3
Mallee lands, characterised by multi-stemmed eucalypts, occur
across southern Australia, generally on wind-formed (aeolian)
landforms, with sandy soils.
Mallee rangelands occur in the 250 to 380 mm rainfall zone.
However, drought is a fact of life in these areas, and the rainfall will
often be less than 100 mm per year. The rainfall tends to fall mainly in
winter in the southern areas, while in the northern mallee areas
(between Ivanhoe and Cobar) rainfall is more evenly spread throughout
the year.
This diagram
shows just how
frequently
droughts have
occurred. We
must expect them
to continue
occurring
regularly.
Siliceous Sand
Calcareous Earth
Another feature that occurs repeatedly in the mallee is fire¾in
fact, mallee is a fire-promoting vegetation type. Major wildfires raged
through large areas of the mallee during the summers of 1957-58,
1964-65, 1974-75, 1976-77 and 1984-85.
In general, mallee soils erode readily once stripped of vegetation
and are low in fertility. The soils on the dunes tend to be sands,
whereas in the swales and plains calcareous red or brown earths are
more common.
The mallee in western NSW is most commonly used for gazing,
although some areas with higher and/or more reliable rainfall have
been developed for cropping. Another significant land use is
conservation of the mallee habitat and land type. In fact, about 1800
km2 or almost 10% of the mallee in NSW is conserved in National
Parks and Nature Reserves. Other land uses in the mallee include
honey production, eucalyptus oil production and harvesting of
broombush for brush fencing.
4
The Mallee Ecosystem
Like many rangeland types, the mallee ecosystem is very
resilient in the face of changes such as drought, fire, rainfall and
even grazing. Changes occur in the quantity and diversity of the
vegetation, but they are rarely permanent.
Mallee trees dominate the vegetation in mallee communities. They
have very deep root systems (roots have been found at depths of 28 m)
and are thus able to obtain soil moisture at depth. This means that their
growth rate is not affected by individual wet or dry periods. In fact,
unlike the more shallowly rooted herbaceous species, mallee eucalypts
tend to grow in summer, even though this is the drier season. The
herbaceous species commonly grow from early autumn to late spring.
The sandy soils of the mallee country tend to favour mallee trees rather
than herbaceous plants because most of the water in the soil is found at
depth rather than near the surface. As well, mallees concentrate rainfall
down their stems to the base of the tree, to such an extent that the
amount of water in the soil around the base can be up to ten times
higher than the actual rain received. Mallee eucalypts therefore
suppress the herbaceous (or pasture) layer in all except wet periods.
Consequently, following a fire, it is possible for the pasture layer to
flourish for a period of time in the absence of competition from the
mallee trees. It is probable that in 'pre-European times’ fire was a more
frequent event than it is today. It has been suggested that if fire were
more frequent now, dense stands of woody shrubs would be less
common, since they are susceptible to fire when young.
Mallee Eucalypts
· pointed mallee (Eucalyptus socialis) and congoo mallee
(E. dumosa) are the most common species
· trees are usually multi-stemmed. The stems or trunks
increase in size yearly in the absence of fire
· main growth period is in summer (October to March)
· litter production is highest in summer
· regeneration is usually from lignotubers (the 'mallee root')
rather than from seed
· seedlings are suppressed, developing mainly after some form
of disturbance - for example, a spring burn followed by good
autumn rain
· highly resilient to natural or wildfire; even if above ground
part of plant is completely burnt, shoots are produced from the
lignotuber
· repeated autumn burns (carried out whenever there is
sufficient fuel - i.e., every four to five years in open mallee
containing speargrass) will reduce mallee density
Mallee Eucalypt - Yorrel
5
Common Mallee
Big Mallee
Mallee Types
Mallee can be classified into many different types according to
different criteria. The types that follow are only one way of classifying
the mallee, based on the type of mallee trees occurring and what other
plants occur with them.
COMMON MALLEE is the most widespread type occurring
in NSW It consists of low, multi-stemmed mallee trees (Eucalyptus
spp.) which are closely spaced. When very dense and low, it is
known as 'whipstick' mallee. Associated trees include sugarwood
(Myoporum platycarpum), rosewood (Heterodendrum oleifolium),
needlewood (Hakea leucoptera) and butterbush (Pittosporum
phylliraeoides). Wattles (Acacia spp.), cassias (Cassia spp.), turkey
bushes (Eremophila spp.), hopbushes (Dodonaea spp.) and other
woody shrubs are also usually present.
