The Forest Ecosystems of the Tablelands region

Coachwood and Ferns

Gazing upon the great natural vistas of the western side of the Greater Blue Mountains, a blue haze settles above a continuous cover of forest canopy. On the surface, it appears to be one uniform forest, but on closer inspection nothing can be further from the truth. It is home to the greatest diversity of eucalypt species on earth and many ancient remnant forests, forming distinct ecosystems.

Altitude, soil, sunlight, wind and geology all contribute to the diversity of plants and animals that come together to form an ecosystem. The Greater Blue Mountains National Park is characterised by dissected plateaus with windswept heathlands, rainforests (in open gullies with richer soils), and open eucalyptus woodlands (in low, dry areas). Forest ecosystems are defined by their vegetation communities. Key forest ecosystems of The Tablelands region include rainforest, Tall Open Forest, Open Forest, Grassy Woodland and riparian (riverside) environments.

Rainforests
Rainforests were dominant before the evolution of eucalypts. They are mainly found in places where soil moisture is high and where they are well protected in gullies and on slopes. They can also be found where the soil nutrients are high, such as on basalt capped mountains. The richest example is found at Mount Wilson, where a warm temperate rainforest, dominated by coachwood, black wattle and sassafras, has formed on the east side of the mountain where it receives moisture from the coast.

The Cathedral of Ferns is a delightful section of rainforest along Mount Irvine Road. It contains a huge eucalyptus, named the ‘Giant Tree’, which is hundreds of years old, as well as huge tree ferns, sassafras, coachwoods, and a wide range of eucalypts. There are other rainforests at Mount Monundilla and Mount Coriaday. Small patches of dry rainforests exist in the Kowmung wilderness. The biggest area is on the south facing slopes of the Kanangra Gorge between 300 and 700 metres. The main tree species of the Kowmung dry rainforest are red cedar, silky ash and kurrajong.

Tall Open Forests contain the giants of the Australian bush, reaching 70 metres or more. They prefer more fertile soils and high rainfall. They have high opened canopies, which sometimes allow luxuriant rainforest understorey to develop, though in some cases it is grassy. In the understorey, soft leaved shrubs, ferns and herbs may grow. The crown trees (tall eucalypts such as ribbon gums and brown barrel) need light to grow while rainforest takes over in the canopy shade.

Tall Open Forests can a tinder box in dry summers. This can lead to a crown forest fire, a very ecologically disturbing event. They are so combustible due to their leaf litter, which is composed of bark, leaves and twigs. Their leaves are full of volatile oils, and they shed bark in long ribbons. These ribbons are like fuses, which when lit and lifted by wind can quickly spread a fire. These ‘suicide forests’ may wait for hundreds of years before igniting a fire hot enough to remove the shady moist understorey allowing the gum seedlings to get enough light to start the process anew.

Animals of the tall open forest include possums and gliders and their predators the Sooty Owl and Powerful Owl. Bats and birds shelter and breed in the hollows of the trees. Eucalypts provide many hollows due to limb, insect, or fire damage. Smaller hollows are found in trees over 120 years and larger hollows are found in trees over 200 years. Consequently many of these forests will never recover from logging in our lifetimes. The canopies attract insect eating birds such as Thorn Bills and Scrub Wrens as well as pollen eating species such as honeyeaters and lorikeets.

The southern escarpment of Kanangra Boyd National Park and the Blue Gum forest below the Three Sisters are examples of Tall Open Forests.

Open Forests contain hard-leaved (sclerophyll) shrubs under an open canopy of smaller eucalypts or she-oaks. Sclerophylly is associated with soil infertility. The trees of the Open Forest are usually between 10 to 30 metres high.

The floor of the Open Forest is home to many of Australia’s best known flowers, such as waratahs, banksias, spider flowers, wattle, pea flowers, native fuschias, boronias, sedges, wax flowers and tea trees. Trees include bloodwoods, scribbly gums, she-oaks and grey gums.

