Having seen that the present mountains are the result of past events, we
should not be surprised to learn that the plant cover of the park is
also dependent on what has occurred before. We are inclined to think of
a plant community, such as a forest, as a permanent fixture; but it is a
dynamic, never-stagnant population of individual living things, and in
some ways resembles a community of people.
Just as human populations ebb and flow through periods of great
numerical growth and dominance, followed by decline and engulfment by
invading peoples, so do vegetation types go through periods of dominance
and decline. When certain conditions of climate and soil prevail, those
kinds of plants best adapted to such conditions will dominate the scene.
As conditions change, the flora will change.
In Rocky Mountain National Park, we assume that toward the end of the
ice age most of the high altitude landscape was either ice-covered or
barren, like our present-day rockpiles above treeline. As the ice melted
and disappeared, the bare rocks of the canyons were exposed, and lakes
occupied what are now the meadows. The climate was changing, though, and
the rather sparse arctic-type plantlife was superseded by another
vegetation complex, except on the very tops of the mountains.
The ice-age vegetation was presumably connected with that of the regions
bordering the Arctic Ocean. The present tundra of the high country in
the park is an island of arctic-type vegetation, surrounded on all sides
by plant communities of lower latitudes. Will it be engulfed some day
and replaced by surrounding plant types? If the climate continues to
moderate, the answer may be "Yes."
Most of the original sparse arctic flora has already disappeared. The
bare rocks were first invaded by lichens--those plant pioneers still to
be seen on rocks in the park. In the thin soil formed by their life
processes, other primitive plants became established. As the climate
moderated and soils formed where bare rocks formerly existed, a new
vegetation complex replaced the old.
We suppose that all sorts of plants got started on this new land, but
only those species which happened to be adapted for the particular
conditions of their time would last long enough to become well
established and to produce ample seeds for future generations. This
selective elimination of plants which were not adjusted to the changing
conditions results in the dominance of certain well-adjusted species. In
this way, according to scientists, a climax vegetation develops for a
particular situation. As long as the climate remains about the same, the
climax vegetation remains relatively stable.
[Illustration: Rugged cliffs and mighty peaks are spectacular
products of geologic forces.]
Although it has been thousands of years since these plant communities
first started on the glaciated bedrock, the struggle for dominance among
the plants still goes on. Conditions are not yet completely static and
probably never will be. The meadows, the forests, and the barrens of
today may be quite different in a distant tomorrow.