A Diverse Community of Natural Beauty: Forested Habitats of the St. Marks NWR
LONGLEAF Pine-Turkey Oak Sandhill community
The longleaf pine-turkey oak sandhill community generally occurs from the Wakulla Unit westward throughout much of the Panacea Unit. It is over 5,500 acres of elevated, well-drained, infertile sand soils that were once coastal sandbars. The habitat is generally open, and consists of low understory. The dominant trees in this community are primarily longleaf pine, turkey oak, and bluejack oak, with lesser numbers of live oak throughout. The understory, which varies in density, is predominately wiregrass with a diverse array of other herbaceous species, such as narrow-leaf aster, spurge nettle, deerberry and lupine. This habitat is home for a number of animals, such as the fox squirrel, gopher tortoise and the increasing rare indigo snake.
Fire plays a critical role in maintaining the longleaf pine-turkey oak sandhills. Not only are most species well adapted to survive frequent fires by resprouting, but many require fire to reduce competition, stimulate flowering and seeding, and prepare seedbeds for regeneration. Some species, such as wiregrass and longleaf pine, even promote frequent fires by producing highly flammable leaves and/or litter.
2. SCRUBBY Flatwoods
Scrubby Flatwoods is a habitat which consists of a widely scattered pine canopy, a patchy, woody understory and occasional patches of bare sand. Slash or longleaf pine usually comprise the overstory while the understory includes saw palmetto, myrtle oak, lyonia, sand-live oak, prickly pear cactus, reindeer moss and greenbrier. Wiregrass is occasionally found in this understory and is generally the only grass present. The best example of scrubby flatwoods on the refuge occurs in the Panacea unit, with scattered pockets occurring elsewhere, particularly near the coast. This unique forested provides habitat for such colorful birds as the Eastern towhee and the Yellow-breasted chat.
Due to the nature of the understory with few grasses and a patchy, often incombustible litter layer, natural fires burned with less frequency here than in the Longleaf pine-turkey oak sandhill habitat.
3. MESIC Flatwoods
Nearly one third of the forestland on the refuge is considered mesic flatwoods. This forest habitat can be characterized by a pure or predominately pine overstory, little midstory and a dense yet variable understory. Hardwoods usually do not occur in this habitat because of the frequency of natural forest fires; however, in some areas, where fire has occurred infrequently or has been surpressed altogether, hardwoods may comprise up to 25% of the overstory.
Longleaf pine is the predominant pine of the mesic flatwoods habitat on most of the Panacea and Wakulla Units, while slash pine comprises nearly all of the mesic flatwoods of the St. Marks Unit. Loblolly and Pond pines also occur as predominant pine in a few stands located throughout the refuge, particularly near the coast. Sand pine and spruce pine are also known to make up some of the mesic flatwoods communities which occur in scattered pockets throughout the refuge. Utilizing this unique forested habitat are a variety of diverse wildlife species, including the Flatwoods Salamander, which has recently been listed as an endangered species, and the red-cockaded woodpecker, also an endangered species.
Mesic understory generally consists of gallberry, saw palmetto, wiregrass, lowbush blueberries, staggerbush, huckleberry, sweet pepperbush and dangleberry.
Like the longleaf pine-turkey oak sandhills, the mesic flatwoods is a fire-dependent community. Without regularly occurring fires these flatwoods are invaded by hardwoods and eventually transform into a mesic hardwood hammock.
4. MESIC Hammock
Mesic hammocks are typically moderate to densely canopied mixed hardwood or pine-hardwood forests which have developed in the absence of frequent fires. Mesic hammocks can be subdivided into two separate groups: the mesic hardwood hammock and the mesic pine-hardwood hammock (where both pine and hardwoods exist).
Typically, mesic hammocks consist of a mix of overstory and midstory trees which may include live oak, sweetgum, laurel oak, water oak, redbay, wax myrtle, persimmon, pignut hickory, yaupon, and/or flowering dogwood. The understory and ground cover are generally sparse to moderate and consist of spike grass, American beautyberry, saw palmetto, poison ivy, gallberry, muscadine, Virginia creeper and witch hazel. The understory plants and trees attract such animals as the gray squirrel and the Northen Parula, both of which can be found in this habitat year-round.
5. WET Flatwoods
The wet flatwoods habitat on the refuge can be subdivided into two very distinctive communities: longleaf pine-wiregrass; and slash pine-sedge.
The longleaf pine-wiregrass community primarily occurs on the Panacea Unit. Its overstory is generally very open and predominately scattered longleaf pine and some slash pine. The ground cover is very diverse and dominated by wiregrass, St. John's wort, club moss, sedges, yellow-eyed grass, various orchids, dwarf wax myrtle, goldcrest and Florida dropseed. This diversity of plants makes this habitat a favorite with such birds as the Common Yellowthroat and the Eastern Bluebird.
Although this community regularly floods, or is wet at least a portion of the year, fire can occur frequently here. The light herbaceous wiregrass readily burns after a few fire-free years even in standing water.
The slash pine-sedge wet flatwoods community occurs on the St. Marks Unit and in some places within the Wakulla Unit. It consists of a variable slash pine overstory with some pond cypress, and a moderate to dense ground cover that is usually dominated by either sawgrass or needlerush. Other common understory plants include various sedges, wax myrtle, musky mint, and pipewort.
Fires will sweep through this community, although apparently not as frequently as the mesic flatwoods community with which it is intermixed. Without fire, the slash pine-sedge wet flatwoods will probably succeed to a habitat that is more adapted to wet soil conditions, or a hydric hammock community.
6. HYDRIC Hammock
Hydric hammocks are differentiated from mesic hammocks by the predominance of species such as cabbage palmetto, diamond-leaf oak, red maple, sweet bay, swamp ash and sawgrass that are adapted to wet soil conditions. Although found on all units of the refuge, hydric hammocks are most prevalent on the Wakulla and St. Marks units where they comprise 30 to 63 percent of the forested habitats. Hydric hammocks can be dominated by hardwoods, pine-hardwoods and pine-cabbage palmettos.
Perhaps the best known subdivision of the hydric hammock is the pine-cabbage palmetto hammocks, which are located throughout the refuge. These hammocks are generally composed of a moderate to dense mixture of taller-growing loblolly or slash pines that tower over the shorter cabbage palmetto. The understory varies with the density of the canopy, but often includes yaupon, saw palmetto, sawgrass, blackberry, poison ivy, and/or cane. With its abundance of berry-producing plants, these palm habitats are a favorite area for birds such as the Swallow-tailed kite and Acadian flycatcher.