Pennyroyal Land System

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Along the northern periphery of the Range, flat-topped spurs and ridges form an irregular band of foothills from Wormbete Creek to Barwon Downs. The terrain is variable, with steep slopes leading away from these gentle hill crests to wide valley floors. The ridge slopes upwards towards the Range and becomes narrower as the local relief increases.

The gentle parts of the landscape are formed on Tertiary clay, silt and sand. These sediments overlie Cretaceous sandstones and mudstones, which outcrop on steep slopes on the valley sides. Soil and vegetation reflect changes in the parent material, with the soils on the upper parts of the landscape being somewhat deeply weathered with sandy surface horizons in contrast to loam or clay loam soils on the Cretaceous outcrops.

Clearing has been widespread and sheep and beef cattle grazing as well as dairy farming are the main land uses. Some hardwood is logged from forested areas, and softwood plantations have been established in the east. Poor management of these hills can lead to rapid surface run-off along the valleys creating problems of gully erosion, siltation and flooding further downstream.

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

Upper gentle slopes are formed on Tertiary clay, silt and sand, while
Cretaceous sandstones and mudstones outcrop on steep slopes along the
valley sides and Recent alluvium is found in the valley floor.

Area: 97 km²	Component and its proportion of land system
Area: 97 km²	1 35%	2 15%	3 35	4 12%	5 3%
CLIMATE Rainfall, mm	Annual: 700 – 1,050, lowest January (35), highest August (80)
Temperature, 0^oC	Annual: 12, lowest July (8), highest February (18)
	Temperature: less than 10^oC (av.) June – September
	Precipitation: less than potential evapotranspiration November - March
GEOLOGY Age, lithology	Tertiary unconsolidated clay, silt and sand. Minor remnants of lateritization			Lower Cretaceous sandstone and mudstone	Recent alluvial clay, silt and sand
TOPOGRAPHY Landscape	Steep rolling hills on the northern periphery of the Otway Range
Elevation, m	135 - 300
Local relief, m	65
Drainage pattern	Dendritic
Drainage density, km/km²	1.9
Land form	Hill				Valley floor
Land form element	Gentle crest	Upper slope, crest	Gentle upper slope	Steep lower slope	-
Slope (and range), %	3 (0-15)	7 (0-25)	15 (3-25)	30 (5-45)	1 (0-2)
Slope shape	Convex	Convex	Linear	Linear	Concave
NATIVE VEGETATION Structure	Open forest	Open forest	Open forest	Open forest	Tall open forest
Dominant species	E. obliqua, E. ovata, E. radiata, E. aromaphloia, E. nitida	E. obliqua, E. radiata, E. nitida, E. viminalis	E. obliqua, E. viminalis, E. radiata, E. ovata, Acacia melanoxylon	E. obliqua, E. radiata, E. cypellocarpa	E. obliqua, E. cypellocarpa, E. globulus
SOIL Parent material	Clay, silt and sand, often deeply weathered	Sand and clay	Clay, silt and sand	In-situ weathered rock	Alluvium
Description	Mottled yellow and red duplex soils	Yellow gradational soils, weak structure	Yellow-brown duplex soils, coarse structure	Brown duplex soils	Grey gradational soils
Surface texture	Sandy loam	Loamy sand	Fine sandy loam	Loam	Sandy loam
Permeability	Moderate	High	Low	Moderate	Low
Depth, m	>2	>2	>2	0.8	>2
LAND USE	Cleared areas: sheep and beef cattle grazing; dairy farming; water supply. Uncleared areas: Hardwood forestry for some sawlogs, posts and poles; softwood plantations; nature conservation; water supply; gravel extraction; passive recreation
SOIL DETERIORATION HAZARD Critical land features, processes, forms	Low inherent fertility and phosphorus fixation lead to nutrient decline. Weakly structured surface soils on steeper slopes are prone to sheet erosion.	Low inherent fertility and high permeability lead to nutrient decline. Weakly structured soils on steepest slopes prone to sheet erosion.	Dispersible clay subsoils on steep slopes are prone to gully erosion. Soils of low permeability on steep slopes are prone to sheet erosion.	Steep slopes lead to sheet erosion, particularly on dry aspects. Clay subsoils on steep slopes subject to periodic saturation are pone to landslips.	High seasonal water table and low permeability lead to seasonal waterlogging, soil compaction and soil salting. High discharge rates, dispersible clay subsoils and dispersible sandy clay parent material of low mechanical strength lead to gully and tunnel erosion.