Visit to longleaf pine savannas

Kathie and I spent a week in South Carolina and part of the time we visited several interesting longleaf pine savannas. The longleaf pine (Pinus palustris) is a fascinating fire-controlled ecosystem that has probably been responsible for the strong use of prescribed fire in southeastern U.S.

The longleaf pine belt extends across a NE/SW tending band from southern Virginia through western Mississippi, with outliers farther west. It is considered one of the most endangered vegetation types in the U.S., but is making a strong comeback because of the wide use of prescribed fire. Every state in the southeast has an active Prescribed Fire Council, and state and federal forestry makes strong use of fire. In our visits to this area, we have been impressed by how extensive the prescribed burns are, with single burn units of thousands of acres.

Historically, the longleaf pine ecosystem was maintained by frequent (3-10 years) low intensity fires, generally caused by lightning or people. Landowners conducted what was called "light burning", and even after fire had almost been suppressed elsewhere in the U.S., fire continued to be used here. However, Smoky Bear eventually made inroads even here, and by the mid part of the 20th century, the use of fire had almost ceased. However, through the strong stimulus of the Tall Timbers Research Station (based on the Georgia/Florida border), prescribed fire has been brought back, and is now considered an "essential" tool in ecosystem management. Everywhere we saw longleaf pines, we saw evidence of fire. In one area in the Francis Marion National Forest, we drove for 3 miles (!) along the edge of a longleaf pine forest that had been burned sometime in the past several weeks (see photo at end of this post). The size of such a burn unit boggles the mind of a midwesterner!

One of the more interesting areas we visited was Lynchburg Savanna Heritage Preserve, a South Carolina site that is equivalent to one of our State Natural Areas. This site was acquired by the S.C. Nature Conservancy and turned over to the state for management. This site is noted for its exceedingly high understory diversity.


Another area we visited was the Carolina Sandhills National Wildlife Refuge, a Fish and Wildlife site where restoration is focused (among other things) on restoring habitat for the red cockaded woodpecker. Here is a quote from the F&WS web site for this area:

"The Carolina Sandhills NWR lies along the fall line which separates the Piedmont Plateau from the Atlantic Coastal Plain. The rolling beds of deep, sandy soils which give the region its name were once host to an extensive longleaf pine forest. The longleaf pine/wiregrass ecosystem, the characteristic habitat of the Carolina Sandhills refuge, once covered more than 90 million acres across the southeastern United States, stretching from Virginia to Texas. This unique ecosystem, shaped by thousands of years of natural fires that burned through the area every two to four years, has been reduced to fewer than two million acres. Today, only scattered patches of this once immense forest remain, with most occurring on public lands. Factors contributing to the demise of the ecosystem include aggressive fire suppression efforts, clearing for agriculture and development, and conversion to other pine types."

One of the sites we visited at Carolina Sandhills reminded me of the sorts of restoration work we do in Wisconsin. An area that had historically been longleaf pine had in 1964 been planted to slash pine (Pinus elliotti), used for pulp, timber, or turpentine. At this site the F&WS removed all the slash pine and in 1998 planted longleaf pine. The sign below tells the story.



The longleaf pine species has interesting adaptations to fire. An early stage in the growth of a new plant is called the "grass stage", because it resembles a clump of grass more than a tree. During this stage, the terminal bud is protected beneath a thick coating of pine needles, so that when fire sweeps through the area, the needles may burn off but the growing bud is protected. During the grass stage, which can last for 1-7 years, the plant remains close to the ground.

When the diameter of the root collar gets large enough (about 1 inch), the plant starts to grow in length, the terminal bud being released from its protective layer of needles. At this stage, which is called the "bottlebrush" stage, growth is extremely rapid, and the terminal bud reaches a height where it is above the frequent low-intensity fires that occur in this sort of ecosystem. Additionally, the terminal bud is in a favorable position in relation to sunlight. At this stage the bark thickens sufficiently so that the plant becomes resistant to fire. From here through the sapling stage and on to the mature plant, the tree establishes a unique fire resistance.

The long needles of the longleaf pine thus play an important role in permitting the early stages of growth to survive fire.

The photo below shows longleaf pine plants that had just been burned a week or so earlier. The photo shows how the peculiar array of needles works to protect the terminal bud from fire damage.




As its name states, the needles of the longleaf pine are exceedingly long, up to 18 inches long. These long needles make the identification of P. palustris fairly easy, since no other pine has needles this long.

A fascinating vegetation!

When we visited the southeast two years ago, it was in the middle of the fire season, and we saw fires everywhere. This year the weather was much wetter (with some snow!), and lots fewer prescribed burns had been carried out, although the fire shown in the photo here, from the Francis Marion National Forest, had been done within the past two weeks.