Research: climate change may reduce conifer regeneration after wildfire

regeneration after wildfire
A decade after a stand-replacement forest fire on the Metolius watershed in Central Oregon, almost no trees have begun to regenerate on one of the dry sites at lower elevation. (Photo courtesy of Oregon State University)

Government employees working for Oregon State University have determined that predicted increases in temperature and drought in the coming century may make it more difficult for conifers such as ponderosa pine to regenerate after major forest fires on dry, low-elevation sites, in some cases leading to conversion of forests to grass or shrub lands, a report suggests.

But even though you paid for it already by funding the research as a taxpayer, it will cost you $35.95 to purchase a copy of their findings, written by Erich Kyle Dodson and Heather Taylor Root of the University’s Department of Forest Ecosystems and Society in Corvallis, Oregon. The for-profit Elsevier corporation headquartered in the Netherlands published the paper. Wildfire Today supports open access to the results of taxpayer-funded scientific research. (UPDATE April 4, 2018: the research is now available for no additional charge.)

Dodson and Root concluded that moisture stress is a key limitation for conifer regeneration following stand-replacing wildfire, which will likely increase with climate change. This will make post-fire recovery on dry sites slow and uncertain. If forests are desired in these locations, more aggressive attempts at reforestation may be needed, they said.

The study, published in Forest Ecology and Management, was done in a portion of the Metolius River watershed in the eastern Cascade Range of Oregon, which prior to a 2002 fire was mostly ponderosa pine with some Douglas-fir and other tree species. The research area was not salvage-logged or replanted following the severe, stand-replacing fire.

“A decade after this fire, there was almost no tree regeneration at lower, drier sites,” said Erich Dodson, a researcher with the OSU Department of Forest Ecosystems and Society. “There was some regeneration at higher sites with more moisture. But at the low elevations, it will be a long time before a forest comes back, if it ever does.”

Similar situations may be found in many areas of the American West in coming decades, the researchers say, and recruitment of new forests may be delayed or prevented – even in climate conditions that might have been able to maintain an existing forest. While mature trees can use their roots to tap water deeper in the soil, competition with dense understory vegetation can make it difficult for seedlings to survive.

Openings in ponderosa pine forests created by wildfire have persisted for more than a century on harsh, south-facing slopes in Colorado, the researchers noted in their report. And fire severity is already increasing in many forests due to climate change – what is now thought of as a drought in some locations may be considered average by the end of the next century.

If trees do fail to regenerate, it could further reduce ecosystem carbon storage and amplify the greenhouse effect, the study said.

Restoration treatment including thinning and prescribed burning may help reduce fire severity and increase tree survival after wildfire, as well as provide a seed source for future trees, Dodson said. These dry sites with less resilience to stand-replacing fire should be priorities for treatment, if maintaining a forest is a management objective, the study concluded.

Higher-elevation, mixed conifer forests in less moisture-limited sites may be able to recover from stand-replacing wildfire without treatment, the researchers said.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.

3 thoughts on “Research: climate change may reduce conifer regeneration after wildfire”

  1. Certainly changing climate will have effects on the landscape. But, currently, many people are actually predicting increases in rainfall along with warming. If it does instead get hotter and on average drier across the US, certainly forests are going to recede and/or not come back after a fire. This has happened in the past; there are parts of the southwest that used to support elk herds that now don’t have enough water even for Joshua trees at lower elevations. Assuming that the stalled warming does restart after its 15-year break, it’s even conceivable to me that, as with snow patterns, you could get moisture winners and losers, with some forests doing better while others die off.

  2. Yes, scientists have “known” for ten years or more that climate change was going to affect the landscape. Just how much and when were open questions. The confidence level of this “knowledge was probably at the 90% level. Now it is closer to 99.999%

    There is a larger question that gets back to policy. “When decisions are made in the political arena, political calculations trump ecological and ethical factors.”
    In the ideal world, policy is based on good science. In the world we live in, policy is too frequently based on fear and voodoo.

  3. Ten years ago, while working on a fire in Ponderosa stands in Okanogan County WA, an older gentleman who was a tree scientist was surveying the area I was assigned to. He told us that in 50 – 100 years, most of the ponderosa forests in the West would be gone due to fires and climate change. He was either prescient, or the scientific community already knew this. The one ray of hope in this article is the concept of restoration treatment, but we know where the money goes, or doesn’t go.


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