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Junction Track Land System

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The junction between Cretaceous and Tertiary 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 Tertiary 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 the Redwater Creek land system. 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 land system 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.
A Study of land in the catchments of the Otway Range and adjacent plains - junction track

A Study of land in the catchments of the Otway Range and adjacent plains - junction track

Most slopes support low woodlands of E. nitida, but outcrops of
Cretaceous sediments can be recognised by the increases soil
fertility and the accompanying change to open forests or tall open
forests of
E. obliqua and E. cypellocarpa.

A Study of land in the catchments of the Otway Range and adjacent plains - junction track


Area: 41 km
2
Component and its proportion of land system
1
30%
2
5%
3
20%
4
30%
5
15%
CLIMATE
Rainfall, mm

Annual
: 1,100 – 1,400, lowest January (55), highest August (150)
Temperature, 0oC
Annual: 12, Lowest July (7), highest February (17)
Temperature: less than 10oC (av.) May – September
Precipitation: less than potential evapotranspiration late November – mid March
GEOLOGY
Age, lithology

Paleocene unconsolidated sand, gravel, silt and clay

Lower Cretaceous sandstone and mudstone
TOPOGRAPHY
Landscape

Dissected hills with broad gentle hill cappings on western periphery of the Otway Range
Elevation, m
30 - 270
Local relief, m
75
Drainage pattern
Dendritic with some radial areas
Drainage density, km/km2
3.5
Land form
Hill
Land form element
Crest, slope
Drainage line
Lower slope
Crest, 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 rock
Description
Grey sand soils, uniform texture
Black sand soils, uniform texture
Grey sand soils with hardpans, uniform texture
Yellow gradational soils, weak structure
Brown gradational soils
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 USE
Uncleared areas: Sand and gravel extraction; hardwood forestry for posts, poles, fuel and some sawlogs on more fertile soils; nature conservation; water supply protection
SOIL DETERIORATION HAZARD
Critical land features, processes, forms
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 water tables lead to waterlogging.
Hardpans restrict vertical drainage leading to seasonal waterlogging. Very low inherent fertility, with some leaching of permeable high 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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