ECOLOGY OF RAINFOREST AND SCLEROPHYLLOUS COMMUNITIES 
79 
layer, but shade tolerant herbs such as Wahlen- 
bergia quadrifida, Op Us menus a emu I us and 
Microlaena stipoides together with the fern Chei- 
lanthes tenuifolia are sometimes present, and 
Lepidosperma laterale is represented in the 
gaps. 
Factors affecting vegetation patterns 
Topography and fire. The ordination of the 
group centroids by the PCOA program separates 
the community types along the three vectors 
(Fig. 3). The first vector carries 71% of the infor¬ 
mation, the second 20%, and the third 9%. Of 
these vectors only the first two are ecologically 
interpretable. Vector I, which is positively 
correlated with rainforest species (i.e. Acmena 
smithii, Acronychia oblongifoUa) and negatively 
correlated with dry sclerophyll species (i.e. 
Phyllanthus hirtellus, Pomax umbel lata ), 
appears to reflect the relative exposure and 
moisture of each community (topographic 
effects). The position of the groups along vector I 
shows a continuum, with a transition from the 
dry sclerophyll communities (groups C2, Cl) 
through to damp sclerophyll (groups B2. Bl) to 
the undisturbed rainforest (group A1). This eco¬ 
logical interpretation of the ordination plot is 
supported by the insolation data which show a 
progressive increase in site insolation for the 
community types listed above (Tables 3, 4). The 
position of groups along vector II is chiefly 
determined by a positive correlation for Pomad- 
erris aspera and this effectively separates the 
damp fire-disturbed Bl community. 
The relationship between the plant communi¬ 
ties and topography also appears to be related to 
the fire susceptibility of the sites. Hotter and 
drier sites on the ridge tops and plateaux are 
generally more fire prone than those in the shel¬ 
tered gorges and gullies, and this is reflected in 
the distribution of community types in the study 
area (Fig. 4). The fire protection afforded by the 
steep gorge walls and surrounding vegetation 
has created a humid microclimate that allows 
the survival of warm temperate rainforest (Fig. 
5A, B). Damp sclerophyll scrub grows on the 
margins of the rainforest and on the cooler eas¬ 
tern-facing slope above the Mitchell River, but 
with increasing exposure on the upper slopes 
and ridges there is a sharp change to the drier 
sclerophyll forests and scrubs. The fire suscepti¬ 
bility implied by the topographic and insolation 
data is supported by direct observation of char¬ 
coal and fire damage in many of the sclerophyll 
communities. 
W\\\m Cliffline 
Community groups: 
| At; Undisturbed rainforest. 
A2: Disturbed rainforest. 
**V. Bl: Damp sclerophyll woodland. 
jHH B -- Layered tall open forest. 
X\ C,: Sclerophyll open forest. 
□ C2: Sclerophyll woodlands 
Fig. 4. Distribution of community types within the surveyed area bounded by the previous limits of Glenaladale 
National Park. Communities are delineated on the basis of the 260 quadrats surveyed in the area. 
