Natural History:

Dry Sclerophyll Forests

Text Alan Fox – Photography Steve Parish

This is the very first description of sclerophyll forest. The giant trees were probably Messmate (Eucalyptus obliqua) growing on the east coast of Tasmania. The bay shore on which the crew had landed was Frederick Hendrick Bay, on the Forestier Peninsula — an area where wet and dry sclerophyll forests overlap. The comment on fire explains why the understorey was so clear of shrubbery.

Eucalypt trees (gums, bloodwoods, ironbarks, stringybarks, peppermints, box, ash and mallee) have thick, leathery leaves, usually with waxy coatings and oil glands — features that evolved to enable these plants to conserve water. They are sclerophyllous (from the Greek sclero meaning hard and phyllon, leaf). Dry sclerophyll forest, then, is a community of tall, closely growing trees that are mostly eucalypts. There are more than 700 species and subspecies in the genus Eucalyptus in Australia. Because these trees grow close together and almost interlock up top, bright sunlight reaches the top of the canopy and much less filters through to the forest below (even though eucalypt leaves generally hang edgeways to the light). The trunks of forest trees are usually much longer than the depth of the forest canopy. Where the woodland trees have hemispherical canopies, most forest trees have a flat, wedge-shaped crown. These tall forests with floors covered with sclerophyllous shrubs, such as acacias and peas, develop on drier ridges and droughtier soils than wet sclerophyll forests, which have dense, wet ferny floors.

Where Are They?
Places with low soil-moisture retention require moderate rainfall to sustain these forests. These conditions are found in New South Wales around the Hunter Valley, the Mid-Clarence Valley, the western edge of the New England region and the Ulan–Tuena area. In Victoria, they exist around Lake Eildon, near Maryborough, in the Pyrenees area, south of Colac, and in the Black Range State Park area. Dry sclerophyll habitat also grows north-east of Launceston (Tas), on west Kangaroo Island (SA), and in South-West Western Australia from Mount Barker to Perth, excluding the Karri–Tingle forests.

What Do They Look Like?
These 25–35 metre high forests of fairly even height have moderately dense canopies that frequently link. The dry to damp forest floor is covered with grasses and shrubs.

Critical Conditions:
Undulating to hilly well-drained country, generally within the 450–650 millimetre rainfall area, with cool winters and warm to hot summers. Soils are usually grey-brown and brown podzolic with an acid reaction and are free of lime
and strongly leached.

Boarding houses of the Sclerophyll forests

Wet sclerophyll forests are sometimes referred to as “tall open forests”, in contrast to the closed forests that are rainforests. Eucalypts, the dominant trees of the open forests, have been called “Nature’s boarding houses” in that they provide excellent shelters for arboreal animals.

Long before trees die, the processes of death have begun. Fungi locate airways up the old, dead cores of trees and spread up these, consuming and decomposing core wood material as the tree grows upwards and leaving a hardwood outer casing inside the growing cambium layer of cells beneath the bark. A pipe develops, which, when it reaches the lower, older branches that also have dead heartwood, allows the fungal community to move into those places. The strength of cellulose is the factor determining the length of these lateral branches. In wet forests where there is considerable tree height, usually above 50 metres, branches rarely exceed 15 metres because, as the heartwood begins to decay, branches fall during strong winds. The jagged hollows of the stump are ready-made shelters for arboreal nesting birds, bats, possums, gliders, reptiles, spiders, insects and numerous other beasts.

