There is something about spring on the prairie that gets me up before
dawn. I like to watch the seasons change their guard over the landscape,
from the wintry cold of pre-dawn dark to the spring-scented morning air
to the hot summer-foretaste of the noon May sun.
Hoarfrost surrounds these patches of pasqueflowers, blue goblets on
downy stems. On this windless night, frost has formed everywhere,
reclaiming for a time its vast winter range, sparkling over the green
handiworks of spring.
But the god of the growing grasslands is the sun, and it now proclaims
itself, stretching out to make the mountains shine. With its assault the
frost collapses, becoming bright beads on grass tip and leaf joint by
which a beetle might refresh itself.
Spring is best perceived ant-level, at its ground beginnings, where the
bright yellow-green tips of new grass shoots reclaim the winter-blighted
land. I look closely at a drag line of spider silk; a necklace of
dewdrops slides down, collects to a moment’s greatness, in which I
briefly see a curved horizon, the morning sunburst, and myself, before
it falls away.
Getting up from my prone position, my belly damp from the prairie earth,
I startle a whitetail jackrabbit; bounding high, it zigzags off. The
commotion disturbs a distant badger, which faces about from its diggings
to confront danger in whatever form it might take. It swings its snout
to scent the air. Somewhat uncertainly, it returns to the business of
hunting, then hesitates, swings about once more and waits, myopic,
patient.
Satisfied at last, the spurt of the now distant rabbit lost in its
brain, the creature snorts a defiance at the mystery and resumes its
morning gopher hunt.
Overhead a marsh hawk skims past, its flight erratic as a butterfly’s.
Far away a magpie rattles at the passing hawk and takes flight, briefly
flashing black and white.
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It is easy to see only pieces in the natural puzzle—a badger throwing
dirt, horned larks dipping into wind, black ants dragging the rosette of
a dead spider—and be satisfied with the scattered scenes. But at last,
to make it meaningful, we must complete the picture. There is that
special joy in discovering larger schemes: green plants utilizing
sunlight; a rabbit building its days at the plants’ expense; the falcon
tearing the rabbit meat for its young; magpies picking at the fallen
falcon; and then, in the end, all returning to the earth.
Here on the prairie, as in every plant-and-animal association, the
ancient drama repeats itself over and over; the distant tundra is a
drastically different stage with different actors, but the cycle is the
same. Life depends upon the interaction of all its many forms. Unseen
bacteria are as necessary to the land as green grass; the meadow vole
and the coyote are as much a part of the prairie as the grasses.
The secret of life rests in the wonder of photosynthesis. Only green
plants can manufacture food from the earth’s raw minerals. This is the
vital first step upon which the great pyramid of animal and plant life
is built. Using energy from the sun, green plants combine water and
carbon dioxide to synthesize sugar, and give off oxygen as a by-product.
The caterpillar takes its energy from the plant tissue, converting to
protein the sugar and minerals in its body. The caterpillar is then food
for a spider or other predator. A yellow warbler may take the spider and
in turn be ambushed by the prairie falcon. Thus the energy produced by
the plant travels through the food chain. When the prairie falcon dies,
scavengers—including insects and other invertebrates, birds, and
mammals—redistribute its wealth among themselves; the rest is decomposed
by bacteria. Thus, eventually, the nutrients on which the plants depend
return to the soil.
When we look at any living organism, whether it is plant, herbivore,
carnivore, parasite, scavenger, or decomposer, we are soon made aware of
its associations with other living things, each puzzle piece leading us
to another and another. We begin to see a picture whole—the fox, meadow
mouse, grasshopper, bunchgrass, and sparrow hawk—all interlocked.
Geologically speaking, grasslands are a recent development. As the Rocky
Mountains were being uplifted, the prevailing warm, moist climate began
to change. The rising mountain mass intercepted moisture-laden winds
that blew in from the Pacific, creating a rain shadow that lengthened
eastward as the mountains rose higher. A continental climate,
characterized by severe winters and dry, wildfire summers gradually took
shape, extinguishing the great forests that had grown across the
continent’s interior. Herbaceous plants, which had been evolving amid
the forests, inherited the land.
Unlike trees, grasses die back to the ground each winter, hoarding their
life-germ beneath the protecting soil. Growing not from the tip but from
the joints, grasses regenerate quickly after fire or grazing. Suspension
of the normal metabolic processes enable the grasses to go dormant and
thus survive periods of severe heat and drought.
Although the great prairie sea washes up against Glacier’s eastern
boundary, with estuaries probing into the mountain valleys on the drier,
south-facing slopes, the grassland community comprises less than 5
percent of the land area of Glacier National Park. This includes the
puddles of prairie west of the Divide that interrupt the dense
coniferous forests along the North Fork of the Flathead River.
From the pasqueflowers that bloom in early May to the asters and
goldenrod of September, these summer-long gardens of grasses and flowers
lean with the wind. Here are timothy, oatgrass and the
bunchgrasses—rough fescue, bluebunch fescue, and bluebunch wheatgrass.
Among the grasses bloom bitterroot, blue camas, lupine, gaillardia,
balsamroot, cinquefoil, sticky geranium, and wild rose.
_continued on p. 68_
[Illustration: The Forests of Glacier
From the lush redcedar-hemlock forest in the McDonald Valley to the
subalpine fir, whitebark pine, and Engelmann spruce struggling for
existence near treeline, the forests of Glacier reflect the
conditions of temperature, exposure, soil, and drainage prevailing;
and each forest has its characteristic association of understory
trees and shrubs, herbaceous ground cover, and vertebrate and
invertebrate animal life.]
[Illustration: Life Zones
Many physical and climatic factors determine the range of Glacier’s
plant-and-animal communities. Boundaries between communities are
seldom sharply defined, but rather merge together in broad zones of
transition.
With elevation gain, average daily temperature drops at the rate of
5° per 900 meters. Precipitation, wind velocity, and evaporation
loss increase. Soil thins. These factors, along with others such as
fire frequency, north or south exposure, and availability of
moisture, combine to determine the range of each community.
In the forest community below 1,800 meters, Douglas-fir, lodgepole
pine, and western larch predominate. In the valleys, Engelmann
spruce and subalpine fir are found. The somewhat lower and much
better watered western valleys of the park support western redcedar
and western hemlock.
Treeline is the upper limit to which the tolerances of trees to
environmental conditions permit them to grow. Because there are so
many controlling factors (wind, temperature, exposure to sunlight,
snow cover, etc.) treeline in the diagram is only approximate. In
Glacier it averages 2,000 meters. Avalanche chutes or sheer cliff
walls may suppress it to below 1,500 meters; on protected slopes it
may be as high as 2,150 meters.
At the eastern edge of the park below 1,200 meters, the forest gives
way to the prairie community, composed mostly of soft-stemmed plants
adapted to the conditions of low precipitation that prevail here in
the rainshadow of the mountain range. Clumps of aspen, found in the
prairie in sheltered spots, occur here in the transition zone
between prairie and forest.]
[Illustration: A Mountain Profile
This diagram represents the eastward-facing slope of a hypothetical
mountain near the eastern boundary of Glacier National Park. Its
life communities are somewhat different from those of mountain
slopes at the western edge, chiefly because of the differential in
annual precipitation.
Illustration: Here, above approximately 2,750 meters, in a realm of
ice, snow, and barren rock, there is little life.