Vegetation of the Australian Alps

cold air drainage basin

'Carpets of snow and silver daisies, gardens of yellow billy buttons and pink trigger plants, fields knee high in colour, stretching to the mountain's end.' (Dick Johnson, 'An Alpine Retrospective.' in Common Ground (1989), Department of Conservation, Forests and Lands, Victoria.)

This bright, colourful alpine scene hides from the casual observer the adaption and strategies that enable each plant to survive in its environment.

Alpine plants are highly adapted to growth in particularly harsh conditions.

Although most of the plant species of the alpine area are recognisably similar to those species growing in other areas of Australia, they have evolved special characteristics in response to a particular combination of cool climate, high precipitation and mountainous terrain.

The cool climate in the Australian Alps, particularly in winter, results in generally low temperatures, frequent frosts and strong winds. Snow persists at the highest altitudes, for 1-4 months in the subalpine zone and 4-9 months in the alpine zone. These factors have major effects on plant growth. Low temperatures, frosts and snow restrict plant growth for most of the year, particularly at high altitudes.

The Australian Alps and mountain areas throughout the world are characterised by a sequence of vegetation communities with distinct altitudinal zones. Vegetation communities are groups of plants living together with similar preferences and tolerances for particular environmental conditions. These communities can be described by differences in species, height and growth form, and structure.

marigold

The most obvious change in communities is the transition, at the altitude known as the treeline, to a treeless vegetation. Above the treeline is the true alpine zone where the vegetation is primarily dwarfed shrubs and ground hugging herbs, with no trees.

Going up the mountain

Travelling up the mountain, you can readily observe distinct zones of vegetation characterised by changes in height and species of the dominant eucalypt, the growth forms of certain plants, and in the density and type of understorey. These changes can be linked to changing climatic factors and soil characteristics. Looking back down the mountain various zones can be recognised by the bands of colour of the canopy at each level from foothills to high peaks.

On the lower slopes or tableland areas of the Alps there are grassy woodlands and dry open forests. Lower-growing trees are well spaced and allow lots of sunlight on to the forest floor. The soils are shallow and hardsetting and merge into clay with depth. The open understorey consists of grasses and small shrubs.

As you move up to the montane slopes, where precipitation is higher, the forest generally becomes taller, wetter, darker and more dense. The dominant trees, a mixture of eucalypts, are taller and grow closer together. The understorey is made up of ferns and small trees. High rates of organic breakdown, characteristic of wet forests, result in deep soils.

At the highest elevation of the montane slopes just below the subalpine and alpine zones, there is a special band of tall open forest dominated by Alpine Ash (also known as Woollybutt because of its butt of rough fibrous bark). This narrow zone has high precipitation levels at temperatures that allow high rates of organic breakdown and vigorous plant growth. Consequently there is a lot of organic matter that can be quickly turned into soil. The soils are deep with plenty of water available to plants and the trees are able to grow tall. Alpine Ash are the tallest eucalypts growing in the Australian Alps. The understorey of this forest, however, is much sparser than that of the tall open forests at lower altitudes, with only a few small trees, and shrubs and herbs forming a groundcover.

Above about 1500 metres there is an abrupt change from tall forests to a low-growing subalpine woodland dominated by Snow Gums. The plants growing here have to endure low temperatures all year round and much of the precipitation is in the form of snow and ice. The trees are stunted and often twisted away from the prevailing wind. The understorey of this zone is either low growing shrubs or grasses and herbs.

heath

Above the treeline you see the most abrupt change in the sequence. The alpine zone, subject to the coldest temperatures and the most persistent snow, is too cold for trees. The treeline generally coincides with mean mid-summer temperatures of about 10 degrees celsius. At this level there is only enough solar energy to provide for day to day living and renewal of leaves. There is not enough photosynthesis for the development of the large root systems and trunks and branches required by trees.

The alpine zone is a mosaic of heathland, grassland, herbfield and bogland, interspersed by bare protruding rock and rock pavements, reflecting drainage patterns of water and cold air and variations in the soils, topography and degrees of exposure. The plants here are mostly ground hugging and reach no more than a metre in height. Soils are shallow and vary enormously. There are stony lithosols on peaks and ridges, loamy soils on the gentle slopes and peats in the lowlying bogs.

