All the plant communities on Mt Canobolas differ significantly in their composition from other similar communities and are likely to be recognised as distinct Plant Community Types in the future. This is particularly true of the heathlands.
The vegetation on Mt Canobolas is superficially similar to that in other high altitude parts of eastern Australia, but when examined closely there are many differences that set it apart (Medd and Bower 2019). The distinctiveness is based largely on the presence of endemic species and the absence of species that are common in similar communities elsewhere.
Seven vegetation communities are recognised in the Mount Canobolas State Conservation Area (SCA) (Hunter 2002) and their significance in relation to similar high altitude vegetation types on the Great Divide to the east is outlined below.
Snow Gum-Mountain Gum Grassy Woodland and Tall Open Forest
Snow Gum-Mountain Gum Grassy Woodland and Tall Open Forest occupies some 52% of the SCA above 900 m altitude. The community is characterised predominantly by Eucalyptus pauciflora, E. dalrympleana subsp. dalrympleana, E. canobolensis in association with E. dives, E. macrorhyncha, E. viminalis and Acacia dealbata. It has a well-developed layer of low and tall shrubs and a dense ground layer of 80 to 100% cover of climbers and trailers, herbs and grasses. Sub-assemblages are recognised within this community.
Conservation of this community within the SCA is important as it represents a relatively undisturbed example and is at the north western limit of its distribution. Elsewhere on the Central Tablelands (CT), the understorey of many remnants of similar assemblages are heavily disturbed, particularly by grazing, highlighting the importance of conservation of this community in the SCA.
This community closely fits the Tableland Basalt Forest in the Sydney Basin and South Eastern Highlands Bioregions Endangered Ecological Community (EEC), which occurs between 600 and 900 m altitude on the Great Divide. On Mt Canobolas, Tableland Basalt Forest occurs in the lower valleys and into the heads of valleys in deep basaltic soils above 900 m altitude. Accordingly, the Mt Canobolas occurrence represents a high altitude variant of the EEC, which has likely moved to higher altitudes owing to the more inland location and consequent climatic differences from its habitats to the east.
Tableland Basalt Forest on the eastern tablelands and GDR encompasses at least three recognised assemblages similar to that on Mt Canobolas. All three are dominated by Eucalyptus dalrympleana, E. pauciflora and E. dives with associated eucalypts that don’t occur on or near Mt Canobolas, including principally E. radiata and E. robertsonii. By contrast, the related assemblages on Mt Canobolas have E. canobolensis as a dominant, a species that is absent in the east. It is likely that future vegetation community analysis will recognise the Mt Canobolas assemblage as a distinct and threatened Plant Community Type (PCT).
Stringybark–Peppermint Shrubby Open Forests and Woodlands
Stringybark–Peppermint Shrubby Open Forests and Woodlands covers around 26% of the SCA in areas above 1000 m altitude. The community is characterised predominantly by Eucalyptus macrorhyncha and E. dives, in association with E. canobolensis, E. pauciflora, E. dalrympleana subsp. dalrympleana, Acacia dealbata, A. melanoxylon and Exocarpos cupressiformis. As with the above it also has a well-developed shrub layer and ground cover of herbs and grasses. The occurrence within the SCA is significant due to the unusual assortment of associated species and the community being at its north western geographic limit of occurrence.
This community, which principally occurs on upper slopes and ridgetops within the SCA, has an unusual assemblage of tree species. Most recognised PCT’s of this type are dominated by E. macrorhyncha and E. dives and occur in drier environments than on Mt Canobolas, as reflected in their understorey shrubs and grasses. The closest type includes E. bridgesiana, E. rubida and E. stellulata. E. bridgesiana occurs sparingly in this community on Mt Canobolas, E. stellulata is absent and E. rubida is replaced on Mt Canobolas by E. canobolensis. This assemblage in the SCA is also likely to merit new PCT recognition in its own right.
Grasslands and Grassy Open Woodlands
Grasslands and Grassy Open Woodlands occupy some 15% of the SCA area above 1200 m altitude. Trees are a minor component of the community, with Eucalyptus pauciflora, E. canobolensis, E. dalrympleana subsp. dalrympleana, Acacia dealbata and A. melanoxylon occurring in low densities. The shrub layer is of low stature and sparse or absent whereas the ground layer of twiners, herbs and grass is well developed. It is likely that this community is poorly conserved across its range and that the occurrence within the SCA is highly significant for conservation.
This assemblage is most similar to other recognised communities where it is regarded as part of the Tablelands Basalt Forest EEC.
Outcrop Heaths and Shrublands and Outcrop Low Open Woodlands
Outcrop Heaths and Shrublands and Outcrop Low Open Woodlands are two closely similar communities found on skeletal soils on rock outcrops. Together they occupy some 6% of the SCA, occurring as highly disjunct and small patches throughout. The main difference between the two is that the first of these communities lacks trees and the shrubs are scattered and depauperate and occur in association with bryophytes and scattered herbs and grasses. These rock outcrops contain the endangered Mt Canobolas Xanthoparmelia lichen community. The second community may have scattered trees of Eucalyptus canobolensis, E. bridgesiana and Acacia dealbata. Both communities are restricted to the SCA and close surrounds, being unique to the mountain, and should be considered vulnerable to inappropriate fire regimes and visitor pressure.
The high altitude basalt rock platform heathlands of Mt Canobolas are unique. No floristically similar heathlands are recognised elsewhere. The endemic Mt Canobolas assemblages are likely to warrant recognition as a distinct and threatened community type.
Waterfall Low Open Woodlands
Waterfall Low Open Woodlands occur at the Federal and Hopeton Falls locations, occupying less than 1% of the SCA. Primarily an open shrub-land community, it occurs with occasional stunted trees of Eucalyptus goniocalyx, E. canobolensis and Acacia melanoxylon in shallow soils around the margins and often with taller Eucalyptus viminalis around the base of the falls.
This community is of very limited extent and it is doubtful that it deserves recognition as an entity distinct from the surrounding vegetation.
Disturbed Creek-lines occur in the north eastern lower reaches of the SCA, occupying about 1% of its area. They are characterised by tall open stands of Eucalyptus viminalis, E. stellulata, E. pauciflora, E. dalrympleana subsp. dalrympleana and Acacia melanoxylon with a scattered to dense shrub layer, ferns and herbs. The community has suffered considerable disturbance but is highly significant as it conforms to the Tablelands Snow Gum, Black Sallee, Candlebark and Ribbon Gum Grassy Woodland in the South Eastern Highlands, Sydney Basin, South East Corner and NSW South Western Slopes Bioregions EEC.
This assemblage is dominated by E. viminalis, E. pauciflora, E. radiata and E. stellulata but E. radiata is missing from Mt Canobolas.
Photo: Phebalium sp. ‘Mt Canobolas’, a possible endemic species currently under study. Photo by Helmut Berndt