Featured Research

from universities, journals, and other organizations

Pacific Northwest trees struggle for water while standing in it

Date:
July 26, 2011
Source:
Oregon State University
Summary:
Contrary to expectations, researchers have discovered that the conifers of the Pacific Northwest, some of the tallest trees in the world, face their greatest water stress during the region's eternally wet winters, not the dog days of August when weeks can pass without rain.

Canopy crane. The Wind River Canopy Crane was used to study the response of conifer trees to different types of water stress, including summer drought and freeze-thaw cycles in winter.
Credit: Photo courtesy of Oregon State University

Contrary to expectations, researchers have discovered that the conifers of the Pacific Northwest, some of the tallest trees in the world, face their greatest water stress during the region's eternally wet winters, not the dog days of August when weeks can pass without rain.

Related Articles


Due to freeze-thaw cycles in winter, water flow is disrupted when air bubbles form in the conductive xylem of the trees. Because of that, some of these tall conifers are seriously stressed for water when they are practically standing in a lake of it, scientists from Oregon State University and the U.S. Forest Service concluded in a recent study.

It's not "drought stress" in a traditional sense, the researchers said, but the end result is similar. Trees such as Douglas-fir actually do better dealing with water issues during summer when they simply close down their stomata, conserve water and reduce their photosynthesis and growth rate.

"Everyone thinks that summer is the most stressful season for these trees, but in terms of water, winter can be even more stressful," said Katherine McCulloh, a research assistant professor in the OSU Department of Forest Ecosystems and Society.

"We've seen trees in standing water, at a site that gets more than two meters of rain a year, yet the xylem in the small branches at the tops of these trees can't transport as much water as during the summer," McCulloh said.

The ease with which water moves through wood is measured as the "hydraulic conductivity," and researchers generally had believed this conductivity would be the lowest during a conventional drought in the middle of summer. They found that wasn't the case.

"We thought if there was a serious decline in conductivity it would have been from drought," said Rick Meinzer, a researcher with the Pacific Northwest Research Station of the USDA Forest Service, as well as OSU. "It was known that air bubbles could form as increased tension is needed in the xylem to pull water higher and higher. But it turns out that freezing and thawing caused the most problems for water transport."

Studies such as this are important, the scientists said, to better understand how forests might respond to a warmer or drier climate of the future. And although this might imply that these conifers could be more resistant to drought than had been anticipated, the researchers said it's not that simple.

"If the climate warms, we might actually get more of these winter cycles of freezing and thawing," McCulloh said. "There's a lot of variability in the effects of climate we still don't understand.

"One of the most amazing things these trees can do is recover from these declines in conductivity by replacing the air bubbles with water," she said. "We don't understand how they do that at the significant tensions that exist at those heights. We're talking about negative pressures or tensions roughly three times the magnitude of what you put in your car tires."

When the field research on this study was done in 2009, the area actually experienced a historic heat wave during August when temperatures in the Willamette Valley hit 108 degrees. During such extreme heat, trees experienced some loss of hydraulic conductivity but largely recovered even before rains came in September. By contrast, greater loss of hydraulic conductivity was observed in the middle of winter.

The study was done at the Wind River Canopy Crane Research Facility, and published in the American Journal of Botany. The research was supported by the National Science Foundation.

"The commonly held view is that the summer months of the Pacific Northwest are extremely stressful to plants," the researchers wrote in their conclusion.

"Yet, our results indicated that the winter months are more stressful in terms of hydraulic function, and suggest that perhaps an inability to recover from increase in native embolism rates over the winter may cause greater branch dieback in old-growth trees than shifts in summer climate."


Story Source:

The above story is based on materials provided by Oregon State University. Note: Materials may be edited for content and length.


Cite This Page:

Oregon State University. "Pacific Northwest trees struggle for water while standing in it." ScienceDaily. ScienceDaily, 26 July 2011. <www.sciencedaily.com/releases/2011/07/110725123701.htm>.
Oregon State University. (2011, July 26). Pacific Northwest trees struggle for water while standing in it. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2011/07/110725123701.htm
Oregon State University. "Pacific Northwest trees struggle for water while standing in it." ScienceDaily. www.sciencedaily.com/releases/2011/07/110725123701.htm (accessed October 25, 2014).

Share This



More Earth & Climate News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

EU Gets Climate Deal, UK PM Gets Knock

EU Gets Climate Deal, UK PM Gets Knock

Reuters - Business Video Online (Oct. 24, 2014) EU leaders achieve a show of unity by striking a compromise deal on carbon emissions. But David Cameron's bid to push back EU budget contributions gets a slap in the face as the European Commission demands an extra 2bn euros. David Pollard reports. Video provided by Reuters
Powered by NewsLook.com
Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Raw: Tornado Rips Roofs in Washington State

Raw: Tornado Rips Roofs in Washington State

AP (Oct. 24, 2014) A rare tornado ripped roofs off buildings, uprooted trees and shattered windows Thursday afternoon in the southwest Washington city of Longview, but there were no reports of injuries. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Fast-Moving Lava Headed For Town On Hawaii's Big Island

Fast-Moving Lava Headed For Town On Hawaii's Big Island

Newsy (Oct. 24, 2014) Lava from the Kilauea volcano on Hawaii's Big Island has accelerated as it travels toward a town called Pahoa. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins