college of forestry

Fuel reduction likely to increase carbon emissions

The study this story is based on is available in ScholarsArchive@OSU: http://bit.ly/vqSGMY


CORVALLIS, Ore. – Forest thinning to help prevent or reduce severe wildfire will release more carbon to the atmosphere than any amount saved by successful fire prevention, a new study concludes.

There may be valid reasons to thin forests – such as restoration of forest structure or health, wildlife enhancement or public safety – but increased carbon sequestration is not one of them, scientists say.

In research just published in Frontiers in Ecology and the Environment, Oregon State University scientists conclude that even in fire-prone forests, it’s necessary to treat about 10 locations to influence fire behavior in one. There are high carbon losses associated with fuel treatment and only modest savings in reducing the severity of fire, they found.

“Some researchers have suggested that various levels of tree removal are consistent with efforts to sequester carbon in forest biomass, and reduce atmospheric carbon dioxide levels,” said John Campbell, an OSU research associate in the Department of Forest Ecosystems and Society. “That may make common sense, but it’s based on unrealistic assumptions and not supported by the science.”

A century of fire suppression in many forests across the West has created a wide range of problems, including over-crowded forests, increased problems with insect and pathogen attack, greater risk of catastrophic fire and declining forest health.

Forest thinning and fuel reduction may help address some of those issues, and some believe that it would also help prevent more carbon release to the atmosphere if it successfully reduced wildfire.

“There is no doubt you can change fire behavior by managing fuels and there may be other reasons to do it,” said Mark Harmon, holder of the Richardson Chair in Forest Science at OSU. “But the carbon does not just disappear, even if it’s used for wood products or other purposes. We have to be honest about the carbon cost and consider it along with the other reasons for this type of forest management.”

Even if wood removed by thinning is used for biofuels it will not eliminate the concern. Previous studies at OSU have indicated that, in most of western Oregon, use of wood for biofuels will result in a net loss of carbon sequestration for at least 100 years, and probably much longer.

In the new analysis, researchers analyzed the effect of fuel treatments on wildfire and carbon stocks in several scenarios, including a single forest patch or disturbance, an entire forest landscape and multiple disturbances.

One key finding was that even a low-severity fire released 70 percent as much carbon as did a high-severity fire that killed most trees. The majority of carbon emissions result from combustion of surface fuels, which occur in any type of fire.

The researchers also said that the basic principles in these evaluations would apply to a wide range of forest types and conditions, and are not specific to just a few locations.

“People want to believe that every situation is different, but in fact the basic relationships are consistent,” Campbell said. “We may want to do fuel reduction across much of the West, these are real concerns. But if so we’ll have to accept that it will likely increase carbon emissions.”

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Fuel reduction

Fuel reduction

Thinning reduces flying squirrel populations – key part of spotted owl diet

The study this story is based on is available in ScholarsArchive@OSU: http://bit.ly/tNqiB3

CORVALLIS, Ore. – Thinning of young Douglas-fir forests in the Pacific Northwest, done in part to help them return to a structure more similar to old-growth forests and aid recovery of the threatened northern spotted owl, also reduces the populations of flying squirrels that form an important part of the owl’s diet.

A recent study by scientists from Oregon State University and the U.S. Geological Survey found that this unwanted impact illustrates the complexity of trying to restore old-growth characteristics in forests that for decades were managed primarily for Douglas-fir timber production.

In the long run, researchers said, a restoration of old-growth structure should be a positive force for both spotted owl recovery and the northern flying squirrel – but in the near term, forest stands that have been thinned support significantly lower densities of flying squirrels than unthinned stands.

“Some of the stands being thinned were probably not great spotted owl habitat to begin with, and the impact on flying squirrel populations may not be permanent,” said Joan Hagar, a researcher with the U.S. Geological Survey and courtesy faculty member in the OSU Department of Forest Ecosystems and Society.

“This is a fairly common problem in restoration ecology, in which there are always winners and losers,” she said. “What this really suggests is that we may not want to thin all of these forest types, we need to preserve some as a refuge that would allow flying squirrel populations to recover in the future.”

Flying squirrels, Hagar said, are a major part of the diet of the northern spotted owl and also help disperse fungi important to tree health. There are millions of acres of even-aged, Douglas-fir dominated forests being considered for thinning, for both spotted owl recovery and other goals, both economic and ecological.

