The diversity of vascular plant species in cool temperate rainforests is considerably lower than that of the tropical rainforests of northern Queensland. It is usual for species richness to be lower in cooler climates or where other factors reduce plant growth rates. However the species richness in Tasmanian rainforests is considerably lower than areas with similar climate in Chile. Some scientists believe past glacial climates in Tasmania led to the extinctions of many forest species. Much of the current land area of Tasmania was alpine or subalpine at the height of the last glacial about 22,000 years ago. Forests were largely restricted to the current coastal regions and lowland river valleys. Of course the land area of Tasmania extended further out into areas now below sea level and these areas were probably vegetated by forest. Some particularly cold tolerant trees probably survived in isolated patches further inland. The isolation of Tasmania from the Australian mainland during interglacial periods has reduced the ease at which species can reach Tasmania from elsewhere.
Many of the rainforest tree species are endemic (ie restricted to the state). The reason for the high endemicity amongst woody rainforest plants is in part related to the isolation of Tasmania and in particular this cool wet habitat from similar areas on the mainland of Australia. It is also because many of these plants have very ancient origins and have evolved insitu in Tasmania from plants of the ancient supercontinent of Gondwana more than 60 million years ago. The following account gives a description of the major species to be found in Tasmania's cool temperate rainforests, but is by no means exhaustive.
Myrtle-beech Nothofagus cunninghamii
The dominant species of the cool temperate rainforest, the myrtle-beech is representative of species that once grew extensively thoughout not only Australia, but also the southern continents of South America and Antarctica. It was part of the distinctive suite of plants that evolved on the supercontinent of Gondwana. Today the species finds its stronghold in Tasmania but also occurs in Victoria.
Myrtle-beech can attain heights of up to 50m and ages in excess of 500 years. Although it is not as shade tolerant as sassafras and leatherwood it maintains its dominance in the forest by having a relatively fast growth rate, being larger and longer lived. When it dies it leaves a very large canopy gap which allows in sufficient light to enable young myrtle seedlings to grow.
Sassafras Atherosperma moschatum
A dominant species within the rainforest, the sassafras is able to reproduce vegetatively by growing stem suckers from the base of the trunk after the main trunk has died. This species has separate male and female flowers that can be seen from September to October. There are no other species in the genus Atherosperma so sassafras has no close relatives. Its closest relative is a plant species that grows in the rainforests of Chile suggesting that they have evolved from a common Gondwanan ancestor.
Sassafras, is usually found in association with myrtle but on the east coast it may be found dominating remnant rainforest patches because it can survive in areas of lower rainfall. It is a plant with a beautiful aroma, which gives the rainforests they occupy a distinctive appeal. It is also the food plant for the Macleay’s swallowtail butterfly, which can be seen on the wing between November and March. It is a commercial timber often used for quality furniture. The black stain often seen in its heartwood is caused by a bacterial infection.
Leatherwood Eucryphia lucida
Found only in Tasmania, the large, delicate nectar-rich flowers of the leatherwood form the basis of Tasmania's leatherwood honey industry. The distinctive paddle-shaped leaves aid recognition outside the flowering period. Flowering period is December to January. This species is most common in the implicate and thamnic rainforests that are common in southwest Tasmania. It is restricted to areas of high rainfall.
A second species of Eucryphia, dwarf leatherwood, (Eucryphia milliganii) is also endemic to Tasmania. It is typical of montane rainforests in southwest Tasmania. The genus Eucryphia is an ancient one, with other species also represented in temperate areas of New South Wales and Chile. Recent taxonomic work suggests that this genus should be placed in the ancient Gondwanan family Cunoniaceae.
Native laurel Anopterus glandulosus
Native laurel is found only in Tasmania, where it is commonly found as an understorey shrub in wet eucalypt forest and rainforest. Unlike most Tasmanian rainforest species, which have fairly small leaves, laurel has large (up to 17 cm long by 4 cm wide), glossy green leaves that may be confused with native plum. It is distinguished by the black oil glands found on the tip of each serration on the leaf margin. This plant flowers in October. This species is a member of the ancient Gondwanan plant family Escalloniaceae.