On the exposed rocky ridges and scree slopes, soils are sparse, shallow and well drained. Vegetation communities tend to be scattered shrubby heathland, ground-hugging feldmark or snowpatch communities. Tall alpine herbfields and tussock grasslands, the most extensive communities of the alpine zone, grow on sheltered, gentle slopes and hilltops where soils are moderately deep and well drained. At the bottom of the basinlike valleys and on poorly drained slopes, where soils are deep and waterlogged, and decay of organic material is incomplete, Sphagnum bogs and bog heathlands are found.

Treeless areas are generally found only above the treeline but cold air drainage also produces treeless communities in valleys below the treeline. On clear still nights cold air drains into basin-like valleys creating alpine conditions at lower elevations. Snow Gums grow on the rims of such valleys and on the knolls above them, inverting the treeline.

Vegetation Communities of the Australian Alps

Vegetation communities of the Australian Alps reflect localised differences in climate, landform and aspect. Communities are described by the most common life form of the plants in that community; either trees (woody, one main stem, tall), shrubs (woody, multiple stems, short <3 metres) or herbs (non-woody, small, short-lived ranging from one season to a few years). True alpine vegetation contains no trees, it is characterised by low-growing shrubs and herbs forming a variety of feldmark, heath, herbfield, grassland, fen and bog communities. The subalpine zone is similar except the mosaic includes some woodland and forest patches.

The structure of the various vegetation communitites is generally the same throughout the Australian Alps, but the key species in each community differ slightly from NSW to Victoria. Also, there are no true feldmark communities in Victoria, and the alpine herbfields are much less extensive. Instead, heath communies are prominent in the Victorian high country. Short alpine herbfields are found on the exposed redgetops and late-lying snowpatches that would generally support felkmark communites in NSW. This is because the Victorian Alps are of lower elevations than the Kosciuszko area.

Woodland

Elevation Zone: Lowland
Dominant Lifeform(s): trees, herbs
Description: Very open community of shorter trees with a generally grassy understorey.
Landform: Lowland foothills, tableland and river valleys.
Environment: Characterised by lower growing Eucalypts and other trees in an open community. Understorey varies with landform and situation.
Distribution: Widespread.
Key Species: Mountain Swamp Gum (Eucalyptus camphora) (Vic), Yellow Box (Eucalyptus melliodora) (NSW, ACT), River Red Gum (Eucalyptus camaldulensis).

Open Forests (Dry Sclerophyll)

Elevation Zone: Montane
Dominant Lifeform(s): trees
Description: Forests of mixed species of eucalypts and other forest trees. Understorey of shrubs and grasses.
Landform: Steep montane slopes and gentler lowland hills.
Environment: Occurring on the drier north- and west-facing slopes of the montane zone; characterised by eucalypt species different from those found in the tall open forests. They are more tolerant of dry conditions, fire resistant and grow to lesser heights. The understorey is usually dominated by low woody shrubs and grasses that can tolerate drier conditions.
Distribution: Widespread. Together with the tall open forests of the moister aspects, the open forests of the Australian Alps make up the most extensive vegetation community of the Australian Alps.
Key Species: Red Stringybark (Eucalyptus macrorhyncha), Broad-leaved Peppermint (Eucalyptus dives) (Vic), White Gum (Eucalyptus rossii).

Tall Open Forests (Wet Sclerophyll)

Elevation Zone: Montane
Dominant Lifeform(s): Trees
Description: Forests of mixed species of tall eucalypts and other forest trees. Understorey of tall shrubs and herbs.
Landform: steep montane slopes
Environment: These occur on the extensive, moister, south- and east-facing slopes of the steep montane zone, on deep well-structured soils built up from aeons of deposition from above, and 'litter' induced by high precipitation and moderate temperatures. The environment is moist and the understorey generally lush and thick, characterised by moisture-loving plants such as ferns. The eucalypts and other forest trees of this zone are generally fire sensitive.
Distribution: Widespread throughout the Australian Alps on the extensive montane slopes.
Key Species: Narrow-leaved Peppermint (Eucalyptus radiata) (Vic), Candlebark (Eucalyptus rubida) (Vic), Brown Barrel (Eucalyptus fastigata) (NSW, ACT), Manna Gum (Eucalyptus viminalis).

