The lake in this photo is at 1900 metre elevation.
Photo by Kelly Sekhon
The low elevation forest
along the coast is often referred to as the rainforest, because of the high
rainfall levels. The higher elevation forest has been called the snow forest,
as snow has more influence here than rain. Although snow cover lasts into the
summer or late spring, the growing season is still long enough for trees to
develop. As you hike through this upper forest, however, there are signs and
indications that you are approaching the high country. Some of these indicators
are the changes in the species of trees themselves. Even if you do not know the
names of these trees, you will still see that they are different from the
familiar trees near sea level. Those familiar trees are gradually replaced by
others which are more adapted to the long winters and harsher conditions.
Redcedar (Thuja plicata) is replaced by yellow cedar (Chamaecyparis
nootkatensis). Western hemlock (Tsuga heterophylla) gives way to
mountain hemlock (Tsuga mertensiana), and Douglas fir (Pseudotsuga
menziesii), which is not actually a true fir, is superseded by amabilis fir
(Abies amabilis). The low elevation forest, because its most common tree
is the western hemlock, is called the Western Hemlock Zone, and the high forest
which is dominated by mountain hemlock is called the Mountain Hemlock
Zone.
There are a number of
features about the Mountain Hemlock Zone which tell you that you have reached
the high elevation forest even before the trees begin to thin out. The thick
snow cover lasts well into the summer, at which time it becomes very hard
and treacherous, especially on steep slopes. At such times it is advisable to
have an ice axe and know how to do a self arrest. Another hazard on these
slopes are deep tree wells. The snow melts away from the sides of the tree
trunks. The trunks are dark and absorb heat, and there is also a small amount
of heat released by the trunks themselves. In early summer the larger trees are
surrounded by these deep vertical shafts. Another reason for carrying an ice
axe. Once the snow has melted another characteristic of the trunks becomes
visible. The tree itself may be vertical, but the base usually curves downhill.
This twist was produced when the tree was young and small. For the large trees
that was centuries ago. The weight of the snow bends small trees. It is only
when they are older that they can become tall and straight, but the evidence of
the long ago formative years remains.
As the growing season
becomes less and less, the trees get smaller and smaller, and farther apart.
This means that sunlight can reach the ground, and is not blocked by the
needles on the trees. If there is enough moisture herbaceous plants are able to
grow, and they do so in great profusion. These are the subalpine meadows, and
in July they present a panorama of colors. They have little time to
flower and set seed, and so they do so rapidly, and with a blaze of glory. With
so many flowers it would seem that there must be an equally large number of
seedlings. But like so many other things in life, this is an illusion. There
are many seeds, but very few seedlings. Unlike the plants at lower elevations,
the harsh conditions of the high country allow only a miniscule number of these
seeds to be successful. As you hike through the meadows, look and see how many
seedlings you can see. Usually there are none at all!
The meadows bloom in two
waves. First there are the plants that are the most cold resistant. These
flower close to the melting snow. As the soil warms the second wave comes into
bloom. By this time the early ones are already in seed. Some of the first
shoots actually push their way through the melting snow, although usually there
is a brown zone of dead vegetation immediately adjacent to the snowbanks, and
outside this is the green zone of emerging shoots. The first flowers to appear
are the yellow snowlilies (Erythronium grandiflorum), the little white
spring beauties (Claytonia lanceolata), and the white flowered western
anemone (Anemone occidentalis). The later stage is dominated by flowers
such as the blue flowered lupins (Lupinus arcticus), and the orange
flowered paintbrushes (Castilleja miniata).
The meadowlands grow where
there is rich soil, and abundant seepage. If you leave the meadows and hike
onto the rocky, dry ridges you find a much more hostile environment. Rain or
snow melt runs rapidly off these sites, carrying nutrients with it. This
moisture and dissolved minerals runs down slope to the lush herbaceous plants
below. There is a striking difference between the dominant vegetation of the
rocky sites and the moist, deep soil slopes below. The ridges belong to small
shrubs with tiny needle-like leaves. These are the heathers (Ericaceae).
Heathers are adapted to live in such extreme environments. Their roots contain
efficient microscopic fungi that help them gather water and nutrients in such
sites. Their leaves are like tiny coniferous tree needles. They are small,
evergreen, and narrow, and have thick surfaces which resist water loss. The
shrubs themselves are short and close to the ground, so that they are covered
by a blanket of protective snow in the winter. Because they grow close together
they are able to lessen the effects of desiccating winds. There are two common
heather species on these ridges, the pink mountain heather (Phyllodoce
empetriformis), and the white heather (Cassiope mertensiana). The
pink flowered species tends to grow at lower elevations than the white one. Its
leaves look like the needles on many conifer trees. The white one is adapted to
more extreme sites where the snow lingers longer. Its leaves are shorter and
pressed close to the stem, like scale leaves on cedars. This is an adaptation
to the more rigorous conditions at these higher altitude ridges.
Where the trees give way to
the meadows or ridges, you may notice that they present some unusual growth
forms. In the meadows there may be a few tree islands. These are spots where
the snow leaves a little earlier, and the growing season is just long enough
for tree seedlings to get started. They usually occupy little hillocks where
the sun can heat the ground a little more. Once one tree gets started it
produces some protection against the wind, and also lessens the accumulation of
snow, and so other trees can get started. In this way a small grove develops
after several centuries. On the ridges trees are often dwarfed, and grow
densely packed together. This growth form is called krummholz, meaning crooked
wood. During the winter these sites are bitterly cold and windy. Any buds or
needles projecting above the snow surface are killed, but those protected by
the covering of snow are able to survive. Therefore, the trees cannot grow
upwards, but they can grow sideways. Hiking along such ridges is difficult
because of the impenetrable shrubby barrier.
One feature you cannot fail
to notice on the alpine rocks are the lichens. Even if you are not consciously
aware of them, they still form part of the subconscious impression of what a
high mountain ridge looks like. The dry surfaces of such rocks are very
inhospitable for living things, but many lichens are specially adapted for
living is such places, especially the ones that form thin crusts. The splotches
on the rocks are usually lichens, not mineral coatings. Although they may not
appear so on casual observation, they are alive, growing and reproducing. Their
growth rate, however, is very, very slow. Most of the year they are covered by
snow, and most of the time when they are not covered by snow, they are dried
out by the sun. It is only during or shortly after rainy periods that they can
actually grow. These splotches can come in a number of different shades and
colors, and are more complex than they seem. They are simple ecosystems
composed of two different organisms. Most of the lichen is composed of fungus
threads, and among these threads are microscopic green plant cells - algae. The
plant cells gather sunlight the way all plants do. They use this energy to
combine water and carbon dioxide into sugars. The fungus part then uses some of
the sugar to build its own cells.
Some of the lichen species seen on rocks above the timberline.
Photo by Kelly Sekhon
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