The report blames the lower rate of regeneration on logging equipment and the dragging of logs, which disturb the soil.
In addition, the researchers say, woody debris left behind by loggers buries new growth.
Those same woody branches and brush can become fuel for potential future blazes. As a result, logging may have increased, rather than decreased, the risk of future destructive fires in the same area, the study reports.
Loggers can, however, clear away debris through prescribed burns and other "fuel management" techniques. Such operations are costly and are not always performed after salvage logging, so they were not figured into the group's research.
"The treatments can have their own effects, and that's something that we want to study next," Donato said.
No Single Solution for Forest Growth
Stopping short of condemning all forms of salvage logging, Donato says data from many diverse forest types are still needed. One management policy won't fit all forests, he adds.
Jim Golden, deputy regional forester for the USDA Forest Service's Pacific Northwest Region, agreed.
"I've done a lot of work with reforestation, and what they reported is almost intuitive to me," Golden said from his Portland, Oregon, office.
"Particularly in these very productive Douglas fir forests [such as where the Biscuit fire occurred], if you run a hot fire through there and you have enough trees that are still standing, you will get regeneration," he said.
"If you log a site, you will lose some of that regeneration. But what concerns me is the conclusions that people might draw from that."
"If, because of this case where a fire went through and more than two years later we logged some of that area, we were to conclude that post-fire logging hurts reforestation, that would not necessarily be the case," Golden said.
"In some places the best thing to do is nothing," he continued. "But in others you have to actively intervene on the property."
More research is needed to help managers better understand post-fire recovery and identify what should be done on a case-by-case basis.
"We've stepped up research in the Forest Service to deal with post-fire recovery and try to shore up what until now has been driven by anecdote and observation," Golden said.
Forest Managers Tied to Bottom Line
Of course, management decisions can also be driven by dollars.
"Weighing the economic value of the timber that was killed against impacts to the site is exactly what the land managers are required to do when we consider something like this," Golden said.
Recovered revenue from timber can be used to help cope with a mounting backlog of forest restoration workan important consideration, given that each year seems to bring more wildfires and tighter budgets than the last.
"We no longer have the wherewithal to do all the work that we need to do in terms of restoration in the national forests," Golden said. "The post-wildfire restoration bill is growing each year, and we think that there is a half billion [U.S.] dollars of backlog work."
In areas where the Forest Service deems restoration work necessary, logging is often the only way to foot the bill.
Yet Donato's research suggests that in some cases dollars may be saved, and forests may be best served, by avoiding salvage logging and letting the forest bounce back without human help.
"Our data suggest that we should at least be open to the possibility that [forests burned by] big fires can regenerate on their owneven in places where we least expect it," Donato said.
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