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DYNAMIC ECOSYSTEMS
BACKGROUND INFORMATION
These notes provide teachers with some background information of the area
and the sites their students will study in a booked visit.
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The forest communities of Healesville have a temperate climate with warm dry summers and a tendency for
maximum rainfall in winter. The weather systems move from west to east, producing a cycle of weather starting
cool, warming up, and rapidly becoming cool again. Although variable, the cycle is usually five to seven days in
length. Landform combines with the westerly frontal systems to account for the predominant pattern of rainfall.
The average annual rainfall in Healesville is 1023mm which reflects its position and elevation (140m) between
the higher peaks like Mt. St. Leonard (603m) with 1375mm and Melbourne (20m) with 655mm.
The geology of the area dates back to the Cambrian period when extrusions of submarine volcanics were followed by extensive marine sedimentation in deep oceanic troughs (geosynclines) resulting in the formation of
mudstones, shales and sandstones. This continued through the Silurian to early Devonian periods (370 million
years ago) and has had a significant impact on the current vegetation by virtue of its low nutrient content.
This was followed by a sustained period of regional instability in which silica-rich volcanic lavas were extruded to
produce the particularly resistant masses which now make up the Dandenongs and mountain massifs between
Healesville and Snobs Creek.
Following the Pleistocene Period (around 2 million years ago) the modern creeks and rivers have dissected
these sediments and eroded wide valleys, in which relatively thin layers of alluvial sediments have been deposited. The Sanctuary itself lies on a thin bed of these sediments.
In response to the generally infertile soils which are low in nitrogen and phosphorus, most plant groups in this
region have developed proteoid roots which are very efficient at absorbing water and nutrients. Those plants
possessing this ability are known as sclerophyll. They are strongly represented in the Australian plant families
of Myrtaceae (tea-trees and eucalypts) and Proteaceae (grevilleas, hakeas and banksias) whose characteristics
include leathery hard, spiny or reduced leaves and relatively short internodes. These plant features are an evolutionary response to poor soils, but also appear to have been a pre-adaption for the drier conditions that now
dominate the Australian environment since its separation from Antarctica and northward drift. This separation
and subsequent drying out has lead to a radiation of suitably pre-adapted plants that has resulted in over 85%
of Australian vascular plants being endemic (found only in Australia).
Australia’s forest communities are dominated by two main genera: Eucalyptus and Acacia. The first, Eucalyptus
contains around 600 species ranging from the tallest flowering plant in the world, Eucalyptus regnans exceeding
100 metres in height and 500 years in age, to some of the smallest trees in the world; Mallee eucalyptus that
are sometimes less than 0.5 metres in height. The diversity can be illustrated by the extensive range of habitats
which include alpine, desert, semi-tropical, tropical, swamp, coastal, montaine and plains. Acacias often accompany eucalypts in forests benefiting from the shelter provided by the Eucalypt canopy. An ancient genus, acacias pre-date the breakup of the southern super continent Gondwana (around 65 million years ago) and have
speciated more extensively than any other flowering plant genus in the world. In the grip of Australia’s driest
period some 10,000 years ago, acacias even replaced eucalypts throughout much of the dry centre of Australia.
The typical forest structure of the Healesville area consists of a:
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canopy
usually dominated by eucalypts, the crowns of which sometimes touch
sub-canopy
understory often consisting of acacias and hazels
shrub layer
can include tree ferns and broad leafed plants ranging from 2 to 4 metres in height
© Zoological Parks and Gardens Board of Victoria 2006— These sheets may be reproduced for teaching purposes. Permission to
reproduce them for other purposes may be obtained from the Zoological Parks and Gardens Board of Victoria.
Dynamic Ecosystems - Background Information
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ground layer
consisting of grasses, herbs, sedges and rushes, tending to be no higher than 1 metre in height
The 174 ha. managed by Healesville Sanctuary contains four distinct vegetation communities:
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Riparian (Badger Creek) Zone
Eucalyptus viminalis and Pomaderris aspera
Floodplain Zone
E. viminalis, Acacia melanoxylon and A. dealbata
Wetland Zone
E. ovata and Melaleuca spp.
Dry Ridge Zone
E. rubida and E. radiata
The location of these plant communities is dependent on several interlinked abiotic factors:
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soil type
hydrology (water table, etc)
aspect
The local environment has undergone considerable change since the arrival of non-indigenous Australians over
200 years ago. The following describes some of the changes that have occurred to the land on which the
Sanctuary is situated.
