Soil/Landform Unit 68

Steeply dissected hills with open forests and woodlands at Mount MacKenzie

Area:

5859 ha

0.44% of CMA region

Steeply dissected hills abut either side of the middle and lower reaches of the Gellibrand River. Dissection into Paleogene clay, silt and sand has resulted in steep slopes and narrow drainage lines. The finely textured Paleogene/Neogene sediments outcropping in these areas have resulted in heavier textured soils than those found in the neighbouring Chapple Vale landsystem (soil-landform unit

). Moisture stress and fertility are not as limiting to plant growth, so open forests of

Eucalyptus obliqua

and

E. baxteri

have developed on most sites. Included in the unit are dissected river terraces along the valley of the Gellibrand River and these possess well developed soils with coarse structured subsoils. The higher parts of the landscape may also possess such soils where Kennedys Creek landsystem (soil-landform unit

) is adjacent, or sandy soils where the Chapple Vale landsystem (soil-landform unit

) is nearby. Most areas remain forested but areas abutting the floodplains have been cleared to provide winter pastures for dairy cattle. Pines have been established on previously forested land. Sheet erosion and landslips have occurred on many of the steeper slopes where the native vegetation has been removed and the rugged nature of the terrain makes most land uses difficult.

Steep hilss abutting Gellibrand River south of Devondale
	Dense woodland of the valley floor

Component	1	2	3	4	5	6	7
Proportion of soil-landform unit	40%	8%	9%	25%	8%	7%	3%
CLIMATE Rainfall (mm)	Annual: 950-1100, lowest January (45), highest August (120)
Temperature (^oC)	Annual: 13, lowest July (8), highest February (18)
Seasonal growth limitations	Temperature: lesss than 10^oC (av.) June-August Precipitation: less than potential evapotranspiration mid November-March
GEOLOGY Age and lithology	Paleogene marine marl, marginal glauconitic sand and gravel; Neogent fluvio-marine sand; minor Cretaceous fluvio-volcanic sediments
Geomorphology	3.2.2 Dissected upland ranges of the Southern Uplands
LANDUSE	Uncleared areas: Hardwood forestry for sawlogs, posts and poles; water supply; nature conservation; quarrying of ironstone; softwood forestry Minor cleared areas: Dairy farming; beef cattle grazing
TOPOGRAPHY Landscape	Deeply dissected hills in the middle and lower reaches of the Gellibrand River catchment
Elevation range (m)	15-180
Local relief (m)	100
Drainage pattern	Dendritic with some radial
Drainage density (km/km²)	2.6
Landform	Hills					Valley floors	Terraces
Landform element	Slope and crest	Crest and spur (mainly in south)	Crest and slope	Slope and crest	Broad slight depression	-	-
Slope and range (%)	33 (4-63)	14 (4-19)	32 (22-45)	37 (31-49)	14 (2-21)	4 (0-7)	5 (1-9)
Slope shape	Convex	Convex	Convex	Convex	Concave	Concave	Convex
NATIVE VEGETATION Structure	Open forest	Open forest	Low woodland	Open forest	Low woodland	Woodland	Open forest
Dominant species	E. baxteri, E. nitida, E. obliqua, E. radiata	E. obliqua, E. baxteri, E. viminalis, E. ovata	E. baxteri, E. nitida	E. baxteri, E. obliqua	E. nitida, E. baxteri	E. obliqua, E. baxteri	E. obliqua, E. ovata, E. baxteri
SOIL Parent material	Clay, silt and sand	Clay, silt and sand	Sand	Clay, silt and sand	Sand, colluvial sand	Plant remains, alluvial sand and clay	Alluvial clay, silt and sand
Description (Corangamite Soil Group)	Brown, grey or yellow gradational soils, weak structure (29, 17)	Yellow-brown gradational soils, coarse structure (29)	Grey sand soils (17)	Red gradational soils, weak structure (17, 29)	Grey sand soils with hardpans (29)	Black sand soils (8)	Yellow-brown gradational soils coarse structure (7, 34)
Soil type sites	OTR497, OTR741, OTR426	OTR750	OTR741	OTR749	OTR608	OTR609, OTR739	OTR750, OTR733
Surface texture	Sandy loam	Fine sandy loam	Loamy sand	Sandy loam	Loamy sand	Loamy sand	Fine sandy loam
Permeability	High	Low	Very high	High	Very low	High	Low
Depth (m)	>2	>2	>2	>2	0.6	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Weakly structured soils on steep slopes are prone to sheet, rill, scour gully erosion and landslips. Low inherent fertility and high permeability lead to nutrient decline.	Dispersible clay subsoils of low permeability are prone to gully erosion	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.	Weakly structured soils on steep slopes are prone to sheet and rill erosion and landslips. Low inherent fertility and high permeability lead to nutrient decline.	Hardpans restrict vertical drainage leading to seasonal waterlogging. Very low inherent fertility with leaching of permeable highly acidic surface soils lead to nutrient decline.	High watertables lead to waterlogging and soil compaction. Rapid runoff from adjacent hills leads to flooding and siltation.	Dispersible clay subsoils of low permeability are prone to gully erosion. Low permeabilities and high watertables lead to waterlogging and soil compaction.

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