Soil/Landform Unit 66

Steep slopes denote the margin of the Redwater Creek landscape with the floodplains of the Gellibrand River at Glenaire

Area:

5670 ha

0.42% of CMA Region

In the southern parts of the Otway Range, gentle hill cappings of Paleogene quartzitic sands occur as remnants on the high parts of the landscape. Most creeks and rivers have dissected through these sands, exposing

Cretaceous

sandstone and mudstone on steep slopes leading down to the drainage lines. The capping of sand overlies Cretaceous sediments at a fairly shallow and uniform depth. The native vegetation on the sands is not dissimilar from that on the surrounding brown gradational soils, consisting of tall open forests of

Eucalyptus obliqua

E. cypellocarpa

and

E. regnans

on the better sites. These tall trees apparently extract nutrients from underlying weathering Cretaceous rocks. Nutrient cycling by leaf fall and decay has built up the fertility of the sands, far above that normally encountered on such parent material. Only minor parts of this unit have been cleared and it appears that a marked decline in soil fertility has resulted. Hardwood and softwood forestry is the main land use, together with a small industry in the cutting of tea-tree stakes.

Harvested pine plantation is now replaced with blue gums
	Forests of the Ford River valley

Component	1	2	3	4	5
Proportion of soil-landform unit	5%	40%	5%	25%	25%
CLIMATE Rainfall (mm)	Annual: 1150-1600, lowest January (60), highest August (160)
Temperature (^oC)	Annual: 12, lowest July (7), highest February (16)
Seasonal growth limitations	Temperature: less than 10^oC (av.) June-September Precipitation: less than potential evaportranspiration December-mid February
GEOLOGY Age and lithology	Paleocene unconsolidated quartz sand and gravel shallowly underlain by Lower Cretaceous sandstone and mudstone				Lower Cretaceous sandstone and mudstone
Geomorphology	3.1.2 Deeply dissected upland ranges of the Southern Uplands
LANDUSE	Uncleared areas: Hardwood forestry for sawlogs and pulpwood; tea-tree stake harvesting; nature conservation; sand and gravel extraction Minor cleared areas: Beef cattle grazing on unimproved pastures
TOPOGRAPHY Landscape	Deeply dissected hills with broad gentle hill cappings in the southern parts of the Otway Range
Elevation range (m)	15-370
Local relief (m)	90
Drainage pattern	Dendritic with some radial areas
Drainage density (km/km²)	3.7
Landform	Rises			Scarps
Landform element	Crest	Crest and upper slope	Swale	Crest and upper slope	Steep slope
Slope and range (%)	4 (1-7)	20 (3-35)	3 (1-5)	8 (3-15)	35 (10-60)
Slope shape	Linear	Convex	Concave	Irregular	Linear
NATIVE VEGETATION Structure	Woodland	Tall open forest	Closed forest	Open forest	Tall open forest
Dominant species	E. nitida, E. baxteri	E. obliqua, E. cypellocarpa, E. regnans, E. viminalis	Leptospermum juniperinum	E. regnans, E. obliqua, E. baxteri, occasionally E. viminalis	E. obliqua, E. regnans, E. cypellocarpa, E. viminalis
SOIL Parent material	Deep deposits of quartz sand	Shallow deposits of quartz sand	Alluvial sand and gravel, organic matter	Shallow deposits of quartz sand and gravel	In situ wathered sandstone and mudstone
Description (Corangamite Soil Group)	Grey sand soils with hardpans (29)	Black sand soils (29, 8)	Black sand soils (29, 8)	White sand soils (29)	Brown gradational soils (7)
Soil type sites	OTR608, CLRA13, OTR426	OTR609, OTR739	OTR609, OTR739	OTR426	OTR414, OTR416, OTR748
Surface texture	Loamy sand	Sandy loam	Silty loam	(Gravelly) loamy sand	Sandy clay loam
Permeability	Low	High	Moderate	Very high	Moderate
Depth (m)	1.2	>2	>2	>2	1.4
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Hardpans restrict vertical drainage, leading to seasonal waterlogging. Very low inherent fertility with some leaching of permeable highly acidic surfaces leads to nutrient decline	Soils of high permeabiity in high rainfall areas are prone to nutrient decline. Steeper slopes with compacted soils (tracks, clear-felled areas) are prone to sheet and rill erosion.	High watertables lead to waterlogging. Runoff from adjacent hills leads to flooding and siltation.	Soils of very low inherent fertility, low nutrient holding capacity and high permeability in high rainfall areas are prone to nutrient decline.	Clay subsoils on steeper slopes are subject to periodic saturation and are prone to landslips. Steeper slopes are prone to sheet erosion.

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