Longleaf Restoration
The ecological condition of the older slash pine plantations, planted before 1960, varies depending on their history of harvest and burning. They are regularly burned, thinned, and treated with herbicides to control undergrowth. The plantations planted since 1960 in the sandhills are viewed as having been planted in soil that is too xeric, off-site. They are now being clearcut, treated with herbicides, and planted with longleaf seedlings and wiregrass seed. Plantations planted since 1960 in the flatwoods, where slash pine invades naturally and is not really off-site, are being treated similarly.
Beyond the ANF, some researchers have tried to convert conifer plantations to other species to longleaf via canopy retention (Palik et al. 1997, 2003). The stand is thinned, usually herbicided, and then underplanted with longleaf seedlings (Franklin 2009). The advantage of this alternative is that the needlecast from the reserved trees contributes to the ability of the area to carry fire. See Hu et al. (2012) and Walker and Wang (2014) for recent examples with loblolly pine plantations. Once the planted the longleaf trees produce their own needlecast, the remaining slash or loblolly pines can be removed. One complaint about this method is that the longleaf seedlings will not get enough light, water and nutrients and that those that survive will grow slowly. But longleaf seedlings are adapted to just this situation, having to wait to grow (Samuelson and Stokes 2012). Longleaf seedlings will develop even under 50 sq ft/acre of pine trees (Brockway et al. 2014; Kara 2015). Thus far, the ANF has been reluctant to use this method. It will be tried only in one stand and without adequate comparisons as nearby controls (see the Soldier Bay Draft Decision Notice).
The ANF did collaborate with C. Hess in a major experiment with interplanting longleaf seedlings in slash pine plantations in both districts of the ANF. The growth of the seedlings was substantial but slow, as expected. The experiment called for burning after 2 years of seedling growth rather than herbiciding, but the burning regime was not maintained. Nevertheless, the underplanting experiment was an attempt to explore an alternative method of longleaf restoration that avoids the landscape trap in flatwoods. It has the important advantage over clearcutting that the burning regime can continue uninterrupted (Hess and Tschinkel 2017).
(3) Conversion of slash pine plantations to longleaf pine
Uneven-aged management is not suitable for slash pine. If slash pine is cut to 40 sq ft/acre BA and not burned effectively (FRI <3 years), it will develop natural pine regeneration, which in this case is undesirable. Some plantations that were planted on xeric soil in sandhills have stagnated and fallen into the “landscape trap”, because they won’t burn with a low intensity fire. They are being clearcut, burned, treated with herbicide, and planted with longleaf seedlings and wiregrass seeds. Slash pine plantations in the flatwoods, if they have 40 sq ft/acre basal area, have enough needlecast to carry fire. They can be converted back to longleaf by interplanting
a. In site-prepared slash pine plantations in flatwoods, burn until you have at least 30% herbaceous groundcover; thin the slash pine to 40 sq ft/acre, interplant longleaf seedlings, and continue to burn every other year.
b. In older slash pine plantations in flatwoods, thin, burn, plant log-landings with longleaf seedlings, repeat. Keep 50 sq ft/acre or higher basal area so you can burn it at a < 3 year FRI. Only go to 40 sq ft/acre if you are going to underplant with longleaf.
c. After every entry log-landings should be planted with longleaf[Re.