The rainfall gradually increases as one proceeds from the 
plains to the higher points of the ranges from about twenty-five 
inches to over forty inches per annum. This variation in rainfall 
determines in part the nature of the vegetation. But it is the 
water-retaining capacity of the soil rather than the amount of 
rainfall which is the decisive factor in determining distribution 
of vegetation, and in the Mount Lofty Ranges the geological 
origin of the soil plays a large part. Generally speaking, the 
lower foothills (or fault blocks), such as those which form the 
entrance of the gorge at Morialta, are composed of slates and 
limestones ; these give rise to a somewhat clayey soil. The main 
mass of the ranges, and including the upper portions of the 
Morialta Gorge, is composed mainly of quartzites, which weather 
to a coarse-grained, highly siliceous, sandy soil. 
Generally speaking, on the slates and limestones with a 
lower rainfall, a savannah woodland is found, whilst on the 
siliceous soils with a somewhat higher rainfall sclerophyll forest 
occurs. A savannah woodland is one in which the trees are 
scattered, giving a park-like effect, tall shrubs are rare, and the 
ground flora is essentially herbaceous. The sclerophyll forest 
is one in which practically all the plants have tough leaves, often 
small and spinv ; there is a dense assemblage of undershrubs with 
leaves of this type and the trees are closer together than in the 
savannah woodlands. 
The Morialta Reserve presents us simply with a sample of 
the Mount Lofty Ranges as a whole, but shows especially the 
nature of sclerophyll communities on steep hills, which cannot 
support true sclerophyll forest. Briefly, we can consider the 
vegetation of this area under four headings: 
1. Savannah woodlands on the low foothills. 
2. Sclerophyll forests on the crests of the high hills. 
3. Sclerophyll communities on the slopes. 
4. The vegetation of the gully bottoms. 
1. Savannah Woodland 
THE dominant trees in the savannah woodlands of the Mount 
Lofty Ranges as a whole are Eucalyptus odorata (pepper- 
mint) and E. leucoxylon (blue gum), the former occurring in 
drier areas than the latter. Apart from the dominant trees, 
which are generally mutually exclusive, the associated plants are 
the same in both woodland types. At Morialta there is no 
extensive area of E. odorata woodland, although isolated trees 
do occur and there are indications that formerly a woodland 
dominated by this tree occupied the upper portions of the plain 
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