Ages of Some Large Giant Sequoias:
General Sherman Keeps Getting Younger
Nathan L. Stephenson, Ph.D
Estimated ages of seven large sequoias ranged from 1650 years for the General Grant tree to 2890 years for the Cleveland tree (Fig. 1), averaging 2230 years. Though all of these sequoias were much larger than CBR26, the longest-lived sequoia known, five had estimated ages at least 1000 years younger than CBR26 (Fig. 1). In fact, the third-largest living sequoia (the General Grant tree) is estimated to be little more than half as old as CBR26. Additionally, CBR26's age lies well outside of the high end of the 95% confidence intervals of the five sequoias (Fig. 1).
While there are exceptions (namely, the Washington and Cleveland trees), the largest living sequoias generally owe their great bulk to rapid growth, not to extraordinary age. For example, average ring width from the cores of the (estimated) youngest sequoia (the General Grant tree, 1.82 mm) was more than three times that of the (estimated) oldest sequoia (the Cleveland tree, 0.58 mm). This notion is further supported by age data from more than 450 sequoia stumps. Huntington's ten largest stumps averaged 6.0 m in diameter inside the bark, but only 1842 years old by direct ring count (the largest was 6.5 m in diameter but only 1347 years old). In sharp contrast, his ten oldest stumps averaged only 4.9 m in diameter inside the bark, but 2822 years old -- 1 m less in diameter but nearly 1000 years older. Membership in the two groups of stumps was almost mutually exclusive; only one stump was both one of the ten largest and one of the ten oldest. Thus, for whatever reason, sequoias that reach great age tend to have grown relatively slowly.
Fig. 1 indicates that there is a 25% probability that the Cleveland tree is older than CBR26, and a similar probability that the Washington tree is older. The probability that at least one of these two living trees (Cleveland or Washington) is older than CBR26 therefore is roughly 1 - (0.75)2, or 44% -- nearly even odds. Given that the seven sequoias examined here are only a small sample of all potentially old, living sequoias (likely candidates would number well over one thousand), it seems highly likely that some sequoias living today exceed the age of CBR26.
Table 1. Giant sequoias selected for analysis:
|Tree Name||Size Rank (by volume)||Bole volume (m3)||Location|
|General Sherman||1||1487||Giant Forest, Sequoia NP|
|Washington||2||1355||Giant Forest, Sequoia NP|
|General Grant||3||1320||General Grant Grove, Kings Canyon NP|
|Boole||7||1202||Converse Basin Grove, Giant Sequoia National Monument|
|Grizzly Giant||27||963||Mariposa Grove, Yosemite NP|
|Cleveland||36||887||Giant Forest, Sequoia NP|
|Sentinal||Not Ranked||790||Giant Forest, Sequoia NP|
NOTE: Future discoveries of previously unrecognized large sequoias will probably change the ranking of sequoias smaller than the Boole tree. For example, the fourteenth largest sequoia known (the Ishi Giant of Kennedy Grove) was identified only in 1993.
Table 2. Confidence intervals for sequoia age estimates based on different numbers and lengths of increment cores (from Stephenson and Demetry 1995).
|Two 60-cm core||One 60-cm core||Two 30-cm core||One 30-cm core|
|50% confidence interval||-6.9 to 9.0||-8.4 to 9.4||-14.1 to 11.1||-13.0 to 11.8|
|95% confidence interval||-23.7 to 19.5||-36.7 to 19.7||-45.8 to 26.4||-48.2 to 27.5|
NOTE: The intervals are expressed as percentage of estimated sequoia age. For example, the -23.7% listed as one endpoint of the 95% confidence interval for two 60-cm cores means that 2.5% of the time, actual tree age will be more than 1.237 times estimated tree age. (Rephrased, 2.5% of the time estimated sequoia age will be at least 23.7% less, expressed in terms of estimated sequoia age, than actual sequoia age.) The 19.5% listed as the other endpoint of the interval means that 2.5% of the time, actual tree age will be less than 0.805 times estimated tree age.
Estimated ages of selected giant sequoias in the year 2000, with associated
confidence intervals. The vertical line within each horizontal box indicates
that trees estimated age. The ends of each box delimit the 50% confidence
interval for that trees age, whereas the "whiskers" extending
from each box delimit the 95% confidence interval. The dotted vertical line
at 3266 years indicates the age of the oldest sequoia yet discovered (see
the text). Because the innermost ring of a long core taken within a fire
scar cavity at the base of the Boole tree has been crossdated to A.D. 143
by E. Wright of the University of Arizona (L. Mutch, personal communication),
the Boole tree is at least 1858 years old, as indicated by the asterisk.
I thank R. Touchan of the University of Arizona's Laboratory of Tree-Ring Research for graciously supplying data on CBR26, and L. S. Mutch for supplying data on the Boole tree. Additional thanks go to V. G. Pile (USGS), who helped me core the Sentinel tree, and D. J. McGraw (University of San Diego), who sent copies of Douglass' original notes and correspondence on the General Sherman tree, and who inspired me to complete this work. A. Caprio, M. Crapsey, W. Flint, J. Keeley, D. McGraw, H. Shellhammer, D. Shenk, R. Touchan, W. Tweed, and two reviewers provided helpful comments on the manuscript.
for Further Reading
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