Stewart (Sw)

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

Area: 41 sq. km (0.2%)

Extremely silty areas of Tertiary and adjoining Devonian sediments have been mapped in Stewart land system. These areas have rounded hills with moderate slopes and some undulating terrain. Broad alluvial floors in concave valleys are fed by seepage from the hills and carry water all year. These floors are characteristically swampy, with peaty surface materials. A diagnostic feature of this land system is the heathy nature of the vegetation which occurs on most of the slopes despite the relatively high rainfall. The silty and clayey parent materials and the moderate to gentle slopes have promoted the development of duplex and gradational soils. These have been strongly leached and are strongly to moderately acidic. The very high silt contents often result in poor internal drainage and this, along with the common, extremely low nutrient contents, leads to the heathy vegetation. Land with moderate slopes and slowly pervious soils is likely to cause a higher proportion of surface run-off, increasing the erosion risk. The badly-eroding road batters indicate that the soils are highly susceptible to erosion.

The vegetation is often a heathy open woodland I or heathy woodland I, though open forest II occurs on better sites. Well-drained alluvial terraces support open forest II or III, often layered or shrubby while swampy drainage areas have a closed scrub or shrubby woodland I.

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

Closed scrub of Melaleuca squarrosa (scented paper-bark) and Gleichenia microphylla (scrambling coral fern) growing in a seepage area

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 - 10), highest February (19 - 21) Temperature <10°C (av.): May - September Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Mainly Tertiary silts and clays; minor Devonian sandstones, siltstones and mudstones
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Rounded hills and undulating terrain with broad swampy valley floors 100 - 280 60 - 120 Dendritic 1.8
PRESENT LAND USE	Mostly uncleared: hardwood forestry (minor timber products); apiculture Minor proportion cleared: grazing of beef and dairy cattle on improved pastures

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

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Anderson1 - graph

LAND COMPONENT Percentage of land system Diagnostic features	1 45 Slopes with very silty soils and heathy woodlands	2 35 Slopes with silty soils and forests	3 15 Swampy drainage depressions	4 5 Well drained terraces
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	15 - 20, (5 - 30) Convex and concave	15 - 20, (5 - 30) Convex and concave	<1, (0 - 2) Straight	<2, (0 - 5) Straight but uneven
SOIL
Parent material	Silt and clay; minor sandstone, siltstone and mudstone		Alluvium and plant debris	Alluvium
Description	Dark greyish brown sand to silty loam topsoil, abrupt or gradual change to mottled, yellowish brown or yellow, generally blocky structured clay (sometimes sandy clay loam) subsoil		Black organic loam over variable mottled grey mineral layer; shallow peat in places	Single observation — probably undifferentiated brown stratified soils, often mottled at depth
Classification	Yellow Podzolic Soils, Yellow Earths Dy3.41, Dy5.21, Gn4.81		Humic Gleys, Acid Peats Uc1.41, O	Alluvial Soils/Yellow Earths Um2.3-
Surface texture	Sand to silty loam		Loam	-
Surface consistence	Soft to hard when dry		Friable to firm when moist	-
Depth (m)	>1.0		>2.0	>2.0
Nutrient status	Extremely low	Low to moderate	Low to moderate	Low to moderate
Available soil water capacity	Low to moderate	Low to moderate	Moderate to high	Variable
Perviousness to water	Slow	Slow	Variable	Variable
Drainage	Poor to somewhat poor	Somewhat poor to moderately good	Very poor to poor	Somewhat poor, in places good
Exposed stone (%)	0	0	0	0
Sampled profile number	53	-	-	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Heathy open woodland I, heathy woodland I: E. consideniana+ and/or E. cephalocarpa+	Open forest II: E. consideniana+; E. obliqua+, E. radiata+ in areas of better drainage	Closed scrub: Melaleuca squarrosa Shrubby woodland I: E. ovata+, E. radiata, with an understorey of Melaleuca squarrosa and/or Leptospermum spp.	Limited data — probably shrubby or layered open forest II, III: E. obliqua+ with E. viminalis and E. radiata observed; E. ovata presumed

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	1,2; moderate - high	Uncommon	Clearing, logging, burning, overgrazing, road 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	1,2,4; moderate 3; high 1,2; moderate - high	Uncommon Uncommon	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 Streambank erosion	1,2; high 4; moderate	Uncommon Uncommon	As for sheet and rill erosion above As for sheet and rill erosion above	Increased sediment load Increased sediment load
Comments: Road batters are prone to collapse and erode, probably aided by perched water tables and lateral seepage. Some minor salting may occur to the east of Newry.

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