Caladenia arenaria Fitzg. Recovery Plan
Threatened Species Unit, Western
The State of New South Wales, Department of Environment and Conservation, 2004
Four of the locations occur on land owned by the Crown. Three locations are State Forest and one is a Travelling Stock Reserve. The fifth location is freehold land in Urana Local Government Area, zoned rural non-urban (0-1a).
The Narrandera and Urana sites have gravelly, sandy-loam soils. At Narrandera the underlying Devonian sandstone outcrops in places. At Urana the soils are derived from Tertiary residual and colluvial deposits of ferricrete, silcrete, poorly consolidated pebbly sandstones, sandstone-mudstones and claystones. In State Forests the soils are sandy loams derived from Quaternary alluvial deposits.
Narrandera, close to the northern populations of C. arenaria, has a climate characterised by warm, dry summers and cool, wet winters. Average summer temperatures are around 30C, while winter temperatures average around 15C. Median annual rainfall is 433.7 mm, based on 32 years of records. There is a marginal winter dominance in rainfall, with approximately 50 mm more rain falling in the period April-September than in October-March.
Further south near the population at Lonesome Pine State Forest rainfall is slightly higher and winter dominance in rainfall more pronounced.
Date source: Bureau of Meteorology.
The common feature at all extant populations is the presence of White Cypress Pine, Callitris glaucophylla. To more closely define habitat preferences is difficult since each of the sites is distinct, with differences in landforms, soils and vegetation, floristic composition and structure. Many of the associated species in the understorey are different at each of the populations, or are species that are widespread and occur in a range of habitats. It is apparent that C. arenaria has fairly broad habitat tolerances, occurring in Callitris glaucophylla - Eucalyptus melliodora (Yellow Box) woodlands, Callitris glaucophylla Allocasuarina luehmannii woodlands and woodlands dominated by a mixture of Callitris glaucophylla, E. dwyeri (Dwyers Redgum) and Acacia doratoxylon (Currawang). Soils vary from skeletal soils over sandstone to clay loams.
One characteristic of the State Forest sites is that most of the C. arenaria individuals are found among dense White Cypress Pine stands. It is not known whether the plants prefer the conditions created by this relatively dense phase of growth, or whether it is an artefact of threatening processes. Both grazing pressure and the weed flora are assumed to be reduced under dense White Cypress Pine. At the Narrandera TSR site the cypress pines are larger, but most plants occur among cypress pines that are closely spaced.