Soil/Landform Unit 72

Exposed steeper south-western slopes of the dissected hills from recent fire. Grey and white
sands are evident on the hillslope

Area:

4028 ha

0.30% of CMA region

The junction between

Cretaceous

and Paleogene sediments on the western periphery of the Otway Range is clearly reflected in vegetation changes. However, the junction is discontinuous and there is a belt of land where the higher parts of the landscape are capped by Paleogene sands with only occasional areas of silts and clays derived from Cretaceous sediments. The lower slopes are often steeper, with outcrops of Cretaceous sandstones and mudstones. Thus, the higher areas carry low woodlands of

Eucalyptus nitida

and

E. baxteri

, while the lower slopes support open forests or even tall open forests of

E. obliqua

and

E. cypellocarpa

. This landscape pattern is somewhat similar to soil-landform unit

in the Redwater Creek landsystem. The major distinguishing feature is that the position in the landscape at which the Cretaceous sediments outcrop is very variable. The deposit of sand above the Cretaceous sediments varies in thickness, but is usually deep enough for the native vegetation to be dependent upon the sand for its nutrient supply. Most parts of this unit remain uncleared and unused. Some sand and gravel extraction pits have been established in the past. Pines have been established on small areas adjoining privately held land.

Cleared land near Chapple Vale currently being used for grazing
	The higher areas carry low woodlands of Eucalyptus nitida and E. baxteri, while the lower slopes support open forests or even tall open forests of E. obliqua and E. cypellocarpa.

Component	1	2	3	4	5
Proportion of soil-landform unit	30%	5%	20%	30%	15%
CLIMATE Rainfall (mm)	Rainfall (mm) Annual: 1100–1400, lowest January (55), highest August (150)
Temperature (^oC)	Temperature (^oC) Annual: 12, lowest July (7), highest February (17)
Seasonal growth limitations	Seasonal growth limitations Temperature: less than 10°C (av.) May–September Precipitation: less than potential evapotranspiration late November–mid March
GEOLOGY Age and lithology	Paleogene unconsolidated marine sand, gravel, silt and clay. Cretaceous fluvio-volcanic mudstone, sandstone and conglomerate
Geomorphology	3.2.2 Dissected upland ranges of the Southern Uplands
LANDUSE	Uncleared areas: Sand and gravel extraction; hardwood forestry for posts, poles, fuel and some sawlogson more fertile soils; nature conservation; water supply protection
TOPOGRAPHY Landscape	Dissected hills with broad gentle hill cappings on western periphery of the Otway Range
Elevation range (m)	30–270
Local relief (m)	75
Drainage pattern	Dendritic with some radial areas
Drainage density (km/km²)	2.6
Landform	Hills
Landform element	Steep crest and slope	Drainage line	Lower slope	Crest and slope	Steep slope
Slope and range (%)	15 (2–35)	3 (0–5)	9 (3–12)	12 (2–25)	30 (20–55)
Slope shape	Convex	Concave	Linear	Convex	Linear
NATIVE VEGETATION Structure	Low woodland	Closed scrub	Low open woodland	Open forest	Tall open forest
Dominant species	E. nitida, E. baxteri	Leptospermum juniperinum, Melaleuca squarrosa	E. baxteri, E. nitida	E. baxteri, E. obliqua, E. radiata, E. nitida	E. obliqua, E. cypellocarpa
SOIL Parent material	Quartz sand and gravel	Alluvial sand, plant remains	Quartz sand and gravel	Clay, silt, sand and gravel	In situ weathered mudstone, sandstone and conglomerate
Description (Corangamite Soil Group)	Grey sand soils (29)	Black sand soils (29, 8)	Grey sand soils with hardpans (29)	Yellow gradational soils, weak structure (29) Brown gradational soils (7)	Brown gradational soils (7)
Soil type sites	OTR742	OTR609, OTR739, OTR740	OTR608, OTR426	OTR497, CLRA13, OTR426	OTR414, OTR416, OTR748
Surface texture	Loamy sand	Silty loam	Loamy sand	Sandy loam	Fine sandy clay loam
Permeability	Very high	High	Very low	High	Moderate
Depth (m)	>2	>2	1.1	>2	1.5
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Very low inherent fertility and high permeability lead to nutrient decline. Steeper slopes with compacted soils are prone to Sheet, rill and scour gully erosion.	High watertables lead to waterlogging.	Hardpans restrict vertical drainage leading to seasonal waterlogging. Very low inherent fertility, with some leaching of permeable highly acidic surfaces, leads to nutrient decline.	Low inherent fertility and high permeability lead to nutrient decline. Weakly structured soils on steeper slopes are prone to sheet erosion.	Clay subsoils on steeper slopes subject to periodic saturation are prone to landslips. Soils of moderate permeability on steep slopes are prone to sheet erosion.

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