Pine flatwoods are characterized by low, flat land; poorly-drained, sandy soils; an open overstory of pines; and frequent fires. While the availability of
water varies with the local topography and seasonal rainfall the soil may stay wet for much of the year since the flatness of the land reduces water run-off. In low elevations the land may hold water for several months.
At higher elevations, where the water table is deep, little or no surface water may be visible.
The high acid content of pine needles, along with limestone bedrock, makes the soils in flatwoods tend to be acidic. As
plant matter decays and contributes nutrients to the sandy soil an organic layer may develop. However, the open, porous nature of the sandy soil causes nutrients to leach out quickly resulting in poor quality soil.
Although the soil is sandy there are frequently clay deposits below the surface that hold water and create small ponds.
The plants that grow in these ecosystems are limited to those that grow well in acid soil and
adapt easily to drought and flood cycles. The density of the trees also affects the type of plants that grow in flatwoods since openings in the canopy allow sunlight to penetrate to the forest floor. An open canopy will
let in more sunlight and facilitate the growth of shrubs and understory plants while a dense, closed canopy will limit the understory to smaller herbaceous plants and grasses.
Pine flatwoods form a natural
gradient into scrub lands so some flatwoods appear to be more scrubby and less treed than others. Many plants that are common to both pine flatwoods and scrub habitats are found in the ecotone
, or transition zone, between these two systems.
Flatwoods forests may be found southern, central, and northern Florida. Many of these areas are now used for pine plantations or livestock grazing.
The role of fire in pine flatwoods
Pine flatwoods are called a fire-dependent ecosystem since they require regular burning to maintain an open plant community of pines, grasses,
and herbs. These frequent fires control vegetation and prevent the forest from being overgrown. They also reduce competition from hardwood trees and other plants. If fire is suppressed for long periods of time
herbaceous plants will be crowded out by larger, woody shrubs while oaks and palmettos will move in and begin to crowd out the pines. Eventually the ecosystem will grow into a hardwood hammock.
Some flatwoods plants
are highly flammable so that fire can easily spread through the forest and maintain the open, park-like conditions. Some plants contain volatile oils that ignite easily in the presence of fire. Lightning causes many
naturally-occurring fires in Florida, but humans also start many fires in the ecosystem. Fire is important in helping to break down vegetative matter and release the nutrients that it contains. Burning the leaf litter
also releases acids into the soil and may stimulate nitrogen fixation in the soil.
Frequent fires are also important in helping many plants to germinate and flower. Plants that require the heat of fire to
release their seeds are called serotinous
species. Sand pine trees are an example. They hold their cones on the branches for many years until a hot fire causes the cones to open and release their seeds. Wiregrass plants will not bloom without the heat of a spring or summer fire.
Many of the plants in pine flatwoods have developed natural adaptations to survive the frequent fires. Longleaf pine and slash pine have thick bark to protect the trees from the excessive heat of fire. Young longleaf
pines have a growth stage that is resistant to fire. These grass-stage plants have long, grass-like leaves that surround and protect the central bud which is covered with fuzzy hair. After a fire, when other competing
plants have been burned away, the buds open and the young longleaf pines shoot up quickly into small trees. Other species in these fire-prone habitats are able to resprout quickly after a burn from underground roots,
stumps, or seeds.
Trees and Plants of pine flatwoods
Several vegetative communities are found in pine flatwoods. All share the same basic structure of an overstory of pines with
an understory of shrubs or herbaceous plants and grasses. The species richness and diversity of these flatwoods varies with the geographic location. Flatwoods in the Apalachicola region have very low tree species
richness but the north central flatwoods have relatively high species richness.
Historically, the dominant trees found in Florida pine flatwoods were longleaf pine (Pinus palustris). Most of the
original longleaf forests have been cut down for land development and replaced by faster-growing slash pine (Pinus elliottii), which naturally occurred mainly around wet depressions in the flatwoods. Also
frequently found in flatwoods are loblolly pine, on dryer sites and pond pine on wet sites. Often mixed in with the pines are a variety of hardwoods such as live oak, water oak, sweetgum, and ash.