Cockatoos and parrots tear away and remodel these hollowed-out “apartments”, making a comfortably shaped lining out of chips and soft, rotting wood tissue. Meanwhile, other animals take up squatter’s rights in the grounded branches. The senile trees of old-growth forests, some 300–400 years old in the case of eucalypts, make the most important contribution to the tall open forest — both from the point of view of total and diverse production as well as wildlife habitat

However, the sclerophyllous leaves of eucalypts are toxic when young, which presents difficulties for haven-seeking animals residing in the trees’ wonderful “boarding house” hollows. If they wished to feed off the trees, arboreal species had to develop specialised chewing and digestive features and habits. Consequently, Koalas developed exceptionally long, 2 metre caecums (similar to the human appendix) to help break down the gumleaf by extra fermentation. Possums, other frequent inhabitants of these forests, developed the habit of feeding their own faeces, containing partially broken down leaf, to their babies. This behaviour also transplanted helpful adult stomach bacteria into the baby’s immature belly. Other arboreal animals, such as the Yellow-bellied Glider, sip a tree’s sap directly by chewing holes through the bark into the tree’s vascular system, while the Sugar Glider sips the nectar of flowers as well as nibbling them. These behavioural techniques bypass the problems presented by the tough sclerophyll leaves

Although a variety of floral species comprise the sclerophyll forest, the eucalypt is the main character. So widespread are eucalypts that most Australian kids have heard of Snugglepot and Cuddlepie, the gumnut babies created by celebrated children’s author May Gibbs. The peaked caps the gumnut babies wear are the little caps, called operculums, worn by the bush gumnuts to protect the budding flower beneath. The French botanist who gave eucalypts their generic name borrowed from the Greek eu (well) and kalyptos (covered) to create the name that describes this defining characteristic of these hard-headed little gumnuts.

Post-fire studies conducted in the Nadgee Nature Reserve (NSW) found that parasitic mistletoes, one of the great thieves of eucalypt nutrients as well as potential tree killers, were killed by crown wildfires. Months after the fire more than 90% of the remaining tree branches were mistletoe-free. In this sense, even though the wildfire caused much damage, it also acted as a “cleaning” agent.

Australia’s typical ‘bush’ habitat

Dry sclerophyll forests and woodlands are probably the nearest communities to the “bush” in its Australian context. The word comes from the Dutch bosch, which was used to describe the natural country of South Africa and which British author Anthony Trollope defined for Australia as “the gum-tree forest”. Dry sclerophyll forest and dry sclerophyll woodland communities occupy a niche midway between desert and rainforest, the two driest and wettest terrestrial communities.

Looking at the map records of drought over Australia in the last century, only 34 years had average (or better) humid years. For the other 66 years, drought affected the greater part of the Australian continent. Drought is normal in Australia, where rainfall is apparently largely accidental. Of course, particular locations had worse or better conditions than the average. Two or three years of successive drought following a couple of years of above-average rainfall is not unusual and leads to ideal conditions for wildfire.

A few times a century, ideal conditions for extreme wildfire occur over a very large area. Species in the genus Eucalyptus, as the dominant tree cover between the semi-arid and humid areas of the continent, have had to become adapted to regular drought and catastrophic wildfire. These adaptations make this genus extremely valuable in a world that appears to be drying out: they protect the trees from death caused by loss of leaf cover — their source of cell energy — but they also protect the tree from animals, mainly insects, that defoliate trees.

Although a variety of floral species comprise the sclerophyll forest, the eucalypt is the main character. So widespread are eucalypts that most Australian kids have heard of Snugglepot and Cuddlepie, the gumnut babies created by celebrated children’s author May Gibbs. The peaked caps the gumnut babies wear are the little caps, called operculums, worn by the bush gumnuts to protect the budding flower beneath. The French botanist who gave eucalypts their generic name borrowed from the Greek eu (well) and kalyptos (covered) to create the name that describes this defining characteristic of these hard-headed little gumnuts.

Post-fire studies conducted in the Nadgee Nature Reserve (NSW) found that parasitic mistletoes, one of the great thieves of eucalypt nutrients as well as potential tree killers, were killed by crown wildfires. Months after the fire more than 90% of the remaining tree branches were mistletoe-free. In this sense, even though the wildfire caused much damage, it also acted as a “cleaning” agent.

