Sierra Nature Notes, Volume 2, January 2002

Continued from Methods & Data:

Estimated 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.

Figure 1. Estimated ages of selected giant sequoias in the year 2000, with associated confidence intervals. The vertical line within each horizontal box indicates that tree’s estimated age. The ends of each box delimit the 50% confidence interval for that tree’s 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.

References for Further Reading
Agee, J. K., M. Finney, and R. de Gouvenain. 1986. The fire history of Desolation Peak. Cooperative Parks Study Unit, University of Washington, Seattle. Final contract report to the National Park Service, Cooperative Agreement CA-9000-3-0004.

Brown, P. M., M. K. Hughes, C. H. Baisan, T. W. Swetnam, and A. C. Caprio. 1992. Giant sequoia ring-width chronologies from the central Sierra Nevada, California. Tree-Ring Bulletin 52:1-14.

Clark, G. 1910. The big trees of California. Yosemite Valley, CA.

Currey, D. R. 1965. An ancient bristlecone pine stand in eastern Nevada. Ecology 46:564-566.

Douglass, A. E. 1919. Climatic cycles and tree growth. Vol. I. Carnegie Institute of Washington Publication No. 289, Washington D.C.

Douglass, A. E. 1945. Survey of sequoia studies. Tree-Ring Bulletin 11:26-32.

Douglass, A. E. 1946. Sequoia survey -- III: miscellaneous notes. Tree-Ring Bulletin 13:5-8.

Echols, R. M. 1969. Powered drive for large increment borers. Journal of Forestry 67: 123-125.

Flint, W. D. 1987. To find the biggest tree. Sequoia Natural History Association, Three Rivers, CA.

Flint, W. D. In press. To find the biggest tree. Second edition. Sequoia Natural History Association, Three Rivers, CA.

Fry, W., and J. R. White. 1930. Big trees. Stanford University Press, CA.

Hartesveldt, R. J. 1962. The effects of human impact upon Sequoia gigantea and its environment in the Mariposa Grove, Yosemite National Park, California. Ph.D. dissertation, University of Michigan, Ann Arbor.

Hartesveldt, R. J. 1965. An investigation of the effect of direct human impact and of advanced plant succession on Sequoia gigantea in Sequoia and Kings Canyon National Parks, California. Report on contract number 14-10-0434-1421, USDI National Park Service, San Francisco, California.

Hartesveldt, R. J., H. T. Harvey, S. H. Shellhammer, and R. E. Stecker. 1975. The giant sequoia of the Sierra Nevada. U.S. Department of the Interior, National Park Service, Washington D.C.

Harvey, H. T., H. S. Shellhammer, R. E. Stecker, and R. J. Hartesveldt. 1981. Giant sequoias. Sequoia Natural History Association, Three Rivers, CA.

Hughes, M. K., R. Touchan, and P. M. Brown. 1996. A multimillennial network of giant sequoia chronologies for dendroclimatology. Pages 225-234 in J. S. Dean, D. M. Meko, and T. W. Swetnam, editors. Tree Rings, Environment, and Humanity. Proceedings of the International Conference. Radiocarbon, Department of Geosciences, The University of Arizona, Tucson, Arizona.

Hughes, M. K., and P. M. Brown. 1992. Drought frequency in central California since 101 B.C. recorded in giant sequoia tree rings. Climate Dynamics 6:161-167.

Huntington, E. 1914. The climatic factor as illustrated in arid America. Carnegie Institute of Washington Publication No. 192, Washington D.C.

Johansen, R. W. 1987. Taking increment cores with power tools. Southern Journal of Applied Forestry 11: 151-153.

Johnston, H. 1983. They felled the redwoods. Trans-Anglo Books, Glendale, CA.

Jordan, D. S. 1907. The alps of the King-Kern divide. A. M. Robertson, San Francisco, CA.

Lara, A., and R. Villalba. 1993. A 3620-year temperature record from Fitzroya cupressoides tree rings in southern South America. Science 260:1104-1106.

Mutch, L. S., and T. W. Swetnam. 1995. Effects of fire severity and climate on ring-width growth of giant sequoia after burning. Pages 241-246 in J. K. Brown, R. W. Mutch, C. W. Spoon, and R. H. Wakimoto, technical coordinators. Proceedings: symposium on fire in wilderness and park management, 30 March - 1 April 1993, Missoula, Montana. USDA Forest Service General Technical Report INT-GTR-320.

Stephenson, N. L. 1994. Long-term dynamics of giant sequoia populations: implications for managing a pioneer species. Pages 56-63 in P. S. Aune, technical coordinator. Proceedings of the Symposium on Giant Sequoias: their place in the ecosystem and society, 23-25 June 1992, Visalia, California. USDA Forest Service Gen. Tech. Rep. PSW-151.

Stephenson, N. L., and A. Demetry. 1995. Estimating ages of giant sequoias. Canadian Journal of Forest Research 25:223-233.

Stewart, G. W. 1930. Big trees of the Giant Forest. A. M. Robertson, San Francisco, CA.

Stohlgren, T. J. 1991. Size distributions and spatial patterns of giant sequoia (Sequoiadendron giganteum) in Sequoia and Kings Canyon National Parks, California. Technical Report No. 43, Cooperative National Park Resources Study Unit, University of California, Davis, CA. USDI National Park Service.

Stokes, M. A., and Smiley, T. L. 1968. An introduction to tree-ring dating. University of Chicago Press, Chicago.

Swetnam, T. W. 1993. Fire history and climate change in giant sequoia groves. Science, 262:885-889.

Willard, D. 1994. Giant sequoia groves of the Sierra Nevada: a reference guide. Privately published by D. Willard, P. O. Box 7304, Berkeley, CA, 94707.