Many Open Forest plants have cunning ways to regenerate after fire. They protect their vital organs through a variety of means: insulating bark, underground roots, or woody fruits that open after fire. Wattles and legumes have tough coated seeds, which lie dormant as seed banks, waiting for fire.

Within Open Forest there is an abundance of nectar and insect feeding birds and smaller animals. Parrots, such as the King Parrot can be found in tree hollows.

Much the sandstone plateau areas of the Tablelands region are covered with Open Forests. The Southern Tableland open forest occupies extensive areas on the drier parts of Great Dividing Range, such as those seen on the hills north of Goulburn. These forests include red stringy bark, inland scribbly gum, Argyle apple, brittle gum, peppermints, black wattle, silver wattle, and broad leaved hickory. Herbs include the blue flax lily, nodding blue lily and many others.

Animals of the Open Forests include possums, echidnas, kangaroos, wombats, wallabies and koalas, though these are now very rare in the Southern Tablelands.

The Blue Mountains ash is the classic image of the mountain forests with its long strands of hanging bark. The more exposed areas have silvertop ash, Sydney peppermint, narrow leaved stringy bark, and in the depressions in damper soils hard leaved scribbly gums. Along the narrow ridges and steep slopes of the Cox and Kowmung, where the soil is poor, are Blaxland’s stringy bark, dry forests of black mountain ash, brittle gum, Blakeley’s red gum, red stringy bark and forest oak.

Above 1200 metres on Newnes Plateau are Montane Forests dominated by white sally and broad leaved peppermint. Extensive sandstone cliffs with Montane Forests provide refuges for highly specialised rock dwelling flora including mosses, ferns, conifers and flowering plants. The most conspicuous are coral ferns and sundews. The rare Microstrobos fitzgeraldii, is a small weeping conifer which is found in the spray zone of half a dozen waterfalls.

The Sydney Montane Heaths occur in areas adjacent to forests in areas where water drainage is impeded, as found at Kanagara Walls and Wolgan Valley. Endemic species include mallee ash. Sydney Montane Forests and Heaths can be seen from the window of the Zig Zag Railway, near Lithgow.

Grassy Woodlands are dominated by eucalypts, typically box and red gums. They have a grassy understorey which contains perennial tussock grasses such as kangaroo grass, weeping grass and many species of wallaby and spear grasses, and herbs such as early nancy, sweet hounds-tongue, candlesticks and plantains. Ground orchids and lilies appear after rain and fire, providing floral displays. Grassy woodlands are home to enormous diversity of plants including eucalypts, grasses, daisies, wattles, legumes, orchids, lilies and many more. Parrots and cockatoos are often seen in grassy woodlands. They make their homes in tree hollows. The seed bearing grasses and other flowering plants such as daisies are important to the ground eating Turquoise Parrot, which can be seen in Abercrombie River and Wollemi National Parks.

With flowers at the canopy level, the yellow box attracts a seasonal influx of nectar feeding birds such as the nomadic and rare Regent Honeyeater. Sadly Bettongs and Brolgas are now gone and the haunting Bush Stone Curlew have almost disappeared. Brush tailed phascogales and koalas still live in these areas, but populations have declined. The small purple pea is a threatened native pea that can be found in this area. It delivers a brilliant display of pink flowers in spring. The old flowers transform into seed pods, which can remain buried in the soil for years and crack open during a fire.

The western slopes of the Abercrombie River are home to dry grassy woodland typified by apple box, Blakelys red gum, yellow box and white box. This is an endangered community group within the Grassy woodlands, and Abercrombie River National Park is one area where the community has been preserved.

Riparian environments are found along rivers and creeks. Fine examples of riparian environments exist at the Abercrombie River including tall river oaks, tea trees and bottlebrushes. Wombats and echidnas live on the slopes and river flats of Abercrombie River National Park. Down by the park's rivers you may see a platypus or a Gippsland water dragon sunning itself on a rock during the warmer months.

In Goulburn the frosty climate prevented river oaks from dominating and the rivers there are characterised by apple box, ribbon gum and cabbage gum, with thickets of apricot coloured bottlebrush along the gravel roads. Sadly most of this was cleared decades ago.