Elsewhere the forests were dim with smoke, and on the Sierra during these centuries the heroic "big trees" received many a scar from fire. But not until 1441 did fire again try this veteran. Soon after this burn was healed there came a third fire. This was less injurious than the preceding ones, for the wound that it inflicted healed in half a century.
Higher and more stately the tree grew, and in 1729 it attained the age of two thousand years. At the age of two thousand and eighty-eight years the fourth fire attacked it. This fire burned an eighteen-foot scar upon the trunk of the old tree. In 1900, after the lapse of almost a century, only a small part of this wound was overgrown. This year, 1900, came the reaper, the axeman, who laid low this aged and monumental tree!
What starts forest fires? Some are started by lightning; others are kindled by meteors that are flung from the sky, or by fire that is hurled or poured from a volcano; a few are caused by spontaneous combustion; and many are set by man. Down through the ages primitive and civilized men have frequently set fire to the forest. These fires are set sometimes accidentally, sometimes intentionally. The forest has been fired to drive out game, to improve pasturage, to bewilder the enemy during war, and to clear the land for the plow.
During one of my Colorado camping-trips a high October wind brought me the information that spruce wood was burning near by. While I was searching for the fire in the thick needle carpet of the forest floor, a spark from above settled before me. A fire was sputtering and starting in a tree top about thirty feet above the earth. This fire was starting where a dead leaning tree-trunk was rasping and rubbing against an upright one. The bark of the standing tree was powdered and tufted with wood-dust which had been ground by friction from the trunks as they swayed and rotated in the wind. This inflammable wood-dust, together with accumulated bark-bits and needles, had been set on fire from the heat generated by these two big sticks rubbing together. Plainly this was a friction fire. The incessant swaying of treetops in the tireless wind occasionally causes a smoke from friction at points where overlapping limbs or entangled trees are rubbing. Within a few minutes after my discovery, this fire was roaring eagerly through the treetops.
Friction fires are rare, but my old notebooks tell of numerous fires that were set by lightning. Before this fire, which was in the Sangre de Cristo Mountains, had died out, a lightning-set fire in the mountains of central Colorado had attracted my attention with massive, magnificent smoke-clouds, which were two or three thousand feet above the mountain-tops. Though thirty miles distant, these clouds occasionally took on the bossy white splendor of big cumuli assembling for summer rain. I resolved to see the fire at close range.
Until burned territory was reached, I followed along sky-line ridges through changing conditions of clear sky, smoke, and falling ashes, ready for swift retreat down a slope in case the fire advanced under smoke cover and surprised me. The burn was entered at the first edge I reached. Millions of seared and blackened trees were standing steadfastly where they had died at their post. All twigs and leafage were burned away, but the majority of the trees still carried their larger limbs and patches of bark. In places only the tree-trunk, a fire-carved totem pole, remained. Whirlwinds of flame had moved, and in places every burnable thing on the surface was consumed, and even tree-roots were burned out two and three feet beneath the surface.
Though weirdly interesting, these ashen fields of desolation were not wholly lifeless. Here, as elsewhere, feasters came to banquet, and good fortune brought favorites to the scene of panic and death. Flocks of gorged magpies were about, and unwontedly bold coyotes, both filled and foraging, were frequently met with. At one place a half-dozen beaver were portaging round a tumble of charred tree-trunks that obstructed the brook-channel. Fire had destroyed the food-supply, and the beaver were seeking home and harvest in other scenes. A grizzly bear was wading their pond and feasting on the dead trout that floated on the surface. Two black bears, despite terrible threats from the grizzly, claimed all the fish that came within reach of the shore. They discreetly kept out of the pond.
Two fawns and their mother lay dead at the foot of a cliff. Either blinded or terrorized by fire or smoke, they apparently had leaped or fallen to death. As I gained the top in climbing to investigate, an eagle swooped angrily at me from a topless trunk. Her mate with scorched feathers lay on the rocks near by. On returning a few days later I found her still watching the lifeless one from the same perch in the dead tree.
In the heart of the burned tract was a thirty-or-forty-acre tract of forest that had escaped the fire. It was surrounded with wide though broken barriers of rock ledges. In this green oasis were numerous wild-folk refugees. Chipmunks, rats, woodchucks, and birds were startlingly abundant, but no big game. Apparently the home people had welcomed the refugees, or had received them indifferently. The only fight noticed was between mountain rats. However, this crowding and overrunning of territory when the exciting fire was over, probably made many terrible pages of animal history, before exodus and death brought a normal readjustment of life to the territory.
Wandering on across the burn toward the fire-line, I came to the place where a ragged-edged and beautiful glacier meadow had reposed, a poetic park among the spruces dark and tall. Commonly these meadows are sufficiently saturated to defy fire, but this one was burning, though slowly and with but little blaze or smoke. The fire was working toward the centre from the edges and eating downward from one to three feet. This kind of meadow usually carries a covering stratum of a kind of peat or turf which is composed almost entirely of matted grass or sedge roots that are almost free from earthy or mineral matter. These meadows lack warmth or soil sufficient to germinate tree seeds or to grow trees. Often they remain beautiful treeless gardens for generations, while wind and wash slowly bring sediment, or until a flood or landslip brings soil. The deep burning of the surface and the consequent deposit of ash on the new surface probably offered an abiding-place to the next adventurous tree seeds. Glacier meadows occasionally have this kind of ending.