BIG MALLEE is dominated by larger 'bull' mallee trees. The
shrub storey is often sparse. Saltbushes (Atriplex spp.) and bluebushes
(Maireana spp.) may be present. In wet years speargrasses (Stipa
spp.) can become abundant. This type of mallee country is reasonably
good grazing country and can be cheaply improved by burning.
SALTBUSH MALLEE is similar to Big Mallee but good
stands of saltbushes (Chenopodium spp. and Atriplex spp.) or
bluebushes (Maireana spp.) are present.
PORCUPINE GRASS MALLEE typically occurs on the sandy
infertile soils of dune crests and extensive inter-dune sand plains. The
understorey is dominated by porcupine grass (Triodia irritans). This
type is unsuitable for clearing because of its highly erodible soils.
SCRUB MALLEE supports a moderate to dense understorey of
shrubs such as broombush (Melaleuca uncinata) and occurs
throughout but is most common in the higher rainfall areas.
Saltbush Mallee
Scrub Mallee
Porcupine Grass Mallee
6
IMPORTANT SPECIES IN THE MALLEE
Of the 270 or so species recorded in the mallee of western
NSW, some have particular significance to the rangeland manager.
Some are important for forage, others are weeds, some have value
as soil binders, and the presence of others can reveal something
about the condition of the pasture. Some examples:
Dodonaea attenuata (narrow-leaf hopbush)
· a mufti-stemmed shrub occurring mainly in open areas and
on abandoned cropping paddocks
· a woody weed - suppresses pasture production and
reduces carrying capacity
· may be browsed, especially by cattle, when other forage is
absent
· seedlings are susceptible to drought and commonly die
during their first or second dry summer
· fire can kill adult plants, and does kill seedlings, but also
promotes germination of seeds
· fire can be used to control invasion of this shrub if there
is sufficient grass fuel, particularly when the plants are
young
· follow-up burns are necessary to control emerging
seedlings
· grazing management is important following fire - seedlings can
be stressed by allowing large quantities of grass to remain over
dry summer periods
· control of outlying shrubs, particularly those less than 1 m tall,
is important in limiting speed of invasion
· large-scale infestations can be controlled on areas where
regular cropping is possible
Dodonaea attenuata
Narrow-leaf Hopbush
Melaleuca uncinata (broombush)
· a mufti-stemmed shrub occurring mainly on the deep red sandy
soils and loams of the eastern mallee lands
· regenerates after fire, shooting from ground level not grazed by
stock
· harvested for brush fences
Sclerolaena diacantha (grey copperburr)
· short-lived perennial plant grows throughout the year,
particularly in the warmer months, if moisture is available
· highly resistant to drought
· responds to isolated rainfall events
· a major herbage species after fire
· good drought forage
Sclerolaena diacantha
Grey copperburr (Photo:
Plants of Western NSW)
Melaleuca uncinata
Broombush (Photo: NPWS)
7
Stipa spp. (speargrasses)
· previously known as 'variable speargrass; there are now a number of
separate species recognised
· short-lived perennial grasses, growing mainly in winter or after
good summer rains
· can respond to rain during any season
· shoots from the butt for a number of years if seasons are suitable
· palatable and good feed when actively growing, that is, in
winter or after summer rain
· seeding generally occurs in spring and early summer
· following a good growing season, seeds can be a serious
problem to stock health, lodging in the eyes, lips and skin
· prolific winter growth is likely to carry over into summer and
provide fuel for fires
Triodia irritans (porcupine grass)
· a hummock-forming grass
· common on dune crests and sandplains but occurs throughout the
mallee
· growth occurs mainly in spring and summer or after fire
a fire-promoting species
· a useful binder of sand dunes
· its presence is an indicator of very sandy soil which is liable
to drift if cleared.
Other species of importance or abundance in the mallee
include:
Stipa sp.
Speargrass
(Photo: Plants of Western NSW)
Asphodelus fistulosus
Atriplex stipitata
Dissocarpus paradoxus
Enchylaena tomentosa
Goodenia spp.
Haloragis odontocarpa
Maireana pentatropis
Myoporum platycarpum
Zygophyllum apiculatum
Triodia irritans
Porcupine grass
onion weed
bitter
saltbush
cannon ball
ruby
saltbush
goodenias
toothed
raspwort
erect mallee
bluebush
sugarwood
gall weed
weed
forage, including
during drought
forage, including
during drought
forage, including
during drought
pasture
forage, particularly
after fire
drought forage
fodder tree
forage
8
GRAZING
There are several grazing systems that can be used on mallee
lands; however, it isn't possible to recommend just one for general
adoption. This is because of the different situation on each property,
with regard to both improvements (water, fences, etc.) and mallee
types.
