Tasmanian Oak

Mountain ash
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El Grande in Tasmania's Styx Valley
Scientific classification
Kingdom:	Plantae
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Myrtales
Family:	Myrtaceae
Genus:	Eucalyptus
Species:	E. regnans
Binomial name
Eucalyptus regnans F.Muell.
Synonyms
Eucalyptus amygdalina var. regnans F.Muell.

The Tasmanian Oak also called Mountain Ash, Victorian Ash, Giant Ash, Swamp Gum, or Stringy Gum (Eucalyptus regnans), is a species of Eucalyptus from Victoria and Tasmania. It can grow to more than 100 m (328 ft) and is the tallest flowering plant in the world.

Description

It is an evergreen tree, the tallest eucalyptus tree, growing 70–120 m (230–400 feet) tall. It has a straight, grey trunk with smooth bark. The leaves are narrow, curved, and end in a point, like a sickle. They grow up to 14 cm (6 in) long and 2.5 cm (1 in) wide. They are green to grey-green with a red stalk. The flowers are in groups of 9-15 together, each flower about 1 cm (0.5 in) diameter with a ring of many white stamens. The fruit is a hard nut, up to 9 mm (0.5 in) long and 7 mm (0.4 in) wide.

Habitat

Mountain Ash are found in cool, deep soiled, mountain areas to 1,000 m (3,281 ft) above sea level, with high rainfall of over 1,200 mm (47 in) each year. They grow very quickly, at more than a metre (3 feet) a year, and can reach 65 m (213 ft) in 50 years. They live for 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, Mountain Ash does not regrow after fire. They grow only from seed which are released from their woody gumnuts by heat. The seedlings need a lot of light, much more than reaches the forest floor normally when there are mature trees blocking the sun. Severe fires can kill all the trees in a forest, which causes a massive release of seed to take advantage of the nutrients in the ash bed. Up to 2.5 million seedlings per 1 ha (2 acres) have been recorded after a major fire. Competition and natural thinning slowly reduces the number of mature trees to about 30 to 40 per hectare. Because it takes roughly 20 years for seedlings to reach become old enough to make seeds, repeated fires in the same area can cause local extinctions. If, however, there are no fires to release seeds, the trees die off after about 400 years and are replaced by other species.

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Giant mountain ash trees, Blackspur Range, Victoria. Photo: Bob Beale

Tallest trees

Eucalyptus regnans is the tallest of all flowering plants, and possibly the tallest of all plants, although no living specimens can make that claim. The tallest measured living specimen, named Centurion, stands 100.5 metres (330 feet) tall in Tasmania. Before the discovery of Centurion, the tallest known specimen was Icarus Dream, which was rediscovered in Tasmania in January, 2005 and is 97 metres (318 ft) high. It was first measured by surveyors at 98.8 metres (324 ft) in 1962 but the documentation had been lost. A total of 16 living trees in Tasmania have been reliably measured in excess of 90 metres (300 ft). The Cumberland Scenic Reserve near Cambarville, became the site of Victoria's tallest trees, in 1939, including one measured at 92 metres (302 ft) high, following the extensive Black Friday bushfires. A severe storm in 1959 blew down 13 of the trees and the tallest tree was reduced to a height of 84 metres (276 ft) after it lost part of its crown. The height of this tree was cited as 81.5 metres (267 ft) in 2002 following further storm damage in 1973. In 2000, a tree at Wallaby Catchment in Kinglake National Park was discovered to be 91.6 metres (301 ft) tall in 2000, however it perished in the Black Saturday bushfires of 2009.

Historically, the tallest individual is claimed to be the Ferguson Tree, at 132.6 metres (435 ft), found in the Watts River region of Victoria in 1871 or 1872. This record is often disputed as unreliable, despite first-hand documentary evidence of it being measured on the ground with surveyor's tape by a senior forestry official (see below). Widespread agreement exists, however, that an exceptionally tall individual was reliably measured at 112.8 metres (370 ft) by theodolite in 1880 by a surveyor, George Cornthwaite, at Thorpdale, Victoria (the tree is known both as the Cornthwaite or Thorpdale Tree). When it was felled in 1881, Cornthwaite remeasured it on the ground by chain at 114.3 metres (375 ft). The stump is commemorated with a plaque. That tree was about 1 metre (3.3 ft) shorter than Hyperion, the world's current tallest living tree, a coast redwood measuring 115.5 metres (379.1 ft).

Some individuals attain much greater diameter; the largest known being "The Bulga Stump", a charred remnant near Tarra Bulga, South Gippsland district, Victoria, Australia which as a living tree had a DBH of 10.77 metres (35 ft 4 in), making E. regnans the third thickest species of tree after the Baobab (Adansonia digitata) and the Montezuma Cypress (Taxodium mucronatum). As a consequence of being both the tallest and thickest Australian trees, E. regnans is also the most massive; that title being currently held by an individual called the "Kermandie Queen" discovered 3.9 kilometres (2.4 mi) west of Geeveston, Tasmania which measures 76.99 metres (252 ft 7 in) in height and has a diameter at breast height (DBH) of 6.88 metres (22 ft 7 in).

