Eucalyptus regnans

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{{Taxobox | color = lightgreen | name = Eucalyptus regnans | image_width = 240px | image_caption = Mountain-ash regrowth in the Otway Ranges,
southern Victoria.
If not logged again, these trees will
more than double in size as they mature. | regnum = Plantae | divisio = Magnoliophyta | classis = Magnoliopsida | ordo = Myrtales | familia = Myrtaceae | genus = Eucalyptus | species = E. regnans | binomial = Eucalyptus regnans | binomial_authority = F.Muell. }}

The mountain ash (Eucalyptus regnans) of southern Australia is the tallest of all flowering plants, and possibly the tallest of all plants. That claim is given credence by the documented fact that in the 1880s the State Surveyor of Victoria measured with a theodolite a mountain ash in Victoria at 114 metres (almost two metres taller than the world's current tallest living tree, a coast redwood); unfortunately that tree was promptly cut down and the stump commemorated with an insignificant plaque that exists today. The tallest specimens encountered by early European settlers are now dead as a result of bushfires, logging and advanced age.

The largest measured living mountain ash, Icarus Dream, was rediscovered in Tasmania in January, 2005 and is 97 metres high (Tasmanian Giant Trees Consultative Committee, ref. 1), though it was also measured as 92 m in 2000 (Forestry Tasmania, ref. 2) so this figure retains a degree of uncertainty. It was first measured by surveyors at 98.8 metres in 1962 but the documentation had been lost. Ten living mountain ash 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 mountain ash 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.

Mountain ash is a straight, grey-trunked tree, smooth-barked for all but the first few metres, and is native to cool, deep soiled, mostly mountainous areas to 1000m in Victoria and Tasmania with very high rainfall of over 1200mm (47 inches) per year. They grow very quickly - at more than a metre a year - and can reach 65 metres in 50 years. They can live for about 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 mainly from seed. Severe fires can kill all the mountain ash 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.

Mountain ash is valued for its timber, not so much because of any particular virtue of the timber itself (it is a heavy, fine-grained eucalyptus hardwood much like several others), but because of the sheer volume that can be harvested. Primary uses are sawlogging and woodchipping. Mountain ash was a major source of newsprint last century. Some large natural stands of mountain ash remain, but substantial areas of regrowth also exist and it is increasingly grown in plantations. Great controversy surrounds its use in its natural range in both Victoria and Tasmania; as the largest eucalypt of all it has symbolic value to conservationists, it provides essential habitat to important birds and mammals (notably the Lyrebird and the endangered Victorian state animal emblem Leadbeater's Possum), and in a land of vast, relatively arid plains, the contrasting lush fertility of mountain-ash forest is particularly dear to nature lovers. Although the status of E. regnans as a species is secure, political opposition to logging it has grown very strong in recent years (particularly in the case of woodchipping), and the extent of future harvesting remains uncertain.

Image:Wood from victoria mountain ash.jpg

Image:Logs at woodmill.jpg

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