Southern Research Station Headquarters - Asheville, NC
![[Images] Five photos of different landscape](/images/imstr1.jpg "[Images] Five photos of different landscape")
Issue 13
The Palustris and Longleaf Pine
What if natural regeneration isn’t an option
by Zoë Hoyle
In 1935, when the Forest Service established the 7,500-acre Palustris Experimental Forest (Palustris) on the Kisatchie National Forest, researchers faced different challenges than those they found later on the Escambia. The Palustris, chosen as representative of southwestern Louisiana and east Texas, had been denuded by railroad and cable logging in the early part of the century. Later attempts to farm on the shallow, poorly drained soil had failed, and once magnificent longleaf pine forests either were gone or existed as sparse stands invaded by scrubby hardwoods and feral hogs.
There simply weren’t enough mature longleaf pine trees left to support natural regeneration on the Palustris. Early researchers started out by introducing loblolly and slash pines to the cutover land, later reestablishing the more disturbance-resilient longleaf pines. In stands where there were no mature trees to shelter natural regeneration, researchers transplanted bare-root longleaf pine seedlings, testing different treatments to find the best methods to help them survive.
Though effective, planting bare-root seedlings proved too labor intensive and expensive for the region’s landowners, who needed to reforest large areas of cutover land. Philip Wakeley and other early pioneers began new experiments on direct seeding. The cone and seed studies of southern pines that Wakeley started in the early years on the Palustris have been used around the world to reforest seemingly barren landscapes. As the stands in the experimental forest grew, researchers studied thinning methods to increase the growth of desirable pine trees and prescribed fire to reduce competition from fast growing hardwoods.
In the 1960s, when SRS researcher (later, project leader) James (Jim) Barnett started working on the Palustris, the focus was still on direct seeding for longleaf pine reforestation. Seeds themselves were still a problem. Landowners and managers had tried unsuccessfully to use the same collection and storage methods for longleaf that were used for other pine species, but in this area—as most others—longleaf proved to be an anomaly. Barnett was instrumental in developing methods for collecting, storing, and planting longleaf pine seeds that increased viability exponentially, but many landowners who planted longleaf from seed were still not seeing good survival rates. By the end of the 1960s, there was a shift back to bare-root seedlings, and Barnett began planting bare-root seedlings on the Palustris, testing them for survival.
Containerize to Thrive
Bare-root seedlings are grown in a nursery bed. When they’re large enough to be transplanted, the seedlings are lifted from the bed and the soil removed from the roots before the seedlings are packaged for shipping. Though the method is cost-effective, Barnett and fellow researchers found that only 40 to 60 percent of bare-root seedlings survived planting—not very attractive odds for landowners trying to reestablish longleaf pine stands.
Barnett began experimenting with growing longleaf pine seedlings in containers. With other trees, sapling survival is usually improved by growing seedlings in containers, but when Barnett started his studies in the 1970s, it was widely believed that longleaf could not be grown in containers. In contrast, Barnett’s studies showed survival rates of container-grown seedlings of 80 to 90 percent, almost double those of bareroot seedlings. Container seedlings also showed superior growth and survival under adverse conditions. “Longleaf is the only pine species that actually needs containers for its seeds and seedlings,” says Barnett. “Almost everything you do with longleaf is different than other pine species, more challenging and more interesting.”
Barnett developed—and though retired, continues to update—what he still calls “interim” guidelines for container-grown seedlings. His work has proved invaluable for both growers and managers as prices for both longleaf pine seeds and seedlings have soared over the decades. In 2002, he published research on another improvement—adding minute amounts of copper to the inside of containers to improve root structure and weight. The copper-treated cells in the containers arrest the growth of lateral roots they come in contact with. This produces a bigger taproot and roots that branch out more naturally. (For more, see Containers, Copper, and Roots on page 33.)
In the 1930s, researchers established studies on the Palustris to compare burned with unburned acres of longleaf pine forests and to evaluate growth and development in relation to different management treatments. Two of these original stands have been continuously managed since that time, providing the long-term datasets that form the basis for the growth and prediction models land managers need to grow longleaf pine more successfully for multiple purposes.
SRS plant physiologist Mary Anne Sword Sayer continues to test the effects of season of prescribed fire on longleaf pine, looking at how season of fire affects sapling growth and leaf area and root carbohydrate dynamics. She is also looking at how drought and prescribed burning interact to affect these and other variables.
SRS research forester Dave Haywood and Sword Sayer also use Palustris plots to study how management practices as diverse as weed control, fertilization, burning, and pine straw gathering and mulching affect the growth and productivity of longleaf pine stands. Their results are important to land managers who want to manage for income from timber as well as other uses, but the greatest application of results from the long-term experiments on the Palustris is towards the restoration of the magnificent longleaf pine ecosystem.
For more information:
James D. (Dave) Haywood: 318–473– 7226 or dhaywood@fs.fed.us
Mary Anne Sword Sayer: 318–473–7275 or msword@fs.fed.us
