Part 8

Obstructing the eastward flow of the moisture-laden Pacific winds, the Divide extracts a heavy annual tribute of precipitation from the air mass, forcing it to rise up the mountain chain, where it cools and condenses. Chief benefactors are the low western valleys, which respond with a lush growth of Pacific coastal-type forests.

The eastern valleys, however, deprived of abundant annual moisture and exposed to the wind and temperature ravages of the prairie’s continental climate, support a dramatically different kind of forest. Here Engelmann spruce and subalpine fir are the climax trees, contrasted with such trees as the western redcedar and western hemlock of the mild and moist McDonald valley.

Elevation exerts an additional restriction on the distribution of tree species. Since climatic conditions vary with change in elevation—lower temperatures resulting in shorter growing seasons, and increased wind exposure resulting in greater loss of moisture through evaporation—we would expect to find the forest composition change as we ascend a mountain slope. In Glacier, eastern valleys average 240 meters higher than western, and thus even if they had more moisture they would not sustain the redcedars and hemlocks. All plants have range limits, some narrow, some broad; and they excel where their particular set of preferences as to moisture, soil, sunlight, and wind exposure are best met. On sites that do not meet their optimum requirements, they face being crowded out by species better adapted to the prevailing conditions.

Physical features of the land determine vegetation also. Certain trees prefer the moist areas along a streambed—the great black cottonwoods, for example. And on steep hillsides, avalanches prevent the growth of climax trees, permitting instead only shrubby, pliant growth—mountain-ash, mountain maple, alder, menziesia.

Forest communities are named for their dominant tree species. Thus, an area in which Douglas-fir dominates is called a “Douglas-fir forest.” Glacier does have forests in which Douglas-fir is the climax species; these are chiefly dry areas, below 1,800 meters, with south and west exposures. But we usually associate the park with its Engelmann spruce-subalpine fir forests, found extensively between 1,200 and 2,100 meters, and with the western redcedar-western hemlock forests in the McDonald valley.

Because forests mature slowly and change is usually imperceptible, we are tempted to think of them as static and eternal. But since a forest is a community of living things, it responds to changes in the environment. Subtle physical or climatic changes, such as a rising or falling water table or a slight increase or decrease in annual precipitation, will favor some species of trees and hinder others, eventually altering the composition of the forest.

Other changes are more dramatic. Most notable of these is fire.

From Fire to Forest

Heat lightning, glimmering soundless behind the western peaks. Then the first low rumble. At first the flashing had been from cloud to cloud, but now, as the storm nears, the first ground-spears appear, lighting up the night. Here is a big storm, many-celled, engulfing more and more territory beneath its angry bulk. Lightning dances into the dry August forest. In their towers the lookouts stay awake.

Close strike and a flare-up! The ridge snag burns like a Roman candle, sending bright embers down. Valley, ridge, and peak blink on and off with blue light as the storm roars like night-firing artillery.

Passing overhead, the low cloud belly brings a sudden lash of rain. But it is not enough: tomorrow will mean long hours of fire watch.

The next day dawns clear, a morning of heavy dew. The ridge strikes did not ignite the forest. Inspecting the storm path, aircraft and lookouts find no evidence of fire.

But two days later, in a morning of high wind, thin smoke plumes rise upward. Smoldering in the thick duff of the forest floor, a lingering hot spot explodes with the fanning wind. It quickly spreads from a hectare to ten while the quadrants are called in and the hot-shot crews dispatched; then to a hundred, bringing in the smoke jumpers and mobilizing the vast fire-control network. A thousand hectares, perhaps ten thousand might burn this week of big fires.

In the resulting skeleton forest, the scene of devastation is almost overpowering: life seems forevermore excluded from this blackened ruin. But fire is nothing new to forest communities. We may think fire demonic because it takes from our life span this block of mature forest, a sight we will never again see in this place. But nature does not operate in terms of human time scales. This forest is simply pushed back closer to its starting point, to begin again its long progression toward a climax vegetation cover.

Forest Succession

Through a series of complex vegetation stages, each characterized by different herbs, trees, and shrubs, the forest slowly returns to the type of vegetation best suited to the physical and climatic conditions of the site; this is called a climax community. The fact that most of Glacier’s forests are in some stage of recovery from fire accounts in part for the mosaic of forest cover found here.

