The forests of the Pacific Northwest hold significant potential to increase carbon storage and help mitigate greenhouse gas emissions, if they are managed primarily for that purpose, a new study found.
In the complete absence of stand-replacing disturbances–via fire or timber harvest–forests of Oregon and Northern California could theoretically almost double their carbon storage, according to scientists in the Oregon State University College of Forestry.
Although it isn’t realistic to expect an absence of disturbance, the estimates were based on average conditions up until now that include variation in forest biomass, age, climate, disturbances and soil fertility. If all forest stands in this region were just allowed to increase in age by 50 years, their potential to store atmospheric carbon would still increase by 15%, the study concluded.
That would be a modest, but not insignificant offset to the nation’s carbon budget, the scientists say, since this region accounts for 14% of the live biomass in the entire United States.
The findings are the result of almost two decades of analysis as part of the North American Carbon Program.
"We have known that forests in this region have high productivity, and in recent years we have learned they have a high potential to store large amounts of carbon even at very old ages," said Beverly Law, a professor of forest science at OSU. "The forests west of the Cascade Range are also wetter and less likely to be lost to fire. We suspected these forests might provide more opportunity for carbon storage than has been recognized, and these data support that."
Many economic, ecological and land management issues come into play, the researchers said, and the recent study does not consider what effect increases in temperature or changes in precipitation might have on these lands, or the implications that might have for catastrophic forest fire. However, looked at from nothing more than a carbon offset perspective, the optimal approach would be to leave the forests alone, the scientists said.
"Increasing carbon storage in this region might be one contribution to what clearly is a much larger global issue, something that policy makers could consider," Law said. "A lot of land management approaches are now being seen as a short-term bridge to a period where we will be using fewer fossil fuels and addressing carbon issues in other ways."
The study also found that about 65% of the live and dead biomass in this region is on public lands, while private lands often have younger age classes of vegetation and less total biomass.
Also, contrary to accepted views on biomass stabilization and decline, biomass is still increasing in stands more than 300 years old in the Coast Range, Sierra Nevada and the West Cascade Range, and in stands more than 600 years old in the Klamath Mountains.
This research was published in the professional journal Ecological Applications.
Another recent study found that the most carbon dense forests in the world are located in temperate regions of Australia, not the tropics, as was commonly believed.
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