Mesic Pine Flatwoods

Mesic pine flatwoods (sensu Stout and Marion 1993) typically exhibit an emergent tree layer of pines with limbless lower trunks and ground layers of low vegetation. However, physiognomy varies markedly with fire regime and moisture. Pine densities in mesic pine flatwoods can range from sparse to dense depending on fire history, seed predation, and seedling predation. Canopy coverage of mature mesic pine flatwoods can range from 10 to 80 percent in unlogged stands. Pine trees are usually abundant enough to dominate the apparent landscape view and canopy, but canopy densities can vary, dependent upon the degree of fire exclusion (Wade et al. 1980). The mesic pine flatwoods habitat is dominated by a slash pine or longleaf pine overstory with an upland understory. Mesic pine flatwoods are distinct from hydric and xeric pine flatwoods in the tendency toward midstory dominance by saw palmetto and scrub species such as fetterbush (Lyonia lucida), tarflower (Befaria racemosa), rusty lyonia (Lyonia ferruginea), cabbage palm (Sabal palmetto), and wax myrtle (Myrica cerifera). Impacted mesic pine flatwoods are dominated by the exotic invaders: Brazilian pepper (Schinus terebinthifolius), Australian pine (Casuarina equisetifolia), downy rosemyrtle (Rhodomyrtus tomentosus), ear-leaf acacia (Acacia auriculiformis) and melaleuca (Melaleuca quinquinervia). Understory includes a wide variety of grasses (Agrostis, Andropogon, Aristida, Dichanthelium, Eragrostis, and Panicum spp., etc.), pawpaws (Asimina spp.), gopher apple (Licania michauxii), legumes (Cassia, Crotalaria, Galactia, Rhynchosia, Tephrosia spp., etc .), milkworts (Polygala spp.), blueberries (Vaccinium spp.), milkweeds (Asclepias spp.), and a wide variety of composites (Aster, Chrysopsis, Emilia, Eupatorium, Liatris, and Solidago spp., etc.).

The taxonomy of the South Florida slash pine has been a matter of significant debate (Small 1913, Little and Dorman 1954, Squillace 1966, Mirov 1967, McMinn and McNab 1971). Pinus elliottii var. densa is more flood- and drought-tolerant than is var. elliottii . Squillace (1966) concluded that the phenotypic plasticity that allows densa to accommodate both upland and wetland conditions, fire, and flood is the result of its evolution under the severe environmental factors of South Florida flood and drought that vary from year to year and fluctuate widely over longer time courses. Mature South Florida slash pine can attain a height of 30 m (110 feet), with a dbh of 40 cm (16 inches) (Duever et al. 1976). In an average southwest Florida mesic pine flatwoods, mature trees typically attained 30 to 41 cm (12 to 16 inches) dbh with 23 to 26 m (75 to 85 feet) of height (Beever and Dryden 1998). Growing season is from February to November, with maximum growth rates attained at the spring and autumnal equinoxes (Langdon 1963). The growth rate of South Florida slash pine has been measured in the Corkscrew area of Collier County at an annual diameter at breast height (dbh) increase of 1.15 cm (0.45 inches) per year and an annual height increase of 60 cm (2 feet) per year. The forestry productivity of southwest Florida mesic pine flatwoods for wood products has been recorded at over 27 cords/acre (242 cubic meters/acre) at age 16 (Wade et al. 1980). Annual net understory productivity is 140 g/m2 (1,250 lb/ac) with a litter fall averaging 130 g/m2/yr (1,160 lb/ac). Decomposition is only 30 percent per year (Duever et al. 1976). This results in an annual net accumulation of litter of approximately 90 g/m2 (800 lb/ac) when fire is excluded. This relatively rapid litter fuel buildup increases the probability of fire ignition and the chance for hot, crowning fires through time. Longleaf pine and slash pine communities are extremely diverse floristically, and contain several rare and endemic plant taxa, making this one of the most important natural systems in the southeastern United States (Hardin and White 1989). Hardin and White (1989) listed 191 rare plant taxa as occurring in the wiregrass ecosystem; seven of these taxa have been proposed for listing or are currently listed as federally endangered, and 61 are listed as threatened or endangered in three states. The wiregrass ecosystem supports 33 locally endemic plant taxa, all from Florida. South Florida slash pine and longleaf pine which are growing in normal mesic pine flatwoods conditions and are subjected to fire, typically display: (1) No buttressing of the lower trunk, (2) Fire-darkened or fire-scarred lower trunks, (3) A straight growth form, (4) Little woody debris and needle litter build-up, and (5) A crowned growth form, with few branches, if any below the top third of the tree. Long (1974) lists 303 species of plants in the mesic pine forest habitat of South Florida, the third highest plant species diversity of any habitat in South Florida. Presently, 482 plant species (115 monocotyledon, 353 dicotyledon, 3 gymnosperm, and 11 pteridophyte species) have been identified from or are documented as present in the mesic pine flatwoods of southwest Florida (Beever and Dryden 1998). South Collier County and lower east coast mesic pine flatwoods have more tropical plant species represented in their understory and a different underlying geology, often composed of marl, and oolitic rockland extrusions (Wade et al. 1980), when compared to the mesic pine flatwoods of central and western South Florida. Of the 482 plant species recorded in literature from mesic pine flatwoods of South Florida, 65 species (13 percent) are typically considered to occur in wetland saturated zones. Four hundred and seventeen species (87 percent) are typically considered upland plants. Twenty-five (5 percent) are exotic, introduced species. These 482 plant species comprise 29 percent of the documented terrestrial flora of South Florida (Wunderlin 1986).

Taken from: U.S. Fish and Wildlife Service. 1999. South Florida Multi-Species Recovery Plan. Atlanta, Georgia. Pp. 3:197, 199-200.

Listed Species Occurring in Mesic Pine Flatwood Habitat

  • Florida Panther
  • Key Deer
  • Audubon's Crested Caracara
  • Kirtland's Warbler
  • Bald Eagle
  • Red-Cockaded Woodpecker
  • Eastern Indigo Snake
  • Beautiful Paw-paw
  • Carter's Mustard