The forest of Huckleberry Mountain on the Camas Creek road was consumed in the 1967 fire. By 1969, among the charred, lifeless trunks of the former forest, lush grass and sunloving fireweed, thistle, and paintbrush were growing. And by 1974 lodgepole pine seedlings along the road were a meter or two high. Lodgepole is a fast-growing tree that requires full sun to germinate. Forest fire is necessary for the regeneration of these trees: the intense heat causes the tightly closed cones to open, releasing the seeds that will establish the forest. So young pines developed among fireweed, spiraea, willow, and mountain maple shrubs.

The lodgepole forest near the western entrance to the park has been developing since 1929, when fire destroyed the redcedar-hemlock forest in the area between Apgar and West Glacier. Beneath the scattered spires of old larch that survived the burn, the lodgepoles have now grown up, forming a canopy that shades the forest floor. Because lodgepole live only about 80 years and will not germinate in shade, this forest will not exist long. Shade-tolerant Douglas-fir, white pine, Engelmann spruce and western redcedar seedlings are now taking hold. But the physical characteristics of this area—the climate, terrain, and soil—are ultimately most favorable for western redcedar and hemlock; and unless other disruptions intervene, this area will eventually again become a dense redcedar-hemlock forest.

But this will not happen quickly. The soil after hundreds of years of collecting debris will again become rich and moist. Young hemlocks will germinate on and near decaying logs. When old larches, firs, and pines fall, the slow-growing redcedars and hemlocks will take their places in the canopy.

Forest succession is a more complicated story than this; it is a fascinating study involving herbs, shrubs, small and large trees, and animal populations. From location to location it will vary; only in its broad outlines is it predictable. It is based on the observation that, given time, a forest—or any other plant community—will progress until it reaches climax—that is, the stage that will perpetuate itself.

■ How then are we to think about fire? Increasingly, experts are concerned not so much with fire suppression as with fire management. For suppression has at least three disadvantages: it allows the accumulation of unburned fuels that can result in “fire storms” when they are finally ignited; an undiversified climax forest is more vulnerable to disease than is a mixed forest; and a dense forest canopy discourages shrub growth, an important food source for deer, wapiti, moose, and smaller animals.

As the well-being of the deer herd depends on the predators that thin its numbers, so the long-term well-being of the forest depends on fire to rejuvenate it periodically. We must realize that wilderness is identified with fire, landslide, avalanche, windfall, and flood. Nature not only has learned to cope with these agents of change—she depends upon them for maintaining the delicate balances between landscape and life. There is in the business of nature, after all, more than the pleasing of man’s eye.

Spruce Morning

Of all times to get a rock in my boot! I had just started out, the morning was still cool in this eastern valley, and the heavy pack was not yet biting into my shoulders. Sitting down beside the trail, I leaned the pack against the base of an old spruce and began unlacing.

I could hear the scratching of the red squirrel descending to investigate, but I didn’t look up until it let go with long indignant chatter at finding its territory invaded. I plunked out the pebble and began relacing my boot. Cautiously the squirrel came down, pausing frequently to scold, its lower jaw quivering with rage and exposing yellow rodent teeth. Neighboring squirrels joined in and soon the trees danced with flicking tails.

Down the squirrel came, almost to the ground, then raced back up the tree, stopping at each lateral branch to deliver a vocal broadside. Finding no danger to themselves, the other squirrels soon quit the uproar and went about their morning business. I was beginning to suspect that I was committing some graver offense than the mere exercise of squatters’ rights—perhaps I threatened its cache of fir cones. Then into the corner of my vision shot another form, streaking soundless as a shadow; the squirrel also saw it—but too late. With a thin terrified squeak, the rodent started to go higher; but the pine marten was above it. The squirrel quickly reversed itself, sending bits of bark showering down.

As the squirrel leaped from the tree in desperation, the marten overtook it in mid-air; they came down together. Clamping the limp creature firmly in its jaws, the marten strode up the incline of a fallen spruce. Before it hopped off onto a shelf of higher ground to disappear, it looked briefly back at me. I fancied I could read, fixed in its eyes, a certain recognition of my having distracted its prey.

A breeze made me shiver, snapping me back from that swift vision of luxuriant fur, that blinding grace which flashed its orange throat-patch through the trees, and I realized I was sweating. For a moment I had been that squirrel, eyes wide with terror, seeing fate bear down, and powerless before the natural order of things.