Horizontal Anodopetalum biglandulosum
Within implicate rainforests of southwest Tasmania the aptly-named horizontal forms tangled thickets. These are the result of its habit of bending over as it grows and sending up new vertical branches, which in turn bend over. The species is well known to bushwalkers as it is a nightmare to walk through! The genus Anodopetalum has only one species, horizontal, which is restricted to Tasmania. It is one of only 20 endemic genera in Tasmania. It is a member of the ancient Gondwanan plant family Cunoniaceae.
Whitey wood Acradenia frankliniae
This plant is restricted to rainforest understoreys by the margins of western Tasmanian rivers. Although locally common along the lower Gordon and Franklin Rivers and some others, the species is considered rare but not threatened so is not listed on the Threatened Species Protection Act. The genus Acradenia has only this one species representing it and occurs only in Tasmania.
Native plum Cenarrhenes nitida
This plant is restricted to rainforest understoreys by the margins of western Tasmanian rivers. Although locally common along the lower Gordon and Franklin Rivers and some others, the species is considered rare but not threatened so is not listed on the Threatened species Protection Act. The genus Acradenia has only this one species representing it and occurs only in Tasmania.
Pandani Richea pandanifolia
Found only in Tasmania, the pandani is the largest heath plant in the world. Although it resembles its near name-sake, the pandanus palms of tropical Australia and South-east Asia, the pandani is in no way related to it. Pandanis are not confined to rainforests, but can also occur in sub-alpine communities. The long, sharp-edged leaves are retained on the trunk to provide insulation. The water that collects in the axils of pandani leaves provides a special habitat for some distinctive invertebrates.
Pandani occurs both in rainforests and in sub-alpine environments. Its leaves are sharp and serrated
Climbing Heath Prionotes cerinthoides
Climbing heath is common in the rainforests of the west and south-west particularly montane areas and also occurs in alpine vegetation. It is a climbing plant, often seen draped around the trunks of trees. It has relatively large and beautiful pink bell shaped flowers from November to April. The genus Prionotes is represented only by this species, and is distinct from most other members of the family Epacridaceae because it has divaricate leaf venation. It is sometimes referred to as the missing link between the family Epacridaceae (southern hemisphere heath family) and the Ericaceae (northern hemisphere heath family). The closest relative to Tasmania’s climbing heath is a species found in the rainforests of Chile.
Batswing fern Histiopteris incisa
The batswing fern is a close relative of bracken. Like bracken, it thrives on disturbance and is abundant in areas where trees have fallen after flooding. Batswing fern are not confined to rainforests, but occur in a variety of plant communities. It is widespread throughout the temperate regions of the southern hemisphere.
Filmy fern Hymenophyllum sp.
As its name suggests, this tiny fern has very thin leaves. In fact, they are just one cell thick. The filmy fern creeps along on rhizomes (hair-like roots) at the base of tree trunks and on tree ferns.
Hard water fern Blechnum wattsii
This plant is one of the most common ferns in Tasmania's rainforests. It also occurs in wet scerophyll forests. It has thick leathery fronds which rattle when walked through -- hence the alternative common name of 'rattle fern'. It is common in forests throughout eastern Australia.
Interestingly, the reproductive fronds of this species are quite different in appearance to the fronds which are involved in photosynthesis.
Mother shield fern Polystichum proliferum
This fern is most common in rainforests on fertile soils, rather than the poor soils that characterise the western rainforests. It resembles a tree fern without a trunk.
Kangaroo fern Phymatosorus pustulatus
A species found as far north as tropical Queensland, the kangaroo fern is typically seen decorating the mossy trunks of rainforest trees such as myrtle-beech and sassafras.
Tree fern Dicksonia antarctica
The trunk of the tree fern is greatly increased in diameter by the outgrowth of fibrous rootlets. This often forms a surface on which large forest trees such as sassafras can germinate and grow. The starchy pith found in the apex of the trunk was a food source for Tasmanian Aboriginal people. Treeferns are common in fertile callidendrous rainforests,wet sclerophyll forests and fern gullies. The genus Dicksonia was widespread on the ancient super-continent of Gondwana but tree ferns are restricted to the southern hemisphere.
Fish-bone water fern Blechnum nudum
This species has its pinnules (leaflets) arranged like the bones joined to the spine of a fish. Like the hard water fern, it is distinguished from other fern families by fertile reproductive fronds, which look very different from the fronds used for photosynthesis.