Bark Beetle Infestation Spurs Multifaceted Study

August 12, 1996

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.


Penn State

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