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Dotted around the area you will note old stumps which indicate that the eucalypts here were logged
around or before the turn of the century
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the absence of signs of a recent bushfire, which is a major natural trigger to spontaneous bush
regeneration and plant community health. The last bushfire burnt part of the Sanctuary in the early
1960’s. It is thought that a possible ecosystem management tool worth experimenting with here might be
regeneration burning on a controlled and limited basis
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ground compaction in the form of paths and roads has affected the water absorbing and aeration
capabilities of the soil with negative implications for plant health
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exhibit and other development works have had the effect of altering natural drainage patterns and
disturbing the root systems, particularly of the major canopy trees
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the invasion over the years of numerous problem exotic weeds has been exacerbated by the past
practice of planting many non-indigenous plants
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the installation of a weir diverting 80% of the flow of Badger Creek upstream from the Sanctuary has
severely altered the hydrology of the site
One notable effect of the above factors has been the extensive loss and fragmentation of the eucalypt canopy
with attendant flow-on effects impacting on the lower plant species and substantially depleting the site’s overall
biodiversity.
Dynamic Ecosystems - Background Information
Abiotic Factors
There are numerous factors involved in shaping the structure and composition of a community of plants and
animals. These include both abiotic (non-living) and biotic (living) factors. The abiotic factors that need to be
considered are:
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Soil structure, which refers to the arrangement of sand, silt, clay, organic matter and the spaces between
them. The structure of the soil will, to a large extent, dictate what plants will grow.
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Temperature directly influences evaporation rates and is most often related to light intensity. Environments
that consistently experience high temperatures are inhabited by animals and plants which have special
adaptations to cope with these temperatures. Eucalypts for example have leaves that hang down from the
tree thereby reducing the amount of midday sun falling directly on their surface.
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Humidity is a function of the air temperature, air movement (wind) and the amount of water available. The
presence of high temperatures and surface water increase humidity while the movement of air through a
community will decrease it. Ferns, for example, generally require humid environments and struggle to
survive when exposed to wind and high light intensity.
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Wind or the degree of air movement through different levels of a plant community can influence such
things as evaporation and seed dispersal. Increasing air movement translates to a decrease in humidity but
also an increase in moisture loss by plants principally through evaporation from the stomata. Plants such
as grasses also rely on wind to perform such tasks as fertilization and often seed dispersal. This is why so
few grasses occur in still, closed forests such as rainforests.
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Light intensity or the amount of light reaching various levels of the canopy, will influence the type and
growth rates of plants. Insufficient light for example is a limiting factor on the growth of grasses.
Vegetation Information
Marker species
The presence of some plant species is a good indication of certain ecological factors.
Riparian Community
Herb Layer
Fishbone Water Fern (Blechnum nudum)
Requires moist well-drained soil rich in humus.
Soft Water Fern (Blechnum minus)
Likes soil rich in humus but is quite adaptable.
Requires moisture, tolerates wet soil extremely well.
False Bracken (Calochlaena dubia)
Prefers permanently damp areas besides streams. Many animal ‘runs’ are located through and underneath these
ferns e.g. bush rats, swamp rats, bandicoots, wombats and wallabies.
Dynamic Ecosystems - Background Information
Shrub Layer
Soft tree ferns (Dicksonia antarctica)
Need plenty of water and prefer good cover from the canopy. They nearly always grow along watercourses.
Rough tree-ferns (Cyathea australis)
Need plenty of moisture but nowhere near as much as soft tree ferns. They can also tolerate more exposure to
the sun.
Sub Canopy Layer
Hazel Pomaderris (Pomaderris aspera)
Common near streams and on previously disturbed sites i.e. floods, fire etc.
Canopy Layer
Manna Gum (Eucalyptus viminalis)
Moist but well-drained areas such as along Badger Creek. Many old specimens have numerous hollows for
potential possum and bird homes.
