Natural burning return to basin?
There hasn’t been a natural-burning wildfire on Lake Tahoe’s east shore since 1871.
Before that, however, the average time between fires was about 10 years. They were low- to moderate-intensity fires, burning mostly just the understory of the forest. They weren’t all small, though. Some moved through huge portions of forest.
The result of those fires was a much different forest than what Lake Tahoe residents and visitors walk, bike and play in today.
That is what Alan Taylor, associate professor of geography at Penn State University, has determined from years of research on Tahoe’s east shore.
“We have been trying to figure out what the fire regime was – how big the events were, in what type of conditions did they burn, how often they burned – before settlement,” Taylor said. “My data tells us the way it was. If the Forest Service wants to use controlled burning, if they want to mimic the natural conditions, (my data) tells them how to do it.”
Taylor began work at East Shore in 1995, and a commitment stemming from the 1997 Lake Tahoe Presidential Forum facilitated more work over the last two summers.
Preserved stumps from trees chopped down during the Comstock – about a three-decade logging period in the middle and late 1800s – still exist at East Shore. Taylor and his students took stump samples from Zephyr Cove to Sand Harbor and, by studying the rings, could determine the frequency and intensity of prehistoric fires.
In the 15,000-acre study area, about 1,200 acres burned each year. That was the case from 1600 to 1870.
Taylor’s research traced a fire back to 1160.
The fire-absent period over the last century is without historic precedent, Taylor said.
What difference does it make?
The lack of fire has changed the makeup of the forests.
In Jeffrey pine-populated areas at low, near-lake elevations, forests today are two to 10 times thicker than they were in 1870. In red fir areas at higher elevations, forests are three to seven times thicker today.
The density of trees has led to an unhealthy forest ecosystem in the Tahoe Basin.
A dense forest forces trees to compete for sunlight, water and nutrients, diminishing the health of all the trees. Because of that and several years of drought earlier in the 1990s, Tahoe forests have become more susceptible to bark beetle infestation, which has killed even more trees. An estimated 20 to 30 percent of the trees in the basin are dead. That large number coupled with the buildup of fuels on forest floors makes the basin very susceptible to the dangers of wildfire. Fire is a natural part of the ecosystem, but the conditions now have changed. A wildfire now could be catastrophic, and it could be dangerous to Lake Tahoe residents.
Mark Johnson, fire management officer for the Lake Tahoe Basin Management Unit, said Taylor’s work is valuable for the Forest Service’s prescribed burning activities.
“There’s good science coming from Dr. Alan Taylor showing fires burned all through the summer and fall here prior to settlement times,” Johnson said. “(When the Forest Service administers burns) we are re-introducing fire into a fire-dependent ecosystem.”
The Forest Service, which administers prescribed burns primarily in the fall and sometimes in the spring, currently is trying to burn 350 acres on East Shore. However, because of wet conditions, they have had some difficulty keeping the fire going. After a several-day delay, the Forest Service hopes to start burning again June 18.
The fact that the agency is having difficulty seems to correspond to Taylor’s research. About 90 percent of the fires happened in the late summer and fall; the rest happened from May to July.
“I’m personally for using (prescribed burning) as one of the tools for managing the ecosystem,” Taylor said. “If you think of it in terms of the past, fire was important for so long; it had to have had some significance on how the ecosystem worked.”
Taylor said the basin prior to settlement likely was more hazy than it is today.
He said it was difficult to guess what kind of impact the smoke would have had on Lake Tahoe’s clarity. While air pollution may have hurt the clarity then, today there are numerous other contributing factors that were absent prior to settlement.
“The atmosphere was pretty smoky before, and the lake was clear in 1870. That’s about all you can say,” he said.
While the Forest Service is using Taylor’s research, the Penn State professor’s work isn’t complete. This summer, he and his students are collecting stump samples on West Shore. The terrain is steeper on that side of the lake; the conditions are more wet.
“We didn’t think the information gathered on East Shore could just be cookie-cuttered over there,” Taylor said. “It looks like it’s going to be really different over there, just from the work we’ve done. I think there were more serious fires on West Shore. I think the results will be interesting and different that way.”
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