Longleaf Pine Forest Restoration

Pine Stands Without a Significant Longleaf Component and without a history of fire

To restore the form and function of a longleaf ecosystem to this forest type requires the re-introduction of fire into the system first. If the period without fire has been extremely long and fuel accumulations are high, some type of fuel treatment may be necessary to avoid damage to the existing stand. These treatments might include mowing and/or herbicides prior to the burn to reduce "laddering" of fuels and get fuels down onto the ground where they can deteriorate prior to the fire. In any event, if fuel buildup is a concern, the first burn should be a cool one. For example, the burn should be in the dormant season on a cool day with moderate humidity, fuel moisture, and wind to carry the heat out of the canopy quickly. The type of fire can vary, but strip headfires with a chain (66 feet) or less between strips is a good compromise between a slow backfire and hotter fires. On-site observations are necessary to prescribe fire correctly. It may be necessary to follow this initial fire with a second dormant season fire within two years under similar conditions. The first fire will reduce fine fuels on the forest floor, but only top kill woody vegetation, creating a potential problem for the next fire. A second dormant season fire will "knock down" and begin to consume some of that dead fuel. An assessment of fuel conditions should be made after the second fire to determine if fuel conditions will allow a growing season fire. If the stand is dense and the owner is patient, a thinning might be performed at this point to encourage ground cover plants. If a thinning is performed, planning for the next fire should take into consideration the resulting slash and protect the residual trees. After the thinning and the first growing season burn, fire should be continued on at least 3-year and preferably 2-year intervals for at least 2 cycles. Ideally, at least 2 successive growing season burns should be performed prior to harvest of the overstory in preparation for reforestation.
The regeneration harvest can take two forms. The typical technique is to clearcut the existing stand and, after site preparation, replant with longleaf seedlings. If the burning regime has been effective, the site preparation can be minimal, consisting of reducing or removing the woody debris to allow the planters access to the site. Spot herbicide treatments might be desirable to control persistent woody clumps, but broadcast chemicals should not be necessary. Optimal growth of the seedlings will require control of the herbaceous vegetation with chemicals, but care should be taken to protect desirable native understory species. Appendix II contains information on common forestry herbicides and their use.
Another less frequently used technique is to leave some of the existing stand intact to act as a fuel source for future fires and to maintain the appearance of a forest while the new stand is coming on. Underplanting with containerized seedlings can be accomplished in the newly created gaps. Growth and survival of the new stand will be affected negatively. Competition by seedlings from the residual trees poses a greater problem. Fire will be necessary to control that regeneration while the longleaf becomes established. Eventually, the overstory should be removed in a series of steps, creating or enlarging existing gaps for underplanting. The size of the gaps is important. If they are much more than ¼ acre in size, it is difficult to get enough fire into the centers to control invading pines or hardwoods. Gaps of that size or smaller allow few resources for the new seedlings and make survival and growth problematic.
In either case, fire must continue to be used regularly to maintain the stand and to encourage desirable native understory plants. The new seedlings can be safely burned within a year of planting. When the seedlings are just emerging from the grass stage (0.5 - 4 feet tall), they are vulnerable to fire and should be burned very carefully or not at all. Once the trees are 4 feet tall or taller, they can be burned fairly safely unless they are candling. Once they are more than 6 feet tall, they can be burned safely in any season. Remember, they are fire-tolerant, not fire-proof. One recommended technique employs narrow strip headfires for the early burns. Later fires can take many forms, but growing season fires should be part of the mix. If the understory does not respond, it may be because the site was farmed prior to the previous stand, not uncommon in the Southeast.