Most of Glacier’s fires are lightning-caused. Strikes may flare up
immediately; or fires may smolder in the forest duff for days until
fanned into flame by wind. _Ground fires_ may race through the
forest understory, causing minor damage; or they may bridge the
understory and reach the canopy, thus becoming rapidly spreading
_crown fires_. Under certain conditions, uncontrollable infernos may
develop, generating terrific winds and heat. These rare
conflagrations are called _fire storms_.
Every type of forest habitat has _climax vegetation_—trees and
shrubs that are best suited to the site and thus maintain themselves
indefinitely if not disrupted.
After a major fire, habitat conditions are usually so altered that
the site must pass through several _seral stages_ before conditions
are such that climax vegetation can return. A _sere_ is a series of
plant communities that follow one another in orderly fashion until
climax conditions are again reached.
[Illustration: Lightning fires occur most often during the hot, dry
weeks of late summer.]
[Illustration: When the forest is dry, lightning often causes quick
flare-ups.]
[Illustration: The forest may continue to burn for days after the
main conflagration has passed.]
[Illustration: After a major fire, sun-loving grasses, shrubs, and
wildflowers quickly invade the former forest. Deer and wapiti
benefit from these new food sources.]
[Illustration: Lodgepole pine, a pioneer species quick to take over
burned areas at lower elevations, grows rapidly. These trees are
five years old.]
[Illustration: This is a Glacier National Park forest 80 years after
a major fire.]
Sudden hammering made me jump. Above the forest darkness, a pileated
woodpecker leaned out from a high larch snag, braced against the trunk
by its specialized, stiff tail feathers. This was the first time I had
seen this big white-and-black bird, the “cock-of-the-woods.” There was
ample evidence of his work: the deep, oblong excavations in the trunk
and the pile of large wood chips at its base, both characteristic of
this species. Again he hammered, and I could see the chips falling.
After a little edge-work around the hole, he extracted a grub and flew
off, yammering against the advancing dark.
Near a stream I stopped to sit down, to listen to the water and maybe
catch sight of some small animal. Across the narrow defile, from a slope
dense with young hemlock, came the buzzing note of a varied thrush.
Several notes followed, all on a different pitch, all drawn out, level
and clear; the quality was pure but songless, disjointed, deliberate,
like someone testing the reed of a strange woodwind. There seemed no
gladness in the heart of this thrush. The song was dark, haunting,
lonely.
On the trail ahead I could make out a bird hopping rapidly along. After
passing the spot I could hear its song. There couldn’t be a hundred
meters between us, yet it seemed to be coming from a great distance. I
listened for as long as it would sing. I tried to hear it for what it
was, a male Swainson’s thrush proclaiming its territory. But the
ethereal, flute-like phrases seemed an evensong made not for man’s ears
but only for the forest itself.
I hurried on after the bird had ceased. It was getting dark beneath the
trees, but I was beginning to be aware of creatures underfoot, the mad
dartings of shrew and vole, more imagined than seen. When a deer mouse
jumped away I got out my flashlight. Soon the beam caught a woodrat
sitting atop a fallen log. The light didn’t bother him in the least; as
I approached, he picked up his bushy tail in his forepaws. Whiskers
twitching, he looked more caricature than real. Then he bounded off the
log with graceful, arching hops, and disappeared into the night.
Against a patch of sky that appeared in a clearing, I could make out
bats, circling and dipping like swallows. Locating a hovering moth, I
kept the light beam on it until it vanished into a furry streak of
silence. It was time to head back.
By now it had become utterly dark within the trees, a moonless,
sightless, alien world, given over to the marble-black eyes of the small
night mammals and the creatures that hunt them. I thought of the
strange, unseen societies of the flying squirrels, the nocturnal
counterparts of red squirrels; of the great-horned owls, inspecting the
same ground the goshawks scanned during the day. Perhaps a foraging red
fox moved through the darkness nearby, or a coyote on night patrol.
The flashlight beam probed ahead along the trail. The exposed roots were
given unnatural shading and they seemed to thicken and squirm as I
approached. On either side the tree trunks appeared to step backward
from the dim glow of the light. I felt lost in this night, thinking of
the great darkness in all the timbered ridges that ran westward from the
Divide. In this vast cathedral of crowded tree and peak, night was stood
on end, the stars shrunken to a circle overhead, as if seen from the
bottom of a well. Mouselike, shivering, insignificant in this
wilderness, I scurried back to find a fire and fill my empty senses with
its heat and snap and light, holding off the fright of night and
thinking of tomorrow’s sun.