Three main
vegetative communities are common in Florida flatwoods. These include longleaf-wiregrass, slash pine-gallberry-palmetto, and pond pine-fetterbush-bay. Each of these community types has its own unique structure while
sharing many species in common. A listing of the trees and plants associated with pine flatwoods appears below.
Also scattered throughout the flatwoods are low-lying 'ponds' that have standing water much longer
than the surrounding flatwoods. Common plants in these 'cypress ponds' are pond cypress, red maple, buttonbush, swamp tupelo, loblolly bay, fetterbush, and poison ivy.
Wildlife in pine flatwoods
Pine flatwoods provide important habitat for many wildlife species. The understory shrubs and grasses are used for nesting, refuge, and forage. Overstory pines and hardwoods provide home sites for
cavity-nesting and tree-nesting species as well as perches for hunting and foraging birds.
Pine flatwoods often have wet areas that are beneficial to many amphibians. There are between twenty and thirty species of
reptiles and amphibians that may be found in these ecosystems. They include pinewoods tree frog, oak toad, eastern box turtle, Eastern diamondback and pygmy rattlesnakes, black racer, and pinewoods snake. Species of
special concern that may be found in southern flatwoods are the Miami black-headed snake, mole snake, and striped newt. Indigo snakes, an endangered species, are also occasionally seen in pine flatwoods.
Mammals that
use flatwoods are black bear, Florida panther, gray fox, white-tailed deer, fox squirrel, raccoon, cottontail rabbit, wild hogs, and armadillo. Several small rodents are also found in these habitats, including cotton
rat and cotton mouse, least shrew and short-tailed shrew. Not all species found in flatwoods are native to Florida. Some exotic species have established in pine flatwoods here. These include the black rat, house mouse,
and greenhouse frog.
Pine flatwoods provide a year-round home for many birds. Others use the habitat while they are passing through during migration in spring and fall. Among the most common resident species
are pine warblers, brown-headed nuthatch, Bachman's sparrow, great-horned owl, American kestrel, bald eagle, wild turkey, and bob-white quail. Red-cockaded woodpeckers, an endangered species, use certain types of older,
flatwoods pines for nesting. They are partial to forests of old-growth longleaf, slash, or loblolly pines that are spaced openly.
Human impact of pine flatwoods
Pine flatwoods
are the most human-influenced ecosystem type in Florida. There are two primary ways in which humans have affected flatwoods. The first way is by clearing and developing the land, because the flat topography in these
areas makes good home sites, cropland, and pasture. Many thousands of acres of flatwoods have been cleared and developed for roads, railroads, agriculture, and other human uses. As these lands are developed
flatwoods habitat is fragmented or eliminated in many areas. Numerous wildlife species may suffer from loss of habitat.
Humans have also affected pine flatwoods with their land management strategies.
Resource management practices that focus solely on the production of timber, pulpwood, and other products may overlook the impact on the natural environment. However, through the use of Best Management Practices (BMPs
) the natural integrity of these valuable ecosystems can be maintained. Extensive livestock grazing may also harm the environment if flatwoods pastures are not carefully managed. The heavy animals cause the
soil to become compact and reduce water filtration through the soil. However, many examples across Florida demonstrate that livestock and open flatwoods ecosystems are compatible. Suppression of fire may cause changes
in the structure and composition of natural flatwoods plant communities. These changes in turn affect the many wildlife species that depend on pine flatwoods.
Summary
Pine
flatwoods represent a unique and valuable ecosystem type in Florida. In addition to the useful products that are made from the trees growing in flatwoods many species of wildlife benefit from the natural food resources
and cover that flatwoods provide. Several threatened or endangered species of animals may be found in these ecosystems. Pine flatwoods are fire-dependent and rely on regular burning to maintain the open structure and
composition of the original plant communities. These habitats have been altered or influenced by humans more than any other ecosystem type in the State.
Pine flatwoods are found scattered throughout
Florida. They are especially common in flat, sandy central and northern regions of the state. The Apalachicola, Ocala, and Osceola National Forests are among the sites to visit in order to explore natural pine
flatwoods. Tosohatchee State Reserve and Oscar Scherer State Recreation Area also have flatwoods ecosystems. Pine rocklands, a southern variation of pine flatwoods, can be seen at Everglades National Park, Fakahatchee
Strand State Preserve, and Big Cypress National Preserve.
