Publications archive - Publications
Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.
Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.
D. Bickerton & M. Robertson
Threatened Species Network, January 2000
Note: This publication has been superseded by the Recovery Plan for Twelve Threatened Orchids in the Lofty Block Region of South Australia 2010
Pterostylis 'Halbury'is listed as nationally Endangered on Schedule 1 of the Commonwealth Endangered Species Protection Act 1991, and as Endangered 2E by Briggs and Leigh (1996). It is endemic to South Australia, where it is confined to one location on the Northern Adelaide Plain, in the Northern Lofty Flora Region (see Figure 1). It is not conserved in any NPWSA park, and the total known population is estimated at 1000 flowering individuals. The ESAC priority for the species is 77. According to the IUCN criteria B1 and B2 (b) and (c) (IUCN, 1994) the species is Critically Endangered because:
Pterostylis 'Halbury' grows in red-orange clay loam over clay, in native pine / mallee woodland (Callitris preissii / Eucalyptus odorata / E. dumosa / E. socialis) in the relatively high rainfall wheatbelt of gentle terrain less than 100km north of Adelaide. The region has been extensively cleared for cropping.
This heavy soil pine / mallee woodland habitat would have been more widespread on the plains north of Adelaide. Most native vegetation on the plains is now confined to sand dunes and linear reserves. The northern Adelaide Plains region has a very low percentage of remnant vegetation and this is highly fragmented. Most remnants have a highly degraded understorey, in contrast to Halbury Parklands, which support a high diversity of indigenous plant species including a number of native orchid species, especially Pterostylis spp. (see Appendix 1). The parkland is an island of vegetation apart from corridors of vegetation on roadside and rail reserve (but not connected to any comparable areas). Management of the area is constrained by the proximity of the township of Halbury and by the partial tenure as recreation reserve.
Although land clearance may have caused the original decline of the species, its habitat continues to be threatened by isolation, weeds, rabbits and human activity. Bridal creeper (Asparagus asparagoides) and soursobs (Oxalis pes-caprae) are the weeds most endangering the orchid. People are also dumping rubbish, riding motorbikes and ploughing amongst the native vegetation.
Pterostylis 'Halbury'is limited to a small isolated remnant of native vegetation of high quality that is also home to numerous other native orchid species. It occurs in a region that has been extensively cleared. Strategies to alleviate the threat to this and other orchid species from the invasion of alien plants, notably bridal creeper and soursobs, will benefit the native vegetation community as a whole. Involvement of the local community in conserving this species will increase appreciation of this and similar habitats.