Silviculture to Restore Southern Fire-Adapted Pines

shortleaf-pine-woodland
This shortleaf pine-dominated woodland is managed with prescribed fire, which benefits grasses. This stand also serves as nesting and foraging habitat for the endangered red-cockaded woodpecker. Photo by Jim Guldin, USFS.

Native, mature southern pine ecosystems are dwindling on the landscape, and the plants and animals that depend upon them are in trouble as well.

“Living and working in Arkansas, I sometimes forget that shortleaf pine as far as the eye can see is uncommon outside of this area,” says USDA Forest Service scientist Jim Guldin.

Guldin, research ecologist and Station silviculturist, studies the ecology and silviculture of fire-adapted conifers such as longleaf (Pinus palustris) and shortleaf pine (Pinus echinata). His recent work focuses on combining different silviculture practices to improve restoration efforts for these trees. His findings were published in Forest Science.

“Active forest management – especially tactics associated with planting, prescribed fire, and partial cutting – is the key to bringing these native pines back to the southern landscape,” says Guldin.

Before European settlers transformed the American landscape, 90 million acres of longleaf pine forests stretched across the Coastal Plain from Virginia to east Texas. By 1970, ninety-five percent of the South’s longleaf-dominant ecosystems had been lost.

Shortleaf pine was once abundant in 23 states – the widest range of any southern yellow pine. It grew happily in the rocky Ozark highlands, across the Louisiana coastal plain, and through the foothills, from Georgia to New York. But stands dominated by shortleaf pine have declined dramatically, down by half since 1980 according to Forest Inventory and Analysis survey data.

The dramatic increase in the area of highly-productive planted stands, especially loblolly and slash pine, is a southern forestry success story. The Southern Forest Futures Project estimates that planted pine stands will cover more than 50 million acres across the South by 2060. These forests are primarily managed for timber and fiber production on short rotations of 30 years or less.

But this progress is not without costs. Fewer mature fire-adapted pine forests 80 years old and older means fewer plants and animals that depend on those open forest and woodland habitats.

longleaf-pine-stand
On the Kisatchie National Forest in Louisiana, this stand includes longleaf pine regenerating beneath a shelterwood overstory. On sites that are already dry, drought – which is becoming more frequent and severe, due to climate change –  may make shortleaf or longleaf even better suited than loblolly pine. Photo by Jim Guldin, USFS.

And that’s a major priority for the Southern Region of the National Forest System. They are partnering with the Longleaf Alliance, the Shortleaf Pine Initiative, and others to maintain, improve, and restore longleaf and shortleaf pine ecosystems on national forests as well as state and private forestlands.

In his recent study, Guldin examines management practices that are critical to these efforts – starting with artificial regeneration.

“The role of planting in the restoration of native southern pine ecosystems is simple to the point of being elementary,” he says. “Planting will let us bring these species back to sites to which they are adapted, but where they are currently absent because of past management decisions.

Prescribed fire is a key to the successful restoration of longleaf and shortleaf pine ecosystems. Longleaf and shortleaf pines are both uniquely adapted to tolerate fire, especially as small saplings.  Longleaf pines are protected from fire because the long needles protect the sensitive terminal bud during all but the most intense fires.

Genetics explain shortleaf pine’s adaptation to fire. Its basal crook shields dormant buds from surface flames. Seedlings that are top-killed by fire are protected below the root collar and can re-sprout and grow again.

Guldin advocates introducing fire as soon as new and shortleaf seedlings and saplings are established. How young? He suggests introducing prescribed fire after saplings are two years old, and then burning every three years after that to continue to favor the pines — and to develop fire-adapted understory plants, especially native grasses.

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This stand on the Ouachita National Forest in Arkansas illustrates the use of burning stands with a young regeneration cohort. Beneath the overstory pines, shortleaf pines and oaks are three to five years old. Photo by Jim Guldin, USFS.

“Shortleaf is a fire-demanding species,” adds Guldin. “We’ve seen evidence of hybridization between shortleaf pine and loblolly pine, especially when the two are growing in proximity. In hybrids, the basal crook is much reduced, and, as a result, the hybrids sprout much more poorly after being top-killed. Prescribed fire is also needed in young shortleaf pine stands to kill any hybrids that might have germinated and started to develop alongside native shortleaf saplings.”

Prescribed fire can be costly and tricky to carry out. Guldin notes that these two tools are likely to make the greatest gains on public lands, where prescribed burning can be implemented at broad scales.

Lastly, Guldin sharpens our thinking on recovering fire-adapted pines in stands where they just a minor component – as little as 20 percent. “Start with a shelterwood harvest to remove the hardwoods and less fire-adapted pines from the canopy,” says Guldin. “Then add in fire to re-establish longleaf or shortleaf pines, either through natural regeneration or by planting.”

“Compared with establishing a new planted stand of longleaf or shortleaf pines, this requires a smaller initial investment for landowners and may provide quicker economic returns,” adds Guldin. “It’s also a shorter time to habitat recovery for the species of flora and fauna that depend on these systems – one decade rather than three or four.”

“We have all of the management tools we need to bring back longleaf and shortleaf pine. They’re well-known and widely-used. Combining these practices – cyclic, prescribed fires plus thinning and releasing pines in mixed stands where they still exist – will let us restore functional habitat for the different flora and fauna of concern in these ecosystems,” adds Guldin.

Read the full text of the article.

For more information, email Jim Guldin at james.guldin@usda.gov.

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