Managing Southern Appalachian Hardwood Forests with Fire

Results of 12-year study on fuel reduction treatments in Southern Appalachian hardwood forests

Each of the treatments in the study created different stand structure and fuel characteristics. The control at top left shows an understory thick with shrubs. The mechanical treatment removed shrubs but left woody fuels that took 5 to 7 years to decompose. Burning reduced shrubs, but woody sprouts dominated the understory. The combined treatment opened the overstory, removed shrubs, but did not increase the abundance of grasses desired for woodland restoration.
Each of the treatments in the study created different stand structure and fuel characteristics. The control at top left shows an understory thick with shrubs. The mechanical treatment removed shrubs but left woody fuels that took 5 to 7 years to decompose. Burning reduced shrubs, but woody sprouts dominated the understory. The combined treatment opened the overstory, removed shrubs, but did not increase the abundance of grasses desired for woodland restoration.

Findings from a study led by a U.S. Forest Service scientist suggest that more frequent use of prescribed fire will be needed to reach common management objectives for the hardwood forests in the southern Appalachian region.

The findings by Forest Service emeritus scientist Tom Waldrop and collaborators were published in a recent issue of the journal Fire Ecology.

The forests of the southern Appalachian Mountains are among the most biologically diverse and complex in the U.S., which means they’re also among the most difficult to manage. The upland hardwood forests that cover almost 80 million acres in the region are the result of a wide range of natural and human disturbances, including fire.

Fires caused by lightning and humans once played a significant role in shaping southern Appalachian hardwood forests, but decades of fire suppression have led to dramatic changes in the density and structure of forests. In addition, the rapid growth of flammable shrubs such as mountain laurel and rhododendron in forest understories has increased concern about wildfire risk, but using prescribed fire and mechanical thinning to reduce fuel loads and help manage these systems is a relatively recent development without many long-term studies to guide practice.

“Three common management objectives include restoration to an open woodland, oak regeneration, and fuel reduction,” said Waldrop. “We used findings from the Fire and Fire Surrogates (FFS) study set up in 2000 on the Green River Game Lands in North Carolina to provide information about reaching these objectives using prescribed burning, mechanical fuel reduction, or a combination of fire and mechanical treatments.”

The three fuel reduction treatments were applied in study plots over 12 years, with prescribed fires applied for burn and combination treatments during March 2003, 2006, and 2012. Mechanical fuel reduction consisted of chainsaw felling of shrubs and small trees in 2002. Each treatment proved to be viable for southern Appalachian sites but produced differing results in relation to the objectives:

  • All the treatments altered stand structure, but none of them restored the area to open woodlands;
  • Areas treated with a combination of mechanical fuel treatment and burning developed the desired overstory structure, but trees and shrubs sprouted on the forest floor, preventing grasses and flowers from establishing;
  • All the treatments increased oak reproduction and reduced the shrub layer, with the degree of fuel reduction differing by treatment; and
  • Prescribed fire and the combination of prescribed fire and mechanical fuel treatment reduced most fuels and probably reduced the severity of a subsequent wildfire in 2014.

“Though the prescribed burning and combined treatments could eventually result in the desired stand conditions, many repeated fires may be needed,” said Waldrop. “Burning more frequently or in a different season might speed the process. Managers may need to decide between moving towards an open woodland with a diminishing overstory through frequent burning — or a more woody community with ingrowth to the overstory through infrequent burning.”

The southern Appalachian study site on Green River Game Lands is the longest-running study in the Joint Fire Science Program Fire and Fire Surrogates network, and is the site of ongoing research from a wide range of collaborators. The study site has already generated over 100 research publications that can be accessed at the Consortium for Appalachian Fire Managers and Scientists (CAFMS) website.

“For over 16 years, this site on lands managed by the North Carolina Wildlife Resources Commission (NCWRC) has engaged researchers from multiple universities as well as two Forest Service research stations,” said Helen Mohr, the Forest Service forester who directs CAFMS. “Without the support of the NCWRC, the continuation of this project wouldn’t have been possible.”

Read the full text of the article.

For more information, email Helen Mohr at hmohr@fs.fed.us.

 

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