Central Florida receives more lightning strikes than any other region in the United States. Lightning-ignited fires have always been a part of life in the scrub. Plants and animals that live in this habitat are dependent on fire to maintain their world. Before Florida became so carved up by cities, roads, and housing developments, fires easily burned through scrub habitat at intervals of 6-20 years. These fires did not burn the landscape completely, but left small unburned patches that served as little refuges from which insects and other small animals could move back into the burned area. Seeds could blow over onto sand left bare by the fire. Other plants resprouted from underground stems. A mosaic of scrub that varied in stages of growth was created by fire.
As more and more people moved into Florida, these wildfires became more threatening. People were afraid of fire and interpreted the dramatic changes as destructive. Instead of being allowed to burn, fires were suppressed for decades. Florida scrub and other fire-maintained habitats such as flatwoods, prairies, and sandhill suffered as a result.
Without fire, the scrub habitat changes. In overgrown scrub, plants create so much shade and leaf litter that the open, sandy patches disappear and so do the species that prefer them. Canopy closure reduces or eliminates habitat for Florida mice, pygmy mole crickets, scrub lizards, and sand skinks. Overgrown oaks produce fewer acorns for animals such as Florida scrub-jays, Florida mice, black bear and acorn weevils. Other fire-dependent animals include gopher tortoises and gopher frogs.
Many scrub plants are also
fire-dependent. Florida rosemary needs fire to reproduce. Rosemary releases a chemical
into the soil that inhibits the germination of its own seeds. When the fire kills the
parent plant, the seeds are able to sprout. And if Florida rosemary disappeared, so would
the emerald moth. The caterpillar of this moth lives exclusively on Florida rosemary and
has two different larval forms. If developing in spring, it mimics a rosemary needle,
while its winter form resembles a gray, knobby, dead rosemary twig.
Grasses in the scrub bloom better after a fire, and the seeds of many
plants such as scrub lupines and other legumes and scrub buckwheat germinate better with
fire. Heat may be a requirement for germination of many types of seeds. Sand pines invite
fire into the tree by growing low, close to the ground branches. Many sand pine cones will
open and drop seeds only after being scorched. Scrub oaks, lyonias, and other shrubs grow
clonally with much of the plant underground. New sprouts will spring up after a fire from
the protected underground stems.
Many species of small animals that inhabit the scrub, such as ants,
Florida mice, gopher frogs, mole crickets, and ox beetles, have ways to flee from fire, or
find refuge in an existing burrow beyond the reach of the heat. Nevertheless, some kinds
of little animals, such as the little caterpillars living in a cluster of blueberry
leaves, or the gall wasps in their galls on oak twigs, are burned up and their populations
are temporarily reduced. But fire is similar to winter in northern states---where many
little plants and animals are killed by hard freezes. These species, however, have winter
built into their long-term survival strategies. Both the insects and the plants are
dependent on winter. If the season were eliminated, many species would disappear.
Now that we realize that many of Florida’s native species will disappear unless fire is introduced back into the habitats, people in charge of preserving and maintaining natural areas are including prescribed burns as part of their management. Prescribed burns, also called controlled burns, are intended to do three things: 1) mimic natural conditions, 2) maintain a variety of plant communities, and 3) decrease the amount of accumulated plant material, and thereby reduce the chance of devastating wildfires. A prescribed burn is not a one-time event, but a process that must be continually applied to the landscape.
The fire triangle can help students remember the three essential elements
of fire: 1) fuel (living and non-living
vegetation), 2) heat, and 3) oxygen. How hot or fast a fire burns can depend on the kind
of fuel, if the fuel
is wet or dry, the quantity of fuel, and weather
conditions.
Prescribed burns require a lot of planning and are only conducted under the appropriate conditions. Drought index , relative humidity, and wind speed and direction must be considered. If conditions have been very dry, a prescribed burn can be very risky. Humidity affects a fire by changing how dry the fuel is. As the relative humidity decreases, fuel moisture decreases and the fire intensity increases. Wind speed will affect how fast a fire burns. Prescribed burns are not conducted on days with strong winds due to the increased risk of escape. Wind direction is important to consider especially if the prescribed burn occurs near homes and roads. Special permits, fire equipment, and individuals trained to work with fire are necessary elements of a prescribed burn.
When a prescribed burn is planned for a specific burn unit, information about relative humidity, fuel conditions, wind speed, wind direction, weather conditions, hazards, smoke sensitive, etc., must be included in the prescription.
A Prescribed Burn on School Property
Donna Tomlinson, a teacher at Cracker Trail Elementary School in Sebring, Florida, regularly took her 4th grade class out to explore a trail on school property. She knew what healthy scrub habitat was supposed to look like and knew their scrub and flatwoods was overgrown. She was also concerned about the accumulated fuels. Donna called the Florida Division of Forestry (DOF) and discovered that the area had not burned in 20 years. In 1997, DOF agreed to do a prescribed burn and wrote a prescription. Then they waited for the small window of opportunity to open. The 15-20 acres they planned to burn was close to school buildings so students could not be present when the burn took place. Finally, when conditions were right, DOF, with the help of many trained volunteers, burned the area in sections. Donna was able to participate by creating black lines with a drip torch.
Initially, students were upset by the "destruction." With Donna’s guidance, however, they eventually saw the value of the burn for themselves. With the principal’s permission, Donna took her students out three days after the fire. Although stumps were still smoldering, plants were already emerging from the charred ground. Her class explored the burn area twice a week for several weeks and watched as plants, spiders, animal tracks, and insects returned.