National recovery plan for Boronia granitica (Granite Boronia)

NSW National Parks and Wildlife Service, July 2002
ISBN 0 731 36889 4

4 Habitat

4.1 Physical environment

Geology

Boronia granitica is restricted to a limited number of areas on the large plutonic masses collectively known as the New England Batholith. The exposed domes of the Batholith are comprised of various intrusive rocks and B. granitica has been found on granite, leucoadamellite and adamellite, but not granodiorite (Hunter and Clarke 1998). Additionally, Quinn et al. (1995) noted that a few plants occur on porphyrite at Severn River.

Topography and soils

The extensive rock sheets and massive outcrops resulting from erosion of the elevated domes of the Batholith form the conspicuous land form element that provides habitat for B. granitica on the northern tablelands and slopes of NSW. The outcropping areas where the species has been recorded lie in the mid elevation range of 700 metres AHD at Severn River to 1200 metres at Parlour Mountain.

B. granitica grows either amongst boulders in the skeletal soils found within narrow rock crevices and fissures, or in adjacent areas on granite scree and shallow soils (Quinn et al. 1995, Clarke et al. 1998). Detailed data are not available concerning the soil types that B. granitica occurs in, although Clarke et al. (1998) noted lithosols and podzolics for the Torrington area and Quinn et al. (1995) noted deep red soils at Severn River.

Climate

The granitic tablelands and slopes of NSW experience both tropical and temperate climatic influences, with predominantly summer rainfall and cool winters with associated frosts. Average temperatures range from summer maxima of 26-31° C to winter minima of -2°-0° C. B. granitica occurs within the relatively low rainfall regions of the tablelands and slopes with average annual precipitation varying with altitude from 700 millimetres at Severn River to 850 millimetres at Parlour Mountain.

4.2 Vegetation

B. granitica occurs in heathland, shrubland and adjacent heathy woodland / open forest associated with granite outcrops (Ross 1983, Weston and Porteners 1991, Quinn et al. 1995, Clarke et al. 1998, Hunter and Clarke 1998, Duretto in press).

In their detailed survey of the vegetation of the New England Batholith, Hunter and Clarke (1998) described the following five vegetation communities that contain B. granitica:

  • Prostanthera staurophylla - Kunzea bracteolata low shrubland (Community 4b, Torrington shrublands) of the central New England shrublands vegetation element;
  • Babingtonia odontocalyx - Brachyloma saxicola shrubland (Community 4c, Torrington woodlands), of the central New England shrublands vegetation element;
  • Calytrix tetragona - Leptospermum novae-angliae shrubland (Community 5a, Kings Plains shrubland) of the Severn shrublands element;
  • Calytrix tetragona - Kunzea obovata shrubland (Community 7e, Parlour Mountain shrublands) of the western New England shrublands and herbfields element; and
  • Babingtonia densifolia - Homoranthus prolixus shrubland (Community 9a) of the Howell shrubland vegetation element.

In a further survey of the Torrington SRA, Clarke et al. (1998) identified and described the following four vegetation types that B. granitica was recorded in. The first two are analogous to the Torrington woodlands and Torrington shrublands communities respectively, as described above:

  • western rocky outcrops (vegetation type 7a), Eucalyptus prava - Callitris endlicheri outcrop woodlands;
  • Mole Tableland rocky outcrops (vegetation type 6), Eucalyptus prava - Callitris endlicheri - Eucalyptus andrewsii, Torrington outcrop heaths;
  • vegetation type 3a, Eucalyptus andrewsii - E. brunnea - E. williamsiana shrubby forest; and
  • vegetation type 3b, Eucalyptus andrewsii - mixed stringybark, Torrington shrubby stringybark forest.

Hunter and Clarke (1998) and Clarke et al. (1998) also detailed other vascular plants frequently occurring in each vegetation stratum within the above listed communities. Further plant species found in association with B. granitica are listed in Table 4 (Quinn et al. 1995, J. Westaway pers. obs.).

Table 4: Plant species associated with Boronia granitica
Kings Plains 'Mystery Face'-Torrington Various other NSW sites
Eucalyptus prava Eucalyptus andrewsii Acacia fimbriata
Eucalyptus crebra Acacia betchei Acacia neriifolia
Leptospermum novae-angliae Bossiaea rhombifolia Acacia triptera
Allocasuarina brachystachya Bossiaea obcordata Angophora floribunda
Calytrix tetragona Brachyloma saxicola Callitris endlicheri
Melichrus urceolatus Gompholobium hueglii Correa reflexa
Homoranthus biflorus Dampiera stricta Eucalyptus prava
Grevillea triternata Patersonia sericea Hibbertia obtusifolia
Hakea dactyloides Hibbertia sp. B Jacksonia scoparia
Persoonia cornifolia Hibbertia spp. Leucopogon melaleucoides
Cryptandra amara Prostanthera staurophylla Leucopogon muticus
Leucopogon neo-anglicus Aotus subglauca Leucopogon neo-anglicus
Xanthorrhoea johnsonii Persoonia cornifolia Melichrus urceolatus
Astrotricha roddii Entolasia stricta Olax stricta
Phebalium rotundifolium Rhytidosporum procumbens Phebalium rotundifolium
Zieria laevigata Xanthorrhoea johnsonii Prostanthera sp.
    Xanthorrhoea sp.