Alpine Ash Forest

Elevation Zone: Montane
Dominant Lifeform(s): trees, herbs
Description: Forest of tall straight trees, generally only one species - Alpine Ash. Fairly open understorey of grasses and herbs, some shrubs.
Landform: Upper levels of the steep montane slopes.
Environment: Moist environment, soils built up from deposition from higher elevations. Fertile as a result of litter buildup, induced by high precipitation and moderate temperatures. The Alpine Ash exhibits seed dormancy which, in contrast to the other montane eucalypt species, enables it to tolerate the colder temperatures of higher elevations.
Distribution: Throughout the Australian Alps at the upper levels of the montane zone.
Key Species: Alpine Ash (Eucalyptus delegatensis), Mountain Gum (Eucalyptus dalrympleana).

Subalpine Woodland

Elevation Zone: Subalpine
Dominant Lifeform(s): trees, herbs
Description: An open woodland community dominated by Snow Gum, the only species of tree that is able to grow at this altitude. The understorey is typically a grassland or herbfield community. At the highest and coldest elevations Snow Gum grow in shrub or mallee form (stunted and with many stems).
Landform: Undulating plateaus
Environment: More sheltered areas of the subalpine zone. Not in rocky situations or very stony or waterlogged soils.
Distribution: Througout the Australian Alps.
Key Species: Snow Gum (Eucalyptus pauciflora).

Alpine shrubby heathland

Elevation Zone: Alpine and subalpine
Dominant lifeform(s): shrubs
Description: Open community sparsely populated by shrubs, generally woody heaths, interspersed with herbs and tussock grasses.
Landform: rocky ridges, stony slopes of high elevations.
Environment: Commonly occupies shallow, stony, well-drained soils, rocky situations and exposed slopes.
Distribution: Throughout Australian Alps.
Key Species: Yellow Kunzea (Kunzea ericifolia), Alpine Grevillea (Grevillea australis), Leafy Bossiaea (Bossiaea foliosa) (Vic), Common Oxylobium (Oxylobium ellipticum) (NSW), Mountain Plum Pine (Podocarpus lawrencei).

Tussock Grassland

Elevation Zone: Subalpine
Dominant Lifeform(s): herbs
Description: Community characterised by separate grass tussocks, the tops of which form a closed canopy of interlacing leaves. The spaces between the tussocks may be occupied by shade tolerant herbs.
Landform: undulating plateaus.
Environment: Tussock grasslands occur in less well drained but not waterlogged situations. Often associated with cold air drainage basins that occur below the treeline.
Distribution: Throughout the Australian Alps.
Key Species: Prickly Snow Grass (Poa costiniana), Mountain Gentian (Gentianella diemensis).

Alpine Herbfield

Elevation Zone: Alpine and subalpine
Dominant Lifeform(s): herbs
Description: A community in which tussock grasses and small herbs occur together to form a continuous cover.
Landform: Undulating plateaus
Environment: Well drained slopes and rolling hilltops, relatively sheltered sites avoiding exposure to strong winds and waterlogged or stony soils.
Distribution: Extensive throughout the Australian Alps mostly above the treeline.
Key Species: Snow Daisies (Celmisia spp.), Snow Grasses (Poa spp.), Billy Buttons (Craspedia spp.).

Alpine Bog

Elevation Zone: Alpine and subalpine.
Dominant Lifeform(s): herbs
Description: Community dominated by hummock forming Sphagnum moss, associated with sedges, rushes and wetland heaths.
Landform: Undulating plateaus, particularly basins.
Environment: Permanently wet sites, bogs are generally spring fed seepages on hillsides and edges of valleys. In still wetter parts, such as valley floors, Sphagnum disappears and the sedges form a fen.
Distribution: Throughout the Australian Alps.
Key Species: Sphagnum Moss (Sphagnum cristatum), Pineapple Grass (Astelia alpina) (Vic), Swamp Heath (Epacris paludosa).

