Giant sequoia, bigtree, Sierra-redwood (Watson 1993).
The sole species in Sequoiadendron J.Buchholz 1939. Syn: Wellingtonia gigantea Lindley 1853; Sequoia gigantea (Lindley) Decaisne 1854, not Endlicher 1847. The latter homonym reflects the species' former inclusion in Sequoia, a conservative placement that still has merit (Watson 1993).
Although the giant sequoia was probably discovered in 1833 by the Walker party as they struggled through the Sierra north of the Yosemite valley, the species did not attract popular attention until its rediscovery in 1852, at what is now called the Calaveras North Grove (see this link for details). In the same year, specimens were received by Albert Kellogg of the California Academy of Sciences, who in May 1855 finally published it as Taxodium giganteum Kellogg and Behr. This was the fifth validly published name, however. The first name had been assigned on the basis of material collected (in the Calaveras grove) in summer 1853 by William Lobb, who was directed to the tree by Kellogg. Lobb dashed back to England, arriving 15 December 1853, and within two weeks the species was published by botanist John Lindley as Wellingtonia gigantea, named in honor of Arthur Wellesley, Duke of Wellington. In fact this name was already in use, Wellingtonia having been described in 1840 for a plant in the Sabiaceae, but this was not realized at the time. Lindley's publication triggered a storm of protest from American botanists who were outraged that the world's largest tree had been named for an English war hero by a botanist who had never seen the tree. The Americans promptly published a spate of different names, none of which are legitimate under current rules of botanical nomenclature. The French then intervened in the person of of Joseph Decaisne, who in 1854 published the species as Sequoia gigantea, a plausible assignment that ultimately won acceptance by British botanists. Thereafter Wellingtonia slowly disappeared from the literature. Unfortunately, Sequoia gigantea was also not a legitimate name, having been previously used by Endlicher to describe a horticultural variety of the coast redwood, and this problem was not satisfactorily resolved until the American John T. Buchholz described Sequoiadendron in 1939. Buchholz' decision to establish a new genus apart from Sequoia was widely criticized by the old guard of California botanists, but his arguments--based on substantial differences in the development of Sequoia and Sequoiadendron seed cones--have subsequently won general acceptance (Hartesveldt et al. 1975). For more on Buchholz and his work with Sequoiadendron see Schmid (2012).
For the genus: "Trees giant, evergreen. Branchlets terete. Leaves alternate, radiating. Adult leaves mostly needlelike, triangular in cross section, somewhat divergent to strongly appressed; abaxial glands absent. Pollen cones with 12-20 sporophylls, each sporophyll with 2-5 pollen sacs. Seed cones maturing and opening in 2 years, persistent to 20 years, oblong; scales persistent, 25-45, valvate, ± peltate, thick and woody. Seeds 3-9 per scale, lenticular, subequally 2-winged; cotyledons (3-)4(-6). x = 11" (Watson 1993).
For the species: "Trees to 90 m; trunk to 11 m diam.; crown conic and monopodial when young, narrowed and somewhat rounded in age. Bark reddish brown, to ca. 60 cm thick, fibrous, ridged and furrowed. Branches generally horizontal to downward-sweeping with upturned ends. Leaves generally with stomates on both surfaces, the free portion to ca. 15 mm. Pollen cones nearly globose to ovoid, 4-8 mm. Seed cones 4-9 cm. Seeds 3-6 mm. 2n = 22" (Watson 1993).
The species has been planted throughout Europe since 1853, and is an especially popular ornamental in the U.K., where the largest specimen (45 m tall and 260 cm dbh) grows at Leod Castle north of Inverness (Hartesveldt et al. 1975). Hardy to Zone 7 (cold hardiness limit between -17.7°C and -12.2°C) (Bannister and Neuner 2001).
In the 1970's, the California Department of Forestry used Sequoiadendron to reforest certain burned areas in the San Jacinto, San Gabriel and San Bernardino Mountains of southern California. Schmid and Schmid (2012a, 2012b) report that the species has now naturalized in these areas, and is "regenerating prolifically" at the San Jacinto Mountains site.
The General Sherman tree: height 83.6 m, dbh 825 cm, crown spread 33 m, located in Sequoia National Park, CA. This tree also has the largest known stem volume, 1473.4 m3. The second largest stem volume is recorded for the General Grant tree in Kings Canyon National Park, CA, which is 885 cm dbh and 81.1 m tall. However, the largest dbh (898 cm) and the largest footprint (87.14 m2) are recorded for the Boole Tree in Kings Canyon National Park (Van Pelt 2001). It is perhaps worth noting that timber scaling data show at least one specimen of Sequoia sempervirens logged in the early 20th Century had a recorded stem volume of approximately 1540 m3 (Robert Van Pelt, e-mail, 1999.07.29). The tallest known giant sequoia is a specimen 94.9 m tall, first measured Aug-1998 by Michael Taylor in the Redwood Mountain Grove, California, but 94.9 m tall in July 2005 (Steve Sillett, pers. comm., 2005.07.28).
