Photo of an open pine savannah from the Summer 2010 issue of the Nature Conservancy Magazine. The photo was taken by Beth Young.
Modern day ecologists are attempting to protect and restore the last remnants of open pine savannahs in the southeast. Open pine savannahs were the most common type of ecosystem in the coastal plain of southeastern North America when Europeans first colonized the continent. They are rich unique landscapes dependent upon frequent light fires that incinerate brush and saplings, creating an environment where pine trees grow far enough apart for grassy glades to exist between the widely spaced conifers. Typically, pine needles slough off the trees, falling on top of tufts of wiregrass. Droughts dry this combustible material which later is ignited by lightning or humans. The fires kill hardwood saplings, but longleaf pines have fire resistant bark, and the grass roots survive underground, thus explaining how the environment becomes dominated by pine and grass. Scientists consider the sloughing off of combustible pine needles as an active evolutionary adaptation by longleaf pines to maintain the type of environment they need to survive–it prevents them from being shaded out in the closed canopy forests that would grow without fire.
Another name for this ecotype is the pine barrens, but this is misleading. On first glance these savannahs may seem monotonous, but they’re quite diverse–over 100 species of plants have been surveyed in as little as 1/4 acre. This is a higher diversity than any other ecosystem in North America. Wiregrass is the most common grass. It co-occurs with many species of grass in the Poaceae family, as well as species of legumes (Faboceae), and flowering asters (Asteraceae). Low bush blueberries love to sprout and colonize fire-prone savannahs, and they abound here. Bird diversity is high too, and one species occuring only here includes the endangered red cockaded woodpecker.
There are different kinds of pine savannahs as well–the types of plants and animals living on them vary according to how well drained the soil is. On the driest sandy sites, where there isn’t enough tinder for even light fires, scrubby oaks predominate. On well drained sites with good soils tall longleaf pines and wiregrass dominate the vegetation, and gopher tortoises and gophers can be found digging their burrows. On poorly drained sites wet pine savannahs are home to sphagnum moss and chimney hill crayfish. And there are areas grading between wet and dry savannah. Rivers, streams, and Carolina Bays are watery barriers that protect some sites from fire, allowing cypress swamps and hardwood forests to grow.
In the 19th century man began the destruction of this ecosystem. Workers harvested resin to manufacture naval stores (turpentine and tar). This killed many trees and degraded the environment. Later, lumbermen and farmers cleared the land and planted horizon-to-horizon field crops such as cotton and peanuts. Fires were suppressed to protect lumber, and loblolly pine replaced longleaf pine as the dominant tree in now closed canopy forests. So today’s coastal plain landscape bares no resemblance whatsoever to the original. Thankfully, at least a few pitiful remnants still exist on military bases, and on lands belonging to hunting clubs specializing in quail which thrive in this type of enviroment. Organizations such as the Nature Conservancy are working to protect these areas.
I don’t think scientists currently studying open pine savannahs are aware that Frances Harper extensively surveyed this ecosystem on the uplands surrounding the Okefenokee while researching his 1927 book, Mammals of the Okefenokee Swamp. They never reference it. Though many areas of the savannah were already damaged from naval store activity, he was able to study them before their final destruction at the hands of clear cutters and agriculturalists. Here’s his list of plant and animal abundance by species, listed from most abundant to least.
Gallberry–a type of holly
Poor grub–Xolisma fruticosa
St. John’s wort
Chinquapin–a dwarf chestnut bush that used to be common but is now rare. Saplings are available for transplant at www.willisorchards.com
Lather bush–Clethra alnifolia
Andropogen sp.–Includes broom grass and prairie grasses like bluestem
Aster Squarrosus–a flowering aster
Rhexia alfifanus–deer grass
Asclepia cinerea–milk weed
Eleocharis baldwinii–road grass
Pterididum aquilinum–bracken fern
Baptisa lanceolata–gopher grass
Sarraceania minor–trumpet pitcher plant
Sarracenai flava–pitcher plant
Pogonia divericata–an orchid
Rynochospora filifolia–beak rush
Chrysopsis graminifolia–silver grass
Opuntia–prickly pear cactus
Scleria glabra–nut rush
Southern flying squirrel
Short tailed shrew
fox squirrel–less common today because they like open forests.
Gray squirrel–more common today because they like closed canopy forests
Frances Harper was 12,000 years too late to record the animals that would’ve thrived on open pine savannahs during the Pleistocene. Here’s my additions. The order of abundance is, of course, unknown.
PLEISTOCENE MAMMALS THAT WOULD HAVE OCCURRED ON OPEN PINE SAVANNAS
Peccaries–two kinds. The flat-headed peccary is thought to have preferred scrubby forests that would’ve been common during dry glacial climate phases.
Harlan’s Ground Sloth
Jefferson’s Ground Sloth
13-lined ground squirrels
Giant Short-faced bears
Scimitar tooth cats
I believe open pine savannahs are a very old ecosystem descended from the first grasslands that evolved during the Oligocene or Miocene. It’s true that Indian-set fires facilitated the extent of these grasslands, but savannahs must have existed prior to the advent of man here. Ironically, pine savannahs were probably more widespread during wetter climate phases because lightning from more frequent thunderstorms would’ve ignited more fires. During cold arid glacial stages, scrubby oak thickets expanded at the expense of pine savannahs due to lessened incidence of lightning-induced fires in an environment so dry that eolian sand dunes rolled across the landscape.
The Pleistocene climate fluctuated between wet and dry climate phases, depending on whether the Laurentide glacier to the north was in a melting or expanding phase. The ratio of pine savannah to oak scrub habitat corresponded to these climate phases–the pine savannah expanding with melt water wet phases; the oak scrub/desert expanding with dry cool expansion phases. But neither habitat was completely eliminated during the climate fluctuations unfavorbable to them. Many pollen studies show these alternating dry and wet climate phases still occur, though they’re not as drastic as the Ice Age fluctuations. Today, we’re in a wetter phase, but 5,000 years ago the climate was much drier.
The bigggest influence on open pine savannahs during the Pleistocene, besides climate, was the megafauna. Cooler climate and megafauna grazing, trampling, and dung-depositing probably caused the savannahs to vary more in composition than they do today, but their basic structure was likely similar, and they were just as widespread as they were when white men invaded the continent.
Especially wet interstadials, however, increased the quantity and size of wetlands which made for barriers that stopped fires, allowing chestnut, oak, and beech forests to occur as far south as what today is Florida. The dry cycles of climate of the LGM restricted the occurrence of these rich hardwood forests on the coastal plain to river sides and springs that didn’t completely dry up, following extended droughts and the dramatic drop in the water table.
The terrain of the piedmont and mountains localized fires and created patchy environments of mixed forests and meadows quite different from those of the coastal plain.