National Geographic : 1951 May
Saving Earth's Oldest Living Things in geologic history, structure, and life habits, Sequoia gigantea is a wonder tree. Ancient lineage as well as age distinguishes the Big Tree. Its earliest ancestors shared living space millions of years ago with giant reptiles-plesiosaurs, ichthyosaurs, dinosaurs, and pterodactyls. In the age of early mam mals sequoias became widespread over much of the Northern Hemisphere. Sequoia gigantea, Sequoia sempervirens, and China's recently found Metasequoia glypto stroboides, the "dawn redwood," are simply last survivors of those ancient forest types. Fossil sequoia cones and foliage differ but little from those of today's species. Trees 1,000 Years Old at Birth of Christ What a fabulous, enduring mechanism the Big Tree is! The life span of some sequoias has paral leled the recorded history of mankind for the last 3,000 years. Some, still vigorous, were seedlings five centuries before the Periclean period of ancient Greece. From pinhead seed to monumental adult bulk, the Big Tree's story is an epic of tenacity and adaptability. It is late winter (February or March) when millions of tiny blossoms gild gigantea's green top. Although it can produce cones before its fifth decade, the great tree is several cen turies old before it reaches full productive maturity. Clouds of male pollen fall on the female blossoms, from which the cones develop. Two and-a-half years later the cones are ripe, having attained about the size, shape, and color of a lime (page 686). The dried cones shed brown, flat, wing margined seeds somewhat resembling dried rolled oats. Weighing 6,700 to the ounce, the minuscule seed carries little stored food with it to the ground; any single seed has less than one chance in a billion of germi nating, sprouting, and growing up. Tiny flakes of maroon gum are released with the seed; they make good reddish-brown writing fluid. With sequoia ink John Muir wrote letters that still are legible today. Big Tree seeds are choosy about where they grow. They need sunlight, plenty of moisture, and soil fairly free of forest litter. Many seedlings spring up on rich, mellowed humus of root craters torn open by the fall of ancient trees. Disturbing and exposing the mineral soil multiplies gigantea's chances for taking hold. Seedlings have come up thick as weeds on cleared land and on worked-over earth of new road embankments. Young sequoias have a symmetrical "Christ mas tree" shape, with dense branches cloak ing the trunk right to the ground. Their feathery foliage is made up of minute over lapping scales (page 686). As the trees weather adolescence (100-200 years old), they lose lower branches and start thickening out in the trunk. Their tops, how ever, hold a flame or spear shape for a few more centuries. Young trees grow much more rapidly than mature ones; a stripling may add an inch of width in six years, while an old tree may take 40 years to achieve the same increase. Rate of growth in mature trees varies greatly with food and water supply. One of the largest trees ever felled (the Dancing Stump in the North Calaveras Grove) re vealed only 1,244 annual rings across the radius of its 27-foot diameter. Another cut-down tree, just 11 feet 7T2 inches across, was 2,017 years old. As gigantea reaches early maturity (500 600 years), it thrusts out stout lateral limbs. Storms and food starvation after fires rob it of smaller branches. Its top, now perhaps 270 feet above ground, takes on a dome shape. Foliage grows in cloudlike tufts. With full maturity and old age (700-3,000 years) often comes a craggy, weather-beaten look. People have said these veteran sequoias look archaic, prehistoric, "too old to die." Foresters estimate that Yosemite's Grizzly Giant has seen 3,500 years come and go. Branches wither and perish; eventually they plunge to earth. Forest rangers call such woody swords of Damocles "widow makers." About 300 feet is gigantea's maximum height. The tallest usually scale between 250 and 290. These Goliaths often show little taper from the ground to their first limbs. The Big Tree's flat pedestal of closely matted roots is disproportionately small to support so huge a trunk; yet the trees grow so erect and nicely balanced that they seldom topple unless undermined by fire or flood. Sawed Through, Sequoia Still Stands Loggers cut completely through the Sawed Off Tree in the Mountain Home Forest about 60 years ago, and it soon died. But the great sequoia still stands, the saw that killed it jammed in the cut. Under the thick outer bark lie the thin, generative cambium layer and the narrow band (a few inches) of cream-colored sap wood, the only living parts of the sequoia trunk (page 695). The vastly preponderant mass of pink-to-purplish heartwood is built of cells that have died.