The giant sequoia is often called the largest living thing on earth. That superlative is basically valid, but is somewhat debatable for two reasons:
1. It is difficult to define "a single living thing" among a group (living things) where it is sometimes impossible to draw a clear line between the individual and the colony. For example, an entire mountainside may be covered with a stand of aspen trees (Populus tremuloides) that are genetically identical and physically connected with each other (i.e., a clone); such a stand could be called "a single living thing". Closer to home, taxonomically speaking, clumps of Sequoia sempervirens may also be composed of genetically identical stems. Even if we restrict the field to identifiable single individual organisms, there are individuals of Ficus religiosa reported from India and Southeast Asia that sprawl over areas of hectares; although a direct comparison has not been made, industrious searching might turn up an individual larger than any Sequoiadendron. At this time the largest documented Ficus that I have heard of, is a banyan (F. benghalensis) in Uttar Pradesh, India, that supposedly covers 2.1 ha (Robert Van Pelt, e-mail, 1999.07.29).
2. A large tree is not alive in the sense that you or I are alive. The foliage and the outer surface of the tree (technically, its inner bark, cambium and sapwood) are composed wholly or in part of living cells. However, the bark and most of the wood (xylem) are dead. In this sense a tree is a little bit like a coral -- we see the living skin of tissue over a dead framework that the tree has built up over the centuries of its growth. Most biologists overlook this point and treat the entire tree, living tissue and dead wood, as "live biomass." In practice, it is extremely difficult to measure how much of a tree is actually living tissue. As an indicator, though, my work with tree rings in Sequoiadendron generally has revealed sapwood thicknesses of about 10 cm in most of the canopy, and this represents the approximate thickness of living wood on the tree. In conclusion, the General Sherman tree has the largest stem volume and probably the largest total biomass of any known individual tree. However, a few colonial organisms, including a variety of plants and some fungi, may have greater cumulative living biomass.
A specimen logged in the 1870's in Converse Basin was sampled by M. Hughes, R. Touchan, and E. Wright and has yielded a crossdated age of 3,266 years (RMTRR 2006). There are also ages of 3,220 years (specimen D-21) and 3,075 years (specimen D-23) collected by Andrew E. Douglass in 1919. These were stump counts (some of Douglass' samples are still in storage at the Laboratory of Tree-Ring Research; they weigh hundreds of pounds). Also, 3,033 years for specimen CMC3 collected by Swetnam and Baisan (Brown 1996). The only species (again, referring only to non-clonal individuals) known to attain greater ages are Pinus longaeva and Fitzroya cupressoides.
The species attracted early attention by Douglass (1945a, 1945b, 1946, 1949, 1950a, 1950b, 1951a, 1951b; retrospective by McGraw 2003) and others. Some extensive recent work has been conducted by Tom Swetnam, Chris Baisan, and Peter Brown et al. (1992), who have assembled a very long fire history. They have a fine web page describing this work, Fire Regimes in Sierran Mixed-Conifer Forests. I have recently (2005-2006) been working on a study that involved coring these trees at heights from DBH to 90 m above ground and looking at variations in ring width and stable isotope (C, O) ratios with height; so far the analysis has not proceeded to the point where I can yet offer a meaningful summary, but we expect to develop some insights into how these trees manage drought stress.
This species has played a pivotal role in the evolution of the American conservation movement, and continues to provoke strong emotions among most people who encounter it on its native range. Sequoiadendron only occurs in groves, so that every place it can be seen, it is found within the native mixed conifer forest as a unique, insular stand of gigantic trees. The stature of the trees, despite their occurrence within one of the world's most impressive mixed conifer forest, is literally awe-inspiring. The Sequoia is the only other tree on earth that can even be compared to a large grove of Sequoiadendron, for although a number of other species approach it in girth, none are in the same class in regard to size, or cover the landscape with such a profusion of large individuals, with the sole exception of Sequoia. The trees are so large that when first discovered in the 1850's, many did not believe that they existed. One tree was killed and its bts bark stripped, to be sent back east for display at a major exposition. It was called a hoax, concocted from the bark of many trees. Later an entire tree was cut and sent back for another exposition, and soon the trees became famous throughout America. One of the first cultural responses to this fame was a concerted effort to log all the trees. The wood is not very useful; its most common use was as fenceposts, matchsticks or shingles. However logging proceeded with abondon, and one of the finest of all groves, the gigantic (3,500 acre) Converse Basin grove, was almost entirely fed to the sawmills. The pioneering American conservationist John Muir spearheaded a public outcry at this destruction, which culminated on September 26, 1890 with the designation of Sequoia National Park, the second national park (after Yellowstone) ever to be set aside in the United States. Now, in 2007, millions of people from around the world come here to view the groves of Sequoiadendron, and it remains with Sequoia as one of the flagship species of forest conservation in the United States.
