Trees

Tallest trees

The heights of the tallest trees in the world have been the subject of considerable dispute and much exaggeration. Modern verified measurement with laser rangefinders combined with tape drop measurements made by tree climbers, carried out by the U.S. Eastern Native Tree Society has shown that some older measuring methods and measurements are often unreliable, sometimes producing exaggerations of 5% to 15% above the real height. Historical claims of trees of 130 m (427 ft), and even 150 m (492 ft), are now largely disregarded as unreliable, and attributed to human error. Historical records of fallen trees measured prostrate on the ground are considered to be far more reliable. The following are now accepted as the top five tallest reliably measured species:

1. Coast Redwood (Sequoia sempervirens): 115.56 m (379.1 ft), Redwood National Park, California, United States[10]
2. Australian Mountain-ash (Eucalyptus regnans): 99.6 m (326.8 ft), south of Hobart, Tasmania, Australia[11]
3. Coast Douglas-fir (Pseudotsuga menziesii): 99.4 m (326.1 ft), Brummit Creek, Coos County, Oregon, United States[12]
4. Sitka Spruce (Picea sitchensis): 96.7 m (317.3 ft), Prairie Creek Redwoods State Park, California, United States[13]
5. Giant Sequoia (Sequoiadendron giganteum): 94.9 m (311.4 ft), Redwood Mountain Grove, Kings Canyon National Park, California, United States[14]

A view of a tree from below; this may exaggerate apparent height
Stoutest trees

The girth of a tree is much easier to measure than the height, as it is a simple matter of stretching a tape round the trunk, and pulling it taut to find the circumference. Despite this, UK tree author Alan Mitchell made the following comment about measurements of yew trees:
“ The aberrations of past measurements of yews are beyond belief. For example, the tree at Tisbury has a well-defined, clean, if irregular bole at least 1.5 m long. It has been found to have a girth which has dilated and shrunk in the following way: 11.28 m (1834 Loudon), 9.3 m (1892 Lowe), 10.67 m (1903 Elwes and Henry), 9.0 m (1924 E. Swanton), 9.45 m (1959 Mitchell). . . . Earlier measurements have therefore been omitted." ”

—Alan Mitchell; in a handbook "Conifers in the British Isles".[15]

As a general standard, tree girth is taken at 'breast height'; this is defined differently in different situations, with most forestry measurements taking girth at 1.3 m above ground,[16] while those who measure ornamental trees usually measure at 1.5 m above ground;[3] in most cases this makes little difference to the measured girth. On sloping ground, the "above ground" reference point is usually taken as the highest point on the ground touching the trunk,[3][16] but some use the average between the highest and lowest points of ground[citation needed]. Some of the inflated old measurements may have been taken at ground level. Some past exaggerated measurements also result from measuring the complete next-to-bark measurement, pushing the tape in and out over every crevice and buttress.[15]

Modern trends are to cite the tree's diameter rather than the circumference; this is obtained by dividing the measured circumference by π; it assumes the trunk is circular in cross-section (an oval or irregular cross-section would result in a mean diameter slightly greater than the assumed circle). This is cited as dbh (diameter at breast height) in tree and forestry literature.[3][16]

One further problem with measuring baobabs Adansonia is that these trees store large amounts of water in the very soft wood in their trunks. This leads to marked variation in their girth over the year (though not more than about 2.5%[17]), swelling to a maximum at the end of the rainy season, minimum at the end of the dry season.

