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: The Forest Community
A forest is organized vertically like an apartment house or office
building, with layers corresponding to stories. The _canopy_ is the
branches and foliage of tall trees that form a roof over the
community. Below the canopy are the _understory_ trees: young
individuals of the canopy species; and small, shade-tolerant trees
that will never become part of the canopy. Beneath the understory
branches is the _shrub layer_, occupied by knee-high-to-man-high
woody plants; beneath that is the _herb layer_, where most of the
ferns, wildflowers, grasses, and smaller woody plants grow. The
_forest floor_ is the zone of mosses, mushrooms, creeping plants,
and forest litter (leaves, twigs, needles, feathers, bits of bark,
animal droppings, etc.). The forest has a “basement,” too,
interlaced by plant roots, mycelia of fungi, and tunnels of myriad
animals.
Each layer of the forest has its characteristic animal species, but
most forage over more than one level. Some nest in one story and
feed in another. The red squirrel races back and forth from the
forest floor to the highest branches.
The forest community also has a socio-economic organization. Every
animal (and plant) takes up space and consumes a portion of the
available nutrients. Each has a place in the community food
chain—as, for example, _herbivore_, _carnivore_, or _scavenger_.
Each directly or indirectly affects all the other organisms.