The clinging habit of the cones of the lodge-pole pine in rare cases causes numbers of them to be caught by the expanding tissues, held, and finally overgrown and completely buried up in the tree like a knot. Commonly the first crop of cones is the one caught. These are usually stuck a few inches apart in two vertical opposite rows along the slender trunk. Each knob-like cone is held closely against the trunk by a short, strong stem.
OVERGROWN CONES IN THE HEART OF A LODGE-POLE PINE
(Showing also the cones as borne on the twigs and an early stage of the overgrowing process)
I have a ten-foot plank from the heart of a large tree which shows twenty-eight imbedded cones. The biography of this tree, which its scroll of annual rings pictured in the abstract, is of interest. The imbedded cones grew upon the sapling before it was thirty years old and when it was less than twenty-five feet high. They appeared upon the slender trunk before it was an inch in diameter. Twenty-six annual wood-rings formed around them and covered them from sight as completely as the seeds the cone-scales clasped and concealed. The year of this completed covering, as the annual rings showed, was 1790. Then the tree was sixty-six years of age; it came into existence in 1724, and apparently, from the forest-history of the place, in the pathway of a fire. This lodge-pole lived on through one hundred and eighty-two years. In the spring of 1906 a woodsman cut it down. A few weeks later two-inch planks were sliced from the log of this tree in a sawmill. The fourth cut split the pith of the tree, and the startled sawyer beheld a number of imbedded cones stuck along and around the pith, the heart of this aged pine. These cones and the numerous seeds which they contained were approximately one hundred and fifty years old. I planted two dozen of the seeds, and three of these were fertile and sprouted.
Old trees may carry hundreds or even thousands of seed-filled cones. Once I counted 14,137 of these on the arms of one veteran lodge-pole. If we allow but twenty seeds to the cone, this tree alone held a good seed-reserve. Commonly a forest fire does not consume the tree it kills. With a lodge-pole it usually burns off the twigs and the foliage, leaving many of the cones unconsumed. The cones are excellent fire-resisters, and their seeds usually escape injury, even though the cones be charred. The heat, however, melts the resinous sealing-wax that holds the cone-scales closed. I have known the heat of a forest fire to be so intense as to break the seals on cones that were more than one hundred feet beyond the side line of the fire.
In most cases the seedlings spring up on a burned-over area the year following the fire. Often they stand as thickly as grain in the field. Under favorable conditions as many as one hundred and fifty thousand will appear upon an acre, and a stand of fifty thousand to the acre is not uncommon. Starting in a close, even growth, they usually suppress for years all other species of trees and most other plants. Their growth is mostly upward—about the only direction possible for expansion—with moderate rapidity. In a few years they are tall but exceedingly slender, and they become poles in from twenty-five to fifty years. The trappers named this tree lodge-pole because of its common use by the Indians for lodge, or tepee, poles.
In overcrowded stands, especially those in which groups or individual trees have slight advantages over their neighbors, a heavy percentage of the growth may die annually for the want of nutrition. If equal opportunities prevail in a crowded tract, all will grow slowly until some have an advantage; these will then grow more rapidly, and shade and suppress neighboring competitors.
The lodge-pole does good work in developing places that are inhospitable to other and longer-lived trees, but it gives way after preparing for the coming and the triumph of other species. By the time lodge-poles are sixty years of age their self-thinning has made openings in their crowded ranks. In these openings the shade-enduring seedlings of other species make a start. Years go by, and these seedlings become great trees that overtop the circle of lodge-poles around them. From this time forward the lodge-pole is suppressed, and ultimately its fire-acquired territory is completely surrendered to other species. It holds fire-gained areas from seventy-five to one hundred and fifty years. It is often supplanted by Douglas or Engelmann spruce. Let fire sweep these, and back comes the lodge-pole pine.
Though it distances all competitors in taking possession of fire-cleared territory, it is less successful than its fellows in entering a territory already occupied by other trees or by grass, because its seedlings cannot endure shade, and its seeds will not germinate or take root except they be brought directly into contact with clean mineral soil. The lodge-pole, therefore, needs the assistance of fire both to acquire and to hold territory. Increase the number of forest fires, and the lodge-pole extends its holdings; if we could stop fires altogether, the lodge-pole would become almost extinct.
The lodge-pole has an astonishing altitudinal as well as latitudinal range. Scattered pretty well over the mountain region of the western United States, thence northward along the coast over much of the head-waters of the Yukon in Alaska, it occupies an enormous area. Over this it adapts itself with marked success to a variety of soil, moisture, and climatic conditions, and covers ragged tracts from warm sea-beaches to dry, cold mountain slopes eleven thousand feet above the sea. In many places it surrenders the traditional pole form of its race and wins success by becoming thick-barked, stocky, and limb-covered from top to bottom.