Continuous grazing needs a permanent supply of water. When
used in paddocks containing more productive open country as well as
areas of dense mallee, stock generally tend to graze the open country.
Whenever there is a flush of pasture growth, they move into the mallee
as well. This results in a form of opportunistic grazing, which is when
the mallee is stocked only in good seasons when there is plenty of feed
and water. Opportunistic grazing is possibly the most commonly used
grazing system in the mallee.
Forms of rotational grazing are not widely accepted in the mallee
and there is no documented evidence as to which is more appropriate.
Some graziers practise drought reserve grazing, allowing stock to graze
the mallee during droughts once the more productive open country on
the property has been used. The logic behind this is that the open
country is rested when it needs it most - i.e., during drought - and
during good seasons the mallee has a chance to recover. However,
other graziers believe that the mallee will be eaten out by vermin
during good seasons if it is not stocked. Some graziers use every
opportunity to burn 'porcupine grass mallee: Any rain that falls will
then produce far more feed in these sites than on the heavier soils in
more open mallee. Summer grazing is also practised. In general stock
can be mustered on water points; however, in wet or humid summers,
when mustering is more difficult, flystrike may result in heavy stock
losses. Take care also during high-fire-risk summers not to place stock
in potentially dangerous situations.
For graziers with significant amounts of other types of
country, or who have mixed farming enterprises, there is the
option of not using the mallee at all, particularly if it is unwatered
or difficult to water.
Stocking Rates and Carrying Capacities
One of the few aspects you can alter to influence the health and
composition of your pasture is the stocking rate. General experience in
semi-arid lands has shown that lighter stocked properties are more
profitable in the long run than more heavily stocked ones. Actual
stocking rates vary according to the type of mallee. Porcupine grass
mallee has the lowest rates with estimates of one sheep to fifteen to
twenty hectares or even lower if there are dense woody shrubs.
Saltbush mallee can carry slightly higher numbers, but the most
productive is Big Mallee with about one sheep to ten hectares. Higher
stocking rates are possible when other rangeland types occur within the
mallee.
Carrying capacities are the numbers of animals that can survive the
greatest period of stress each year on a given land area without causing
degradation. Soil conservationists are available to assess the carrying
capacity of your property if desired. In doing so, they take into account
rainfall, soil characteristics, drought forage, pasture, tree and shrub
cover and property improvements. If stocking rates are adjusted to the
suggested carrying capacity, the country will stay in good condition for
up to twelve months into a drought. Further adjustments (destocking)
will be required to maintain the country in good condition if the
drought continues longer than twelve months.
For more information on low-risk stocking and grazing rates,
see Range Notes 1 and 2, produced by the Soil Conservation
Service.
9
Drought
No-one in the mallee can avoid drought; however, it is possible
to plan for it and reduce its total cost. Being prepared for a drought knowing when to destock, etc. - can make life a lot easier. Make
decisions related to drought as early as possible. Keep stocking rates
low enough during good years to ensure that grasses and drought
forage are not depleted. Resist the desire to restock immediately
following a drought as the risk of degradation to pastures is
highest at this time.
Dense speargrass growth
following rain
Grass Seeds
Grass seeds become a problem to stock following
particularly wet seasons. Speargrasses produce sharp seeds that
pierce the sheep's skin causing loss of appetite and condition. The
seeds can also accumulate under the chin and around the legs to such
an extent that they inhibit movement. The physical irritation to the
sheep can be so extreme that they may die of starvation or thirst
rather than track through dense speargrass areas. Solutions to this
problem include:
· deliberate overgrazing of small areas to prevent seeding
· slashing tracks through dense, mature stands so stock can
move between watering points and 'safe' grazing areas
· the running of cattle, which are reported to remove seed heads at
flowering time
· occasionally cropping paddocks in suitable areas, decreasing the
occurrence of speargrasses, and providing a refuge in 'grass seed
years'.
Mustering Problems
Mustering can be a time-consuming process in mallee
country because vision is limited by the dense vegetation. As
well, stock in mallee country tend to disperse into small flocks,
spread over a wide area.
There are several techniques that can be used to make
mustering quicker and easier. During hot, dry periods, stock can be
mustered off water points. In cooler periods, some graziers have
had success mustering along windward fencelines after two or three
days of continuous strong wind because sheep tend to graze into
the wind. Mustering is also easier if the mallee has been opened up
by fire or by mechanical means.
