EUCALYPTUS REGNANS

'''Eucalyptus regnans''', known variously by the common names 'Mountain Ash', 'Victorian Ash', 'Tasmanian Oak' or 'Stringy Gum', is a species of ''Eucalyptus'' native to southeastern Australia, in Tasmania and Victoria.

Contents

Description

Habitat

Tallest specimens

Uses

Conservation

See also

References

Gallery

Description

It is an evergreen tree the tallest of the eucalypts, growing to 70-90 m, with a straight, grey trunk, smooth-barked except for the rough basal 5-15 metres. The leaves are falcate (sickle-shaped) to lanceolate, 9-14 cm long and 1.5-2.5 cm broad, with a long acuminate apex and smooth margin, green to grey-green with a reddish petiole. The flowers are produced in clusters of 9-15 together, each flower about 1 cm diameter with a ring of numerous white stamens. The fruit is a capsule 5-9 mm long and 4-7 mm broad.

Habitat

It occurs in cool, deep soiled, mostly mountainous areas to 1000 m altitude with high rainfall of over 1200 mm per year. They grow very quickly, at more than a metre a year, and can reach 65 metres in 50 years, with an average life-span of 400 years. The fallen logs continue supporting a rich variety of life for centuries more on the forest floor.
Unusually for a eucalypt, it tends not to recover by re-shooting after fire, and regenerates only from seed. The seeds are released from their woody capsules (gumnuts) by heat and for successful germination the seedlings require a high level of light, much more than reaches the forest floor when there is a mature tree canopy. Severe fires can kill all the trees in a forest, prompting a massive release of seed to take advantage of the nutrients in the ash bed. Seedling densities of up to 2.5 million per hectare have been recorded after a major fire. Competition and natural thinning eventually reduces the mature tree density to about 30 to 40 individuals per hectare. Because it takes roughly 20 years for seedlings to reach sexual maturity, repeated fires in the same area can cause local extinctions. If, however, no fires regenerate an area, the trees die off after about 400 years and are replaced by other species.
Recent research has challenged the belief that Mountain Ash are fire intolerant and require catastrophic fires for reproduction. This research is revealing that the species can recover from fire and a supposedly 'old growth' stand of Mountain Ash in Victoria is actually a multi-age stand due to fire and has experienced seven fires since the 1400s (Lindenmayer, in prep.). It is worth noting these inaccurate beliefs are promoted by forestry agencies as a convenient justification for current destructive logging practices.

Tallest specimens

''Eucalyptus regnans'' is the tallest of all flowering plants, and possibly once the tallest of all plants. The tallest measured specimen is officially taken as 114.3 metres. The tree, Cornthwaite Tree or Thorpdale Tree, was first measured by theodolite in 1880. Next year it was felled and then measured by tape and there was close agreement. (Ken J. Simpfendorfer. "Big Trees in Victoria"). The stump commemorated with an insignificant plaque that exists today. The tree was about 1 metre shorter than the world's current tallest living tree, a Coast Redwood, 115.55 metres. The tallest specimens encountered by early European settlers are now dead as a result of bushfires, logging and advanced age.
The tallest measured living specimen, Icarus Dream, was rediscovered in Tasmania in January, 2005 and is 97 metres high (Tasmanian Giant Trees Consultative Committee, ref. 1). It was first measured by surveyors at 98.8 metres in 1962 but the documentation had been lost. 15 living trees in Tasmania have been reliably measured in excess of 90 metres (Tasmanian Giant Trees Consultative Committee, ref. 3). Few living specimens in Victoria exceed 90 metres; old records of logged trees make varied claims of extreme heights, but these are difficult to verify today. The famous Ferguson Tree, a specimen in Victoria that fell after a bushfire, was measured by tape by a government surveyor, William Ferguson, on 21 February 1872, at 133 metres (436 feet), though this figure is not now generally accepted. Its crown had broken off and the diameter of the trunk at that point was still one metre, leading to claims that when it was intact the tree would have exceeded 150 metres (500 feet); this however presupposes that the break occurred in a hitherto undamaged tree. A more realistic scenario is of a shorter tree with several episodes of breakage and regrowth building up a stout stem without at any time attaining the claimed height.

Uses

''Eucalyptus regnans'' is valued for its timber, and has been harvested in very large quantities. Primary uses are sawlogging and woodchipping. It was a major source of newsprint in the 20th century. Much of the present woodchip harvest is exported to Japan. While the area of natural stands with large old trees is rapidly decreasing, substantial areas of regrowth exist and it is increasingly grown in plantations, the long, straight, fast growing trunks being much more commercially valuable than the old growth timber.

