ECOLOGY OF RAINFOREST AND SCLEROPHYLLOUS COMMUNITIES 
The restriction of the rainforest to fire-shel¬ 
tered sites is obvious at present, but observa¬ 
tions at the study sites suggest that in the absence 
of fire the rainforest may spread from the shel¬ 
tered gorges. The presence of the simplified rain¬ 
forest communities (A2) in more exposed sites 
may indicate that the rainforest has the ability to 
expand to these areas. Similarly, the occurrence 
of rainforest seedlings in the damp sclerophyll 
vegetation suggests that these communities are 
being invaded by the rainforest. 
Fire and clearing disturbances also appear to 
be important factors in determining the floristic 
patterns of the sclerophyll communities (Fig. 4). 
Fire has allowed the establishment of Pomader- 
risaspera , a serai species in the succession after 
fire (Cunningham & Cremer 1965), in the damp 
sclerophyll woodland (group Bl). Furthermore, 
it is suggested that the occurrence of the dry scle¬ 
rophyll scrub communities (group C2) on the 
flatter terrain in the south and on the broad cen¬ 
tral spur between Woolshed and Bull Creeks is, 
in part, the result of historical disturbance. 
These areas which were cleared, grazed and 
burnt (as evidenced by the presence of ring- 
barked trees, stumps and charcoal) have under¬ 
gone prolonged secondary' succession both 
before and after the 1965 bushfire. Clearing 
appears to have allowed the invasion of Kunzea 
ericoides. Moreover, the severe fire of 1965 has 
seemingly enabled the establishment of thick 
Acacia mearnsii scrub and enhanced the regen¬ 
eration of A: ericoides (Fig. 5C). Similar behav¬ 
iour of K. ericoides has been noted in New 
Zealand where this shrub is regarded as a serai 
species following fire and soil disturbance in 
closed forests and agricultural land (Pavton et al. 
1984, Mark et al. 1989. Partridge 1989). 
In the open sclerophyll forest (group Cl), 
where disturbance has been less severe, the 
ground stratum is generally dominated by gram- 
inoids. and gap phase shrubs are relatively rare 
(Fig. 5D). Similarly, on the lower slopes of the 
sclerophyll woodland communities where 
eucalypts have survived the fire and regener¬ 
ated, thick Acacia mearnsii and Kunzea eri¬ 
coides scrub is limited to small patches occurring 
in gaps formed by the collapse of larger trees. 
Acacia mearnsii in particular is commencing to 
senesce in the normal course of secondary suc¬ 
cession following the 1965 fire; however, dying 
shrubs are creating gaps which are being colon¬ 
ized by seedlings of AT. ericoides without the 
intervention of fire. Similarly, K. ericoides has 
established in gaps within the rainforest commu¬ 
nity created by endogenous disturbances. 
Throughout the study site Kunzea ericoides 
appears to act as a persistent and aggressive 
colonizing species, consistent with observations 
by Judd (1990) in open forests in central Vic¬ 
toria and southern Gippsland. 
Water availability. Site moisture plays an impor¬ 
tant role in the distribution of vegetation at the 
study site. The climate of the Mitchell River area 
is relatively dry with regard to the rainforest 
communities, the average annual rainfall 
(730 mm) being significantly less than the mean 
annual rainfall of 1004 mm for what Webb et al. 
(1984) have determined to be the average cli¬ 
matic region for microphyll vine-fern rainforest 
types. Moreover, rainfall at the Mitchell River 
site falls below the 750 mm annual rainfall limit 
which has been suggested as the lower threshold 
for the maintenance of rainforests in temperate 
zones (Beadle 1981, Webb & Tracey 1981). Cer¬ 
tainly, the moisture gradient indicated by the 
relative water potentials of species across the 
Woolshed Creek gully seems to limit the exten¬ 
sion of rainforest up the side of the gully, as even 
on the unburnt slopes the rainforest is restricted 
to the lower half of the gully. Observations in 
this area indicated that Acmena smithii plants 
higher on the slopes were killed during severe 
droughts in 1972 (D. FI. Ashton pers. comm.). 
Moisture availability, rather than shelter, also 
seems to limit the distribution of Tristaniopsis 
lamina , which appears to be drought intolerant, 
as this species is present in riparian situations, 
both in the sheltered gullies in the unburnt rain¬ 
forest (group Al) and as a dominant species in 
the relatively exposed sites on the river where 
the rainforest has been disturbed bv fire (group 
A2). 
Similarly, moisture is an important factor for 
the presence of damp sclerophyll scrub and rain¬ 
forest elements on the easterly slope above the 
Mitchell River. The concave profile of this slope 
implies that land slumping has occurred (Easton 
1938), a phenomenon often associated with fea¬ 
tures of subterranean drainage (Strahler 1973). 
The possibility of drainage at this site would 
enhance the establishment of moist communi¬ 
ties. This is supported by field observations 
which revealed a tendency for the base of this 
slope to be moist, even during summer, while 
elsewhere at the study site wet sclerophyll spe¬ 
cies were wilting. In contrast, the dry sclerophyll 
communities dominate the dry plateaux and 
ridge tops, where insolation is greater and water 
tables are likely to be much lower. 
