Aire Land System

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The steeply dissected spurs and ridges in the wetter parts of the Otway Range comprise the Aire Land System, the largest land system in the study area. Rapid downcutting of streams following uplift of the Range has been responsible for forming this rugged landscape, with many slopes more than 60% and cliffs and bluffs in the central part north of Apollo Bay.

The soils are young and moderately fertile. Tall open forests of Eucalyptus regnans reach heights approaching 100 m in the Calder River catchment, but most of the tallest trees have now been milled. E. obliqua and E. cypellocarpa are also common, while E. viminalis occurs in the west and E. globulus is found close to the coast.

Pine forests cover large areas of this land system and other parts have been cleared for agriculture. The main hazards to land use are landslips and sheet erosion. Losses in organic matter and soil structure are often apparent following clearing.

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

Some areas of the Aire land system have been cleared for agriculture,
but the terrain is difficult to manage and many areas have become covered
in bracken an non-productive scrub.

Area: 762 km²	Component and its proportion of land system
Area: 762 km²	1 10%	2 80%	3 10%
CLIMATE Rainfall, mm	Annual: 1,100 – 1,750, lowest January (60), highest August (170)
Temperature, 0^oC	Annual: 11, lowest July (7), highest February (16)
	Temperature: less than 10^oC (av.) May – September
	Precipitation: less than potential evapotranspiration December – February
GEOLOGY Age, lithology	Lower Cretaceous feldspathic sandstone and mudstone
TOPOGRAPHY Landscape	Deeply dissected hills of the Otway Range
Elevation, m	90 – 560
Local relief, m	165
Drainage pattern	Trellis pattern with isolated radial areas
Drainage density, km/km²	4.7
Land form	Hill
Land form element	Crest	Upper and middle slope	Lower slope, drainage line
Slope (and range), %	20 (5-30)	40 (25-80)	25 (5-40)
Slope shape	Convex	Linear	Concave
NATIVE VEGETATION Structure	Tall open forest	Tall open forest	Tall open forest to tall closed forest
Dominant species	E. obliqua, E. cypellocarpa, E. regnans, E. ovata, E. globulus, E. viminalis, Acacia melanoxylon	E. regnans, E. cypellocarpa, E. obliqua, E. ovata, E. viminalis, E. globulus	E. regnans, E. obliqua, Acacia melanoxylon, Nothofagus cunninghamii, E. cypellocarpa, E. ovata, E. viminalis, E. globulus
SOIL Parent material	In-situ weathered rock	In-situ weathered rock	Alluvium and colluvium
Description	Brown gradational soils	Brown gradational soils	Dark brown gradational soils
Surface texture	Loam	Loam	Loam
Permeability	Moderate	Moderate	High
Depth, m	1.4	1.2	>2
LAND USE	Uncleared areas: Hardwood forestry for scantlings, posts, pole and pulpwood; softwood plantations for sawlogs and pulpwood; nature conservation; water supply; passive recreation. Minor cleared areas: Beef cattle grazing and dairy farming on mainly improved pastures; row cropping on gentler slopes.
SOIL DETERIORATION HAZARD Critical land features, processes, forms	High rainfall, moderate permeability and leaching plus loss of organic matter and soil structure upon disturbance lead to nutrient decline and soil compaction, also sheet erosion on steeper slopes.	Clay subsoils on steep slopes subject to periodic saturation are prone to landslips. Steep slopes are prone to sheet and rill erosion. High rainfall, moderate permeability and leaching plus loss of organic matters and soil structure upon disturbance lead to nutrient decline and soil compaction.	Rapid surface run-off from adjacent hills lead to scour gullying, siltation and flooding. High rainfall, high permeability and leaching plus loss of organic matter and soil structure upon disturbance lead to nutrient decline and soil compaction.

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