It is a medium weight timber (about 680 kg/m³) and rather coarse (stringy) in texture. Gum veins are common. The wood is easy to work and the grain is straight with long, clear sections without knots. The wood works reasonably well for steam-bending.
Primary uses for sawn wood are furniture, flooring (where its very pale blonde colour is highly prized), panelling, veneer, plywood, window frames, general construction. The wood has sometimes been used for wood wool and cooperage. However, the wood needs steam reconditioning for high value applications, due to a tendency to collapse on drying. This wood is highly regarded by builders, furniture makers and architects. [1]

Conservation

Great controversy surrounds the logging of old-growth ''Eucalyptus regnans'' in its natural range in both Victoria and Tasmania. Aside from its symbolic significance as the largest eucalypt of all, ''Eucalyptus regnans'' has value to conservationists in provides essential habitat to important birds and mammals (notably the Wedge tailed eagle, the Lyrebird and the endangered Victorian state animal emblem Leadbeater's Possum). In a land of vast, arid plains and desert, the contrasting lush fertility of mountain-ash forest is particularly dear to nature lovers.
Although its status as a species is secure, old-growth forests of ''Eucalyptus regnans'' are particularly susceptible to destruction by fire and clearfell forestry. For this reason stands of very old and very tall trees exist only in pockets. Very few such stands of trees fall within those areas that have been listed as National Park or World Heritage environments. Most lie within areas controlled by state forestry management authorities and their heritage value is balanced against the commercial value of harvesting and then planting fast-growing and more productive monoculture timber crops on these comparatively well-watered and fertile areas.
In Tasmania, over 85% of old growth ''regnans'' forests have been logged. The trees continue to be clearfell logged by Gunns. Out of control: the tragedy of Tasmania's forests, , Richard, Flanagan, The Monthly,
Political opposition to the logging of old-growth forests by the process known as clearfelling has grown very strong in recent years (particularly in the case of woodchipping), and the extent of future harvesting remains uncertain. This is controversial, because studies conducted in the Twentieth Century by T. M. Cunningham and David H. Ashton suggest that its re-growth habit requires open space, and an ash layer and that clearfelling (as opposed to selective logging methods) is essential to the successful germination and growth of seedlings[2][3][4]. However, recent research has challenged the belief that Mountain Ash are fire intolerant and require catastrophic fires for reproduction. This research is revealing that the species can recover from fire and a supposedly 'old growth' stand of Mountain Ash in Victoria is actually a multi-age stand due to fire and has experienced seven fires since the 1400s (Lindenmayer, in prep.).

The clearfell, burn and sow (CBS) technique was developed in the early 1960s, based largely on the pioneering work of Dr Max Gilbert in Tasmania and Dr Murray Cunningham in Victoria. It involves clearing of all the trees in coupes usually ranging from 10 to 100 ha, burning of the harvest residues to create a seedbed and artificial sowing of eucalypt seed of species that came from the coupe. The technique was developed, as a means of achieving reliable regeneration in tall wet forests with dense understoreys. Prior to its introduction, cut-over wet eucalypt forest lacked regeneration except where stand-replacing wildfires had initiated regrowth. In drier forests, with sparse understoreys, eucalypt regeneration can occur in canopy gaps and partial harvest systems are used. Seed is supplied naturally from retained trees. Some 55% of the annual harvest in public native forests is now by partial harvesting.
Clearfelling attracts public concern, particularly when applied to tall oldgrowth forests, because of its high initial impact, the smoke nuisance posed by burning, a reduction in rainforest species, rotting logs and hollow-dependent birds and mammals and a reduction in special species timbers and leatherwood nectar. However, clearfelling is used in tall wet eucalypt forests because it’s the safest for forest workers, it gives the highest return to the forest owner (the Tasmanian public), burning creates seedbed, maximises eucalypt growth and reduces the subsequent wildfire risk. The CBS system has some congruence with natural regeneration processes after stand-replacing wildfires (although wildfires leave more structure behind). Clearfelling also results in the least disturbance to the forest, in total, for a given level of wood supply. Recent research indicates that plant and beetle species composition is similar in logged regrowth and wildfire regrowth of the same age. This suggests that a single application of CBS in tall oldgrowth forests allows a modest ‘legacy’ of oldgrowth species (e.g. myrtle) and structures (e.g. large stumps and logs) to be passed onto the new stand. However, it has been predicted that a reduced legacy will be passed on if the regrowth is re-logged on the planned 90-year rotation cycle.

''Alternatives to clearfell silviculture in oldgrowth forests''
John Hickey, Division of Research and Development, Forestry Tasmania[5]
The clearfell process can lead to spectacular and uniform regrowth if managed appropriately. However this method has often been used to justify the unreasonable exploitation of a lucrative resource in certain areas. The clearfell process was however unavailable until the arrival of white settlers (indigenous people practiced a mozaic burn system that kept the forest open but didn't remove or clearfell large amounts of timber[6]) and the usual method of regrowth was through intense bushfire that catastrophically destroyed the forest allowing regeneration from seed.

See also

★ ''Eucalyptus delegatensis''

★ Manna Gum

★ For other trees named ''Mountain Ash'', see Mountain ash

References

# Tasmanian Giant Trees Consultative Committee New Tallest Tree for Tasmania 2005
# Forestry Tasmania The tallest ''Eucalyptus regnans'' measured as 92 m in 2000 (.pdf file)
# Tasmanian Giant Trees Consultative Committee Tasmania's Ten Tallest Giants 2006
# Association of Societies for Growing Australian Plants: ''Eucalyptus regnans''
# Victorian Eucalypts: ''Eucalyptus regnans''
# International Society of Arboriculture, Australia Chapter: Australia's Biggest, Tallest and Oldest Trees
# "Wood in Australia" by Keith R Bootle

Gallery