Forest
Surveys in 1940 and
the late 1980s show that the forests of Shenandoah National Park
have changed dramatically in 50 years. The changes include the
percentage of forested lands, and the ages, sizes, and species of
trees.
In 1940, Shenandoah
was a young park. It was authorized by act of Congress in 1926 and
established in 1935.
For almost 200 years before the park was
established, people had harvested and used the resources of these
mountains. Timbering, grazing, hunting, and cultivation ceased when
these lands became a national park.
In 1940, the park
was 85% forested. The rest of the park was open ground, including
grasslands, cultivated fields, and old fields reverting to forest.
Previously grazed areas were being occupied by bear oaks and pitch
pines. By 1990 the park was 95% forested. In the more mature forest,
bear oak stands had disappeared and pitch pine numbers had dwindled.
In 1940, there were
no yellow poplar stands and cove hardwoods covered only 6% of the
area. By 1990, yellow poplar stands covered 16% of the park and cove
hardwoods covered 15%. These forest types grow in moist sites. Their
increase is evidence of more organic matter in the soil and more
adjacent protective forest canopy cover.
In 1940, chestnut
oaks and northern red oaks covered 72% of the park. By 1990, their
numbers were down to 59%. Since 1990 repeated defoliation by
non-native gypsy moth caterpillars has contributed to the deaths of
even more oaks.
What do these
changes mean? The answer is not simple. For example, fewer oaks mean
fewer acorns. Acorns are food for deer, bear, wild turkey, and other
animals. In the short-term it also means there are more forest
canopy openings.
These openings
result in greater diversity of species in the forest. This means
more berries and soft nuts that birds, bear, and deer use. Sometimes
the result of forest change is the complete loss of a species or
loss of the species from the park. It can also afford the
opportunity to non-native species to invade. These changes in
species diversity are not desirable.
Aside from change brought about by
sudden events such as flooding, ice storms, or wild land fires, most
park visitors will not witness forest change. Seasonal change,
response to natural disturbances, and encroachment of non-native
species occurs gradually, taking years or decades. Despite the
apparent snail’s pace, change is vital to properly functioning
ecosystems.
Page 1 of 1
|