LONGLEAF PINE FOREST
During the colonial period of our country longleaf pine (Pinus palustris) dominated the landscape of the southeastern United States. During William Bartram’s visits in the late 18th century he described a forest landscape of pines where you could see for miles. As a matter of fact many travelers from the northeast described the trip to the Gulf coast as monotonous and boring. The trees in this forest were several feet apart, over 100 ft tall, and 3-4 ft in diameter. These majestic pines would also produce large cones 8-12 inches long. Such was the world of the native longleaf forest; today over 90% of this forest has been removed.
The pine forest system is fire dependent. Longleaf pines release seeds each year but the number of seed consuming predators assures that most will not germinate. However after a fire the tree releases so many seeds that the animals can not consume them all and the next generation will sprout. Longleaf are slow growing and the saplings can resist ground fires. This allows the pines to grow and eliminates the competition form hardwood trees. The open canopy allows sunlight to reach the forest floor and the ash from the burn provides nutrients to the developing trees. Fires are started primarily by lightning strikes, which occur mostly in the summer. However the pine itself can actually start its own fire. Older trees are attacked by fungi and develop an internal condition called “heart rot” where the heart wood is decomposed. During a burn this heart rot can catch fire and continue to smolder over time even during rain and storms. At some dry point down the road the smoldering embers from within the tree can be exposed, fall to the ground, and generate their own fires. On a natural cycle the burns occur about every seven years and so the peak growing cycle for the longleaf is the same, about every seven years a mass release of seed is produced.
After a burn a wide variety of grasses and herbs begin to sprout. The dominate grass in the under story is wiregrass (Aristida stricta) but many flowering legumes and herbaceous plants can be found here. Longleaf pines tend to do well in sandy, well drained soils found in uplands and sandhills. The great variety of grasses supports a high diversity of animal life. There are multitudes of grass and seed eating insects with a variety of insect consuming birds, amphibians, reptiles, and mammals. Upper level carnivores include raccoons, hawks, owls, snakes, fox, weasels, bobcat, and the Florida Black Bear (Ursus americanus). Fallen trees and stumps provide habitat for another whole community of organisms. All of the organisms are either directly or indirectly dependent on the forest periodically burning.
There are a variety of species connected to the longleaf pine that are declining in numbers as the acreage of longleaf declines. The fox squirrel is a large species of squirrel and one of the few that can actually feed on the longleaf seeds and cones. Without their ability to do this less seed would be dispersed and the food chain would be considerably shorter. Though they feed on longleaf cones they do require hardwoods to build their nests in. In a natural longleaf habitat the lower portions of the hilly terrain tend to collect water and remain wet for most of the year. This retards the ability to burn fire and here the hardwoods can actually grow. The fox squirrel requires both systems and therefore burning is essential. Each fox squirrel has a home range of about 50 acres. So in addition to fire suppression by humans, the loss of habitat has caused their numbers to decline and further upset the balance of this ecosystem.
The Red-Cocked Woodpecker (Picoides borealis) is one of the few animals that can form a cavity within a living longleaf pine. The do require older pines (70 years or older) to do so because the only way they can “chisel” their way in is to find a spot with “heart rot”. The woodpeckers live and feed in clans and each clan requires about 125 acres of old longleaf pine habitat. There are multitudes of organisms that use the abandoned woodpecker cavities including flying squirrels and this list the woodpecker as a keystone species in this system. Like the fox squirrel, the red-cocked woodpecker is declining from fire suppression, the move away from longleaf pine to loblolly and slash pine but tree farmers, and the general loss of habitat.
One other keystone species that is in decline is the gopher tortoise (Gopherus polyphemus). This tortoise prefers high dry sandy soils for burrowing and consumes many of the grasses found in the understory of the longleaf habitat. Though the tortoise can be found in other habitats it is most commonly found here. The tortoise burrow only has one entrance/exit but harbors more than 350 species of animals who depend on these burrows at sometime of the year; this includes the eastern diamondback rattlesnake (Crotalus adamanteus) and the endangered eastern indigo snake (Drymarchon corais).