The stoutest living single-trunk species in diameter are:

1. African Baobab Adansonia digitata: 15 m (49 ft), Big Baobab, Limpopo Province, South Africa.[18]
2. Montezuma Cypress Taxodium mucronatum: 11.62 m (38.1 ft), Árbol del Tule, Santa Maria del Tule, Oaxaca, Mexico.[19] Note though that this diameter includes buttressing; the actual idealised diameter of the area of its wood is 9.38 m (30.8 ft).[19]
3. Giant Sequoia Sequoiadendron giganteum: 8.85 m (29 ft), General Grant tree, Grant Grove, California, United States[20]
4. Coast Redwood Sequoia sempervirens: 7.44 m (24.4 ft), Prairie Creek Redwoods State Park, California, United States.[citation needed]

Charles Darwin reported finding Fitzroya cupressoides with trunk circumferences of up to 40 m (130 ft)[21] implying a diameter of about 12 m (40 ft), but this may be an anomaly as the largest known measurements are about 5 m.[22]

An addition problem lies in cases where multiple trunks (whether from an individual tree or multiple trees) grow together. The Sacred Fig is a notable example of this, forming additional 'trunks' by growing adventitious roots down from the branches, which then thicken up when the root reaches the ground to form new trunks; a single Sacred Fig tree can have hundreds of such trunks.[1]

Occasionally, errors may occur due to confusion between girth (circumference) and diameter.[23]
Largest trees

The largest trees in total volume are those which are both tall and of large diameter, and in particular, which hold a large diameter high up the trunk. Measurement is very complex, particularly if branch volume is to be included as well as the trunk volume, so measurements have only been made for a small number of trees, and generally only for the trunk. No attempt has ever been made to include root volume. Measuring standards vary.

The top four species measured[24] so far are:

1. Giant Sequoia Sequoiadendron giganteum: 1,487 m³ (52,508 cu ft), General Sherman[24]
2. Coast Redwood Sequoia sempervirens: 1,203 m³ (42,500 cu ft), Lost Monarch[25]
3. Montezuma Cypress Taxodium mucronatum: 750 m³ (25,000 cu ft), Árbol del Tule[26]
4. Western Redcedar Thuja plicata: 500 m³ (17,650 cu ft ), Quinault Lake Redcedar[24]
5. Kauri Agathis australis: circa 400 m³ (15,000 cu ft), Tane Mahuta tree[24] (total volume, including branches, 516.7 m³/18,247 cu ft)[27]

However, the Alerce Fitzroya cupressoides, as yet un-measured, may well slot in at fourth or fifth place. The largest angiosperm tree is currently a Tasmanian Blue Gum (Eucalyptus globulus) in Tasmania, with a volume of 368 m³.[28]
Oldest trees

The oldest trees are determined by growth rings, which can be seen if the tree is cut down or in cores taken from the edge to the center of the tree. Accurate determination is only possible for trees which produce growth rings, generally those which occur in seasonal climates; trees in uniform non-seasonal tropical climates grow continuously and do not have distinct growth rings. It is also only possible for trees which are solid to the center of the tree; many very old trees become hollow as the dead heartwood decays away. For some of these species, age estimates have been made on the basis of extrapolating current growth rates, but the results are usually little better than guesswork or wild speculation. White (1998)[29] proposes a method of estimating the age of large and veteran trees in the United Kingdom through the correlation between a tree's stem diameter, growth character and age.

The verified oldest measured ages are:

1. Great Basin Bristlecone Pine (Methuselah) Pinus longaeva: 4,844 years[30]
2. Alerce Fitzroya cupressoides: 3,622 years[30]
3. Giant Sequoia Sequoiadendron giganteum: 3,266 years[30]
4. Sugi Cryptomeria japonica: 3,000 years[31]
5. Huon-pine Lagarostrobos franklinii: 2,500 years[30]

Other species suspected of reaching exceptional age include Ginkgo Ginkgo biloba (over 3,500 years[32]), European Yew Taxus baccata (probably over 2,000 years[33][34]) and Western Redcedar Thuja plicata.

The oldest reported age for an angiosperm tree is 2293 years for the Sri Maha Bodhi Sacred Fig (Ficus religiosa) planted in 288 BC at Anuradhapura, Sri Lanka; this is also the oldest human-planted tree with a known planting date.[citation needed]