given area (Tansley 1935). Davis and others (1991) present soil nutrient data for a
variety of Florida ecosystems. Figure 7.27 shows available Ca, Mg, K, P, and Fe in
Florida communities ranging from a xeric pine community to a hardwood swamp. The
differences in nutrient availability are greater between xeric pine and wetland systems,
but there are subtle differences even between wetland types.

 Figure 7.28 shows the nutrient signatures or available plant nutrients found in
 constructed forested wetlands. When comparing nutrient availability in constructed
 forested wetlands from this study with natural systems, calcium levels were up to two and
 one half times that of the mean found in hardwood swamps. Magnesium and phosphorus
 were found in excess of three times that of natural systems. Available iron was within
 the range found in natural hardwood swamps. Available potassium fell below the mean
 of hardwood swamps in all but two of the constructed forested wetlands in this study.
 Wharton and others (1982) reported P (11.2 ppm) Ca (607 ppm), Mg (98 ppm), and K
 (48 ppm) values for blackwater swamps in the southeastern United States. These values
 show the greatest similarity to the values for cypress domes reported by Davis and others
 (1991) in Florida. Calcium, magnesium, potassium and phosphorus concentrations in
 constructed forested wetlands show even greater differences from the values reported by
 Wharton and others (1982).

 Across a topographic gradient, greater values of nutrients have been reported at
topographic lows where higher soil water content is often found. Lower nutrient
concentrations are often found higher up the gradient into increasingly drier areas of a
community (Wharton and others 1982). Graetz and Reddy (1997) found increasing
concentrations of calcium, magnesium, potassium and iron in the A horizon on a gradient
from upland to wetland in several constructed wetlands. This may be a consequence of
leaching and transport from upland to wetlands. In the case of constructed forested
wetlands in this study, nutrient concentrations in wetlands were already higher than
natural wetlands. Data from this study showed weak trends of increasing available
calcium and phosphorus with time. Therefore, self-organization of constructed forested
wetlands may not result in nutrient signatures typical of natural Florida wetlands.


SUCCESSIONAL TRAJECTORIES OF SINGLE PARAMETERS

 Some vegetative structural categories show trends over time within constructed
forested wetlands. Canopy tree height and percent cover each show strong trends,
increasing with time. The trend in diameter at breast height is only slightly less
significant. There appears to be greater variability in tree diameter at breast height than
in the other two parameters. Percent transmittance of sunlight through the canopy
decreased with time and is inversely related to increases in percent canopy cover.


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