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A Guide to the Giant Sequoias of Yosemite National Park (1949) by James W. McFarland


Distribution Map of Giant Sequoias (Yosemite Museum, U.S.N.P.S.)
From Shirley, Redwoods of Coast and Sierra, courtesy University of California Press.

The giant sequoia is native only on the western slopes of the Sierra Nevada in central California, occurring mostly at elevations of 5,000 to 8,400 feet, in a narrow belt for a distance north and south of about 250 miles. The most northerly grove, six standing trees, is on the Middle Fork of the American River in Placer County, and the most southerly is on Deer Creek in Tulare County. The trees do not grow in a continuous belt but occur on favorable or protected spots where the soil is deep, rich and moist, and thrive in a region where the average annual precipitation is from 45 to 60 inches. Most of this is in the form of snow which frequently lies from 10 to 14 feet deep and stays on the ground for from three to seven months in the year. The temperature in winter often falls to zero or below.

Mariposa Grove is the largest of the more northerly groves. However, farther south the groves approach forest dimensions, are more closely spaced, and occasionally are almost connected by scattered individual trees.

An explanation of the present distribution of giant sequoia in often widely separated groves has been of great interest ever since John Muir put forth the theory of the glacial origin of the lakes and valleys of the Sierra Nevada. The explanation is that many years ago the forests of giant sequoia were quite continuous and more extensive on the west slope of the Sierra Nevada than they are today. During the last glacial period, rivers of ice formed and moved down the Sierra slopes, eroding mountains, gouging valleys and destroying all plant life that lay in their path. Such was the fate of most of the giant sequoias. To the south “occurs the wide sequoia-less channel . . . of the ancient San Joaquin and King’s River mer de glace; then the warm, protected spots of Fresno [Nelder] and Mariposa groves; then the sequoia-less channel of the ancient Merced glacier; next the warm sheltered ground of the Merced and Tuolumne groves; then the sequoia-less channel of the grand ancient mer de glace of the Tuolumne and Stanislaus.5 [5 Muir, Mountains of California, p. 196. The Century Co., New York, 1894. ] Glacier scars and debris, which are not found within the old, well-established groves, bear mute evidence to the devastation that was wrought in all but relegating “nature’s masterpiece” to the ranks of the extinct species of plant life.

Many of the sequoias are far from the beaten path, still almost as little known as they were when first discovered by the white man a hundred years ago, so that the visitor has somewhat the exhilaration of an explorer discovering a new form of life when he comes upon them. In all the groves—even those most frequently visited—one has a deep feeling of peace and reverence, as within a cathedral.

The species escaped extinction during the last glacial epoch, but there are probably fewer than 20,000 giant sequoia trees in the world today. These occupy less than 15,000 acres.

This is greatly contrasted with the distribution of the coast redwood which comprises a vast, almost continuous forest 450 miles from the north to south within the summer fog belt along the coast of California and southern Oregon.

Many people are of the opinion that the giant sequoia is a dying race. In spite of the fact that the older trees rain down millions of seed annually, the chances of an individual seed to germinate, survive and grow into a mature tree are less than one in a billion because of their particular growth requirements. There is little stored food in the tiny seed which weighs less than 1/6720th of an ounce. This makes it all the more necessary that the seed on germination have rich soil, constant supply of moisture and sunlight with which to make food. Only seedlings growing under continuously favorable circumstances have a chance for survival. A deep forest duff, heavy shade and severe root competition take a large toll of the relatively few seeds which germinate each year. Browsing deer stunt the growth and often pull up bodily the younger trees.

However, despite the difficulties of growth and the apparent scarcity of seedlings, the species is in no danger of extinction through lack of reproduction. There are young trees of almost every age in each of Yosemite’s three groves of giant sequoias.6 [6 In some areas, especially in the Upper Mariposa Grove, the larger saplings or young tree stages are entirely lacking except in especially low, wet situations. There have been at least ten large fires, probably caused by lightning, whose record is indelibly written into the trunks of the trees, since the more general devastating fire of 1710 which seems to have destroyed all but the larger, more mature giant sequoias. ] Again, the mature trees are so conspicuous that most people do not notice the young trees or mistake them for trees of some other species. Reproduction studies in Mariposa Grove in 1934 revealed that in some exposed areas, where the mineral soil had been mulched in 1932, there were more than 50 seedlings per square foot. This, in spite of the fact that germination of the seed is usually less than 15 per cent and as low as 3.3 per cent.

Few visitors see the flowers of the giant sequoia as they appear in winter from February to as late as May while deep snow is still on the ground. The tiny, bright yellow male blossoms burst forth in a solid mass and change the color of the crown from deep green to gold for a short time.

Clouds of yellow pollen are released. The female flowers, or cones, having been formed in clusters at the tips of branches during the previous year, are then pollinated, although fertilization does not occur until the last week in August. Then, the tiny seeds begin to develop but require still another season tc mature. Thus, the small, flat seeds, 150 to 300 of which are formed in each egg-shaped cone, do not approach maturity until July of the second year.

John Muir demonstrated the fruitfulness of the giant sequoia by two specimen branches, one and a half and two inches in diameter, on which he counted 480 cones.

The Douglas squirrel or Sierra chickaree (Tamiasciurus douglasii albolimbatus) is the happy harvester of most of the giant sequoia cones. With the first days of July he may be seen, hilariously exuberant, a couple of hundred feet up and out on the tip end of a branch cutting off the heavy cones with his ivory sickles at the rate of 20 to the minute, just as if there remained only a few moments in which to harvest his winter food supply. The prodigious activity of this small animal is shown by the great caches of cones in hollow logs, in one instance being more than 38 barley sacks of cones and their seed harvested by a single squirrel within a period of about 12 days.

Unless cut off by the squirrels the cone scales open, releasing the seed together with tiny flakes of reddish gum. Dissolved in water, this substance makes a good reddish-brown writing fluid. Letters which John Muir wrote with sequoia ink while in Mariposa Grove are still legible after 65 years. The cones, themselves, may remain on the tree for twenty years.

Saplings and even nursery stock a few feet high may bear cones, but tests have shown that their seed is infertile. Large quantities of fertile seed are normally produced only when the tree has reached several hundred years of age. As long as the tree survives it continues to develop large numbers of cones and fertile seeds. One can merely speculate on the vast numbers of seeds produced by a veteran that has withstood storms, fires and even geological changes during its life span.

Although erosion, fire and storm have taken their toll of the larger trees, nature has provided that the disaster which ends the life of one tree shall prepare the way for a dozen more. Ninety-four young seedlings were counted on a patch of sandy, flood soil once occupied by four large sugar pines. Eighty-six vigorous saplings were noted upon a piece of fresh ground prepared for their reception by fire. However, most reproduction occurs in the rich, mellowed soil of root craters left by the fall of old trees. Thus many trees are planted for every one that falls.

In every giant sequoia grove the thirsty traveler will find water. From this fact it has been assumed that this tree grows only in well-watered places. However, a more logical explanation, after a thorough study of the tree in its various habitats, is that a growth of giant sequoia creates these streams. The roots of this immense tree fill the ground for several acres, forming a thick sponge that absorbs and holds back the rain and melting snow, only allowing it to ooze and flow gently. So great is the retention of water in many place that bogs and meadows are created by the killing of the trees. A single trunk falling across a stream in the forest forms a dam 200 feet long, and from ten to thirty feet high, giving rise to a pond. Such a dam has been formed across Rattlesnake Creek in Mariposa Grove just below the Mariposa Grove Museum by the fall of several giant sequoias across the stream.

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