. Earth Science News .
Danger Lurks Underground For Oak Seedlings

File image: Vole.
by Staff Writers
West Lafayette IN (SPX) Mar 06, 2009
Scientists trying to understand why oaks are starting to disappear from North American forests may need to look just below the surface to find some answers.

Purdue University researcher Robert Swihart found that pine voles, small rodents that live underground, prefer oak roots to those of other commonly growing seedlings. The study identifies the rodents as a possible factor leading to high oak mortality rates that are threatening the resource base of the hardwood industry.

"You see a lot of mature oaks, but you don't see a lot of oaks in the understory beneath the canopy. If you don't see them there, you won't see mature oaks in 20 to 30 years," Swihart said. "We are facing a period in our history that could lead to a great crash in oak availability."

Swihart offered pine voles a selection of tree roots to eat in the laboratory, and they overwhelmingly gravitated toward oak roots. Voles caused more than twice as much damage to white oak roots than northern red oak and black cherry, and more than six times more damage to white oak than black walnuts. The voles snubbed yellow poplar roots altogether.

"Either the oak roots were much more nutritious and had higher energy content, or they contained fewer toxins, or some combination of those factors. Those are the main reasons an animal will choose one food item over another," Swihart said.

Swihart's study has been published in the current edition of the Canadian Journal of Zoology.

Under a variety of growing conditions, oak seedlings have comparatively high mortality rates, allowing other trees such as shade-tolerant maples and sun-loving, fast-growing tulip poplars to make up larger percentages of hardwood forests. Most of the studies on why oaks have a hard time regenerating have focused on competition from other seedlings, the use of acorns as food for small animals above the ground and the use of oak seedlings as food for deer.

"A lot of the focus has been on what's occurring above ground. We decided to look at what's going on below the ground," Swihart said. "We know pine voles can do a lot of damage in apple orchards, but there is little, except for a few anecdotal accounts, of what they do in their natural environment."

Swihart got the idea for his study from Ron Rathfon, a Purdue Extension forestry specialist in southern Indiana who has studied oak mortality issues. Rathfon found in 2006 that animals, later determined to be pine voles, had been responsible for killing at least 19 percent of the dead oak seedlings observed in his study area. He said the voles, which are common to eastern deciduous forests, were likely responsible for the majority of oak seedling mortality because many seedlings went missing, suggesting the voles had eaten or removed the entire plants.

There is little overall loss of oak forest to date, but Rathfon said that might change if foresters, the timber industry and landowners do not implement practices that better manage long-term oak growth and development.

"We do see some data that more shade-tolerant trees - particularly sugar maples - are becoming more prominent," Rathfon said. "It is a gradual, subtle shift that is taking place." Swihart said the loss of oaks would have other serious effects besides losses to the hardwood industry.

"Oak mortality could reduce the capacity of hardwood forests to support wildlife populations that rely on oaks for food - everything from deer and turkey down to mice and songbirds," Swihart said. Purdue undergraduate student Leslie Schreiber worked with Swihart on the pine vole study. Funding for the work came from Purdue Agriculture.

Share This Article With Planet Earth
del.icio.usdel.icio.us DiggDigg RedditReddit
YahooMyWebYahooMyWeb GoogleGoogle FacebookFacebook



Related Links
Purdue University
Forestry News - Global and Local News, Science and Application



Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


Drought threatens Amazon, speeds global warming: study
Paris (AFP) March 5, 2009
Drought is killing off trees in Brazil's fragile Amazon rain forest and depleting the region's carbon reservoirs -- an ecological double-whammy with devastating implications, according to a study published Thursday.







  • Corruption linked to China TV tower blaze: report
  • Landslide kills schoolchildren in PNG
  • Pilot in California crash opted to fly over homes
  • Landslide buries Peru village, 13 dead, 30 missing

  • 'Albatross' gone, India offers hand to US
  • Climate Change Heating Up Future Wars Part Three
  • Washington new center of global warming battle
  • EU confident Obama will follow its lead on climate change

  • Scientists Expose Buried Fault That Caused Deadly 2003 Quake
  • GOES-O Satellite Arrives At KSC For Final Pre-Launch Testing
  • Earth-Observing Landsat 5 Turns 25
  • Three ESA Earth Science Missions Move To Next Phase

  • Analysis: Forum in Iran to discuss energy
  • Analysis: Mexico offers new oil fields
  • Analysis: Russian gas reservoirs for EU?
  • Schwarzenegger tells techies to go 'green'

  • Wild birds likely caused HK H5N1 outbreak: official
  • Update Presented On Disease In Pork Plant Workers
  • Predicting When Invasive Species Can Travel More Readily By Air
  • HK and US scientists develop new bird flu vaccine

  • New footage shows rare rhinos in Indonesia: WWF
  • Oldest Fossil Brain Found In Kansas And Imaged In France
  • Invasives Threaten Salmon In Pacific Northwest
  • Climate change bad news for most birds: study

  • Nitrogen And Phosphorus Reductions Needed To Combat Eutrophication
  • Commercial Ships Spew Half As Much Particulate Pollution As World's Cars
  • Polluters pay under Obama's 'green' budget
  • Russian navy accepts blame for oil spill off Ireland

  • Malaysian archaeologists find site of pre-Angkor civilisation
  • Evidence Appears To Show How And Where Frontal Lobe Works
  • Chilli Peppers Continue To Help Unravel Mechanism Of Pain Sensation
  • Analysis: Congress on Mex border violence

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement