Soil/Landform Unit 118

Stony rises and plains west of Mount Gellibrand

Area:

43 694 ha

3.27% of CMA region

The stony rises between Rokewood and Armytage were among the first areas grazed in this part of Victoria. The two main occurrences include one extending from the Western Upland boundary south of Mount Mercer to Wingeel, and the other further south around Ombersely. The stony rises are both interconnected and solitary and they slope southwards towards the Barwon River. The area is found north of the Princes Highway, but occasional vents or old cones also occur within these rises. The nature of the native vegetation is difficult to determine. Many early reports describe the area as a treeless plain, but there are occasional specimens of

Acacia melanoxylon, A. implexa

and even

Eucalyptus viminalis

in roadside reserves. Thus, there may have originally been a low open woodland prior to settlement, which has disappeared following grazing and burning. Stony rise landscapes in other parts of Victoria possess woodland or low woodland communities. The soils are black

self-mulching

clays (

Vertosols

) and black gradational soils (

Dermosols

) on the rises, and (strongly

sodic

) mottled black texture contrast soils (

Sodosols

) and grey cracking clays (Vertosols) on the plains and depressions. Soil nutrient levels are high on these basalt outcrops, especially in the less weathered soils. The abundance of rock floaters and outcrops makes cultivation difficult even on infilled swamps between the rises. The plains and depressions may be susceptible to waterlogging,

compaction

and structure decline. Annual rainfall is greater in the southern occurrence of the unit with more intensive grazing, while sheep grazing and cropping occurs in the drier occurrence to the north.

Stony shelf overlooking lower plains towards The Sanctuary
	Plain (possibly former swamp) with stony rises in the distance of this unit

Component	1	2	3	4
Proportion of soil-landform unit	15%	70%	5%	10%
CLIMATE Rainfall (mm)	Annual: 620
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	October-April
GEOLOGY Age and lithology	Quaternary basalt
Geomorphology	6.1.3 Volcanic Western Plains with poorly developed drainage
LANDUSE	Uncleared areas: Water supply, nature conservation Cleared areas: Sheep and beef cattle grazing; cropping (cereal)
TOPOGRAPHY Landscape	Stony rise, undulating plain with occasional steep hills (volcanic cones)
Elevation range (m)	70-301
Local relief (m)	3-8
Drainage pattern	Centripetal
Drainage density (km/km²)	0.8
Landform	Rises		Plain and gentle slopes	Alluvial flat
Landform element	Broad crest	Rise slopes	Plains	Depressions and drainage lines
Slope and range (%)	6 (2-12)	2 (0-6)	1 (0-2)	1 (0-3)
Slope shape	Convex	Convex, Straight	Straight	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassland / Plains Grassy Woodland Mosaic (0.3%)
Dominant species	Acacia melanlxylon, A. implexa, Eucalyptus viminalis
SOIL Parent material	Basalt	Basalt	Basaltic colluvium	Basaltic colluvium and alluvium
Description (Corangamite Soil Group)	Shallow self-mulching black cracking clays (39) and shallow friable loams (40)	Shallow self-mulching black cracking clays (39) and shallow friable loams (40)	Alkaline mottled black and mottled yellow texture contrast soils (35)	Grey cracking clays (39)
Soil type sites	SW101, SW102, SW26	CLRA49, CLRA51, CLRA52	MM109, SW86, CLRA51	SFS2, SW37, CLRA62
Surface texture	Light clay, clay loam	Clay loam	Clay loam	Light clay
Permeability	High	Moderate to high	Low	Very low
Depth (m)	<0.7	<1.5	<2, >2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Expansive clays and uniform loams, moderate water holding capacity and nutrient holding capacity in varialbe depth soils. High permeability. Friable surfaces, including self-mulching. Common stone, minor low stone areas are cropped. Moderately rapid site drainage. Some sheet erosion.	Uniform loams and expansive clays, moderate to high water holding capacity and nutrient holding capacity in variable depth soils. High (loams) to low permeability. Friable surfaces including self-mulching. Common stone, low stone areas are cropped. Moderately rapid site drainage. Some sheet erosion.	Texture contrast soil with moderate water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. Low permeability. Generally, strongly sodic subsoil. Slow site drainage.	Texture contrast soil, moderate water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. Low permeability, sodic (often strongly) subsoil. Slow site drainage.

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