All wild Sequoiadendron groves are protected, nearly all are on public lands, and most are relatively easy to visit. Particularly impressive and accessible groves are found in Yosemite, Sequoia and Kings Canyon National Parks; of these the most popular, and among the largest, is the Giant Forest in Sequoia National Park (Hartesveldt et al. 1975). The President, shown here, can be seen on the Congress Trail in the Giant Forest. It was originally (in 1923) called the Harding Tree, an appellation that fell from popularity along with the late President.
As early as 1938, Buchholz noted that Sequoiadendron cones can live, remain green, and potentially shed viable seed for a period of decades. Evidently the cones initiate and mature on the common 2-year conifer cycle, but then rather than ripening and dying, they remain green and contain viable seed for many years. Some seeds are commonly released at infrequent intervals, but a severe stress event (such as a ground fire) can trigger release of all seeds. The precise physiological mechanism has not been determined. This phenomenon of retaining living green cones with viable seed for a period of decades has not been observed in any other conifer species.
A few more bits of interesting data emerged when one of the largest living Sequoiadendron trees, the Robert E. Lee tree, was studied in detail during July of 2007 (contact me for details). This one tree has approximately five times the living leaf biomoss of the largest Douglas-fir (Pseudotsuga menziesii) ever measured, and has approximately 2.8 billion living leaves.
The protection of Sequoiadendron received further formal recognition when President Clinton designated Giant Sequoia National Monument on April 15, 2000. The Proclamation establishing the Monument recognizes, among other things, that
"These giant sequoia groves and the surrounding forest provide an excellent opportunity to understand the consequences of different approaches to forest restoration. These forests need restoration to counteract the effects of a century of fire suppression and logging. Fire suppression has caused forests to become denser in many areas, with increased dominance of shade-tolerant species. Woody debris has accumulated, causing an unprecedented buildup of surface fuels. One of the most immediate consequences of these changes is an increased hazard of wildfires of a severity that was rarely encountered in pre-Euroamerican times. Outstanding opportunities exist for studying the consequences of different approaches to mitigating these conditions and restoring natural forest resilience."
A great deal of work has been done studying the role of fire in this ecosystem and the importance of maintaining an appropriate fire regime in Sequoiadendron forests. A fine review of this subject, including PDF files of important papers and many informative links, is available online at the Fire Information Cache Bibliography and the related page, Research on Fire in Sequoia and Kings Canyon National Parks. The USGS also has a good site on the subject, Fire and Sequoia Reproduction.
The genus is named for Sequoia, the generic name of coast redwood, and the Greek DENDROS, tree (Watson 1993). The tree was (apocryphally) discovered in what is now the North Grove at Calaveras State Park; this has since become the most-visited of all the groves, thanks to easy access (Flint 1987).
Although the giant sequoia has primarily attracted attention due to its extremely large size, recent studies (Sillett et al. 2000) have revealed that trees, like mountains, tend to become structurally complex when they grow very large. A canopy exploration of what was then the second-largest tree, the Washington tree in Giant Forest, found that the tree's canopy included 46 secondary trunks, and that the main trunk was hollow: a 35 meter deep, 2-3 meter wide pit extended into the trunk below an entrance 58 m above the ground. Alas, the Washington tree died when a prescribed fire went awry in 2002; the burnt trunk fell a few years later, and now nothing remains but a giant charred stump.
The lower photo at left shows a burnt stump in Sequoia National Park. John Muir once visited it, and in a story he tells in "The Mountains of California" (Muir 1894, chapter 8), cut away the char (which extends to the center of the stump) and counted over 4,000 growth rings. You can still see the stump, and the places where he cut the char away to do his count. This is the only place I know where John Muir left physical evidence of his time in the Sierras. Muir was in error, though; a later researcher determined that he had counted one series of rings twice, and the stump in fact has a record of about 3,000 years.
Redwood, including both Sequoiadendron giganteum and Sequoia sempervirens, is the state tree of California (Watson 1993).
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Last Modified 2014-12-05