(photo by Webber 1952.1)
Kingdom: Plantae
Phylum: Spermatophyta
Subdivision: Gymnospermae
Order: Coniferales
Family: Taxodiaceae
Genus: Sequoiadendron
Species: Sequoiadendron giganteum
(Harlow, 1979)
San Francisco State University
Geography 316: Biogeography
The Biogeography of the Giant Sequoia
(Sequoiadendron giganteum)
by Jennifer Daly, student in Geography 316, Fall 2000
(photo by Webber 1952.1)
Kingdom: Plantae
Phylum: Spermatophyta
Subdivision: Gymnospermae
Order: Coniferales
Family: Taxodiaceae
Genus: Sequoiadendron
Species: Sequoiadendron giganteum
(Harlow, 1979)
The tree known as the giant sequoia goes by many names: big-tree, mammoth-tree, Sierra redwood, Sequoiadendron giganteum, Sequoia giganteum, Sequoia washingtonia, and Sequoia wellingtonia, among others. A lot of debate seems to be going on (or has gone on) about the exact genus and species of the giant sequoia. The debate as to what genus and species name should be used most likely stems from the big variance in theories about who found and identified the Big-tree first. According to Peattie (1953), Giant Sequoias were first discovered by Mr. A. T. Dowd in the Calaveras North grove in 1853 - specimens were collected and given to Dr. Albert Kellogg, a botanist, who named the tree Sequoia wellingtonia. Fry (1942), who does mention Dowd, says that the first Europeans to find the Giant Sequoias were actually members of Captain Joseph R. Walker's party, who traveled through the area in 1833. The kingdom, phylum, subdivision, order, family, genus, and species listed above seem to be the most commonly accepted in publications since the 1970s.
Description of Species:
While the giant sequoia is very tall - a large bigtree is 250 to 280 feet
tall - it gets its name more for its giant diameter, which can be anywhere from 10 to 32
feet in a full-grown tree (Harlow 1979). To get a sense of the massive size of the giant
sequoia, view the above picture, showing a woman standing in a grove of giant sequoias.
The bark of the giant sequoia can be 10 to 24 inches thick on mature
trees, ranging in color from orange-tan to cinnamon-red (Peterson 1975). The bark is soft
and almost spongy, and is composed of fine fibers, pieces of which constantly break off
causing "litter" to form at the base of the tree (Crittenden 1977). Its
awl-shaped, blue-green leaves are 1/8 to 1/4 inch long and overlap each other on the twigs
(Peattie 1953). The giant sequoia is an evergreen.
Habitat:
Crittenden (1977) tells us that the big-tree grows on low ridges and
slopes near the heads of streams, very rarely in exposed areas, and that they can grow in
many different types of soil if they have enough moisture. In fact, Barbour (1995) says
that soil moisture during the summer drought is the most critical factor for survival of
the big-tree. Contrary to that, Sudworth (1908) says that the big-tree needs lots of
sunlight, except when the tree is a seedling. According to Peterson (1975), the giant
sequoia lives primarily at an elevation of 4,000-8,000 feet above sea level, while
Crittenden (1977) estimates their optimum elevation to be 5,000-8,000 feet above sea
level. Peattie (1953) gives the elevation to be 6,000-8,000 ft. Sudworth (1908) claims
that the giant sequoia lives where it does for many reasons; the area has moderate
temperatures (-12 to +100 degrees F) and moderate rainfall, with 18-60 inches per year.
Snow falls in these areas, sometimes burying the trees up to about 30 feet (Peattie 1953).
There are no big-trees growing in the arid mountains of Southern California, nor have they
ever grown there; no fossils of this or related species have been found in Southern
California (Barbour 1995).
Natural History:
One of the things the giant sequoia is most noted for is
its age. Sudworth (1908) says that the giant sequoia can live as long as 4,000-5,000
years. Peattie (1953) says that there have been claims of trees 10,000 years old, but
there is no evidence for that - there isn't even any evidence for John Muir's claim that
he found and counted the rings on a tree that was about 4,000 years old; The oldest
documented giant sequoia is about 3,200 years old.
