14 
Cunninghamia 
Vol. 1 (1): 1981 
The community is not very disturbed, since it is restricted to poor soils which 
are little used agriculturally. It is widespread over much of the sandstone plateau 
area around Sydney. Good examples have been preserved in adjacent Dharug 
National Park. 
Structure and floristics 
Structural and species richness data for the four communities are presented in 
Table 2. Canopy height ranges from 10 to 25 m, mainly along a gradient related to 
exposure, i.e. from exposed ridgetop to sheltered gully. Projected foliage cover 
for almost all sites, except one in woodland was within the Mid-Dense (30-70%) 
category of Specht (1970). Basal area figures for all sites, except the woodland 
site were scattered between 20 and 50 m 8 /ha, the ranges of different communities 
overlapping. Greatest basal area was in A. costata-E. piperita open-forest, a com¬ 
munity that has been less severely logged or disturbed than the tall open-forest 
and other open-forest communities, which generally have a high number of small, 
even-sized trees or coppice regrowth. Disturbance in these latter two communities 
is indicated by the high stem density and low mean stem diameter figures. 
Total number of species/site was lower for the woodland than the other com¬ 
munities, the sites in the former showing evidence of more recent fire than those in 
the forest communities, though all sites, except two in tall open-forest, showed signs 
of past burning. Although all sites were selected as being the least disturbed in a 
particular area, exotic species were recorded only in the tall open-forest and E. 
tereticornis-E. eugenioides open-forest. This may be due in part to the greater 
disturbance these communities have suffered, but may also be due to the unsuitability 
to exotics of the habitats on unmodified Hawkesbury Sandstone soils, even when 
disturbed. 
TABLE 3 
Czechanowski similarity coefficients for community pairs calculated from the total species lists for 
each community 
Plant community 
E. tereticornis- 
E. eugenioides 
Open-forest 
A. costata- 
E. piperita 
Open-forest 
E. eximia-E. 
gummifera-E. 
punctata 
Woodland 
Eucalyptus deanei-Angophora floribunda 
Tall open-forest 
0.63 
0.35 
0.17 
Eucalyptus tereticornis-E. eugenioides 
Open-forest 
0.38 
0.19 
Angophora costala-Eucalyptus piperita 
Open-forest 
0.39 
Floristic differences between the communities on the two major geological units 
are indicated (Table 3) by the Czechanowski similarity coefficients (Clifford & 
Stephenson, 1975). As sites sampled were chosen as representative of each com¬ 
munity, similarity coefficients were not calculated for all site pairs but only from the 
total species lists for each community. The two communities on Narrabeen Group 
geology, Eucalyptus deanei-Angophora floribunda tall open-forest and E. tereticornis- 
E. eugenioides open-forest are most similar to one another and least similar to the 
E. eximia-E. gummifera-E. punctata woodland on Hawkesbury Sandstone. The 
Angophora costata-E. piperita open-forest is intermediate between the woodland and 
the Narrabeen Group communities. 