The northern flying squirrel is considered a “keystone species” by ecologists and an indicator of forest health. They do best in forests with many large live trees and well-developed understories, characteristics that are now largely lacking in many young forests.

This research studied various types of thinning treatments, and found that the heavier the thinning, the heavier the impact on flying squirrel populations. It was one of the longer-term studies done on this issue, for up to 13 years after thinning.

The findings “would seem to argue for caution in carrying out commercial thinning across large portions of the Pacific Northwest landscape, especially if one eventual goal is to sustain the primary prey of the northern spotted owl,” the researchers said in their conclusion.

Continued monitoring of northern flying squirrels and their habitat will help determine when flying squirrel populations begin to recover in thinned stands, in which treatment levels this occurs most quickly and which habitat features are most important, the scientists said.

The study was supported by the USDA Forest Service. It was published in Forest Ecology and Management, a professional journal.

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Joan Hagar, 541-737-6574

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Northern flying squirrel

Northern flying squirrel

Southwestern Oregon streams: a flawed view of the past

CORVALLIS, Ore. – The hands-off approach to riparian zones in southwestern Oregon is perpetuating congested, conifer-dominated streams that bear little resemblance to pre-European settlement conditions, and may be detrimental to long-term ecosystem health and some goals of the Northwest Forest Plan, a new study concludes.

Contrary to common assumptions, stream sides in this region were an open forest dominated by a mix of conifers and hardwoods until the 1850s, according to an Oregon State University study.

The forest cover prior to settlement varied, ranging from an open savannah at low elevations to a low-density forest at mid-elevations, with grass and shrubs in the understory that provided more food for fish. There was likely less shade and woody debris than the conifer-dominated streams seen today.

In a study published in Forest Ecology and Management, researchers said there is a flawed perspective about the historic nature of these streams before settlers arrived. At least some thinning and use of prescribed fire may be necessary to regain those conditions, they said.

“The major changes in these streams at first had little to do with logging or fire suppression, and actually started around 1850,” said David Hibbs, a professor in OSU’s Department of Forest Ecosystems and Society.

“Settlers brought in grazing animals, cleared land, and Native American populations declined,” he said. “These and other changes allowed more Douglas-fir to move in and displace the oak, madrone and other hardwood trees and shrubs that used to be a major part of the forest. At mid-elevations, white fir has even begun to replace the Douglas-fir.”

Before settlement, these riparian zones were actually more similar to the upland areas, with well-spaced trees, grasslands, and shade-intolerant tree species that could deal with more frequent fire, researchers said.

“They were quite open compared to what you see today,” Hibbs said. “And with our current policies of fire suppression and no timber removal, they are moving even further from their historic condition. Our vision of what these lands used to be is inaccurate. The question is where to go from here.”

In the days before European settlement, Hibbs said, the streams probably had less shade to cool them than many of them do today, more and higher quality leaf litter, and less woody debris. Both water temperature and woody debris are important to stream health. But deciduous trees and shrubs also provided greater volume and higher quality of litter that feeds insects and ultimately fish.

This description probably applies to forests of southwestern Oregon and parts of the northern Sierra Nevada range in California, Hibbs said, but not to streams in other locations that are not as hot or dry.

The researchers did a historical analysis of this region by analyzing existing tree species, tree rings, fire scars and other evidence to gain a better perspective on what these stream ecosystems looked like when affected only by Native Americans.

The report observed that:

  • Many of these stream ecosystems developed with more frequent but low- or mixed-severity fire and were dominated by a mix of conifers, deciduous trees and shrubs.
  • Major changes in forest composition began in the late 1800s – of the live conifers in some areas, five times as many germinated between 1850 and 1900 as in the 280 years before that.
  • Fire exclusion in the 20th century has allowed the changes begun in the 1800s to continue.
  • The change in tree and shrub composition is now reducing food and habitat for both aquatic and terrestrial wildlife, including a primary food source for the northern spotted owl.
  • A century and a half of fire exclusion and, more recently, regulations against any tree removal have created congested forests that may be moving even further away from historic conditions and ecosystems.

“The policy for riparian management areas in the Pacific Northwest, though well-intentioned, may be detrimental to the long-term health of riparian forests in regions shaped by fire,” the researchers wrote in their conclusion.

