Reestablishing Longleaf Pine

With the loss of millions of acres of longleaf pine forest in the southeast, there has been a push in natural resource management to reestablish this species in old field and native groundcover systems. An added benefit is that longleaf carry fire easier then old field pines, an imperative tool to manage both systems.

Land managers have used many methods to capture natural regeneration of existing mature longleaf, and many of those methods are the same for site preparation to plant containerized longleaf seedlings. What methods you decide to use for site prep/seed capture depend on your site. Typically site prep and seed capture are implemented in August and September due to the timing of native seed fall and planting recommendations of containerized seedlings. Typical planting or seed capture objectives include good seed to soil contact, adequate sunlight, and decreased competition. Methods to achieve these objectives include disking, mowing, burning and chemical application used singularly, or in conjunction to meet site preparation objectives.


Disking is a common site preparation technique

In old field systems, disking in canopy gaps or under and around mature longleaf have worked well to prepare the seed bed and ensure adequate seed to soil contact. This method gives managers the ability to control where the regeneration is caught, and/or to define the area where seedlings are planted. One drawback of this method is that disking selects for forbs (weeds) in the groundcover, which results in poor fuels for subsequent prescribed burning. Also, disking in native areas (wiregrass dominated systems) should not be conducted, as many of the groundcover species will be negatively impacted by this intense groundcover disturbance.

Mowing and roller chopping have also been used for site prep; these techniques allow sunlight to reach the germinating and planted seedlings. Negative impacts include mowed/chopped debris on the ground, which can inhibit good soil to seed contact, and potentially the build up of too much fuel for burning that can be damaging to new seedlings. Mowing “selects” for grasses, but like disking, roller chopping selects for forbs resulting in reduced fine fuels and soil disturbance of native groundcover.

Mowed vegetation after burn

Under specific conditions only mowed vegetation will burn

Chemical applications or herbicides have been used for decades for site preparation. With today’s selective herbicides, a manger can select for increased grasses (Garlon4 – Triclopyr) or forbs (Arsenal – Imazapyr) depending on their groundcover objectives. The treatments reduce the competition of hardwoods and other groundcover species for germinating or planted seedlings. Negative impacts may include the reduction of plant diversity, and burns after herbicide treatment are significantly higher in fire intensity, which could damage or kill the longleaf seedlings.

Prescribed fire is another tool that is utilized and is imperative in managing both old field and native systems. Fall burning offers excellent seed to soil contact, reduced groundcover competition in the short term, hardwood control, and allows adequate sunlight to the ground. Negative aspects of fall burning include lack of suitable habitat for wildlife until the spring growing season, and if not performed under the correct weather conditions, scorching of mature pine over-story can occur. Burning too late or clean can expose seeds to rodent and bird predation, reducing establishment. Burning in early fall or late summer allows the groundcover to respond, protecting seeds.

Lastly, managers often utilize multiple tools to meet their site prep objectives. Herbicide application followed by burning, or mowing and burning will reduce fuels loads and competition while increasing seed to soil contact. To minimize the negative wildlife issues, managers on old field lands can disk fire breaks around small (1/2 to 1 acre) target areas for seed capture or planting to minimize the number of acres of barren ground throughout the winter. Wet lines (fire breaks utilizing only water) are typically used in the native system, but can be utilized in old field situations too.

Mowing and burning for Longleaf pine replantingThis year at Tall Timbers, we used two treatments for our site preparation for planting containerized seedlings: 1) mowing and burning in September, and 2) chemical application of Triclopyr in July, followed by mowing and burning in September. The planting of seedlings will occur in November or December of 2015. The site we are planting is hilly, and besides planting longleaf, we also want to increase the grass component, therefore we are not using fire breaks around our planting areas, which would select for forbs and potentially increase erosion. Instead of fire breaks, we burned the areas two days after we mowed, under weather conditions in which mowed vegetation would burn and standing, un-mowed vegetation would naturally extinguish the fire. In the 1-year roughs, we burned with low relative humidity (RH) ~25%, in the 2-year roughs; we burned with ~45% RH. Another advantage to this technique is that when the entire burn unit is burned again, the planted areas will have six months less fuel build up, so fire intensity will be lower in the planted areas to ensure no harm to the new seedlings. In years to come we will continue to develop this mow and burn without firebreaks technique to capture more natural regeneration from our mature trees, thereby reducing our need to buy containerized longleaf seedlings. Whichever tools you use, understanding how sites will burn under various weather conditions is critical when burning without fire breaks, and to meet groundcover, over-story, and wildlife objectives.

If you are trying to restore your forest to longleaf it is important that you first consider your site, your soils, and your objectives for the forest. After carefully considering these objectives, you will be better able to determine what method of site preparation will work best for your landscape and will most quickly meet your needs.

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