Al Carder notes that in 1888 a cash reward of 100 pounds was offered there for the discovery of any tree measuring more than 400 feet (120 m). The fact that such a considerable reward was never claimed is taken as evidence that such large trees did not exist. Carder's historical research, however, revealed that the reward was offered under conditions that made it highly unlikely to be collected. First, it was made in the depths of winter and applied only for a very short time. Next, the tree had to be measured by an accredited surveyor. Since loggers had already taken the largest trees from the most accessible Victorian forests, finding very tall trees then would have demanded an arduous trek into remote wilderness and at considerable altitude. In turn, that meant that searchers also needed the services of experienced bushmen to be able to guide them and conduct an effective search. Only one expedition actually penetrated one of the strongholds of E. regnans at Mount Baw Baw but its search was rendered ineffectual by cold and snow and managed to measure only a single living tree – the New Turkey Tree: 99.4 metres (326 ft) – before appalling conditions forced a retreat, Carder notes.

Ferdinand von Mueller claimed to have personally measured one tree near the headwaters of the Yarra River at 122 metres (400 ft). Nurseryman David Boyle, claimed in 1862 to have measured a fallen tree in a deep gully in the Dandenongs at 119.5 metres (392 ft), and with a diameter at its broken tip that indicated it might have lost another eight metres (26 ft) of trunk when it broke, for 128 metres (420 ft).

Von Mueller's early records also mention two trees on the nearby Black Spur Range, one alive and measuring 128 metres (420 ft) and another fallen tree said to measure 146 metres (479 ft), but these were either based on hearsay or uncertain reliability. David Boyle also reported that a tree at Cape Otway measured 158 metres (518 ft), but this too was based on hearsay.

None, however, had been verified by direct documentation until 1982 when Ken Simpendorfer, a Special Projects Officer for the Forests Commission Victoria, directed a search of official Victorian archives. It unearthed a forgotten report from more than a century earlier, one that had not been referred to in other accounts of the species up to that time. It was written on 21 February 1872, by the Inspector of State Forests, William Ferguson, and was addressed to the Assistant Commissioner of Lands and Surveys, Clement Hodgkinson. Ferguson had been instructed to explore and inspect the watershed of the Watts River and reported trees in great number and exceptional size in areas where loggers had not yet reached. Ferguson wrote a letter to the editor in the Melbourne Age newspaper.

"Some places, where the trees are fewer and at a lower altitude, the timber is much larger in diameter, averaging from 6 to 10 feet and frequently trees to 15 feet in diameter are met with on alluvial flats near the river. These trees average about ten per acre: their size, sometimes, is enormous. Many of the trees that have fallen by decay and by bush fires measure 350 feet in length, with girth in proportion. In one instance I measured with the tape line one huge specimen that lay prostrate across a tributary of the Watts and found it to be 435 feet from the roots to the top of its trunk. At 5 feet from the ground it measures 18 feet in diameter. At the extreme end where it has broken in its fall, it (the trunk) is 3 feet in diameter. This tree has been much burnt by fire, and I fully believe that before it fell it must have been more than 500 feet high. As it now lies it forms a complete bridge across a narrow ravine" .... William Ferguson, The Melbourne Age, 22 February 1872.

It is also possible that individual trees will again attain such heights. Author Bob Beale has recorded that the tallest trees in the Black Spur Range now measure about 85 metres (279 ft) but – due to major bushfires in the 1920s and 30s – are less than 80 years old and have been growing consistently at the rate of about 1 metre (3.3 ft) a year.

Eucalyptus regnans is the tallest of all flowering plants, and possibly the tallest of all plants, although no living trees can make that claim. The tallest tree, named "Centurion", stands 99.6 metres tall in Tasmania. There are 16 living trees in Tasmania that have been measured taller than 90 metres. The tallest tree ever found was the "Ferguson Tree", at 132.6 metres, found in the Watts River region of Victoria in 1872. It had fallen over and was measured by William Ferguson, the Inspector of State Forests. The top of the tree had broken off, but the trunk was still more than one metre in diameter. Ferguson guessed the tree would have been more than 152 metres in height.

Uses

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At 92 metres "The Big Tree" at the centre was until recently thought to be the tallest remaining Mountain Ash.

Eucalyptus regnans is valued for its timber, and large areas of trees have been cut down. The main uses are building timber and woodchipping. It also used for newsprint in the 20th century. Most of the woodchips are sent to Japan. While the area of natural stands with large old trees is rapidly decreasing, large areas of new trees exist. It is increasingly grown in plantations where the long, straight, fast growing trunks are more valuable than the old growth timber.

The timber is rather rough (stringy) in texture. It is easy to work and the grain is straight with long, clear sections without knots. The wood works reasonably well for steam-bending. It is used for furniture, flooring, woodpanelling, veneer, plywood, window frames and general building.

Logging Eucalyptus regnans in Tasmania

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The Styx River in Tasmania runs through a forest of Eucalyptus regnans, myrtle beech and tree ferns. The mountain ash rise high above the forest.

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"The Big Tree" (previously thought to be the tallest remaining), is about 15 metres (49 ft) around the base. The sign at its base states its dimensions and the tonnage of timber that could potentially be cut from it. A few such trees of extreme size have been recorded by Forestry Tasmania as worthy of preservation.

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The stump of one of the largest Eucalyptus regnans to be logged in Tasmania. The man is 1.86 m (6 ft 1 in).

File:Tasmania logging 05 Styx logging road.jpg

A very tall mountain ash by a logging road. Trees that have been identified as above the permissible height for logging are left isolated when the forest around them is logged. If reduced in height by storm, the tree becomes loggable.

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Clearfelled old-growth forest of Eucalyptus regnans near the Styx Valley in southern Tasmania, prior to bull-dozing and burning.

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Eucalyptus regnans forest replaced by Pinus radiata plantation

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Mountain ash logs. Older trees are often hollow and are only suitable for woodchip.

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High grade woodchip for the papermills of Japan being exported from Burnie in 2001

References

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