Short Alpine Herbfield

Elevation Zone: Alpine and subalpine
Dominant Lifeform(s): herbs
Description: Similar to 'alpine herbfield' but shorter.
Landform: undulating plateaus
Environment: Found below long lasting snowpatches where the environment is much colder, growing season shorter and soils frequently wetter than the 'alpine herbfields'.v
Distribution: Throughout the Australian Alps.
Key Species: Alpine Marsh Marigold (Caltha introloba), Alpine Wallaby Grass (Danthonia nudiflora) (Vic), Alpine Plantain (Plantago sp.), Alpine Trachymene (Trachymene humilis) (Vic), White Purslane (Neopaxia australasica) (NSW).

Feldmark

Elevation Zone: Alpine
Dominant Lifeform(s): low shrubs, herbs
Description: Open community of dwarf plants dominated by cushion forming or prostrate species only a few inches high. Bare earth and rock are a notable feature of the community.
Landform: exposed ridges, highest elevations of plateaus.
Environment: harsh, exposed, high winds, coldest temperatures, severe frosts.
Distribution: Highest elevations in NSW only.
Key Species: Rock Heath (Epacris petrophila), Chionohebe (Chionohebe densifolia), Spreading Coprosma (Coprosma pumila), Hard Cushion Plant (Colobanthus pulvinifica).

Variation within the zones

Variations in vegetation communities within altitudinal zones are associated with variations in topography, soils and aspect.

The topography of the Alps varies enormously from sheer escarpments and deep gorges to rolling hilltops and shallow basins. The relief of differing land forms contributes to the development of a range of soils that vary in depth, structure and content, all of which are important factors in determining vegetation communities.

In the alpine zone, for example, shallow lithosols found on rocky exposed ridges and scree slopes, support shrubby heathland. The soils of the gentle slopes and rounded hilltops are deeper and loamy and carry alpine herbfields and tussock grasslands. Bog plant communities are found on peats developed in the bottoms of basin-like valleys.

Aspect is a major factor in governing vegetation communities. Forests of the steep montane slopes, for example, vary from wet tall forests on the south-east slopes to dry tall forests on the north-east slopes. Conditions are always drier on the north-western slopes. The sun rises in the east, shining on the eastern slopes in the early part of the day when temperatures are low and there is still lots of moisture around from the night before. Temperatures remain moderate and the vegetation remains moist.

As the sun moves into the western sky the temperatures for the day have reached their maximum, the hot sun streams down directly on the western slopes and any excess moisture is quickly evaporated.

sun path

At the top of the mountains in the alpine zone, the drier north-west aspect is generally also exposed to the prevailing winds, often carrying snow and ice. Here you find the hardiest species best adapted to exposure. On the leeward side (sheltered from the prevailing winds and the hottest sun), species tend to be taller and less hardy.

At the highest elevations snow is blown off the exposed aspect onto the leeward side (usually the south-east facing slope) where it accumulates in deep drifts. These drifts, known as snow patches, are sheltered from the hottest sun and remain almost all year round, only melting at the height of the alpine summer.

winds

A particular vegetation community adapted to these conditions, the short alpine herbfield or snowpatch community generally grows below snowpatches where the environment is much colder than elsewhere. Some of the plants of the snowpatch communities such as the Marsh Marigold Caltha intraloba have adapted to grow beneath the melting snow. Sometimes they actually flower beneath the snow.

Adaptations of some plants of the alpine and subalpine zones

The combination of geographical isolation and adaptation to the extreme conditions of the high elevation environment, has led to the evolution of a considerable number of species that do not occur anywhere else. These are known as endemic plants. Ten percent of the plants in the Australian Alps are endemic, a much higher percentage than most other areas.

Plants of the alpine and subalpine zones have developed a number of behavioural and physical adaptations in response to the characteristically low temperatures, extreme summer temperature fluctuations, high levels of precipitation (winter snow and summer rain), frequent frosts and strong winds of these high elevations.

Rapid Growth Period

The Alps are have an extremely short growing season following a long, cold and snowy winter-spring period Most species are dormant in winter, then rapidly, flower and set seed during the short growing season of 4-5 months from November to April.

Growth Form and Size

Rosette plants, tussock grasses and dwarf shrubs are common plant types in the alpine zone. Small size and a ground hugging habit are essential for most alpine plants to avoid the strongest winds and take advantage of the warmer conditions close to the soil.

Taller shrubs have flexible stems so that they bend rather than break under the weight of snow. Snow Gum branches are not so flexible and many are pruned each year during heavy snow falls.

