AGE OF THE GIANT SEQUOIAS
A CONSIDERABLE VOLUME of fact and fiction has been printed and many conflicting claims have been made regarding the age of sequoias as well as of other species of trees. Such stories and claims have created considerable confusion.
The age of a large woody tree can be determined accurately only by an actual count of the annual growth rings on a cross section of the stump or butt log after the tree is cut down. All trees, except the group of monocotyledons to which the palm belongs, customarily produce a narrow layer of new wood just under the bark each year. There is a slight difference in the appearance of the wood cells produced in the spring and those produced in the summer. In some species this variation is more evident than in others, but it usually provides a visible series of concentric annual rings that may be counted. An estimate of the growth rate may be secured by using an increment borer to obtain a core showing the annual rings. It is not practical, however, to remove a core more than 2 feet deep in most trees, so that accurate information concerning only the more recent growth may be obtained.
All trees grow faster during their youth than later. For example, during the first 75 years in the life of a giant sequoia it may increase in diameter at an average rate of an inch every 3 to 5 years, but in some veterans it may require more than 20 years to produce a diameter increase of an inch. It is impossible to say with any appreciable degree of accuracy just how old a large standing and living tree may be.
The most accurate data for estimating the age of standing trees are obtained from fallen or cut trees of comparable size which grew under similar conditions and whose growth rings have been counted. Such counts made on a large number of sequoias of various sizes reveal that there may be a wide variation in the age of trees of approximately the same size. For example, ring counts made on two giant sequoias about 15 feet in diameter above the butt swell revealed that one was 2,410 years old and that the other was a mere youth of only 1,740 years.
Claims of great age have been presented for many species of trees. The baobab of Africa has been estimated to reach an age of perhaps 4,000 years, but to date no authentic ring count has been presented. The banyan of India has an estimated age of 3,000 years, which is fairly well authenticated by historical data. The tule cypress of Oaxaca, Mexico, has been variously estimated to be from 2,000 to 5,000 years old, with 3,000 the estimate of the most expert investigator. Claims of age of living trees up to 12,000 years have been made for several species, including the Macrozamia of Australia which is a cycad and does not produce annual rings. The age of palms, cycads, and other monocotyledons is estimated by counting the number of persistent leaf bases on the trunk and dividing by the number of leaves probably produced each year. This, of course, may be variable and the result inaccurate. It is significant to note that in practically every case where careful study and comparisons of very large trees have been made by scientists age estimates have been materially reduced from the claims made by enthusiastic boosters, in some cases to less than 1,000 years.
Since actual ring counts on many fallen and cut sequoias show that the age of this species frequently exceeds 3,000 years, and since one was proved to be 3,210 years old, some of the larger trees may exceed 3,500 years in age. On the basis of present verified evidence, the giant sequoia is the oldest living thing on earth.
Last Updated: 02-Feb-2007