Delburn (Dl)

	Area: 46 sq. km (0.2%) In the South Victorian Uplands, erosion has removed most of the Tertiary sediments and associated, weathered products overlying the Older Volcanics. Some areas however, still retain part of the weathered kaolinized, basaltic regolith and these have been mapped in Delburn land system. They occur mainly in the western part of the Morwell River Catchment. Topography consists of hills and long slopes with a broad. dendritic-dissection pattern. The areas of elevated volcanics from which erosion has removed most or all of the kaolinized regolith, are mapped as Neerim and Thorpdale land systems.	Deep soils mantle the gentle slopes of Delburn land system; grazing is the main land use
Basaltic rocks weather to clays and silts and where these are kaolinized much of the original iron content has been removed. Consequently the soils on this kaolinized basalt are predominantly pale brown or yellowish brown and clayey with a medium blocky structure. They contrast with the finely-structured, bright-reddish-brown soils that have developed on the less-weathered basalt in Neerim and Thorpdale land systems. The soils in Delburn are also leached, acidic and generally gradational, though there is a tendency towards a more developed, duplex profile on the gentler slopes of component 2. Most of the native vegetation, probably mainly open forest II with more shrubby understories in valley floors, has been cleared.

CLIMATE Rainfall, mean (mm) Temperature, mean (°C) Seasonal growth limitations	Annual 700) - 1200; lowest January or February (40 - 70), highest August or October (90 - 120) Annual 12 - 14; lowest July (8 - L0), highest February (19 - 21) Temperature <10°C' (av.): May - September Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Tertiary basalts (Older Volcanics), highly and deeply weathered
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Long slopes and hills with a broad dissection pattern 40 - 260 20 - L40 Dendritic 0.9
PRESENT LAND USE	Mostly cleared: softwood forestry: some grazing of beef and dairy cattle on improved pastures Minor proportion uncleared: hardwood forestry (minor timber products with some general construction timber); apiculture

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

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

LAND COMPONENT Percentage of land system Diagnostic features	1 40 Crests and upper slopes	2 30 Gentle to moderate slopes with pale kaolinitic soil	3 20 Protected shorter slopes with deeper reddish soils	4 10 Drainage depressions, often swampy
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	5 - 10, (0 - 20) Convex	5 - 10. (5 - 30) Straight tending concave	15, (5 - 30) Straight tending convex	2, (0 - 5) Concave
SOIL
Parent material	Weathered, mostly kaolinised basalt			Mainly fine-textured alluvium
Description	Brown loam to clay loam merging into slightly reddish brown or yellowish brown blocky clay subsoil	Brown sandy clay loam to clay loam merging into pale brown or brownish yellow blocky clay subsoil	Dark greyish brown to dark reddish brown loam to clay loam merging into reddish brown or brown blocky clay subsoil	Limited observations — probably mainly dark silty clay loam over strongly mottled yellowish brown clay subsoil
Classification	Xanthozems, Yellow Podzolic Soils Gn3.91, Gn4.31, Gn4.51, Gn4.81, Dy3.41	Yellow Podzolic Soils. Xanthozems Dy3.11, Dy3.21, Gn3.71	Krasnozems. Brown Earths Gn3.11. Gn3.52. Gn4.11. Gn4.51	Probably Wiesenboden, Humic Gleys -
Surface texture	Loam to clay loam	Sandy clay loam to clay loam	Loam to clay loam	-
Surface consistence	Friable when moist	Friable when moist	Friable when moist	Friable when moist
Depth (m)	1.5 –2.0	1.5 - 2.0	1.0 - >2.0	>2.0
Nutrient status	Low to moderate	Low to moderate	Low to moderate	Low to moderate
Available soil water capacity	Moderate	Moderate	Moderate	Moderate to high
Perviousness to water	Moderate to rapid	Moderate to rapid	Moderate to rapid	Slow to moderate
Drainage	Good	Moderately good	Good	Poor
Exposed stone (%)	0	0	0	0
Sampled profile number	-	-	-	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Open forest II: Mixed forests with predominant species and composition variable including E. obliqua (usually predominant), E. cypellocarpa, E. radiata, E. sieberi (mostly on crests) and E. viminalis		Open forest II, III: Mixed forests with predominant species and composition variable — as for components 1 and 2	Shrubby open forest II: E. ovata+ with or without E. radiata+

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
Alteration of vegetation: — reduction in leaf area, rooting depth and/or perenniality	Reduced transpiration, resulting in increased deep percolation and leaching	Nutrient loss	1.2,3; low	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	1.2,3; moderate	Not determined	Clearing, logging, burning, overgrazing, road and dam building and other earth-moving activities, rabbit burrowing, 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	L.2.3; moderate 4: high 1,2,3: moderate	Not determined Not determined	Loss of organic matter from topsoil As for sheet and rill erosion above	- Increased flash flows
Increased soil disruption	Increased soil break-up	Gully erosion	1.2; moderate 3; low	Not determined	As for sheet and rill erosion above	Increased sediment load.
Comments: -

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