Long after the ice age ceased generally in North America it continued among the high Sierras of California, and the bigtrees to this day give a hint of it in the peculiar outlines of their range. They are scattered north and south along the face of the Sierra Nevada mountains in California, a distance of 260 miles, and at elevations from 4,500 to 8,000 feet.
The aggregate of the total areas is about fifty square miles. The stand is not continuous, but consists of “groves,” that is, isolated stands with wide intervals between, where no trees of this species are found. The arrangement suggests that the bigtree forest was cut in sections by glaciers which descended from the high mountains to the plains, a distance of one hundred miles or more, crossing the belt of sequoias at right angles. The glaciers withdrew thousands of years ago, and their tracks down the mountain slopes have long been covered by forests; but the bigtree groves, for some unknown reason, never spread into the intervening spaces, but today are separated by wide tracts in which not a seedling or an old trunk or log of that species is to be found. This is one of the mysteries which add interest to those wonderful trees--why they cannot extend their range beyond the circumscribed limits which they occupied thousands of years ago.
It was claimed for a long time and was quite generally believed that bigtrees were not reproducing, that there “were no little bigtrees.” That was conclusively disproved by Fred G. Plummer, geographer of the United States Forest Service, who made a scientific study of a small grove, measured the trees, and actually counted and classified them. His work showed that there were in the area which he investigated:
Trees containing 100,000 to 120,000 feet each 2 Trees containing 80,000 to 100,000 feet each 13 Trees containing 60,000 to 80,000 feet each 49 Trees containing 40,000 to 60,000 feet each 112 Trees containing 20,000 to 40,000 feet each 251 Trees containing less than 20,000 feet each 353 “Little bigtrees” 2,682 ----- Total 3,462
Bigtree is distantly related to southern cypress, and the shapes of very old trees of both species bear some resemblance. Bigtree leaves do not fall annually as those of bald cypress do. They are from one-eighth to one-fourth of an inch long, and on the leading shoots they may be half an inch in length. Cones are from two to three and a half inches long, and they ripen their seeds the second year, but the empty cones may adhere to the branches several years. The seeds are a quarter of an inch long, and have wings sufficient to carry them a hundred yards or more. The trees bear abundance of seeds, in proportion to the small number of branches. Though shapely and well clothed with limbs when young, the crown contracts with age, and consists of a few enormous, crooked limbs, almost destitute of twigs and small branches. One of these trees may actually bear more twigs when the trunk is only a foot in diameter than will be on the same trunk when it is fifteen or twenty feet in diameter. The old tree trunks are often without limbs to a height of 100 or 150 feet.