10
CLEARING/CROPPING
Clearing, either for cropping or for encouraging pasture growth,
is an option that in some cases may be worthwhile considering.
However, it is not always advisable to clear mallee. In many cases,
if there is other, more productive country available, the best idea is to
leave the mallee unused and concentrate on other country on your
property. However, if you do decide to clear some of your mallee
land, you must first apply to the Western Lands Commission, as all
clearing in the Western Division is subject to the Commission's
approval.
How to Clear
Mechanical clearing is usually carried out in winter. A common
method involves bulldozers linked by heavy chains. Bulldozing with
scrub rakes is also common. This is followed by windrowing, stump
removal and mechanised stick-raking. It is particularly important to
remove stumps if the land is being cleared for cropping.
(This gives more options with the type of tillage equipment you
can use.) Where clearing is for pastoral purposes only, the clearing
program may run over several years; if clearing is for cropping, it is
generally no more than three years from the start of clearing to the first
crop.
Another method of clearing is by using fire. In mallee
communities where speargrasses are abundant, a series of autumn
burns (say, three times in seven to ten years) will effectively thin the
mallee without causing the soil disturbance associated with
mechanical clearing. More details on clearing mallee using fire can
be found in the following section.
Several phases are needed in the clearing process to
overcome the repeated regeneration of the mallee tree from
lignotubers (stumps).
Where to Clear
There are a number of points to consider when deciding where
on the property to clear. Firstly, any mallee on dunes should not be
cleared at all - the soil on dunes is very sandy and unstable if exposed
and may erode if the protective vegetation is removed. Also, the dunes
are the least fertile areas and can conserve only very low amounts of
water. Mallee on swales and flats is more suited to being cleared.
Other points to consider include:
• proximity to the homestead (due to the possibility of dust
during clearing and cultivation)
• ease of watering
• proximity to sources of vermin (which can damage crops)
• accessibility to transport (if intending to crop the cleared land).
Big mallee is more easily cleared than the denser whipstick
mallee. In fact, dense whipstick mallee is rarely cleared other than for
specialised purposes, such as laneways for ease of mustering or
through speargrass-affected areas and clearing for fencelines or for
holding paddocks.
It is important to retain shelterbelts around cleared areas. They
help reduce wind erosion and also act as reserves for native species,
including forage plants. The Western Lands Commission imposes
conditions regarding width, location, etc., of shelterbelts. Copies of the
schedule of conditions are available from the Western Lands
Commission.
Benefits of Clearing
When correctly carried out, clearing and cropping can:
• generate additional income
• help control woody weed infestations
• permit easier access for fire control
• provide opportunity for more productive pastures to be
sown
Erosion caused by clearing
and cropping
11
· increase carrying capacity
· help control vermin by removing habitat provide drought
· fodder if some of the crop is stored, either as hay or grain
· reduce grass seed problems.
Limitations
Because clearing and cropping alters the natural soil/vegetation
balance so drastically, there are a number of limitations, besides
salinity, to be aware of. The first, and most important, is that clearing
can lead to soil erosion if cleared land is not managed properly.
Poor management practices include bare fallowing (rather than
stubble retention) and the overgrazing of pasture between crops.
Erosion will also occur if the crop fails or if it is not sown once the
initial cultivation has produced a bare surface. Cultivating at high
speed using conventional tillage methods also encourages soil erosion
by damaging what little natural soil structure there is. Successful
opportunistic cropping in these areas ultimately depends on
equipment that retains, rather than destroys, vegetative residues.
Change in the pasture composition is another form of
degradation that can accompany clearing and cropping. The useful
native perennial species decline and are replaced by annuals (often
weeds) and less useful perennials. This results in less protection of the
soil during dry periods, which are regular features of western NSW.
One of the problem perennial weeds that invades is onion weed. It
becomes more abundant with both irregular cultivation and
overgrazing.
Salinisation is a third form of degradation that may occur as a
result of widespread clearing. The effect of mallee clearing on soil
salinity and groundwater levels has not yet been fully determined, but it
has been shown in Victoria and South Australia that clearing on some
sandy soil types increases waterflow to groundwater systems by up to
300 times. Although water tables in NSW are still mainly 20 m or more
below the surface, there is concern among scientists that widespread
clearing could see water tables rise to the level where productivity
could be seriously and permanently affected, particularly along the
Murray River.
× Erosion caused by clearing and cropping
× Invasion of punty bush
following cropping of
cleared land