This year, they turned to ash.
"Really big logs take a really long time to dry out," said Smith, fire ecologist at Yosemite National Park. "They are indicators that something bigger is going on."
Idaho's Elk Complex burned through trees in an area that had just been logged and through thousands of acres of state forest land that had been aggressively managed for 20 years. In the moister Sierra forest, Smith watched the Rim Fire burn through foothills with four different forest types up to the high-elevation lodgepole pine.
"If four different types of forest wouldn't stop the fire, no fuel treatment would," Smith said.
WHAT WE'VE LEARNED FROM 25 YEARS OF FIRE
Fire scientists say that the West's ecosystems evolved with fire. We can't stop it. When we do temporarily, we end up triggering the even bigger fires we see today.
In Southwest Idaho, most of the landscape has burned in the past 30 years. More than 56 percent of the Boise National Forest has burned since 1985 and 71 percent of the Payette, according to Forest Service numbers compiled by the Idaho Conservation League.
The forests have grown back where many of the older fires were, presenting land managers with new challenges. They not only have to mechanically thin and prescribe-burn to lessen fire risk in unburned areas, they also have to do the same with forests that have grown back from earlier fires.
"If we do not do these treatments outside of the fire season, it will be impossible to catch up," said Paul Bryant, Boise National Forest resource and planning officer.
Some previously burned areas are burning again on their own. The Pony Fire burned young ponderosa pines that were growing back after the Foothills Fire of 1992. Foresters are watching whether the forest will shift to brush.
On the Elk Complex, the fire burned so extreme in many areas that all of the seed source is gone, said Boise Forest silviculturist Ray Eklund. He's determining now where the agency should try to replant ponderosas, where it can expect natural regeneration and where it should let the area change to rangeland.
He looks back to the 1989 Lowman Fire area, where replantings died within a couple of years. Foresters planted ponderosa again on the north slopes, which have wetter soils. Many survived.
But the south slopes have now largely converted to brush.
Eklund's decisions are based both on ecology and economics: With tight budgets, there isn't the money to replant every acre when many trees won't survive.
"We have to be more judicious where we plant," Eklund said.
Monica Turner, a landscape ecology professor at the University of Wisconsin, has studied the forests of Yellowstone National Park since 1988. She has seen reduced regeneration where fires occur before the trees grow big enough to produce sufficient seed and where post-fire drought prevents germination.
She hopes to expand her studies to the entire Northern Rockies to determine how climate change will transform the forests. Right now she and agency scientists have little data on which to make predictions for the future.
Overall, she expects the brush and rangelands to replace some of the region's forests. She expects ponderosa pine to replace Douglas fir in the higher elevations as the frequency of fires there increases.
"Aspen may be one species that benefits from more frequent fires," Turner said. "I think we will see more areas of no forest or areas turn to a woodland scrubland. That doesn't mean we'll lose our native species or our wildlife."
Boise State University geomorphologist Jen Pierce has been studying the changes in the ponderosa pine forests in Southwest Idaho historically and agrees with Turner on the trend.
"They always have been adapting to change," Pierce said. "They're just changing faster."