Floodplain Community
Herb Layer
Saw Sedge (Gahnia radula)
Forest Wire Grass (Tetrarrhena juncea)
Mat-rush (Lomandra longifolia)
Tussock Grass (Poa labillardieri)
Fire weed (Senecia linearifolius) seasonal, not winter
All of these species like moist soils and are tolerant of poor drainage, though permanent soil water logging would
cause their demise. These tangled mixed herb layers are important food sources and shelter sites for many of
the smaller ground-dwelling animals.
Shrub layer
Prickly currant Bush (Coprosma quadrifida)
Moist - well drained soil in wet and damp sclerophyll forest.
Sub Canopy Layer
Silver Wattle (Acacia dealbata)
Prefers deep moist soil in wet, damp and valley sclerophyll forests.
Blackwood (Acacia melanoxylon)
Prefers deep moist soil.
Canopy Layer
Manna Gum
Prefers deep moist soil.
Dynamic Ecosystems - Background Information
Ridge Top Community
Herb Layer
Velvet Tussock Grass (Poa morrisii)
Well-drained soils in dry and valley sclerophyll forests.
Grey Tussock Grass (Poa sieberiana)
Canopy Layer
Narrow-leaved Peppermint (Eucalyptus radiata)
Found in the foothills where drainage is very good and summer conditions can be very dry.
Red Stringybark (Eucalyptus macrorhyncha)
Also a foothills plant.
Animal Species
A variety of animal species inhabit the three vegetation communities present on the Coranderrk Nature Trail.
Some inhabit more than one community while others like the ones described below will be specialised to the
degree that they are generally only found in one particular community.
Yellow-bellied Glider (Petaurus australis)
Found only in Manna Gum (Eucalyptus viminalis) and mostly along margins of the creek in this forest.
Manna Gum (Eucalyptus viminalis) provides large enough hollows for these large possums and also provides a
large portion of the animal’s food requirements i.e., leaves.
Bush Rat (Rattus fuscipes) & Swamp Rat (Rattus lutreolus)
Two local rat species are commonly found in the Manna Gum forest. (Floodplain and Riparian vegetation
communities) Swamp Rats prefer the ground cover to be dense and to consist of grasses and sedges which form
part of their diet. Bush rats are more commonly found where the cover is made up of ferns or bushes such as
those found along Badger Creek. Both these ground cover types are found in the Manna Gum forest.
Swamp Rats are also found in areas of the Peppermint forest (Ridge-top Community), where the ground flora is
very thick.
In the Peppermint Gum forest there is less stratification in the tree canopy compared to the Manna Gum forest.
This, and the lack of heavy ground cover, reduces the diversity of mammals found there.
There is also less tendency for Narrow-leaved Peppermint (Eucalyptus radiata) to form hollows and this is another
factor which reduces the number of mammal species found there.
Eastern Whipbird (Psophodes olivaceus)
Found in Manna Gum forest and particularly, because of their preference for a dense understorey, in the fern belt
along the creek.
Grey Fantail (Rhipidura fuliginosa)
In Manna Gum forest especially when open areas are bordered by Silver Wattle (Acacia dealbata). The
degeneration of Silver Wattles may have some implications for this species. These wattles are short-lived (up to
40 years in this area) and require fire for regeneration - an interesting management problem.
White-throated Treecreeper (Climacteris leucophaea)
Spend most of their time in the Narrow-leaved Peppermint (E. radiata) even though they can occasionally be seen
in the Manna Gums (E. viminalis). They have adapted to seeking their food in the many crevices and tangled
fibres of the bark on the Narrow-leaved Peppermints’ (E. radiata) and Stringy Barks (E. macrorhyncha).
Copperhead Snake (Austrelaps superbus)
Are also found in the Manna Gum forest due to the preference of their prey for damper conditions, i.e. frogs, small
ground mammals and small reptiles.
Dynamic Ecosystems - Background Information
Common Froglet (Crinia signifera)
Can often be heard calling in the Manna Gum forest in sections of the floodplain that are low lying and often
quite damp.
Invertebrate Species
Land Yabbies (Engaeus sp.)
These are all found in the Manna Gum forest and in particular along the creek line. The presence of terrestrial
yabbies is obvious as indicated by the large cones thrown up from their diggings (particularly on the pathway
adjacent to the creek). These animals dig down to the water table (not far in this area) where they create a
chamber in which to live. They filter the water in their chamber to obtain food.
