I’m a “big” tree guy, but nothing had primed me for my first encounter with the Giant Sequoias of the Sierra Nevada Mountains. You can read the statistics – 275 to 300 feet in height (max 325), over 30 feet in diameter at the base, and a corresponding trunk circumference of over 94 feet – but that does not really prepare you for the immensity of the specimens.
Giant Sequoias (Sequoiadendron giganteum) are the largest trees in the world – by volume. It is not the tallest – that title belongs to its cousin, the Coastal Redwood (Sequoia sempervirens), which can reach heights of 350 feet (max is 375). For comparison, the mature Coastal Redwood is typically 8 to 12 feet in diameter. It is the bulk of the Giant Sequoia that strikes you.
Spending time amongst Giant Sequoia trees is such a unique experience that it just needs to be written about – if for no other reason than to allow me to count my blessings for having experienced it.
I have seen the Coastal Redwoods, and while impressive, they did not have the same impact on me that the Giant Sequoias did. Perhaps it was because their bases are not as massive – or perhaps it is because I’m 25 years older and more introspective. Regardless, the Giant Sequoias really impacted me.
We noted some specimens as we first entered Yosemite National Park, but drive-bys don’t count. It was walking up to them on a more personal level, as captured in the title photo and below that humbles you.
And then you find yourself in a grove and you are just in awe.
Perhaps the best way to examine Giant Sequoias is to look at them through their life cycle.
Like all conifers, the future Giant Sequoias begin life as a seed in a cone. The cone is small relative to the parent tree.
A cone contains about 400 seeds, each about the size of an oat flake, and each tree makes approximately 400,000 seeds per year.
Fire plays an important role in Sequoia germination, first by clearing the forest floor of competition, and secondly by causing the cones to open, releasing their seeds to the wind. Sequoia cones can remain closed on a tree for up to twenty years, till they are exposed to fire.
The germination rate for the seeds is much less than one percent – basically needing an ideal composite of soil, sun, and moisture. But when conditions are right – success – and the race begins to see who can out compete its siblings. The photo below displays a cluster of young Sequoia seedlings that germinated under ideal conditions.
The “young” Giant Sequoia is considered a rapidly growing tree, and over the first two to three centuries of its life, with growth of up to 2 to 3 feet per year, it can reach its mature height of nearly 300 feet. Scientist feel that the height of the trees is limited by the tree’s ability to deliver water and nutrients to the crown. We saw many of these “adolescent” Sequoias on our hikes, tall lean boles, not yet with the characteristic broad base and trunk.
Then it takes on a different growth form, where it adds to its circumference – adding “girth” – with its trunk getting ever wider. It is thought that many of the largest specimens of Sequoia are two to three thousand years old.
Of course the final stage in life for the Sequoia is, in fact, its death. Here they have unique qualities as well. Because they have high levels of tannins in their tissues, which makes them resistant to decay by fungi and insects, the Sequoia carcass can remain on the forest floor for centuries, in a very slow process of decomposition. For this reason they are sometimes integrated into the trail and roadway infrastructure of the parks.
The architecture of the Giant Sequoia is worth noting. They have a characteristic form, with a large section of branchless trunk that extends for a hundred feet or more, and then a limited number of very large branches that typically arise from the trunk at a 90 degree angle. These lateral branches can be up to eight feet in diameter and would be considered a large tree in their own right.
The crown of the Sequoia is an ecosystem of its own, hosting birds, bats, squirrels, insects, fungi, mosses, and occasionally a separate tree. These branches are amazingly strong and it is rare that you will see one broken away from the tree.
The trunk has a fascinating coloration pattern, being cinnamon brown at the base, and grayish white at the top.
The leaves of the Sequoia are not at all similar to the classic evergreen trees like pines, spruces, or firs. By that I mean they are not needle like. They are in fact more like those of the Redcedars and Arborvitae, with a scale like appearance.
An interesting characteristic of the Sequoias is the nature of its trunk. Its base is ridged with cords of tissue. These rod-like sections seem to act as cables providing strength against the forces of nature that could bring a tree down.
The bark of the Sequoia is also unique. When I first looked at it I expected the smooth softness of Redcedar or Bald Cypress. But in fact its texture was quite coarse – similar to dragging your finger across Velcro. Different from any other bark that I have ever touched. But why? What role does this coarse bark play in the life cycle of the tree? Does it help protect it from the ever present threat of fire?
Perhaps this photo provides some explanation. It is purely speculation on my part, but does the roughness of the bark assist it in collecting wind blown debris at its base? It was something that we saw over and over as we walked through the forest – a pile of debris for several feet around the trunk. Does the debris act as a mulch helping to save moisture? Does it provide some protection from fire since much of it appeared to be sand?
Another interesting thing about the Sequoia bark is its thickness. In the mature specimens, many of which have diameters over 30 feet at the base, the bark can be up to two feet thick. This helps protect the vascular tissue and heartwood from fire damage. If the vascular tissue and heartwood survive the tree survives.
Fire is an ever present danger in the Sierra Nevadas, but in fact, it is actually beneficial to the Sequoia species. Fire removes competition from the forest including the other trees that will compete for canopy space such as Ponderosa Pine, White Fir, Sugar Pine, and Incense Cedar. Everywhere you look you see evidence of Sequoias encountering fire, but surviving to grow and reproduce.
Fire is a factor in the development of the “snag” top of many of the oldest Giant Sequoias. Fire can damage the base of a tree, which lessens the tree’s ability to deliver water and nutrients to its crown, making the top weaker and more susceptible to the winds of winter storms. The tops can then snap off. Even with the damage the tree can live on for hundreds if not thousands of years. This “snag” form is seen in two of the most iconic Giant Sequoias:
General Sherman of Sequoia National Park, the largest tree in the world,
and The Grizzily at Yosemite.
It turns out that the “fire suppression” philosophy that took root in the early twentieth century was detrimental to the Sequoia species. The lack of fire limited the release of Sequoia seeds from the cones and a fire free understory allowed for overgrowth of other species that prevented germination of Sequoia seeds. Now forest managers mimic the natural cycle of fire exposure every 5 to 20 years through the use of prescribed burns.
The Giant Sequoia occurs only on the western slopes of the Sierra Nevadas at altitudes of 4000 to 8000 feet. The remoteness of this location and their size made the majority of them difficult to lumber. In addition, the wood is considered brittle from a structural quality, and therefore, thankfully, only 34% of the original population have been harvested. Peak logging occurred from 1880 to 1900 and prompted calls for protection of these icons, which led to the establishment of Yosemite and Sequoia National Parks in the 1890s. Now 92% of the remaining Giant Sequoias are on public lands, primarily in national parks and national forests.
In summary, the Sequoia is something that just has to be experienced and I hope that everyone who desires such, has a chance to do so. Words and photos just seem so futile in trying to explain the immensity of the tree and the uniqueness of its ecosystem. But I did find this poem by Gyaneshwari Dave that does a pretty good job.
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Photo credits to Peggy Juengling Burns, Patrick Burns, Caroline Burns, James Grizzle, Ellen Burns, Marie Burns Dawson, and Joe Dawson.