Young trees (which according to Sudworth [1908] are those that are about 10-20 inches in diameter) and new branches on much older trees have bark that is mostly gray in tone and is very thin, smooth and unbroken. The crown is long for the first 200-300 years, with the upward-pointing branches being close together; the lower branches begin to thin out and begin to droop under the weight of the wood, eventually breaking off when the weight becomes too great; the middle branches then do the same. Eventually the trunk is nearly branchless for 80-125 feet off the ground.
According to Crittenden (1977), The cones of the bigtree are
5-8 cm long and 3 cm wide, are reddish-brown in color, and have
"squashed-diamond" shaped scales, which separate just far enough for the tiny
seeds (91,000 seeds = one pound) to exit; the scales do not turn out like those of a pine
cone. The big-tree has anywhere from 96-304 seeds per cone (Peattie 1953), with 4-6
seeds growing under each scale (Sudworth 1908). The cones take about two seasons to mature
(Harlow 1979) and do not fall off of the branches - if squirrels do not cut them down, the
cones will stay on the tree for as many as 8-10 years, proven by the growth rings on the
cone stems (Crittenden 1977). Harlow (1979) mentions that the seeds do not often come out
of the cones while the cone is alive and on the tree.
The big-tree begins producing seeds around the age of 20 (Harlow 1979). Seeds, once released from the cone, have many things they must overcome. Only about half of the seeds produced are viable, and of these, some are eaten as seeds, others fall where there is no hope of germinating, and some never make it out of the cone (Peattie 1953). Harlow (1979) estimates that only about 35% of seeds actually germinate. Once the seed has begun to grow, it has a new set of problems it needs to overcome. Again they could be eaten, this time by deer or other larger animals, as opposed to squirrels and chipmunks; they are attacked by black wood ants or cutworms; they can die from lack of moisture or from the extreme winter cold; or they could perish from lack of adequate lighting (Peattie 1953). Old trees, though they produce fewer cones, still produce viable seeds (Peattie 1953)
While these very tall trees have a very small taproot, proportionately,
the root system goes out quite far around the tree (Harlow 1979). This taproot only grows
for about 6-8 years, and after that all growth is in the lateral roots (Peattie 1953). For
this reason, it is important to keep the areas around the trees clear of roads, camping,
and other activities that would harm them roots of the tree (Peterson 1975). Peattie
(1953) mentions that if there was a tree 300 ft. tall, its lateral roots would extend 200
ft. in each direction, making the diameter of the root system taller than the tree itself.
Evolution:
The Giant Sequoia is descended from various species of Sequoia that were
found all over the Northern Hemisphere in the fossil record of the Cretaceous and Tertiary
periods (Harlow, 1979). At least twelve fossil species have been found, many of them in
Northern Europe, Iceland, Greenland, and Alaska (Fry 1942). Barbour (1995) says that the
giant sequoia probably had a wide range during the Tertiary, but became restricted to its
current location. The giant sequoia's closest living relative is the other tree in the
Sequoia genus - the Coast Redwood (Sequoia sempervirens). The genus Sequoia's
closest living relative is the bald cypress (Taxodium distichum), which lives in
the southern United States (Sudworth, 1908).
Barbour (1995) believes that the giant sequoia used to cover a nearly
continuous area; the shift to higher elevations reflects an inability of seedlings to
sprout at lower, hotter, and drier altitudes. In the southern portions, the trees became
confined to the high elevations because the canyons between the present groves contained
ice streams during the last ice age (Barbour 1995).
