Wet Pine Savannas; Herbaceous Bogs (Flatwood Bogs); Hillside Bogs
Represent a unique and fascinating vegetation type that occurs mainly in the Atlantic and lower Gulf Coast plains from southeast Virginia to southeast Texas from 250-370 N latitude and 750-950 W longitude.
Commonly called pitcher plant bogs, also called moist pine barrens, grass-sedge bogs or savannas. They differ from bogs in the northeast U.S. in lacking the accumulation of Sphagnum moss, but nevertheless, are characterized by bog inhabiting species.
Once occupied about 75% of the area in the southeastern Gulf Coastal Plain. Due to habitat modification less than 3% remains. Much of the remaining is degraded and does not resemble pre-settlement conditions.
This habitat type is developed primarily on relative level to gently rolling terrain. In Louisiana, east of the Mississippi River bog are found in St. Tammany, Tangipahoa, and southern Washington parishes. West the Mississippi River pitcher plant bogs occur mainly in central and southwestern LA (Natchitoches, Rapides, Vernon, Beauregard parishes).
Hillside bogs, an unique habitat type, occur where water flows through a permeable surface layer of soil underlain by an impervious layer of clay. Such bogs are best developed in Natchitoches Parish, but occur elsewhere.
Soil characteristics
Upper layers are sandy to sandy loams; acid (pH 3.5-5.0); low in nutrients; water saturated during wet periods; organic accumulation is low due to frequent fires.
Water movement through the substrate is slow; flooding seldom occurs; input of nutrients from outside the bogs is minimal; nutrient cycling is dependent on the organisms present and on the release of nutrients by fire
Vegetation
Woody Trees: longleaf pine Pinus palustris and slash pine P. elliottii. In wetter depressions bald cypress, pond cypress, tupelo gum (Nyssa biflora), red maple, sweetbay (Magnolia virginiana), titi, swamp cyrilla (Cyrilla racemiflora), littleleaf snowbell (Styrax americana). The shrubby layer is poorly developed unless fire has been excluded for some length of time. Shrubs: inkberry (Ilex glabra), large gallberry (Ilex coriacea); waxmytrle (Myrica cerifera), southern bayberry (Myrica heterophylla), bedstraw St. Johnswort (Hypericum galioides).
Herbaecous. Beaked sedges (Rhynchospora spp.), umbrella sedges (Fuirena spp.), nut sedges (Scleria spp.), pipeworts (Eriocaulon spp.), yellow-eyed grasses (Xyris spp.), colic root (Aletris spp.), gold-crest (Lophiola americana), red root (Lachnanthes caroliana), pitcher plants (Sarracenia spp.), sundew (Drosera spp.), bladderwort (Utricularia spp.), butterwort (Pinguicula spp.), club mosses (Lycopodium spp.). sunflowers (Helianthus spp.), Stokes’ Aster (Stokesia laevis), Rhexia, Sabatia, candy root (Polygala spp.), flat-topped goldenrod (Biglowia nudata), toothache grass (Ctenium aromaticum), little bluestem (Schizachyrium scoparium) Andropogon spp., Panicum species, Paspalum species, and numerous species of orchids.
Many of the herbaceous species are unique to bog habitats and under natural conditions will grow nowhere else.
Carnivorous plants:
Species diversity of carnivorous plants is perhaps the highest in the world. Over half of the 45 North American species occur along the Gulf Coast with as many as 13 species found in a single bog.
Genera of carnivorous plants: sundew (Drosera spp.), bladderwort (Utricularia spp.), butterwort (Pinguicula spp.), and pitcher plants (Sarracenia spp.).
The role of carnivory: not fully understood;
*breakdown of prey may serve to fertilize the surrounding soil
*may be important only under conditions of nutrient stress.
*Soil acidity and low nutrient levels inhibits invasion of competing species
*Anaerobic soil conditions resulting from frequent saturation favors growth of water tolerant species.
*Periodic fires repeatedly eliminate fire-intolerant species; fire is the most important of the three factors listed.
Importance of fire
Bogs are a fire subclimax community that succeed to other vegetation types when fire is eliminated. Fire eliminates competitor species; releases many nutrients bound up in organic matter (nitrogen is largely volatilized by burning and does not typically increase in soils after fire. The season during which fire occurs may influence the floristic composition of the bogs. Natural fires are ignited by dry lightening strikes and are most frequent in late spring and early summer. Frequency of fires at a particular site is greater than every 10 years.
Without periodic fire, bogs are invaded by a variety of woody species that change the light regime and result in increased transpiration which lowers the water table and provides for further species invasions.
Increased drainage associate with conversion of wet savannas to cropland; pasture; timber production; subdivision construction; and road building will eliminate bog species.
Platt, W. J. Southeastern pine savannas. Pp. 23-51. In: Anderson, R. C., J. S. Fralish, and J. M. Baskin, eds. 1999. Savannas, Barrens, and Rock Outcrop Plant Communities of North America. Cambridge University Press, Cambridge, England.
Abrahamson, W. G. and D. C. Hartnett. Pine Flatwoods and Dry Prairies. Pp. 103-149. In: Meyers, R. L. and J. J. Ewel, eds. 1990. Ecosystems of Florida. The University of Central Florida Press, Orlando.