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Forrest Land System

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From Upper Gellibrand to Peters Hill, steep spurs and ridges with long straight slopes and narrow valleys form the rugged northern margin of the Otway Range. The climate is significantly drier than in other parts of the Range, with most areas receiving an annual rainfall of about 900 mm. The inland extent of the land system marks the northern boundary of continuous Cretaceous outcrop, although sporadic outcrops occur in the adjacent Pennyroyal land system.

The separation of these drier spurs and ridges from the rest of the Range is well reflected by changes in the structure and composition of the native vegetation. In particular, Eucalyptus radiata becomes a prominent member of the dominant stratum and the understorey changes from mesophytic species to drier sclerophyllous species such as Acacia mucronata, A. verticillata, Cassinia longifolia and Epacris impressa.

Most of this land system remains forested and is selectively logged for millable timber. Some parts of the eastern areas have been cleared for grazing, but management is difficult due to rugged terrain. Softwood plantations have also been established. Landslips and sheet erosion have been severe in some areas, and rapid run-off from these hills creates problems of gully erosion in the Barwon River land system.
A Study of land in the catchments of the Otway Range and adjacent plains - forrest


A Study of land in the catchments of the Otway Range and adjacent plains - forrest
On the areas that have been cleared weeds such as blackberries
and ragwort become a problem.
A Study of land in the catchments of the Otway Range and adjacent plains - forrest


Area: 41 km
2
Component and its proportion of land system
1
10%
2
50%
3
4%
4
35%
5
1%
CLIMATE
Rainfall, mm

Annual: 900 – 1,100, lowest January (45), highest August (130)
Temperature, 0oC
Annual: 12, lowest July (7), highest February (17)
Temperature: less than 10oC (av.) June – September
Precipitation: less than potential evapotranspiration mid November – mid March
GEOLOGY
Age, lithology

Lower Cretaceous feldspathic sandstone and mudstone
TOPOGRAPHY
Landscape

Deeply dissected hills of the Otway Range
Elevation, m
150 – 400
Local relief, m
150
Drainage pattern
Dendritic
Drainage density, km/km2
3.8
Land form
Hill
Land form element
Steepest slope
North and west facing slopes
Crest, upper slope
South and east facing slopes
Lower slope, drainage line
Slope (and range), %
60 (20-70)
45 (25-65)
20 (5-30)
45 (25-65)
20 (1-35)
Slope shape
Linear
Linear
Convex
Linear
Concave
NATIVE VEGETATION
Structure

Woodland

Open forest

Open forest

Tall open forest

Tall open forest
Dominant species
E. radiata, E. cypellocarpa
E. obliqua, E. radiata, E. cypellocarpa
E. obliqua, E. radiata, E. cypellocarpa
E. cypellocarpa, E. obliqua
E. cypellocarpa, E. obliqua, E. ovata, Acacia melanoxylon
SOIL
Parent material

Colluvium

In-site weathered rock

In-situ weathered rock
Description
Stony brown gradational soils
Brown duplex soils
Brown duplex soils
Brown gradational soils
Brown gradational soils, weak structure
Surface texture
Fine sandy loam
Loam
Loam
Loam
Silty loam
Permeability
Very high
Moderate
Moderate
High
Loam
Depth, m
0.5
0.9
0.9
0.9
>2
LAND USEUncleared areas: Hardwood forestry for sawlogs, posts and poles; softwood forestry; nature conservation; active and passive recreation; water supply.
Cleared areas: Beef cattle grazing on mainly unimproved pastures.
SOIL DETERIORATION HAZARD
Critical land features, processes, forms
Stony shallow soils with weak structure and low water holding capacity on steep slopes are prone to sheet erosion and landslips.
Dry aspect, steep slopes and weakly structured surfaces lead to sheet erosion. Clay subsoils on steep slopes subject to periodic saturation are prone to landslips.
Steeper slopes are prone to sheet erosion.
Steep slopes are prone to sheet erosion. Clay subsoils on steep slopes subject to periodic saturation are prone to landslips.
Weakly structured soils receiving run-off are prone to scour gullying, siltation and flooding.
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