Forest Service planning virtual Tahoe forest sofware

Friday, Oct. 16, 1998 | 10:43 a.m.

"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," says Mark Johnson of 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 stems 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.

Stumps still remain from trees cut down 130 years ago. From those, researchers cut off the top layer - about 6 inches - of the stump and study it.

The sample shows 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.

And 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.