The
ponderosa pine is the most widely distributed species of its genus
in North America. It is generally found in a sub-humid area deficient
in summer rainfall. The tree reproduces through seeds produced in
cones, which require 2 years to mature.
The Black Hills
forest is dominated by the ponderosa pine tree. Where conditions
permit, other trees such as the birch, white spruce, quaking aspen,
and elm also grow.
Wind Cave National
Park can be divided into two major vegetation types: the ponderosa
pine forest and the mixed grass prairie. Twenty-five percent of
the park is tree covered. The forested area includes ponderosa pine
forests and scattered groves of elm, aspen, bur oak, boxelder, and
birch. These scattered groves are generally found along drainage
areas. The ponderosa pine forest occupies the higher elevations
in the park.
The ponderosa
is an extravagant user of readily available moisture. It sends down
a fast growing taproot which enables it to obtain moisture from
many levels. As a seedling it also possesses the ability to withstand
prolonged drought. The trees are capable of growing exceptionally
fast if conditions are good for them. Because of the taproot, the
trees can generally withstand high winds. When "wind throw"
does occur it is often because the tree has root rot or the root
systems are shallow because of the rock on which the tree is growing.
Ponderosa pines are considered fire resistant,
damaged only when the fire "crowns" and sixty percent
or more of the tree is destroyed. Some observers feel that a natural
thinning process has largely disappeared because of organized fire
protection. As a result even-aged, stagnating stands of the species
have developed.
Ponderosa pines
are prolific and pine seedlings grow in the shade of mature trees.
If not kept in check, young trees will form exceptionally thick
stands. Because of the intense competition for nutrients, moisture
and sunlight, very few trees develop fully. This creates a stagnant
situation for all the trees and even the grasses and forbs in the
area.
Fires
kept the forest in check and opened the land to grasses and other
vegetation. Fires burned young seedlings so that only a few healthy
ones survived to replace large trees that were dying. In this way
the trees of the forest were in different stages of development
and the forest was healthier.
In a healthy
forest, insects, such as the mountain pine beetle, have less chance
to destroy trees. The pine beetle attacks trees that are about 9
inches in diameter and are close together. In a mature, fire controlled
forest, this situation rarely developed.
After
a century of use and misuse the ponderosa pine forest of the Black
Hills has developed into a vast area of even-aged trees. These trees
are susceptible to insect infestation and destruction by fire. Also,
because they are so prolific, the trees are encroaching upon the prairie
and using so much of the land's moisture and nutrients that other
plants can not thrive. |