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La Trobe (Le)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system La trobe- geoArea: 707 sq. km (3.5%)

La Trobe land system is mapped on hilly terrain with Ordovician, Devonian and Silurian sediments. It occurs mainly in the south-west of the East Victorian Uplands. Topography is of the ridge-and-ravine type although some ridge crests are rounded; slopes are steep and moderately long. This land is similar geologically and topographically to the Wonnangatta land system but is much more humid.

Deep, well-structured soils result from the combination of high rainfall, medium- and fine-grained sedimentary rocks and less-active soil creep. Both gradational and duplex type soils are common, with the former probably dominant. The soils tend to be leached, acidic and probably of low fertility.

Shrubby open forest II predominates. The vegetation on protected slopes or in local drainage depressions varies from shrubby or layered open forest III or IV to closed fernland.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system La trobe- image
Timbered hillslopes, typical of La Trobe land system, with cleared alluvial terraces in the foreground.

    CLIMATE
    Rainfall, mean (mm)
    Temperature, mean (C)

    Seasonal growth limitations


    Annual 800 - 1400; lowest January or February (50 - 90), highest August or September (120 - 180)

    Annual 8 - 12; lowest July (3 - 7), highest February (16 - 20)

    Temperature <10C (av.): April - October
    Rainfall < potential evapotranspiration: January, February; occasional winter snow

    GEOLOGY
    Age, lithology
    PHYSIOGRAPHY
    Landscape
    Elevation range (m)
    Relative relief (m)
    Drainage pattern
    Drainage density (km/km2)

    Steep hills with ridge-and-ravine topography

    100 - 1080
    100 - 260
    Dendritic
    1.3
    PRESENT LAND USE

    Mostly uncleared: hardwood forestry (minor timber products); apiculture; bush grazing of cattle.

    Minor proportion cleared: grazing of dairy and beef cattle

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system La trobe- csA study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system La trobe- graph

LAND COMPONENT
Percentage of land system
Diagnostic features
1
75
Exposed slopes
2
10
Protected slopes
3
5
Broad rounded ridge tops
4
5
Peat and organic
deposits in seepage-fed
minor drainage depressions
5
5
Terraces along
major valley flats
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
20-25, (10 - 60)
Straight
20 - 25, (10 - 60)
Straight
5 - 10, (0 - 15)
Convex
<2, (0 - 5)
Concave
<2, (0 - 5)
Straight or concave
SOIL
Parent material
Mudstone, siltstone, sandstone and shale
Locally derived alluvium and colluvium
Mixed alluvium
Description
Generally dark sandy loam to sandy clay loam topsoil with crumb structure; yellowish brown or red clay subsoil, acidic and usually with medium blocky structure. Occasionally shallow and stony; profiles gradational or duplex
Shallow peat and mineral soils with high surface organic matter
Variable; red gradational
soils; brown undifferentiated
stratified sand to
sandy clay loams
Classification
Yellow and Red Podzolic Soils, Lithosols
Gn4.11, Gn4.81, Gn4.51, Gn4.64, Gn2.81, Gn3.34, Dy3.21, Dy3.41, Dy5.21, Um4.13, Um6.46
Brown Earths, Acid Peats
Gn4.52, O
Alluvial Soils, Red Earths
Gn2.41, Um6.14, Uc1.41
Surface texture
Fine sandy loam to clay loam
Sandy loam to clay loam
Sand to sandy clay loam
Surface consistence
Slightly hard when dry, friable when moist
Friable when moist
Variable
Depth (m)
0.8 - 2.0, in places very shallow
>2.0
>2.0
Nutrient status
Low
Low
Low
Available soil water capacity
Moderate
Moderate
Variable
Perviousness to water
Slow to moderate
Moderate
Moderate to rapid
Drainage
Good
Very poor to poor
Often good
Exposed stone (%)
Generally 0
0
0
Sampled profile number
-
-
-
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Shrubby open forest II: E. sieberi+, E. obliqua+; one or more of E. baxteri E. cypellocarpa, E. radiata, and E. dives usually associated
Shrubby or layered open forest III: E. cypellocarpa+, E. obliqua+, usually with E. radiata, E. sieberi
Shrubby or layered open forest II: E. cypellocarpa+, E. obliqua+, E. sieberi, sometimes E. consideniana+
Limited data — probably closed fernland of Dicksonia antarctica
Open forest III, IV, often layered: E. viminalis+, E. cypellocarpa, E. obliqua, E. radiata

Disturbance
Affected process and trend
Primary resultant deterioration
Casual activities
Primary off-site process
Form
Susceptibility of components
Incidence with components
    Alteration of vegetation:
    — reduction in leaf area, rooting depth and/or perenniality
    — reduction in density of tree roots
    Reduced transpiration,
    resulting in increased
    deep percolation



    Decreased root-binding
    Nutrient loss





    Soil creep
    Not determined





    1,2; moderate
    Not determined





    Uncommon
    Removal of trees





    Accelerated by major disturbance of the native vegetation
    Increased movement of water to groundwater; increased base-flow of streams


    Increased sediment load
    Increased exposure of surface soil
    Increased overland flow and soil detachment
    Sheet and rill erosion
    1,2,3; moderate
    Uncommon
    Clearing, logging, burning, overgrazing, road 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
    1,2,3; low - moderate
    4; high


    5; moderate
    12,3; moderate
    Uncommon



    Uncommon
    Increased trafficking, export of organic matter


    As for sheet and rill erosion above
    -



    Increased flash flows
    Increased soil disruption
    Increased soil break-up
    Gully erosion


    Streambank erosion
    12,3; moderate


    5; high
    Uncommon


    Uncommon
    As for sheet and rill erosion above

    As for sheet and rill
    erosion above
    Increased sediment load


    Increased sediment load
    Comments: Soil creep has been observed on a steep slope in this land system
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