If historic and more natural conditions are desired, they said, partial harvest treatments and use of prescribed fire in some riparian areas would help to gradually restore them.

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David Hibbs, 541-737-6077

Climate change causing movement of tree species across the West

CORVALLIS, Ore. – A huge “migration” of trees has begun across much of the West due to global warming, insect attack, diseases and fire, and many tree species are projected to decline or die out in regions where they have been present for centuries, while others move in and replace them.

In an enormous display of survival of the fittest, the forests of the future are taking a new shape.

In a new report, scientists outline the impact that a changing climate will have on which tree species can survive, and where. The study suggests that many species that were once able to survive and thrive are losing their competitive footholds, and opportunistic newcomers will eventually push them out.

In some cases, once-common species such as lodgepole pine will be replaced by other trees, perhaps a range expansion of ponderosa pine or Douglas-fir. Other areas may shift completely out of forest into grass savannah or sagebrush desert. In central California, researchers concluded that more than half of the species now present would not be expected to persist in the climate conditions of the future.

“Some of these changes are already happening, pretty fast and in some huge areas,” said Richard Waring, professor emeritus at Oregon State University and lead author of the study. “In some cases the mechanism of change is fire or insect attack, in others it’s simply drought.

“We can’t predict exactly which tree (species) will die or which one will take its place, but we can see the long-term trends and probabilities,” Waring said. “The forests of our future are going to look quite different.”

Waring said tree species that are native to a local area or region are there because they can most effectively compete with other species given the specific conditions of temperature, precipitation, drought, cold-tolerance and many other factors that favor one species over another in that location.

As those climatic conditions change, species that have been established for centuries or millennia will lose their competitive edge, Waring said, and slowly but surely decline or disappear.

This survey, done with remote sensing of large areas over a four-year period, compared 15 coniferous tree species that are found widely across much of the West in Canada and the United States. The research explored impacts on 34 different “eco-regions” ranging from the Columbia Plateau to the Sierra Nevada, Snake River Plain and Yukon Highlands.

It projected which tree species would be at highest risk of disturbance in a future that’s generally expected to be 5-9 degrees Fahrenheit warmer by 2080, with perhaps somewhat more precipitation in the winter and spring, and less during the summer.

Among the findings:

  • Some of the greatest shifts in tree species are expected to occur in both the northern and southern extremes of this area, such as British Columbia, Alberta, and California.
  • Large declines are expected in lodgepole pine and Engelmann spruce, and more temperate species such as Douglas-fir and western hemlock may expand their ranges.
  • Many wilderness areas are among those at risk of the greatest changes, and will probably be the first to experience major shifts in tree species.
  • Some of the mild, wetter areas of western Oregon and Washington will face less overall species change than areas of the West with a harsher climate.
  • More than half of the evergreen species are experiencing a significant decrease in their competitiveness in six eco-regions.
  • Conditions have become more favorable for outbreaks of diseases and insects.
  • Warming will encourage growth at higher elevations and latitudes, and increased drought at the other extremes. Fire frequency will continue to increase across the West, and any tree species lacking drought resistance will face special challenges.

“Ecosystems are always changing at the landscape level, but normally the rate of change is too slow for humans to notice,” said Steven Running, the University of Montana Regents Professor and a co-author of the study. “Now the rate of change is fast enough we can see it.”

Even though the rate of change has increased, these processes will take time, the scientists said. A greater stability of forest composition will not be attained anytime soon, perhaps for centuries.

 “There’s not a lot we can do to really control these changes,” Waring said. “For instance, to keep old trees alive during drought or insect attacks that they are no longer able to deal with, you might have to thin the forest and remove up to half the trees. These are very powerful forces at work.”

One of the best approaches to plan for an uncertain future, the researchers said, is to maintain “connective corridors” as much as possible so that trees can naturally migrate to new areas in a changing future and not be stopped by artificial boundaries.

Also collaborating on the research was Nicholas Coops at the University of British Columbia. The work has been supported by NASA, and the study is being published in two professional journals, Ecological Modeling and Remote Sensing of Environment.

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Richard Waring, 541-737-6087

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Dying trees
Dying trees

Temperature increases
Temperature change

Precipitation changes

Precipitation change