90% of the original longleaf pine forest is gone. This began with the lumber and turpentine industry in the area. Longleaf pine is an excellent wood for building and there were large markets for turpentine, including Europe. One problem this industry had was the slow growth rate of longleaf, so as the forest were cut they were replaced with faster growing loblolly (Pinus taeda) and slash pine (Pinus elliotti). This community switch was detrimental to several species including the Red-Cocked Woodpecker. The second major problem was the suppression of fire. Fire is natural to theFlorida landscape and many species depend on these periodic burns. However the human population is nervous with wild fires burning near homes and so fires have been eliminated from the natural cycle. This has caused an increase of hardwood trees growing in the under story and the loss of the natural grasses. This, in turn, has caused the decline of many native species. The third strike against the longleaf was simply habitat loss, as the human population grows the demand for land has increased and millions of acres have been converted into farms or housing projects. There has been a renewed interest in Florida,Alabama, and Georgia of restoring longleaf on much of the private timber land. Loblolly and slash pine do not produce as good a wood product as longleaf and many in the lumber industry are beginning to plant longleaf on their property. Another pastime that was lost with the loss of longleaf was quail hunting. Many private landowners are now planting longleaf so that quail will return and they can market hunting on their property.
As the name implies flatwood habitats, unlike the hilly terrain of the longleaf pine, is flat. These areas are generally found at the base of the sand and clay hills and can stretch for miles. The terrain of Floridais basically flat and so there were more flatwood habitats here than any where else in the southeast. At one time flatwoods covered almost 50% of the state; but most of this has been developed. Flatwood communities have to be very tolerant of extreme conditions. Unlike the dry porous soils of the sand hills flatwoods can hold rain water for many days, even months. Plants that live here must be able to tolerate standing water, soil with low oxygen, and periods of extreme drought. Many of the flatwood communities do experience burns from fires but the lower wetter areas may never burn. The soils here are generally sandy but low in nutrients and acidic.
Despite these harsh conditions plant diversity is actually quite high. Few trees can tolerate the standing water and acidic soils, generally less than 1 / acre, but there are over 100 species of ground cover plants that do quite well here, saw palmetto (Serenoa repens) being one of them.
Most of the animals here are small. They include numerous kinds of insects and spiders, salamanders and frogs (including the locally endangered Flatwoods Salamander, Ambystoma cingulatum), snakes, turtles, insect eating birds, birds of prey, and the wild turkey (Meleagris galloparo). Mammals found here are small and large including mice, shrews, raccoon, opossum, rabbit, fox, bobcat, deer, and even the Florida black bear and the Florida panther (Felis concolor). This ecosystem is fire dependent despite long periods of standing water and many times fires begin by jumping from longleaf pine communities.
Because fire is so common due to the amount of lighting strikes that reach Florida hardwood hammock ecosystems were uncommon during the early colonial period; somewhere between 1-2% of the landscape. However since the rise of the human population and the suppression of these natural fires hardwoods are becoming more common and actually many residents believe that these areas are what Florida use to be like. Historically hardwoods could only grow in locations where fires could not reach such as slopes of ravines, low wetlands, or around sinks. Today they cover between 10-20% of the land area of our state.
The diversity of hardwood ecosystems is a function of both climate and soil type. There are basically two distinct climatic systems: the temperate hardwoods of north Florida, and the tropical systems of south Florida. The soil types are divided into three distinct systems: xeric (very dry soil), hydric (wet/saturated), and mesic (which is in between). The xeric areas are prone to burning and are limited to live oak and laurel oak. Live Oak (Quercus virginiana) can actually survive low heat burns. Hydric soil hardwoods include cabbage palm and red cedar forests. The highest tree diversity can be found in the mesic hardwood systems because they are transition zones between the two above. They include the trees mentioned but also include magnolia, hickory, holly, and beech trees. These forests generally have a thick canopy and very little sunlight reaches the forest floor. This changes the undergrowth biology tremendously. Instead of the grasses and palmettos we see in the other two systems we find a great variety of fungus, ferns, and mosses. New trees can only germinate when an adult tree falls and allows sunlight to reach a small part of the forest floor. Leaf litter is thick here and instead of the ash from a fire the decomposition of this leaf litter provides the majority of the nutrients for the trees. Fallen trees also leave mounds of earth that provide habitat for small micro-communities of mosses, ferns, and fungi.
Almost of the animal life here is arboreal (tree-dwelling). There are many different forms of insects, millipeds, centipeds, spiders, and worms on the forest floor that can provide food for the larger animals that live in the trees. 45 species of woodland birds call this habitat home and some are unique to these systems. Squirrels, raccoons, opossums, box turtles, and some snakes call this place home as well. Larger predators such as black bear and fox can be found and the barred owl is more common than the great horned due to its ability to navigate and hunt the many branches of this semi-closed ecosystem.
Resources: Earley, L.S.,(2004), Looking for Longleaf; the fall and rise of an American forest, the UniversityofNorth CarolinaPress,Chapel HillNC, pp. 322.
Whitney, E., D.B. Means, A. Rudloe, (2004), Priceless Florida; natural ecosystems and native species, Pineapple Press,SarasotaFL, pp. 423
Photos: Molly O’Connor – Roy Hyatt Environmental Center