Burning Longleaf Pine Stands

Although weather conditions most of last week prevented the burning of some larger grassland tracts, the staff at the Audubon Center at Francis Beidler Forest was able to burn a small Longleaf Pine (Pinus palustris) stand when conditions improved on Thursday.  There are numerous reasons for denying a burning permit, but last week it was cool air aloft that would prevent the smoke from rising thereby causing a low-visibility driving hazard to nearby motorists.

Starting prescribed burn - Image by Mark Musselman

Longleaf Pine evolved with periodic fires that burned low to the ground, eliminated competing tree species, and exposed the soil to receive Longleaf Pine seeds. Longleaf Pine has thick bark to protect the trees from low-intensity fires that readily kill or burn other tree species.  The stand we burned on Thursday is the same stand where we planted wiregrass (Aristida stricta) and burned in November 2008 (blog entry).

Today, longleaf pine is an ecosystem in trouble everywhere in the South. Of the estimated 90 million acres in the pre-settlement forests, only about 2 million acres of mostly second-growth longleaf pine remain in scattered patches. Less than half of that is found on public lands. Those stands of longleaf in private ownership continue to decline, as landowners replace the longleaf with faster growing species such as loblolly pine. And, despite our increasing knowledge about the beneficial role of fire, especially fire during the growing season, many landowners still do not burn their longleaf pine forests, or do not burn them often enough. -- U. S. Fish & Wildlife

The key to keeping the fires low in intensity is to ensure that the excess fuel (leaves, needles, dead branches) does not accumulate on the forest floor. Note the difference in the before and after sections of the images taken during the burn.

Longleaf Pine pre-burn - Image by Mark Musselman

Longleaf Pine during burn - Image by Mark Musselman

Drip torches containing a 4:1 mixture of diesel to gasoline were used to set the fire on the downwind side of the stand, which allowed the fire to burn into the wind at a slower, steadier pace than if the fire were started on the upwind side of the stand. 

Drip torch - Image by Mark Musselman

Prescribed burn - Image by Mark Musselman

A fire break was plowed around the entire stand to ensure the fire did not migrate beyond the stand's boundaries.

Fire break - Image by Mark Musselman

Once the fire began in earnest, the smoke rising into the clear blue sky was undoubtedly visible from a great distance, especially if one had a seat high in that sky.  At one point, the roar of engines could be heard approaching at jet-like speed.  As the planes neared our burn site, the engines slowed and two pairs of F-16s circled leisurely around the pine stand.  After apparently sating their curiosity, the jets accelerated and made a thunderous exit to the west.

Pilot's log: Investigated fire...everything normal.  That's how we like it!