Flora of the dry sclerophyll forests

Dry sclerophyll eucalypt canopies let sunlight through to the forest floor, so numerous smaller sclerophyllous plants, shrubs and grasses can grow there. The environment these plants occupy is even drier than the tree layer, so they must have very water-efficient growth strategies. These strategies include leaves protected against water loss; rapid take-up of available groundwater by the roots; small, stem-clasping leaves; and a capacity to store water.

Acacias, banksias (and others of the Proteaceae family) and heath-like plants are particularly well suited to the living conditions in dry sclerophyll forests. They frequently form a dense, prickly understorey, as in the Silvertop Ash forests of the continent’s south-east, the stringybark forests of Glenrowan (Vic), and the Pilliga forest (NSW). West of Batemans Bay (NSW), and verging on wet sclerophyll forests, are unusual great Spotted Gum forests with an understorey of cycads. Eucalypts of all bark types — gums, ashes, bloodwoods, stringybarks, peppermints and ironbarks — are present in this environment.

Classic plants:

Spotted Gum; White Gum; Blackbutt; Mulga Ironbark; White Mahogany; Pink Bloodwood; Silvertop Ash; Red Stringybark; Messmate; peppermints; Manna Gum; Tasmanian Blue Gum; Jarrah; Marri; Tuart; Pink Summer Calytrix; Swan River Myrtle; Old Man Banksia; Dryandra spp.; Silver, Cootamundra, Sunshine, Spreading, Knife-leaf and Prickly Moses Wattles; Prickly Hakea; Forest Woody Pear; Sword-leaf, Hickory, Deane’s and Gosford Wattles; hopbushes; Pultenaea spp.; Stypandra spp.; Dianella laevis; Basket Grass (Lomandra longifolia); Stipa spp.; False Sarsaparilla; Pink Heath; grass-trees; Drumsticks; Cherry Ballart; Handsome Flat Pea; Grey Everlasting; Bitter Pea; Prickly Bitter Pea; Daviesia spp.; Yellow-eyed Flame Pea; Golden Glory Pea; spider orchids; Blue China Orchid; Wedding Bush; Bitter Pea; Bush Pea (Pultenaea spp.); Hyacinth Orchid (Dipodium roseum); Geebung (Persoonia salicina); Pine-leaf Geebung (Persoonia pinifolius); Gymea Lily (Doryanthes excelsa); Pink Five-corners (Styphelia tubiflora); Austral Indigo (Indigofera australis); Spike Wattle (Acacia oxycedrus); Myrtle Wattle (Acacia myrtifolia); Queensland Silver Wattle (Acacia podalyriifolia); Wax-lip Orchid (Glossodia major); Grey Spider Flower (Grevillea buxifolia); Silky Grevillea (Grevillea sericea); Sydney Boronia (Boronia ledifolia); Crowea saligna.

Classic Mammals:

The dry forests and woodlands are the real Australian bush and the continent’s most characteristic bushland animals call it home, including the Whiptail Wallaby of the central east, the ubiquitous Common Brushtail Possum, the Common Wombat and the Eastern Grey Kangaroo. In the south-west is the Western Grey Kangaroo, as well as many wallabies, the Common Wallaroo (or Common Wallaroo), possums and a number of gliders, along with predatory quolls. Numerous small mammals scramble about the trunks, branches and canopy of these forest trees, or forage among the leaf litter. Some of the most ferocious small dasyurid mammal predators are common, preying primarily on invertebrate fauna.

Like all rich and sustaining habitats, these forests contain food, water, shelter and specialised space for each species to carry out a fulfilling social and sexual life. They are multi-storeyed habitats, from the floor litter and logs and the grassy understorey to the tree structures and the tree-top “boarding houses”. Human habitat destruction aside, fire too has the capacity to greatly simplify resources and thereby reduce habitat, population and species diversity.

