Leaf litter and soil protect acorns from prescribed fire

Jul 18, 2012

U.S. Forest Service scientists have found that prescribed fires with the heat insulation of leaf litter and soil can help restore oak ecosystems.

Forest Service researchers are helping land managers find the best time to use prescribed fire when oak regeneration from acorns is a concern.

"Acorns inside the or in the soil are for the most part protected from fire," says Cathryn Greenberg, Forest Service Southern Research Station (SRS) researcher and lead author of the study published in July in the journal . "However, when acorns lie on top of the leaf litter, even low intensity surface fires will kill most of them."

Prescribed fire is increasingly used as a tool in oak ecosystem restoration, with the goal of reducing competition and creating light and seedbed conditions that help germinate and flourish. Forest Service researchers are helping land managers find the best time to use prescribed fires when oak regeneration from acorns is a concern.

To see how fire affected acorns, researchers placed nuts on the leaf litter surface, inside the duff (leaf litter plus smaller fragments of plant material), and underneath the duff, about 2 inches into the soil. The temperature of the , measured just above the surface of the leaf litter, ranged from less than 174o F to almost 700 o F.

After the burn, researchers retrieved the acorns and placed them in ideal conditions for germination. "Almost all the acorns that were on the leaf litter surface and exposed to fire died," says Greenberg. "However, acorns in the duff or in the soil were better protected from , and generally unaffected by low intensity fires."

When acorns fall to the forest floor they don't stay on top of the leaf litter too long. Squirrels, jays, chipmunks and mice bury acorns, or they settle into the litter because of weather, falling leaves and gravity. Once acorns are blanketed by leaf litter or soil, low-intensity burns are usually safe. However, should consider the timing and size of acorn crops, as well as the forest floor condition when determining the timing and frequency of prescribed burning.

"Frequent burning that reduces litter and duff depth could compromise the availability of 'safe sites' where acorns are insulated from high fire temperatures," says Greenberg.

Explore further: Pact with devil? California farmers use oil firms' water

More information: Access the full text of the article: www.srs.fs.usda.gov/pubs/40794

Related Stories

Presence of snails points to forest recovery

Feb 16, 2010

A team of Catalan researchers has studied the changes in the make-up of animal populations following forest fires, and have concluded that malacological fauna are a good indicator of forest recovery. The conclusions ...

Recommended for you

Gimmicks and technology: California learns to save water

20 hours ago

Billboards and TV commercials, living room visits, guess-your-water-use booths, and awards for water stinginess—a wealthy swath of Orange County that once had one of the worst records for water conservation ...

Cities, regions call for 'robust' world climate pact

20 hours ago

Thousands of cities, provinces and states from around the world urged national governments on Thursday to deliver a "robust, binding, equitable and universal" planet-saving climate pact in December.

Will climate change put mussels off the menu?

20 hours ago

Climate change models predict that sea temperatures will rise significantly, including in the tropics. In these areas, rainfall is also predicted to increase, reducing the salt concentration of the surface ...

As nations dither, cities pick up climate slack

Jul 02, 2015

Their national governments hamstrung by domestic politics, stretched budgets and diplomatic inertia, many cities and provinces have taken a leading role—driven by necessity—in efforts to arrest galloping ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.