Sand pine occurs on the driest, least fertile, sandy soils, typically in areas referred to as “scrub.” Other species inhabiting these sites include sand live oak, myrtle oak, Chapman’s oak and rusty lyonia. Because these areas are composed mostly of thick, woody vegetation and lack significant amounts of fine, flammable grasses and herbs, fire frequency is much more infrequent than other natural communities in Florida, in the range of every 20 to 80 years. Consequently, fire only burns in this community under extreme conditions such as low humidity, drought and high winds. The resulting fires have a high intensity and can become catastrophic, resulting in the sand pine overstory (tree tops) being killed and the shrub layer being burned back to ground level (stand replacement burn).
Sand pines help promote intense stand-replacing wildfires by retaining their lower branches. These lower branches serve as ladders, helping the fire to climb into the canopy. While an individual sand pine tree is not adapted to survive fire, the species as a whole has adapted to survive fire. Sand pines develop a combination of regular and serrotinous cones. Serrotinous cones protect the seed from the fire and open to release their seeds when heated. Seeds from serrotinous cones are released on the bare soil created by the fire. Because all these seeds are released at once, sand pine stands are typically even-aged.
Sand pine possesses other unique characteristics that, under natural conditions, limit its range to the extreme conditions of scrub. Most pine species in Florida occur in areas of frequent low-intensity fires, and they survive by having a thick bark that insulates the cambium as the fires pass. However, sand pine has a thin bark and is killed by even low-intensity fires. Therefore, frequent fires in natural communities surrounding scrub areas prevent the spread of sand pine. If fire is excluded, sand pine can spread rapidly into other natural communities, displacing native species. On the other hand, if stand-replacement burns are excluded from sand pine scrub, the community will eventually succeed to oak scrub or xeric hammock. Sand pine has a relatively short life cycle for pine trees, typically 40 to 60 years. This short time frame allows the species to complete a life cycle between fire events. If fire is excluded, the trees begin to over-mature and succumb to high wind and/or root disease. Oaks begin to dominate, and new sand pine seedlings are out-competed.
While the art and science of prescribed burning has progressed a great deal since its inception in the early 20th century, prescribing stand-replacement fires is seldom an option. Flame lengths in a stand-replacement burn can easily reach 100 feet; therefore, fire lines would need to be 150 to 250 feet in width in order to keep the fire within the prescribed area. Typically, fire lines of that size are seldom an option. Additionally, the conditions required to conduct such a burn with any reliability are extreme and dangerous.
Because of these difficulties, land managers have developed mechanical techniques that mimic the disturbance of catastrophic fire. Clearcutting, drum chopping and mowing are used to remove the overstory and the shrub layer. These mechanical techniques are usually followed with prescribed fire. Prescribed fire is much easier and safer to implement when the overstory and the shrub layer have been altered or removed. Such mechanical techniques are supported by research and used by the Florida Forest Service, the Florida Department of Environmental Protection, the U.S. Department of Agriculture Forest Service, the U.S. Fish and Wildlife Service, the Brevard County Environmentally Endangered Lands Program, and The Nature Conservancy.
