Above an altitude of approximately 9,000 feet, the forests show a
different aspect. This is another zone, called the Subalpine by some
botanists and Canadian by others. It is characterized by forests of
stately ENGELMANN SPRUCE and SUBALPINE FIR. You can tell one from the
other by touching the needles. Spruce needles are 4-sided, rigid to the
touch, and sharp-pointed; fir needles are flattened and softer to the
touch. From your car, you can spot the firs by their erect, dark-colored
cones, mostly high in the tree. This type of forest is the climax
developed in this climatic belt, which receives twice as much snow and
rain as the zone below. This relatively abundant moisture (much less,
however, than in most of the Eastern States with their broadleaf
forests) supports a luxuriant conifer cover. Wildflower gardens of rare
beauty and startling luxuriance are found in natural openings within the
forest. The distinctive blue COLORADO COLUMBINE, which ranges from the
lowest elevations up to 13,000 feet, seems to reach its best development
here.
Other plants of the open forests in this zone include WHITE GLOBE-FLOWER
with its cream-colored, cup-shaped flower; COLUMBIA MONKSHOOD, with its
helmeted blue or white flowers; ELKSLIP MARSH-MARIGOLD, with numerous
oval white sepals often mistaken for petals; and the strikingly
beautiful PARRY PRIMROSE, with clusters of brilliant purple flowers,
often growing along the edge of a stream. Common shrubs include GREENES
MOUNTAIN-ASH, whose large clusters of white flowers are replaced by
bright red berries in autumn; BEARBERRY HONEYSUCKLE, better known in the
Rockies as twinberry, a honeysuckle with large ovate leaves 3 to 5
inches long and pairs of yellow flowers; and wild AMERICAN RED
RASPBERRY, with prickly stems, 5-petaled white flowers, and delicious
red fruit, relished by birds and hikers alike.
In the cool, shadowed depths of the forest where light is dim, another
community of plants is found, including CALYPSO, or "fairy-slipper," a
dainty orchid with rose-colored blossoms formed in a curious slipperlike
shape; the PYROLAS, a group of low, hardy perennial herbs with white or
pink flowers having 5 thick petals and 10 stamens; SPOTTED CORALROOT, a
plant which, getting its nourishment from decaying vegetation, has no
green leaves, but bears purple-spotted flowers on its brown stem; and
AMERICAN TWINFLOWER, a trailing plant of the honeysuckle family, often
forming dense mats with upright, forked flower stems bearing a pair of
pink, bell-shaped flowers.
[Illustration: Blue columbine--Colorado's State flower.]
After fire or other catastrophe wipes out the spruce-fir forests, a
cycle of natural revegetation must take place before the climax forest
again becomes established. The first step in this recovery process is
the appearance of fireweed and many annual herbs, among which shrubs
such as CLIFF JAMESIA, or "waxflower," become established, and aspens
begin to appear as succession plant types. They are replaced eventually
by longer-lived lodgepole pines, also sunloving and tolerant of burned
or denuded sites. The trees increase the wetness of the forest floor,
provide the shady sites necessary for seeds to grow in, and shelter the
young spruce and firs as they slowly increase and approach maturity.
Eventually, the spruces and firs crowd out the pioneers which have
helped them get established. This dense spruce-fir forest seems to
resist competition of other species and will maintain itself
indefinitely by gradual replenishment of its own kind, unless it is
again fire-swept or there is a change of climate. The spruce-fir forests
of the park seem to be as nearly fixed and static as forests can be; or,
in the scientists' words, they are the _climax forest_ for the sites
they occupy.
[Illustration: Lodgepole pine forests along Trail Ridge Road.]
The higher part of the Subalpine zone (10,500 to 11,500 feet) is often
called Hudsonian for its biological similarity to the region around
Hudson Bay. It is a sort of frontier zone where the climate is more
severe. Not only is it colder, but it is much windier, and loss of water
by evaporation is much greater than it is a thousand feet lower.
Although spruce and fir remain the dominant species, they are usually
shorter and less symmetrical in appearance. Near the upper limits of
this zone the trees are twisted and grotesque, often flat and
ground-hugging, sprawled behind boulders or fingering into the dwarf
willow clumps so characteristic of the alpine mountaintops. Here, also,
the only 5-needle pine in the park, LIMBER PINE, a rocky-soil tree of
the Subalpine zone, assumes its most picturesque aspect. Limber pine at
treeline is readily identified by its grotesque, twisted, ragged
appearance. Several splendid specimens can be seen beside Trail Ridge
Road about a half mile above Rainbow Curve. The name, limber pine, comes
from the ease with which the branches can be bent without breaking. The
cones are often 6 inches long, the largest of any conifer in Colorado.
The limber pine stands in the shadow of threatened extermination by
blister rust. This fungus disease, which attacks, girdles, and destroys
all species of 5-needled pines, has wrought havoc in many parts of the
country. Like so many virulent forest diseases, it was introduced from
abroad. Since no known natural checks on it exist in this country, it is
almost impossible to eradicate. It spreads to pines only from its
alternate hosts, wax currant and other species of _Ribes_; if these are
eradicated from the vicinity, the pines can be preserved. Though such
control measures are costly, without them the limber pine might be lost
forever from the park. The Government has been doing this work in
selected forests on the northeast slope of Longs Peak and near Estes
Cone, where many splendid specimens of this tree occur.