Threatening processes:Caladenia concolor shows a familiar pattern of decline seen in many rare species, particularly orchids, in the Midland natural region. Features of this pattern include: wide distribution with no apparent shortage of habitat but with many of the records from last century or the early 1900s; only a few small or very small extant populations known; severe threats, particularly weed invasions; a vast area of potential or former habitat alienated for agriculture. It is probable that the end result of this process will be extinction. Given the small size of more recently examined populations and the serious weed invasion occurring in the sites, there can be no doubt that recruitment is not keeping pace with mortality in this species. The species is threatened across most of its range by gold exploration and mining operations. Unauthorised collection from the wild is a continuing problem (Backhouse and Jeanes 1995). Crimson Spider Orchid is palatable and readily eaten by stock, rabbits and other mammalian herbivores. Rabbits are likely to be present at all sites and could damage or destroy plants by grazing and digging. At the several locations reported (e.g. Chiltern Regional Park) weed invasions are severe, the most seriously invasive species being Quaking Grass (Briza maxima) a Mediterranean annual. At Chiltern at least, this and other weed species will undoubtedly eliminate the orchid in a few years. Weeds directly compete with established plants causing their death by competition for light and water, and prevent seedling recruitment. All known populations of Crimson Spider-orchid are small with less than about 20 flowering plants seen at any one time (J.Jeanes pers. comm.; G. Carr pers. comm.).
Reservation: Statewide, the species is present in one state park and several small nature reserves but in such low numbers that its future survival prospects are poor (Backhouse & Jeanes 1995).
Management: A Draft Action statement is being prepared for the species.
Rosella Spider-orchid Caladenia rosella
Description: A dwarf, non-tussock forming graminoid geophyte 10-15 cm tall. Single flower of 3-4 cm in diameter and a single, broad, hairy and upright basal leaf of grey-green colour. Distinguishing characters include the light to dark pink floral segments and broad, dark pink labellum containing 6 rows of calli (Carr 1988).
Tenure of next largest proportion of Central Highlands population
Distribution:Caladenia rosella is confirned to occur at two sites, on private land at Cottlesbridge and in the One Tree Hill Flora and Fauna Reserve in Christmas Hills. Another small population occurred at Research on private land which was to be developed. Its current status is unknown.
Habitats: Box Ironbark Dry Foothills on soils that are generally dry.
Reproduction: Although very little is known of the biology of the orchid, it appears that reproductive maturity takes 3-5 years and a seedling leaf is produced in each of these years. On maturity, it apparently flowers for up to 5 consecutive years, beyond which time the "pseudo-bulb" is incapable of leaf initiation. There is no significant storage of seed. The majority of seedlings are dispersed within one metre of parent plants. Regeneration can be habitat dependent on particular rare and unpredictable (stochastic) events, e.g. fire, flood, unusual combination of seasonal conditions - between such events the plants may appear to be absent.
ISSUES & STATUS IN CENTRAL HIGHLANDS
Threatening processes: The primary colony at Cottlesbridge occurs within 50 meters of a dwelling and roadway and its location is well-known, increasing the likelihood of disturbance and interference. The long-term viability of this population is insecure: apart from three plants it is contained on private land. Between 35-45 flowering plants near the dwelling have been eliminated by earthworks, weed invasion, rubbish dumping, path development, off-road turning of vehicles, digging and trampling. Pressure from grazing by White-winged Choughs (Corcorax melanorhampos), European Rabbits (Oryctolagus cuniculus) and Common Brushtail Possums (Trichosurus vulpecula) and trampling by Eastern Grey Kangaroos (Macropus giganteus) at Cottlesbridge is a problem as the area sustains large populations of these species. Given the amount of searching undertaken and the extent of loss of suitable habitat, the species is considered as one of Victoria's most threatened and localised plant species. As the population has become fragmented and depleted, so too has the native pollinating agent. The rate of natural pollination in each colony of the Cottlesbridge population has declined and natural recruitment is inadequate to reverse the declining population size. Population maintenance is now dependent on hand pollination. Weed invasion poses another threat, especially the annual grass Briza maxima (Large Quaking-grass), which smothers plants directly and reduces the area available for the recruitment of seedlings. Late autumn burns are detrimental because the species is early flowering, with leaf initiation occurring during April.
Reservation: The primary colony occurs on private land protected by conservation covenants. The other colony occurs in a conservation reserve.
Management: A Draft Action Statement has been prepared for the species that specifies a program of research, monitoring and propagation for re-establishment into the wild. Field surveys will be undertaken in appropriate habitat for the species. Fire management and appropriate grazing controls will be incorporated as a tool into land protection programs. Access to the colonies will be restricted. Liaison with landholders and raising public awareness of the orchid will be incorporated into prescribed management.
Curly Sedge Carex tasmanica
Description: A short but wiry, clumped perennial sedge, to 50cm high. The narrow linear leaves end in distinctive curls. The minute greenish flowers appear in the warmer months of the year, in dense short spikes, at the end of long stems that extend beyond the foliage. The chaffy, stiff seed heads have rib-like margins and bold divergent teeth at the apex.
Tenure of largest proportion of Central Highlands population
Tenure of next largest proportion of Central Highlands population
Distribution:Carex tasmanica occurs along 1-2 kilometers of Merri Creek near Craigieburn and a few plants are present at a minor stream near Bald Hill (Frood 1992). Both sites are on private land.
Habitats: Seasonally moist to waterlogged ponds associated with drainage systems on sticky, heavy, grey to black clay soils developed on basalt plain. The mean annual rainfall is around 600 mm with a moderate to pronounced spring maximum. River Club-sedge (Schoenoplectus validus) is a conspicuous dominant, with Common Spike-sedge (Eleocharis acuta), Nodding Club-sedge (Isolepis cernua) and the introduced Strawberry Clover (Trifolium fragiferum) common. This zone is fringed by Common Tussock-grass (Poa labillardieri) dominated grassland (Frood 1992).
Reproduction: Curly Sedge relies on disturbance for its regeneration. Most of the Tasmanian populations are on seepage lines where soil disturbance occurs following heavy rainfall, particularly on steeper slopes, and those in grazed areas would be periodically disturbed by grazing animals seeking water. It is a species that resprouts after fire, and fire may stimulate seed germination. Regeneration is mainly achieved through division, and few germinates have been observed during demographic studies. Germination has only been achieved with fresh seed with approximately a 50% germination rate and it has not been possible to germinate seed more than 3 months old (Gilfedder 1991).