The grass tussock is another successful alpine life form. Its leaves, both living and dead, provide protection for new growth at the tussock base against low temperatures and needle ice.

Seed Dormancy and Stratification

The seeds of many alpine plants remain dormant over the winter period and will not germinate until subjected to stratification, that is, a 6-8 week moist period at low temperatures which breaks the dormancy. Overwintering beneath the snow provides a natural stratification treatment and the seeds are ready to germinate quickly the following spring, taking full advantage of the short growing season during which they must establish successfully to endure the following winter. This mechanism protects them against germination late in the growing season just before the snow comes.

Photosynthesis and Respiration

Photosynthesis and respiration occur at high rates for short periods when light and temperature are favourable. Optimum photosynthetic rates of alpine plants occur at lower temperatures than for plants in non-alpine zones.

Even so, only a limited amount of energy can be harnessed because of the shorter daily photosynthetic periods and shorter annual growth periods, resulting in less growth over long periods of time in alpine plants. Hence dwarf alpine shrubs, such as the Mountain Plum Pine may be much older than they appear.

Early development of root systems in seedlings

Most of the early growth of alpine plants is below the soil surface. A well-developed root system is essential for contending with needle-ice heave. On exposed ridges and in frost hollows (cold air drainage basins), needle ice will lift and break the roots of poorly-anchored young plants.

Drought Tolerance and Cold Hardiness

The frozen world of the alpine zone in winter has much in common with the waterless environment of the desert. Water locked up in snow and ice is unavailable to plants. The leaves of alpine and desert plants have similar adaptations to drought to help reduce moisture loss through the leaf surface. Leaves are often small, and thick and leathery or folded or rolled. Many hairs on leaf surfaces help reduce moisture loss by restricting air circulation across the leaf surface, which reduces evaporation of moisture.

Alpine plants are clearly adapted to their environment. The adaptations that enable plants to grow in these harsh conditions are repeated in high mountains throughout the world. Although the climate of the Australian Alps is comparatively mild, our alpine plants display most of these universal characteristics.

Alpine islands

The alpine and subalpine mountain peaks and ridges were once higher and more continuous, connected by large alpine or subalpine tracts. Over a long period of time rivers have worn deep valleys forming extensive areas of montane slopes. This dissection has separated the alpine areas, whilst climatic changes such as global warming since the last ice age, have caused them to recede.

alpine islands

Alpine and subalpine zones, particularly in Victoria where the degree of dissection is greater, have become small islands isolated from each other by geographical distance, different climatic conditions and different vegetation communities. These small pockets are vulnerable because each is of limited area and adapted to particular climatic conditions.

Study Directions

The vegetation of the Alps helps capture the water and regulate its release to the major rivers that feed New South Wales, Victoria, South Australia and the Australian Capital Territory. Discuss the impacts that different land uses have on the vegetation in the Alps.

Open communities of tussock grasslands and alpine herbfields are important communities for grazing stock, providing a range of palatable species and allowing easy mobility. Investigate the impact on these communities from continuing cattle grazing. What has happened in NSW? In Victoria?

Tall straight even-aged Alpine Ash forests are a valued resource for the timber industry but are also a vital part of the natural features of the Alps. Discuss.

Resources

Costin, A.B., Gray, M., Totterdell, C.J. and D.J. Wimbush, (1979), Kosciusko alpine flora. CSIRO and Collins.

Costin, A.B., (1981), Alpine and sub-alpine vegetation In Australian Vegetation. Ed. R.H. Groves, Cambridge Uni Press.

Land Conservation Council, (1977), Alpine Study Area Report, LCC.

Mosley, G, (1988), Australian Alps World Heritage Nomination Proposal, Victorian National Parks Association.

Nankin, H., (1983), Victoria'a Alps. An Australian endangered heritage. Australian Conservation Foundation.

Rowe, R.K., (1972), A study of the land in the catchment of the Kiewa River. Soil Conservation Authority, Victoria.

Bogong High Plains vegetation map and guide to alpine flora: Bogong sheet, Hotham sheet, Pretty Valley sheet, Rocky Valley sheet. Victoria Conservation Trust.

The Australian Alps Education Kit

For more information please refer to the Australian Alps national parks list of references