Some Management Problems at Healesville Sanctuary
We employ similar studies to those carried out by the students participating in the Community Studies program
to monitor the bushland here at the Sanctuary.
There are a few problems that we need to monitor closely, such as:
Bell Miner / Psyllid insect infestation
Forest regeneration (and controlled burning)
Phytophthora (cinnamon fungus)
Common Brushtail Possum
Bell Miner/Psyllid insect infestation
Psyllids are insects that feed by extracting sugars from plant leaves. They also construct protective cones over
themselves (lerps). The cone, or lerp, is white and made of sugar.
In large numbers, the psyllid insects put great pressure on the trees. If the trees are already stressed by
something else (e.g. fungal attack, modified drainage patterns), they can die. The bell miners complete the
picture as they often eat the sugary lerps of the insects but generally leave the insect. This causes the insect to
extract more sugar to rebuild the cone. Bell miners are also very territorial birds and will chase other birds out
of their territories. This means that birds that would normally feed on the psyllids are often absent and so major
insect infestation occurs and trees die.
Losing trees like this also opens up the canopy and makes the remaining trees more susceptible to wind
damage. We now believe that psyllid attacks usually occur on already weakened trees.
Stressor (Phytophthora)
psyllid attack
bell miners
increased psyllid attack
death of
trees.
One method which was employed to deal with this particular management problem was to reduce the Bell Miner
population inhabiting the area. The birds were continually disturbed and nests destroyed during the breeding
season. As a result the bell miner population in the area reduced in size and other species of birds that had
been driven out of the area by the very territorial bell miners returned. Unlike the miners many of these birds
when feeding on the lerps on the leaves of the trees also eat the pysllids. This has had the effect of reducing
the pysllid infestation of the trees and in turn slowed down the process of dieback that was occurring.
Forest Regeneration
Fires are an integral part of the ecology of most of our native forests. The forest at Healesville is no exception.
Control burns are conducted in various parts of the forest at different times. Most burns are conducted in late
March/early April when winds, temperature, and fuel (dead wood, etc.) are deemed to be at appropriate levels.
This stimulates regrowth.
The last time a fire passed through the Coranderrk Nature Trail was in 1961. It is currently under consideration
to do control burns in sections of the Nature Trail and adjoining Coranderrk Bushland.
Macropod Grazing
Regrowth of young trees on the Nature Trail and in the Sanctuary has been affected adversely by the artificially
large numbers of free range macropods in that area that tend to crop off young growth.
Dynamic Ecosystems - Background Information
It was estimated that at least 30 Swamp Wallabies were inhabiting the 30 hectares of the Sanctuary and Nature
Trail. Under normal circumstances in the wild, an area of this size would be utilised by no more than three
wallabies. In 2000 the following management strategy was implemented. The majority of the wallabies were
caught up and transferred to nature parks seeking to acquire wallabies. Three wallabies were left on the site with
the existing male being vasectomised.
Phytophthora (Phytophthora cinnamoni)
Phytophthora (cinnamon fungus) is a fungal disease which in the past caused die-back in some eucalypts at the
Sanctuary. The effects of phytophthora can be seen in the eucalypts on the Coranderrk Nature Trail here at
Healesville Sanctuary.
It is not clear where the fungus came from originally. We suspect that it has always been in the soil but only
became a problem due to other ‘stressors’ on the trees causing an imbalance. Phytophthora moves with water
movement through the ground and is also transported by human activity, e.g. soil on shoes, or machinery with soil
on tyres, etc.
The disease does not affect all species of eucalypt to the same degree. Most species that are adapted to damper
conditions seem to be more tolerant of the disease. Phytophthora thus has serious implications for water and soil
movement here at Healesville. It is now believed that the imbalances which caused the phytopthora outbreak have
been fixed.
Common Brushtail Possum
Due to an over abundance of hollows (as well as shelter in buildings), and a plentiful food supply, brushtails have
increased dramatically in number. They eat the new growth on young saplings and, unfortunately, this eventually
kills the saplings. This presents a major problem for the revegetation program at the Sanctuary. Possible
solutions are currently being sought. Tree guards are being trialled.