LACLAIRE: UPLAND TEMPORARY POND VEGETATION IN FLORIDA


decomposition. Its stalks may remain standing even if a pond has not filled for
several years, and it is able to survive many years of dry pond conditions, as
exemplified by the results from DP. Due to its tendency to grow in thick,
monotypic stands, it probably acts to maintain the wetland environment by
inhibiting the growth of upland species and reducing the oxidation of the soil
organic matter that is crucial for nutrient cycling in the pond basin. In this way, P.
hemitomon protects the wetland environment; the hydric soil and seedbank remain
intact until another flooding event.


 Pond Zonation


 The results of this study and previous work in upland temporary pond basins in
north and north-central Florida (Franz and Hall 1991; LaClaire and Franz 1991;
LaClaire 1992) have revealed a pattern of zonation with similarities to other
descriptions of temporary ponds (Fig. 1). Water-filled ponds often contain
floating-leaved plants and submergents in the deepest areas (Water Lily Zone) and
tall and short emergents at the pond edge (Sedge Prairie Zone). When the ponds
dry, emergent grasses fill these zones in the previously flooded portions of the
basin. Further upslope, a band of Hypericum fasciculatum (Sandweed Zone)
commonly occurs, typically followed by a band of Andropogon spp. (Bluestem
Grass Zone). Continuing upslope, additional bands of vegetation are found in dry
meadows (Dry Meadow Zone) that occur as transitional zones adjacent to the
longleaf pine dominated uplands. In some ponds, a fire shadow is present upslope
of the Dry Meadow Zone which contains fire intolerant evergreen shrubs
(Evergreen Shrub Zone) and oaks (Xeric Hammock Zone).
 The two most common plant species found in the study ponds, Panicum
hemitomon and Andropogon glomeratus, created the most obvious zonation in the
pond basins overall. Both of these species are perennials with tall, persistent stems
that are resistant to decomposition. Panicum hemitomon was the dominant species
in the Sedge Prairie Zone and often defined its boundaries. Andropogon
glomeratus defined the Bluestem Grass Zone. In temporary ponds, P. hemitomon
reproduces most commonly vegetatively, but A. glomeratus sets seed that are wind-
dispersed. The result of these differences in reproduction can partially explain
overlapping zones in some of the ponds. Panicum hemitomon occurred generally
as a uniform zone. Andropogon glomeratus was generally present along the outer
edges of the pond, but it was also present in dry pond centers probably as a result of
conditions appropriate to its seed germination.
 The six additional species considered most common in the combined data sets
represented typical plants of temporary pond zones with the exception of
Eupatorium leptophyllum. Species dominance and the extent of zonation within