The ability of a damaged ecosystem to repair itself,
if left alone. For example, clear-cutting all trees in a well-defined
watershed, then leaving them lie in place was the basis for a simple
yet important experiment in the Hubbard Brook watershed of New Hampshire
conducted by Dr. Gene Likens, while he was a
faculty
member at Dartmouth University. The downed trees and under story
were sprayed with a mild herbicide for three years after the initial
cutting to discourage the growth of seedlings, and then the entire system
was left alone and carefully monitored. It is still being studied today
as part of a long-term ecological study plan initiated by the National
Science Foundation. It was demonstrated that the leaching of nutrients
from unprotected soil was accelerated during the first three years,
then returned to normal. During the first three years, pioneer species
of plants grew out and provided shade for the shade tolerant tree species
and held soil in place at the same time. These activities are referred
to as ecosystem services. Eventually the trees overshadowed the shade
intolerant pioneer species and they died out leaving only the trees.
The aquatic conditions of the Hubbard Brook returned to normal after
the third year. Resiliency was the term used to describe these events.
It was postulated that resiliency of the Hubbard Brook watershed was
due to a variety of factors, not the least of which was the fact that
tree seeds were long lived in the soil and germinated after the clear-cutting.
These studies give hope for other ecosystems damaged by the heavy hand
of commercial logging and other forms of encroachment. The intimate
connection between river and forest cannot be emphasized enough.
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