University Park, Pa. -- A beetle infestation near Lake Tahoe, Nev.,
may lead to a better understanding of pre-European contact forest ecology
and shed light on the early history of the area, according to a Penn State
geographer.
Researchers are looking at the history of the forests, the incidence of
fire and signs of the early settlers -- including Chinese laborers and Basque
shepherds -- in this area closely linked with exploitation of the Comstock
Lode.
The reason for the sudden interest in this area is a bark beetle infestation
in the Lake Tahoe Basin. The insects have killed or damaged large stands
of wood, which pose a major fire hazard for the area. The solution is to
allow salvage harvesting and controlled burning, so that the forests can
return to a healthy state.
"Many environmentalists are concerned because they believe this area
is old growth forest," says Dr. Alan Taylor, associate professor of
geography. "It's not, but it is second growth forest."
That is actually part of the problem, most of the forests were last cut
140 years ago to supply fuel and timbers for mining the Comstock Lode near
Virginia City, Nev. In the early 1900s, fire eradication on federal land
became mandatory and most state and local governments followed suit.
The regrown forests are now 120 years old and are two to ten times more
dense than the original forests. These trees now compete intensely for resources,
especially water. Drought, combined with the absence of fire which thins
forests, has predisposed the trees to the beetle attack which is now killing
them off.
However, before salvage logging or controlled burning can take place, a
full investigation of the archaeological sites and the environment is underway.
Archaeologists have already surveyed the area for mill sites, camp sites,
remnant roads and both prehistoric and historic occupation.
The Comstock Lode, which was discovered in 1859, supplied silver to the
Union troops during the Civil War. Working in the mines, building the roads
and cutting the wood were a conglomerate of immigrants. Included among these
workers were large numbers of Chinese laborers.
"The archaeologists don't want to disturb the archaeological sites
or destroy the tree stumps which can give them information about dates,"
says Taylor. "I'm looking at the tree stumps to try to reconstruct
the forest structure before lumbering, the history of fire in the area and
the age of the trees before they were cut."
Because many trees have rings that grow one per year or one per season,
tree ring dating -- dendrochronology -- is often used to determine the age
of trees and their dates of cutting. Climate information, the history of
droughts and wet periods, can also sometimes be garnered from the rings.
Archaeologists use tree rings to identify the age of archaeological sites
from the cutting dates of construction materials.
Taylor is using tree rings to date the episodes of fire in the forest. On
some trees, fire-damaged rings can be identified and then dated. A compilation
of burning dates and locations can reveal the fire pattern in the area,
including both frequency and extent. The severity of the fires can be estimated
from the burn scars.
A survey of the ages of trees at specific fires can give a cross sectional
view of the age composition of the forest.
"We have had to develop a tree ring chronology specific for this area,
from living trees," says Taylor. "With a chronology that goes
back far enough, we can determine the dates of the logs in cabins and the
tree stumps."
An understanding of what the forest was like before European settlement,
during logging and how it grew back afterwards, could help environmentalists
and resource managers plan the future of these forests which surround some
of the last pristine lakes in the U.S.