72 
D. R. MELICK 
bance and edaphic factors in the occurrence of 
rainforest and adjacent sclerophyll communi¬ 
ties. 
THE STUDY AREA 
The survey covered an area of 143 hectares in 
the Mitchell River National Park (latitude 
37°42'S, longitude 147°22'E), Victoria, some 
220 km east of Melbourne (Fig. 1). The limits 
were determined by the boundaries of the 
former Glenaladale National Park, which was 
included within the new Mitchell River 
National Park in 1987. The area is noted for its 
rugged topography, including steep sandstone 
cliffs and limestone formations, and the pre¬ 
sence of isolated warm temperate rainforest 
patches in sheltered sites amid sclerophyll vege¬ 
tation. 
Climate. The climate of the area is generally 
mild and, although at the southern fringe of the 
highlands, is tempered by the proximity to the 
coast 30 km to the south. At Glenaladale North 
(5 km south) the annual rainfall is 730 mm with 
a uniform seasonal distribution. The coefficient 
of variation is relatively high (27.7%) and 
extremes have led to prolonged droughts, as in 
1965, 1972 and 1982 when the annual rainfalls 
were as low as 340 mm, or to severe floods, as in 
1952, 1971 and 1978 (Ashton & Frankenberg 
1976, and Bureau of Meteorology records) when 
annual rainfalls reached 1200 mm. 
The mean annual temperatures at Bairnsdale 
(25 km south-west) range from 8.7°C to 19.9°C. 
At Glenaladale the range is likely to be 
Fig. 1. Location of the Mitchell River National Park in 
Victoria. 
somewhat greater, and although frosts occur 
they are not severe. Winds are predominantly 
from NW to SE with a strong SE component de¬ 
rived from east coast cyclones or from summer 
sea breezes. In winter, NW winds descending 
from the highlands result in milder conditions 
than at other sites in southern Victoria (Linforth 
1969). The steep valleys and gorges in the park 
provide sheltered sites for vegetation in the 
area. 
Physiography and geology. The physiography is 
dominated by the gorge of the Mitchell River 
which, following uplift in late Tertiary times 
(Easton 1938), has incised its bed 140 m into a 
low featureless plateau 170-200 m above sea 
level. Its tributaries in this area, Woolshedand 
Bull Creeks, have cut narrow rocky gorges for 
some distance from the Mitchell River. Instabi¬ 
lity of the rock faces has produced large-scale 
slumping and talus slopes, which have modified 
the form of the valleys. The increased meanders 
of the Mitchell River, in part due to the land 
slumps, have resulted in great variation in ero¬ 
sion and deposition. Deep scour holes alternate 
with shallow boulder areas and, where the velo¬ 
city of the stream diminishes, point bars of sand 
have built up against major boulders. Geologi¬ 
cally the region is part of the Avon River 
sequence of Late Devonian red-brown sand¬ 
stones interbedded with soft shales and con¬ 
glomerates (Easton 1938). Calcareous bands 
have been exposed along both the Mitchell River 
and the upper reaches of Bull Creek, but are 
most graphically displayed in the formation of 
the “Den of Nargun” on Woolshed Creek. This 
large cavern is the product of differential ero¬ 
sion, where intermittent stream action has 
undercut a hard calcareous bar by eroding away 
the underlying soft shale. Calcium carbonate 
leached from the sandstone has accumulated as 
stalactites and stalagmites in the Den. 
Soils. Soils in the area are generally podzolic 
with sandy to sandy loam topsoils over yellow to 
reddish loam or clay loam subsoils, The depth of 
soils is highly variableand, being related to topo¬ 
graphy, is very shallow on upper slopes and 
plateau edges and relatively deep on lower 
slopes. On talus slopes soils are intermittently 
developed on small areas of calcareous rock 
bands and soils are brown loams to sandy loams, 
but in some places seepages occur on steep valley 
sides precipitating limestone shawls. On steeper 
slopes such lithological effects in soils are blur¬ 
red by soil creep. 
100 km 
