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

On the areas that have been cleared weeds such as blackberries
and ragwort become a problem.

Area: 41 km²	Component and its proportion of land system
Area: 41 km²	1 10%	2 50%	3 4%	4 35%	5 1%
CLIMATE Rainfall, mm	Annual: 900 – 1,100, lowest January (45), highest August (130)
Temperature, 0^oC	Annual: 12, lowest July (7), highest February (17)
	Temperature: less than 10^oC (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 USE	Uncleared 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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