Logging After Wildfires Can Retard Regeneration, Heighten Fire Risk

CORVALLIS, Oregon, January 7, 2006 (ENS) - Allowing trees to naturally regenerate after a wildfire works about as well or better than logging and replanting, according to new research conducted on the area burned in the 2002 Biscuit Fire in southwestern Oregon - the largest fire in Oregon history.

In research results that contradict the premise of the Bush administration's Health Forests Restoration Act, the first data about forest regeneration in this vast, burned area suggests that logging, by itself, would increase the levels of slash that could fuel another fire in the near future.

Combustible slash and waste wood left behind on the forest floor after trees are felled and processed could fuel more fires, the researchers found, concluding that other fuel reduction approaches besides logging would still be needed, entailing additional expense.

"Surprisingly, it appears that after even the most severe fires, the forest is naturally very resilient, more than it's often given credit for," said Dan Donato, a graduate student in the Department of Forest Science at Oregon State University and lead author on the study.

Trees burned in the Biscuit fire stand near the junction of McGrew Trail and Forest Service road 4402. (Photo courtesy Friends of Living Oregon Waters)

The research by scientists from Oregon State University (OSU) and the Institute of Pacific Islands Forestry in Hawaii, a division of the U.S. Forest Service. was published Friday in Sciencexpress, the online issue of the journal "Science."

Even following a high severity fire such as this, which covered more than 450,000 acres, the natural conifer regeneration on study sites was about 300 seedlings per acre, and 80 percent Douglas fir, the study found.

But logging reduced the regeneration by 71 percent, and would require manual planting to restore seedling levels that otherwise would have occurred naturally.

The U.S. Forest Service is implementing a formal decision reached in 2004 to manage the lands charred in the Biscuit Fire on the Rogue River-Siskiyou National Forest by logging 370 million board feet of fire-killed wood, building 300 miles of fuel management zones, reforesting 31,000 acres, and completing 70 miles of road work including closure, decommissioning, and stabilization. No permanent roads will be built.

"This is extreme logging at its worst," said Rolf Skar, campaign director with the Siskiyou Project, and a critic of the Health Forests Restoration Act. "With this over-the-top logging plan, the Bush Forest Service will leave no tree behind."

"Logging has sometimes been cited as a way to reduce fuels that could feed future fires," said John Campbell, a faculty research associate in the Department of Forest Science. "But not everything leaves on the log truck. We found that the process of logging in this type of situation actually produces a large amount of fine fuels on the ground that, unless removed, could increase fire risk, not decrease it."

Mechanical fuel removal can work, the report said, but is often precluded by its expense. After logging, options are to leave the fuels and live with high fire risk, or to treat them, generally by prescribed burning, which can lead to additional impacts such as further soil damage and seedling mortality.

Logging of old growth after the Biscuit Fire (Photo courtesy Native Forest Network)

But OSU Distinguished Forestry Professor John Sessions took issue with these conclusions, saying that the three years since the Biscuit Fire have been unusually moist for this area that is often dry and difficult to reforest.

"The authors suggest that fire-killed trees will be lower fire risk if left standing," Sessions says. "All standing fire-killed trees eventually fall, the smaller trees in the first decade or two and the larger trees will follow. Downwood loads, and thus risk from heavy fuels, will peak in several decades and remain high for decades."

The study acknowledges that the years immediately following the Biscuit Fire included a good "seed year" for surviving trees and favorable soil moisture conditions, which is a concern in this comparatively dry region of southwest Oregon, where reforestation has traditionally been very difficult.

This research was focused on regeneration potential after fire, effects of post-fire logging on regeneration, and fire risks. It did not consider the economics of salvage logging. Nor did it address the long-term fate of conifer seedlings in competition with shrubs and hardwoods – although early initial regeneration is one key to winning that battle.

Sessions says, "The real test for regeneration is survival to mature tree size. Thousands of seedlings per hectare or more may exist following a good seed year and adequate spring moisture. Seedling counts of first year, second or third germinates is recognized as a weak test for conifer survival in southwest Oregon. Few will survive the first five years given the shrub and hardwood competition."

One of the consequences of logging, the study concludes, is that the use of heavy equipment, log skidding, soil compaction and burial of seedlings by excess woody debris took a heavy toll on naturally regenerated seedlings, which in this case began taking root almost immediately after the fire.

The logging of dead, burned trees might add more debris than logging of green trees, researchers said, because without foliage to catch the wind, burned trees often fall more quickly and shatter more readily than living trees.

When left to natural regeneration, the trees that did not die acted as a seed source for fairly wide areas around them, researchers say. And contrary to some assumptions, even severe forest fires rarely kill every tree – rather, they usually move through an area in a mosaic of burned trees and some stands left living.

"What this study does make clear is that natural regeneration does not necessarily fail to achieve our goals for conifer establishment," said Beverly Law, an OSU associate professor of forest science. "Strong numbers of seedlings regenerated naturally, and they have a good foothold. So far, so good. Only time will tell how the conifers will compete with shrubs in the long run."