Nothofagus cunninghamii, commonly known as myrtle beech or Tasmanian myrtle, is the dominant species of cool temperate rainforests in Tasmania and Southern Victoria. It has low fire resistance and grows best in partial shade conditions. It has rough bark covered in mosses and epiphytic growth. Its leaves are triangular-shaped, small, and dark green with differentiated margins. It has white unisexual flowers.
Description and habit
N. cunninghamii range from trees of up to 50 meters in protected rainforest valleys to low-growing alpine shrubs less than 1 m tall in exposed conditions. Maximum height is about 55 m. The leaves are simple and alternate, growing 0.5–1.5 cm long, and in Victoria up to 2 cm (0.8 in) long. The leaves are dark green, with new growth brilliant red, pink or orange in spring. They are triangular with irregular minute teeth with craspedodromous veins with all secondary veins terminate at leaf margins and spread from a central primary midrib vein. The tertiary veins are poorly defined. The plants have separate unisexual male and female flowers on the same tree. Male flowers have hanging stamens and grow solitarily while female flowers lack stamens and cluster by leaves near the tips of branches. They flower in November and December. The fruit is small (about 6 mm) and woody. They contain three small-winged nuts with fertile seeds from December to February. Seeds germinate in 6–8 weeks. N. cunninghamii is a fairly robust species, requiring around 900 mm of rain spread throughout the year. It is also frost tolerant to –7 °C. It can grow in full shade, albeit slowly, through to full sun, given enough water, but grows best in partial sun conditions. It grows best in moist and well-draining soil.
Distribution and habitat N. cunninghamii is the dominant species in cool temperate rainforest across Tasmania and southern Victoria.
It is most common in Tasmania, where it occurs in most regions except the drier Midlands and east coast. The largest remaining tract of N. cunninghamii-dominated rainforest is takayna/Tarkine in the Northwest of Tasmania. It is the largest remaining tract of cool temperate rainforest in Australia. In Victoria, N. cunninghamii grows best in the deep red mountain soils or in highly organic soils in the Central Highlands, Strzelecki Ranges, Otway Ranges, and Wilsons Promontory.
Taxonomy and naming
The beech or Fagaceae family includes nine genera: Fagus, Nothofagus, Lithocarpus, Castanopsis, Colombobalanus, Castanea, Chrysolepis, Quercus, and Trigonobalanus. Nothofagus means "false beech" although there is some suggestion that this is due to a misspelling of the intent NOTOfagus, meaning "southern beech." There is a suggestion that the genus was changed due to a spelling error. There are about 40 species of Nothofagus, with only three occurring in Australia: N cunninghamii, gunnii, and moorei. Nothofagus gunnii is a deciduous beech endemic to Tasmania that grows in low-fire, alpine regions. Nothofagus moorei, or Antarctic beech, is another cool temperate rainforest evergreen found in patches in New South Wales and Southern Queensland. Nothofagus cunninghamii is named for the 19th century botanist and 'explorer', Allan Cunningham, who is best known for his plant collection career throughout Australia. In 2013, N. cunninghamii was proposed to be renamed Lophozonia cunninghamii. This is due to the other species in the family Nothofagaceae with significant differences in morphology and genetics throughout South America, New Zealand, Australia, and other relict Gondwanan rainforests. There has been controversy over the change in name from Nothofagus to Lophozonia with the argument that the phylogenetic history suits retaining the genus Nothofagus.
Ecology
Occasionally one may see round, orange-like fruiting bodies of a fungus protruding from the trunk; this is Cyttaria gunnii. Cyttaria are obligate biotrophic associates of myrtle beech and have co-evolved with Nothofagus. It grows in temperate rainforest with other rainforest species including southern sassafras (Atherosperma moschatum), leatherwood (Eucryphia lucida), horizontal(Anodopetalum biglandulosum) and celery-top pine (Phyllocladus aspleniifolius). They also form important habitat for birds who use the tree for nesting and safety. N. cunninghamii grow throughout a variety of ecosystems but establish best in partial sun in wet sclerophyll understory. In mixed forests, the tree species will be made up of primarily N. cunninghamii and sassafras with a tall eucalyptus overstory. Once these remaining eucalypts die, the myrtle beech will become the dominant species forming a pure rainforest. This process takes several hundred years. This ecosystem is retained by rare fires in wet conditions that prevent eucalypt seeds from germinating. In the event of a big fire, the pure rainforest will be replaced by eucalypts and the process of reestablishing a rainforest will restart. Myrtle beech rarely survives intense fire, and must re-establish from neighbouring areas. They can, however, survive light fires by regenerating from seed or vegetatively from basal epicormic shoots.
Both N. cunninghamii and the closely related N. moorei are excellent hosts for epiphytes.
Evolution Nothofagus is an ancient relict that was present in Gondwanan rainforests and today grows across the Southern Hemisphere. N. cunninghamii is most closely related to N. moorei, the other species of evergreen Nothofagus endemic to Australia. The two likely evolved from a Paleogene ancestor. Due to cooling since the Paleogene, leaves may have been pressured to evolve to smaller sizes in colder environments. This may explain the evolution toward smaller leaves than their ancestor as well as the northern boundary for N. cunnninghamii where it is replaced by the larger-leafed N. moorei in warmer Northern environments.
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