The Tasmanian cool temperate rainforest is composed of two alliances, the myrtle-beech
(Nothofagus cunninghamii) alliance and the pencil pine (
Athrotaxis cupressoides) alliance. The former is made up of callidendrous, thamnic and implicate, whilst the latter is all open montane.
Callidendrous rainforest This is the simplest rainforest community in Tasmania; it is typically represented by medium to tall forests dominated by
Nothofagus cunninghamii and/or
Atherosperma moschatum, often together with
Leptospermum lanigerum (woolly tea-tree) or
Acacia melanoxylon (Australian blackwood). Typically, these forests are at least in height. Trees are usually well formed and widely spaced, and the
understorey is open and often described as park-like. Fern diversity is high in many areas, and in these areas,
epiphytes often flourish.
Histiopteris incisa (bat's wing fern) and
Hypolepis rugosula (ruddy ground-fern) occur in disturbed sites such as along roads where there have been breaks in the canopy. As elevation increases, the height of the forest decreases,
Nothofagus cunninghamii becomes multi-stemmed, develops crooked leaning stems and abundant epiphytic
bryophytes, and lichens produce a patterned effect on the trunks. The typical understorey becomes dominated by
Tasmannia lanceolata (mountain pepper) and
Telopea truncata (Tasmanian waratah), and the ground layer becomes host to
Oxalis megellancia and
Lagenophora stipitata (blue bottle-daisy). The
pteridophyte diversity decreases and only small species such as
Lycopodium fastigiatum (alpine club moss),
Hymenophyllum peltatum,
Grammitis billardierei (common finger-fern) and
Blechnum penna-marina (Antarctic hard-fern) persist. Callidendrous rainforests occurs in the eastern half of the state and in northwestern and central Tasmania. Table 1 Lyrebird nature walk, Mt Feild, Tasmania:
species composition and structure of a mixed Callidendrous and Thamnic rainforest community; Height ~, 90% of ground litter cover, 5% rock and 5% bare ground.
Thamnic rainforest Thamnic rainforests are characterised by well-formed trees of medium height, well below , and a distinct shrub layer. The canopy is typically dominated by a mixture of 2–5 species, including
Nothofagus cunninghamii,
Eucryphia lucida,
Atherosperma moschatum,
Lagarostrobos franklinii,
Eucryphia milliganii (dwarf leatherwood),
Phyllocladus aspleniifolius (celery-top pine),
Athrotaxis selaginoides and, rarely,
Nothofagus gunnii (tanglefoot-beech). Fern diversity decreases, as a result, because of the decrease in light from the understorey.
Parablechnum wattsii (hard water fern) is the main ground fern; it prefers damp shaded areas and forms a very dense layer in some areas but can be absent in others. Small epiphytes are widespread, these include
Hymenophyllum rarum (a filmy fern) and
Grammitis billardierei.
Apteropteris applanata can occur in areas containing
Athrotaxis. Other larger epiphytes are usually present, but they are rarely prominent. At higher elevations, the general appearance resembles that of a callidenderous rainforest, but the floristic differences remain the same. Thamnic rainforests occur mostly in western and southwestern Tasmania. Cenarrhenes nitida,
Telopea truncata,
Agastachys odorata, Comprosma nitida,
Archeria eriocarpa,
Archeria serpyllifolia,
Archeria hirtella, Olearia persoonioides, Trochocarpa cunninghamii, Trochocarpa gunnii,
Richea pandanifolia,
Richea scoparia,
Dracophyllum milliganii and Prionotes cerinthoides
are all typical shrubs or small trees that comprise these communities. The ferns are dominated by Parablechnum wattsii but small epiphytes do prevail: Hymenophyllum rarum, Hymenophyllum marginatum,
Grammitis billardierei and Apteropteris applanata
occurs in communities where Athrotaxis are present. – occur mostly in western and southwestern Tasmania. Small species such as Hymenophyllum peltatum
and Apteropteris applanata'' can sometimes make an appearance. – occur on the
Central Plateau but can extend as small outliners to the mountains further south. ==Biological factors==