5ABlue Mountains Heath and Scrub

5A Blue Mountains Heath and Scrub

(5A) Blue Mountains Heath and Scrub

Blue Mountains Heath and Scrub consists of a well-developed shrub layer, with no tree layer or only a sparse layer of scattered low trees, sometimes with a mallee habit (low, multi-stemmed shrub eucalypts). It occurs primarily in exposed sites with very shallow soils on Narrabeen Group and Hawkesbury Sandstone geology. Typical situations are cliff tops and high, rocky ridges, especially on the westerly aspect and with skeletal soils. The vegetation structure is typically an open-heath, less often a closed-heath, and may be interspersed with patches of open-scrub or closed-scrub formed by stands of mallees or Leptospermum species. It is also typically interspersed with areas of bare rock. It can occur on the fringes of or within so-called hanging swamps and in such situations it can also intergrade with vegetation of the Riparian Complex. There is also considerable intergradation between forms of woodland to open woodland with an Eucalyptus sclerophylla canopy with Blue Mountains Heath and Scrub forming the understorey in such communities.

Blue Mountains Heath and Scrub has a mixed and variable species composition. Common shrub species include Allocasuarina distyla, A. nana, Banksia ericifolia, Epacris microphylla, Eucalyptus stricta, Hakea laevipes, Hakea teretifolia, Kunzea capitata, Leptospermum trinervium and Petrophile pulchella. Common herb and sedge species include Actinotus minor, Platysace linifolia, Lepidosperma filiforme, L. viscidum, Lepyrodia scariosa, Ptilothrix deusta and Schoenus villosus.

Two forms of Blue Mountains heath have been distinguished (Keith and Benson 1988, Smith and Smith 1995a–e): montane heath above about 850–900 metres elevation and lower Blue Mountains heath below this level. The two forms intergrade between Wentworth Falls and Katoomba. Montane heath is characterised by the presence of high altitude species such as Allocasuarina nana, Darwinia taxifolia and Phyllota squarrosa, while lower Blue Mountains heath is characterised by the presence of low altitude species such as Allocasuarina distyla, Darwinia fascicularis and Phyllota phylicoides. However, most of the more common heath plants occur across the full altitudinal range.

It is also possible to distinguish two forms of lower Blue Mountains heath: a Hawkesbury Sandstone form at lower altitudes (chiefly in the Faulconbridge to Woodford area), and a Narrabeen Sandstone form at intermediate altitudes (Hazelbrook to Wentworth Falls). The Hawkesbury Sandstone form is characterised by species such as Acacia oxycedrus, Baeckea brevifolia and Eucalyptus burgessiana that are absent from heath on Narrabeen Sandstone.

In the prolonged absence of fires, the heath shrubs grow taller and thicker, transforming the vegetation from an open-heath to a closed-scrub, especially in relatively moist and sheltered sites. These communities may be floristically similar to the closed heaths described above but are structurally unique. Shrubs including Banksia ericifolia, B. serrata, B. spinulosa, Hakea laevipes, H. teretifolia and a range of Leptospermum species may all attain heights of up to 8 metres over a generally grassy, herbaceous understorey. In locally moist areas, the fern Gleichenia dicarpa may become common in the ground stratum.