In those sites where canopy tree species occurred in the understory, their
 frequency of occurrence ranged from 0.04-0.71; in other words, they were recorded in
 4%-71% of the sample quadrats. A frequency of over 0.50 was recorded only in sites
 over fifteen years old. Frequency ofMyrica cerifera and Salix caroliniana seedlings was
 highest in intermediate age sites (8-14 years) and lower at both younger and older sites.
 Late successional subcanopy species seedlings (those species other than M. cerifera and
 S. caroliniana) were found only in sites greater than six years old. Frequency of
 occurrence of early successional shrub species ranged from 0.06-0.80. Frequency of
 occurrence of late successional shrub species ranged from 0.07-0.50. Frequency of
 occurrence of vines ranged from 0.32-1.0. Vines most frequently occurred in Sink
 Branch (18 years) and Morrow Swamp (17 years).


 Soil Development

 Table 7.12 provides a summary of soil characteristics of constructed forested
wetlands in the central Florida mining district including available macronutrients (Ca,
Mg, K, P, and Fe), bulk density, percent moisture and-percent organic matter.

 Soil macronutrients (Ca, Mg, K, P, and Fe) are evaluated in two ways. First, soil
macronutrients are expressed in terms of mg of nutrients per kg of soil. Second, they are
expressed on an areal basis (kg of nutrient m2 soil to a depth of 20 cm). The second
method takes into consideration differences in soil bulk density and more effectively
quantifies available nutrients within the rooting zone of vegetation. Figure 7.10a
provides calcium concentrations (mg Ca kg'- soil), while Figure 7.10b represents calcium
areal availability. There are no differences in soil calcium (mg kg-1) between sites when
bulk density is considered are the lack of significant differences is easily observed. The
same is true for other soil macronutrients (Figure 7.10c-7.10j)

 Table 7.13 and Figure 7.11 show the relationships between KC1 extractable NO3-
N and NH4-N and site age. Figure 1 la, 1 c, and 1 le provide nutrient values in mg kg'
 -2
of soil and g m-2

 The relationships between three soil properties were evaluated. Bulk density was
plotted as a function of soil water content and soil organic matter and soil organic matter
was plotted as a function of soil water content. As expected, Figure 7.12 shows that bulk
density decreases exponentially with increasing soil water content (r2 = 0.92; p < 0.01)
and soil organic matter (r2 = 0.85; p < 0.01). Soil organic matter increased with
increasing soil water content (r2 = 0.75; p < 0.01). Soil water content explains more of
the variation in bulk density than does soil organic matter in the developing soil of these
sites.

 Figures 7.13, 7.14, and 7.15 show each of the relationships depicted in Figure
7.12 for the chrono-sequence of the research sites. The sites are presented in
chronological order. Soil samples represent a cross section of wetland perpendicular to
the moisture gradient from wetland edge to center.


7-58