 1800 mm at Barren Grounds with the higher rainfall isohyets closely correlated to the top of the escarpment (Mills & Jakeman 1995).
The distribution of rainfall within the area can also be attributed to winds blowing from the south (Hazelton 1992). One third of mean annual rainfall in the area occurs in January, February and March with a marked secondary rainfall peak in June (Hazelton 1992).
Westerly airflows dominate the weather during winter producing cooler drier conditions although few or no frosts occur on the coastal plain (Hazelton 1992). Drought conditions can occur in the area and rainfall data indicates the occurrence of distinct runs of wet or dry years which last between six and eight years (Mills & Jakeman 1995).
Table 5 shows the distribution of D. sp. C Illawarra sub-sites by altitude class. The altitudinal range of the species is 10 to 280 metres.
|Altitude Class||(m) Sub-sites|
|0 - 50||8 (15%)|
|51 - 100||19 (37%)|
|101 - 150||12 (23%)|
|151 - 200||9 (17%)|
|201 - 250||2 (4%)|
|251 - 300||2 (4%)|
D. sp. C Illawarra occupies the rainforest understorey. Associated vegetation is dominated by dry rainforest aligned species although subtropical or warm temperate rainforest species are also present to varying degrees. Emergent Eucalypts (including E. quadrangulata and E. pilularis) are present at sites that are located near the ecotone of rainforest and sclerophyll forest. An emergent Casuarina cunninghamiana was recorded at one site.
Vegetation descriptions for each of the sub-sites that were surveyed during the preparation of this plan are contained in Appendix 2.
The vegetation present at D. sp. C Illawarra sites is consistent with the following NSW rainforest sub- alliances described by Floyd (1990):
- Subtropical rainforest sub-alliance no. 14 (Doryphora - Daphnandra micrantha - Dendrocnide - Ficus - Toona);
- Dry rainforest sub-alliance no. 23 (Ficus - Streblus - Dendrocnide - Cassine); and
- Warm temperate rainforest sub-alliance no. 42 (Acmena - Doryphora - Dendrocnide - Ficus).
The vegetation present at D. sp. C Illawarra sites is also consistent with the following Illawarra rainforest types described by Mills and Jakeman (1995):
- Subtropical rainforest (type 1);
- Moist subtropical rainforest (type 2);
- Dry subtropical rainforest (type 3); and
- Mixed subtropical/ warm temperate (type 5).
Illawarra Subtropical Rainforest, which includes the rainforest types 1, 2, and 3 of Mills & Jakeman (1995), is listed as an endangered ecological community on Schedule 1 of the TSC Act.
NPWS (2002a) describes the following vegetation communities located in Wollongong LGA (and the Calderwood Valley area of Shellharbour LGA) as providing habitat for D. sp. C Illawarra:
- Illawarra Escarpment Subtropical Rainforest;
- Lowland Dry Subtropical Rainforest;
- Moist Coastal White Box Forest; and
- Moist Box - Red Gum Foothills Forest.