Soil/Landform Unit 86

Landform Unit Description

Unit 86 image a
View north towards Fergusons Hill
      Area: 6851 ha
      0.51% of CMA region

      Most outcrops of Neogene sediments to the west of the Otway Range are either steeply dissected or have deeply weathered soils. However, some ridges and spurs are only mildly dissected and their soil profiles are only weakly developed. These areas are found at Ferguson Hill, just south of Simpson, along Pipeline Road and in an additional small area near Cape Otway. The parent material is Neogene sand, silt and clay, with some minor areas of ferricrete. The soils vary according to the nature of the outcropping beds, but in general their structure is weak and often the A and B horizons are not clearly differentiated. Profile drainage is good on all but those areas with hardpans, and these are the only areas prone to waterlogging despite the high annual rainfall. Eucalyptus obliqua and E. baxteri colonise most areas and often reach heights in excess of 30 m on the better drained soils. However, these stands are decreasing in area as much of the land is being cleared for agriculture. The soils are naturally quite stable and the major problems are likely to arise from nutrient decline.
Unit 86 geomorphology

Unit 86 image b
Slopes with devined dendritic drainage on southern
slopes of Ferguson Hill
Unit 86 cross section

Unit 86 graph
Unit 86 image c
Woodlands of the broad ridge of Ferguson hill

Component
1
2
3
4
5
6
7
8
Proportion of soil-landform unit
15%
20%
25%
5%
8%
15%
10%
2%
CLIMATE
Rainfall (mm)

Annual: 1000-1100, lowest January (4), highest August (130)
Temperature (oC)
Annual: 13, lowest July (7.5), highest February (9)
Seasonal growth limitations

Temperature: less than 10oC (av.) June-August
Precipitation: less than potential evapotranspiration mid November-March
GEOLOGY
Age and lithology

Paleogene marine carbonaceous clay to sand, Neogene fluvio-marine sand and marine marl.
Geomorphology
LANDUSE
Uncleared areas: Hardwood forestry for sawlogs, posts and poles; water supply; nature conservation; gravel extraction
Cleared area: Sheep and beef cattle grazing; dairy farming; water supply
TOPOGRAPHY
Landscape

Undulating hills and ridges
Elevation range (m)
30-230
Local relief (m)
40
Drainage pattern
Dendritic
Drainage density (km/km2)
1.7
Landform
Hills
Drainalge lines
Broad ridges
Scarps
Landform element
Lower slope
Slope
Crest
Midslope
-
Crest and upper slope
Crest
-
Slope and range (%)
4 (1-7)
14 (5-37)
5 (2-9)
11 (3-15)
4 (2-9)
4 (0-11)
4 (0-7)
29 (25-37)
Slope shape
Straight
Straight
Convex
Straight
Concave
Convex
Straight
Concave
NATIVE VEGETATION
Structure

Open forest

Open forest

Low woodland (variable)

Open forest

Open forest

Open forest

Tall woodland

Open forest
Dominant species
E. obliqua, E. ovata
E. baxteri, E. nitida,
E. obliqua
E. nitida, E. baxteri
E. baxteri, E. radiata,
E. obiqua, E. cypellocarpa
E. obliqua, E. baxteri
E. baxteri, E. obliqua
E. baxteri, E. obliqua
E. obliqua, E. baxteri,
E. ovata, Acacia malanoxylon
SOIL
Parent material

Clay and silt

Clay, silt and sand

Sand

Sand, silt and clay

Alluvial sand, silt and clay

Clay and silt; some lateritic remnants

Clay and silt; some lateritic remnants

Colluvial lateritic ironstone
Description
(Corangamite Soil Group)
Grey-brown gradational soils (29)
Yellow gradational soils, weak structure (29)
Grey sand soils with hardpans (29)
Red sandy loam soils (29)
Grey gradational soils (17, 34)
Mottled brown, grey, yellow or red gradational soils (17)
Red gradational soils, weak strcture (17)
Stony red gradational soils (17)
Soil type sites
OTR497, CLRA13
-
OTR733, SW23
OTR782
OTR749
-
Surface texture
Fine sandy loam
Sandy loam
Loamy sand
Sandy loam
Sandy loam
Sandy loam
Sandy loam
Gravelly loamy sand
Permeability
Moderate
High
Very low
Very high
Low
Moderate
High
Very high
Depth (m)
>2
>2
>2
>2
>2
>2
0.9
>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS
Minor hazards
Weakly structured surfaces on steeper slopes are prone to sheet erosion. Low inherent fertility and high permeability lead to nutrient decline.
Weakly structured sands on hardpans are prone to sheet erosion and seasonal watrlogging. Permeable surface sands of high acidity and low inherent fertility are prone to nutrient decline.
Low inherent fertility and high permeability lead to nutrient decline.
High seasonal watertable leads to soil compaction.
Low inherent fertility, phosphorus fixation and permeable surfaces lead to nutrient decline.
Low inherent fertility and high permeability lead to leaching of nutrients.
Steep slopes with weakly structured surface soils of low water holding capacity are prone to sheet erosion.
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