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Virtual walk through old Tahoe forests in future

Andy Bourelle

The forests in the Lake Tahoe Basin have changed.

That is why the U.S. Forest Service is in the process of trying to develop forest visualization software that will allow people to take a “virtual walk” through a Lake Tahoe forest – in the present and the past.

“It’s very hard for people to understand that the forest looks different now than it did 120 years ago. That software will be a tool for us to show that,” said Mark Johnson, acting fire management officer for the Lake Tahoe Basin Management Unit. “It will be like a computer-generated walk through the forest, in pre-settlement times and now. A year ago that technology wasn’t available but it’s there now. This is down the road, but we’re in the process now of talking about this very subject.”



The plan for the computer software is just one project resulting from a comprehensive study of East Shore forests by Penn State Associate Professor Alan Taylor.

Taylor studied the area in 1996 and 1997, and, as a result of the 1997 Presidential Summit at Lake Tahoe, returned this summer to collect more samples.



He is studying stand composition – meaning the proximity of the trees to one another – and the historical presence of fire on the western slope of the Carson Range on the east shore of Lake Tahoe.

Johnson said Penn State hopes to start a West Shore study next summer.

The East Shore was perfect for the study, Johnson said, because stumps still remain from trees cut down 130 years ago. From those, researchers can cut off the top layer – about 6 inches – of the stump and study it.

The sample can show the age of the tree and, because of scarring, the “detectable fire-return intervals” – how often natural fires used to occur.

So far, the East Shore study has revealed detectable fires occurred every three years on average from 1160 to 1871 – what Taylor calls a conservative estimate.

The study also reveals that trees in a current East Shore acre are about five or six times as dense as a pre-settlement acre of forest. Before settlement, about 68 trees occupied a hectare – a measurement equaling 2.471 acres. More than 340 trees now occupy a hectare.

The study reinforces what the agency has believed all along – that fire was a natural tool in the Tahoe Basin for thinning the forest and adding to the overall health of the trees.

Not only that, but since fire has been virtually eliminated in the basin since the 1800s, the danger of a catastrophic wildfire has increased.

The last fire recorded in the study area was in 1871.

“Think of how many fire return intervals we’ve missed. There’s been 125 years for those fuels to build up,” Johnson said. “All those surface fuels have accumulated over the years. The fact that those stumps are still there shows that the other fuels probably haven’t decomposed either.”

The natural fires are believed to have been low- to moderate-intensity fires that thinned the lower vegetation and kept the forests thin. A fire now would likely be a very intense fire because of the vast amount of fuels in the forest.

In the forest service’s several-year-long East Shore Project, the workers thinned the area of study with mechanical treatments and prescribed burning. But much of the basin remains in potential danger, and current projects of forest thinning are under way.

Additionally, a dense forest forces trees to compete against each other for sunlight, water and nutrients, which diminishes the health of all the trees. Because of that and several years of drought earlier in the 1990s, Tahoe trees have become more susceptible to bark beetle infestation, which has killed even more trees and added to the fire danger.

The original forests of the Tahoe Basin were more open, less dense and composed of trees with a wide variety of diameters. Over a three-decade period beginning in the late 1870s, the forest was essentially removed to supply timber for the Comstock mines in Virginia City.

In addition to the amount of trees, the types of trees have changed. Historically, Jeffrey pine were most common in lower elevations; red fir, Western white pine and white fir were common in higher elevations; and Lodgepole pine and Sierra juniper in the upper elevations. The post-settlement forest has less Lodgepole and less white fir, and all of the trees are similar in size, opposed to the great variation in size of the pre-settlement forest.

Most of what the study has revealed was not unexpected information. However, the forest service previously had no solid, scientific information backing up its beliefs.

“This will serve as a template for future vegetation management projects that we will propose,” Johnson said. “In order to manage the forest now, we have to know what the former condition was. Now we have good science to back us up.”

Tahoe Daily Tribune E-mail: tribune@tahoe.com

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