Westbury 1 (W1)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Westbury1- geo

Area: 166 sq. km (0.8%)

Westbury 1 land system occurs on the earlier Pleistocene terrace and on the more distal parts of the Tertiary flood plain deposits. These deposits have been dissected to form low hills and sloping to undulating plains and most of the original land surface has been removed. Westbury 1 differs from Westbury 2 land system in having a drier climate with associated changes in vegetation and from Redgum 1 land system in having greater relief.

The materials of Tertiary and Early Pleistocene deposits were pre-weathered and further weathering has taken place. The soils are deep, leached and almost invariably have yellowish brown duplex profiles. There is some variation in texture and consistence of the topsoil, in the degree of subsurface mottling and in the reaction of the lower subsoil which may range from strongly acid to neutral. The subsoils with neutral reaction are probably highly dispersible and prone to gully erosion.

The remaining native vegetation is mainly an open forest II, often shrubby. Similar vegetation was probably predominant prior to clearing.

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Westbury1- image

The cleared gentle slopes contrast with the timbered steeper slopes of the Tambo land system.

CLIMATE Rainfall, mean (mm) Temperature, mean (°C) Seasonal growth limitations	Annual 600 - 900; lowest July or August (30 - 50), highest October (50 - 80) Annual 12 - 14; lowest July (8 - 10), highest February (19 - 21) Temperature <10°C (av.): June - August Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Distal parts of Tertiary floodplain deposits and some Lower Pleistocene terrace deposits; gravels, sands, silts and clays
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Sloping to undulating plains and low hills 0 - 200 10 - 120 Dendritic 1.0
PRESENT LAND USE	Mostly cleared: grazing of beef cattle and sheep on improved pastures; softwood plantations (limited) Minor proportion uncleared: bush grazing of cattle (limited); apiculture

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Westbury1- cs

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Westbury1- graph

LAND COMPONENT Percentage of land system Diagnostic features	1 10 Almost flat plateaux remnants	2 80 Gentle to moderate slopes, rarely steep	3 10 Drainage depressions, in places permanently wet
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	2, (0 - 5) Straight	4 - 8, (0 - 15) Variable	2, (0 - 5) Concave
SOIL
Parent material	Mainly clay, silt and sand with some intermixed quartz gravel		Locally derived alluvium
Description	Very dark greyish brown, sometimes black, sand to sandy clay loam topsoil grading into greyish brown or yellowish brown sandy clay loam subsurface soil, sometimes mottled. Abrupt change to yellowish brown, dark yellowish brown or reddish brown strongly mottled clay subsoil. Subsoil generally moderately to strongly acidic, sometimes neutral at depth		Limited observations — probably variable; dark grey deep sand and strongly mottled grey clay; soil reaction acidic
Classification	Mostly Yellow Podzolic Soils; some Solodic Soils, Soloths; rarely Brown or Red Podzolic Soils Dy3.21, Dy3.41, Dy3.42, Dy3.31, Dy2.21; rarely Db2.11, Db2.21, Db4.21, Dr5.21		Alluvial Soils, Humic Gleys Uc1.21, Gn3.91
Surface Texture	Sand to sandy clay loam; mostly sandy loam		Sand to sandy clay loam
Surface consistence	Friable when moist		Friable when moist
Depth (m)	>2.0		>2.0
Nutrient status	Low		Low
Available soil water capacity	Moderate		Variable
Perviousness to water	Very slow to slow		Very variable
Drainage	Mostly somewhat poor		Mostly very poor to poor
Exposed stone (%)	Usually 0		0
Sampled profile number	55, 67	49, 51	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Open forest II, often shrubby: Mainly mixed forests, though occasionally pure stands, species including — E. globoidea, E. sieberi (most common predominants), E. tereticornis, E. bosistoana, E. cypellocarpa, E. baxteri (often predominant), E. melliodora and E. sideroxylon		Open forest II, III often shrubby: E. bridgesiana+ and/or E. globulus+ often occurring in association with E. ovata, E. radiata or E. melliodora

Disturbance	Affected process and trend	Primary resultant deterioration			Casual activities	Primary off-site process
Disturbance	Affected process and trend	Form	Susceptibility of components	Incidence with components	Casual activities	Primary off-site process
Alteration of vegetation: — reduction in leaf area, rooting depth and/or perenniality	Reduced transpiration, resulting in increased deep percolation	Nutrient loss	Not determined	Not determined	Removal of trees	Increased movement of water to groundwater; increased base-flow of streams
Increased exposure of surface soil	Increased overland flow and soil detachment	Sheet and rill erosion	1; low 2; moderate	Not determined	Cultivating, overgrazing, road and dam building and other earth-moving activities, trafficking by stock and vehicles.	Increased flash flows and sediment load.
Increased physical pressure on soil	Increased compaction With Reduced infiltration	Structure decline Sheet and rill erosion	1,2; low 3; low – high 1; low 2; moderate	Not determined Not determined	Increased trafficking, cultivation, overgrazing, export of organic matter As for sheet and rill erosion above	- Increased flash flows
Increased soil disruption	Increased soil break-up	Gully erosion	1,3; low 2; moderate	Not determined	As for sheet and rill erosion above	Increased sediment load and turbidity in streams
Comments: No observations of deterioration

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