| Distribution: | |
 (map source CalFlora 2000) |
According to Crittenden (1977), the big-tree is now endemic to the
western slope of the Sierra Nevada in California, stretching from the southern part of
Placer County south to nearly Kern County. Barbour (1995) believes that this is because of
the relatively mild climate in this region. The seven highlighted California counties on this map - Placer, Calaveras, Tuolumne, Mariposa, Madera, Fresno, and Tulare, from north to south - all have native groves of giant sequoia scattered within them. There are only about 75 groves of Sequoiadendron giganteum, often with as much as 50 miles between individual groves in the northern portion (Crittenden 1977). Barbour (1995) gives Kings River as the dividing line between the northern portions (where there can be almost 90 kilometers between groves) and the southern portions (where there is never more than 7 kilometers between groves). According to Peattie (1953), the location of these groves can best be described as being between the 36th and 39th parallels - a distance of about 250 miles. |
| Other interesting issues: The
bark of the giant sequoia is nearly resistant to fire - this is because it is
non-resinous, and the sap contains a chemical called tannic acid, which is used in fire
extinguishers (Peattie 1953); the heartwood, or interior wood, is also non-resinous and
has tannic acid, and doesn't burn easily (Peterson 1975). There are many documented cases
of trees that have been burned quite severely on the inside but continue to live long,
healthy lives. A photo of one such tree can be seen here - note the size of the sign in
comparison to the massive tree. |
 (photo by Webber 1952.2) |
It is nearly impossible to kill a big-tree with fire, and they do not have a major problem with disease or insects (Peattie 1953). So how, other than from logging and other human-caused distruction, do big-trees die? Lightening. Thunderstorms often come to this area with summer rain, and since the giant sequoia is so tall, they often get struck by lightening, sometimes cleaving a tree in two (Peattie 1953). Over the years, many individual trees have been given names. The General Sherman tree is 275 ft. tall and 32 ft. in diameter at its base (Harlow 1979). Fry (1942), who devotes nearly a whole chapter to this single tree, says this tree weighs over 2,000 tons, and, if cut down, would provide 600,120 board feet of lumber, assuming all could be used, making it the largest big-tree in terms of board feet. (Peattie [1953] mentions that the lumber is not worth the time and energy it takes to cut down a big-tree, due to the fact that the wood shatters upon impact with the ground, and that no lumber mills are able to process wood from such a large tree; Sudworth [1908] estimates that only 25-30% of the wood can actually be used.) The next-largest tree in terms of board feet is the General Grant tree, which is 271 ft. tall, with 542,784 board feet; to give a sense of just what this means, Fry (1942) provides an example - a 5-room house uses 17,000 board feet. Sudworth (1908) and Fry (1942) both give extensive details about sequoia groves: name, location, moisture, number of big-trees in the grove, etc. And "sequoia" is the only word that contains all five vowels. |
|
Bibliography:
Barbour, Michael G. and Jack Major, eds., 1995, Terrestrial Vegetation
of California, California Native Plant Society Special Publication.
CalFlora: Information on California plants for education, research and conservation. [web application]. 2000. Berkeley, California: The CalFlora Database [a non-profit organization]. Available http://www.calflora.org. (Accessed: Oct. 11, 2000)
Crittenden, Mabel, 1997, Trees of the West, Celestial Arts, Millbrae, CA.
Fry, Walter and John R. White, 1942, Big Trees, Stanford University Press, Stanford University.
Harlow, William M., Ellwood S. Harrar, and Fred M. White, eds., 1979, Textbook of Dendrology, McGraw-Hill Book Company, San Francisco.
Parchim, Elden Ashley, 1965, Factors Influencing Reproduction in Sequoiadendron giganteum (Lindl), San Francisco State College.
Peattie, Donald Culross, 1953, A Natural History of Western Trees, Houghton Mifflin Company, Boston.
Peterson, P. Victor and P. Victor Peterson, Jr., 1975, Native Trees of the Sierra Nevada, University of California Press, Berkeley, CA.
Sudworth, George B., 1908, Forest Trees of the Pacific Slope, U.S. Department of Agriculture, Government Printing Office, Washington.
Webber, Charles, 1952.1, photo of woman in a giant sequoia grove, California Academy of Sciences, UC Berkeley Digital Library Photo ID: 8076 3101 4736 0128, http://elib.cs.berkeley.edu/photos/flora/
Webber, Charles, 1952.2, photo of tree with burned heartwood, California Academy of Sciences, UC Berkeley Digital Library Photo ID: 8076 3101 4736 0129, http://elib.cs.berkeley.edu/photos/flora/
Webber, Charles, 1955, photo of Giant Sequoia twigs and leaves,
California Academy of Sciences, UC Berkeley Digital Library Photo ID: 8076 3101 4736 0132,
http://elib.cs.berkeley.edu/photos/flora/
Other Helpful Web Links:
Some great
photos on the Southwest Parks website
The CalFlora taxon report for Sequoiadendron giganteum
USDA Natural Resources Conservation Service plant profile
Big-tree information from the School of Natural Resources at the University of Vermont
Yahoo
categories for the Giant Sequoia
send comments to bholzman@sfsu.edu
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