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Hotham (Hm)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Hotham- geoArea: 309 sq. km (1.5%)

Steep mountainous terrain with ridge-and-ravine topography in the alpine and subalpine tracts is mapped in Hotham land system. Lithology varies and mountain peaks tend to be acute on Ordovician, Devonian and Silurian sediments and steeply domed on the Wellington Rhyolites and quartzites of the Snowy Plains Formation. Rocky outcrops and rockslides are common and at higher elevations solifluction lobes occur.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Hotham- graph
Exposed slopes, crests and scarps with open heath, herbfield and tussock grassland in the Mount Speculation area.

Active slope processes, a cold climate and high precipitation tend to produce soils which are shallow, stony,
friable and acidic with very high concentrations of organic matter in the topsoil and with little textural change down the profile. Slopes facing south-east and east appear to have the shallowest soils. Deeper soils, including remnants of old soil mantles, have been observed on north- and west-facing slopes. These soils have excellent infiltration characteristics but saturation at the surface and run-off can occur when the subsoil is frozen. Both surface erosion and slow, shallow mass movement (solifluction) can occur under these circumstances.

Disturbance of the highly organic topsoil by mechanical processes, such as the freeze/thaw of ice or by trampling, followed by drying can render it fluffy and vulnerable to wind erosion.

Most of the area is in the subalpine tract and carries a shrubby woodland I. On lower, more-protected sites or on areas that have been recently fired, the woodland may be replaced by shrubby open forest I or II or, in more exposed areas, by tussock grassland or open heath. Alpine herbfield occurs along with open heath and tussock grassland in the alpine tract.

CLIMATE
Rainfall, mean (mm)
Temperature, mean (C)
Seasonal growth limitations

Annual 900 - 1600; lowest January or February (70 - 100), highest August or September (150 - 180)

Annual 4 - 8; lowest July (-2 - 0), highest February (11 - 13)
Temperature <10C (av.): April - October
Rainfall < potential evapotranspiration: February; frequent winter snow
GEOLOGY
Age, lithology

Variable; commonly
Ordovician, Silurian and Devonian sandstones and shales; Carboniferous siltstones; Devonian rhyolites and some basalts
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

Steep mountains with ridge-and-ravine topography

1100 - 1860
80 - 540
Dendritic
0.6
PRESENT LAND USEUncleared: summer bush grazing of cattle; apiculture (limited); recreation — bushwalking, skiing

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

LAND COMPONENT
Percentage of land system
Diagnostic features
1
45
Exposed wooded slopes
2
40
Less exposed forested slopes
3
10
Treeless peaks and crests
4
5
Scarps and rockslides
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
30 - 50, (20 - 80)
Straight
30 - 50, (20 - 80)
Straight
10 - 25, (0 - 50)
Convex or straight
-, (>60 - occasionally vertical)
Straight
SOIL
Parent material
Variable; sandstone, shale, some rhyolite and basalt
Description
Commonly shallow and stony; friable black or very dark organic loamy sand to sandy clay loam merging into dark brown or dark greyish brown loamy sand to sandy clay loam
Rock outcrops and very stony soils
Classification
Lithosols, Alpine Humus Soils
Uc1.44,Urn 1.44, Um6.11, Um6.21, Um6.24, Um6.42
Lithosols
-
Surface texture
Variable, depends on parent rock; loamy sand to sandy clay loam
Surface consistence
Soft to slightly hard
Depth (m)
0.1 - 0.6(generally)
Nutrient status
Low to moderate
Available soil water capacity
Moderate to high
Perviousness to water
Moderate to rapid
Drainage
Good
Exposed stone (%)
Extremely variable;
commonly 30 - 60
>60 (generally)
Sampled profile number
-
-
-
-
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Woodland I:
E. pauciflora+, occasionally with
E. rubida
Shrubby open forest I, II:
E. pauciflora+ and/or E. rubida+
Predominantly tussock grassland of Poa spp. with open heath on drier sites
Alpine tract with open herbfield and, in eroded areas, feldmark of Ewartia nubigena
Mosaic of tussock grassland with Poa spp. and open heath of Hovea longifolia+, Oxylobium alpestre+ and O. ellipticum+

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
    Reduced transpiration,
    resulting in:

    a) increased deep percolation



    b) decreased fog drip



    c) increased rate of snow-melt


    d) increased depth of soil freezing




    Nutrient loss




    -



    -



    Solifluction




    Not determined




    -



    -



    1,2; low




    Not determined




    Not determined



    Not determined



    Not determined




    Removal of trees




    Usually after the removal of native vegetation


    Usually after the removal of native vegetation


    Usually after the removal of native vegetation




    Increased movement of water to groundwater; increased base-flow of streams

    Decreased stream base flow

    Increased spring and decreased summer

    -

    Increased exposure of surface soil
    Increased frost heave and soil detachment



    Increased overland flow and soil detachment
    Wind, sheet and rill erosion


    Sheet and rill erosion
    1,3; moderate
    2; low



    1,2,3; moderate
    Common: especially on exposed sites



    Common
    Burning, road and other earth-moving activities, trafficking by stock and humans

    Burning, road and other earth-moving activities, trafficking by stock and humans
    Increased overland flows, flash flows and sediment load


    Increased overland flows, flash flows and sediment load
    Increased physical pressure on soil
    Increased compaction

    With

    Reduced infiltration
    Structure decline


    Sheet and rill erosion
    1,23; moderate – high


    1,2,3; moderate
    Unknown



    Common
    Increased trafficking, overgrazing, export of organic matter

    As for sheet and rill erosion above
    -



    Increased flash flows
    Increased soil disruption
    Increased soil break-up
    Gully erosion
    1,2,3; high
    Uncommon
    As for sheet and rill erosion above
    Increased sediment load
    Comments: Compaction and soil disruption by stock has been observed in Component 3, resulting in severe erosion and recolinisation of the area by a feldmark of Euatina nubigena. Regeneration of vegetative cover is slow and difficult because of the unfavourable climate.
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