Classic Mammals: Eastern Grey Kangaroo; Western Grey Kangaroo; Swamp Wallaby; Wallaroo; Whiptail Wallaby; Rufus Rat-kangaroo; Tammar Wallaby; Tasmanian Devil; Eastern Quoll; Western Quoll; Spotted-tailed Quoll; Dingo; Brush-tailed Phascogale; Red-tailed Phascogale; Yellow-footed and Dusky Antechinus; Common Dunnart; White-footed Dunnart; Numbat; Short-nosed Bandicoot; Long-nosed Bandicoot; Common Wombat; Koala; brushtail possums; Yellow-bellied Glider; Greater Glider; Eastern Pygmy-possum; Western Pygmy-possum; Honey Possum; Potoroo; Tasmanian Pademelon; Red Flying-fox; Lesser Long-eared Bat; Chocolate Bat; White-striped Mastiff-bat; Gould’s Wattled Bat; Southern Forest Bat; Bush Rat.

Classic birds:

Birds that occupy woodlands also live, to a lesser or greater degree, in the dry forest, largely because this community thins out to become woodland. Birds have the great advantage of being able to bridge gaps in habitats, so the spacing of trees provides few problems and indeed some advantages for birds wishing to protect susceptible young from predation. Flight also means that the forest or woodland home can be isolated from food or water sources. The forest may only be one essential part of a bird’s habitat. Thus the Pied Butcherbird may nest in a forest tree but may also forage across grassland for small lizards or mice. The Scaly-breasted Lorikeet makes the forests of the east coast its habitat, settling for a period to nest in a hollow before living the life of a wanderer, following the seasonal flowering of forest trees. For the Superb Fairy-wren, a tight little grass nest near ground level may well be the centre of the world. However, as the wren’s brood grows, the whole family (conveniently camouflaged by non-breeding brown plumage) scatters about the brownish, grassy ground storey on its hunt for insects. The Helmeted Honeyeater, an endangered subspecies of the Yellow-tufted Honeyeater, is threatened by loss of habitat due to clearing and the impact of the advancing threat of human activity. A species has no greater threat than the destruction or modification of its habitat.

Classic Birds: Parrots and cockatoos; Bell Miner; Wedge-tailed Eagle; Little Eagle; Square-tailed Kite; Black-shouldered Kite; Pacific Baza; Grey Goshawk; Brown Goshawk; Common Bronzewing; Wonga Pigeon; Powerful Owl; Channel-billed Cuckoo; Sulphur-crested Cockatoo; Short and Long-billed Black-Cockatoos; Purple-crowned Lorikeet; Regent Parrot; Western Rosella; Red-capped Parrot; Shining Bronze-Cuckoo; Southern Boobook; Barn Owl; Rainbow Bee-eater; Splendid Fairy-wren; Painted Button-quail; Dollarbird; Spotted and Forty-spotted Pardalotes; Yellow and Buff-rumped Thornbills; Black-headed Honeyeater; Flame and Scarlet Robin; Western Yellow-Robins; Crested Shrike-tit; Rufous Whistler; Mistletoebird; Restless Flycatcher; White-winged Triller; Olive-backed Oriole

Classic reptiles:

Marauders of the forest floor are the monitors, which scrounge a living from invertebrates, small mammals and smaller reptiles as well as any luckless ground-nesting birds. Eggs are a delicacy and monitors will often climb into forest trees in search of nesting animals there.

Classic Reptiles: Marbled, Stone, Bynoe’s, Lesueur’s, Southern Leaf-tailed and Barking Geckoes; Tree Dtella; Jacky Lizard; Bearded Dragon; Gould’s, Lace and Rosenberg’s Monitor; Tree Skink; Ctenotus spp.; Dwarf Skink; Blotched Blue-tongue Lizard; Diamond Python; Brown Tree Snake; Green Tree Snake; Common Death Adder; Yellow-faced and Collared Whipsnake; White-lipped Snake; Red-naped Snake; Pale-headed Snake; Broad-headed Snake; Black Tiger, Island Tiger and Eastern Tiger Snakes; Red-bellied Black Snake; Eastern and Western Brown Snakes; Bandy Band

An extract from ‘Wild Habitats: A Natural History of Australian Ecosystems ‘ ABC Publishing 

Dry Sclerophyll Forests gallery – click and scroll