bind soils. Overburden hummocks fell in the middle in terms of changes in cross-
sectional area and percent cover.

 There are several possible explanations for organic soils depleting more than the
others did, the most likely being decomposition. The organic material was made from
composted yard waste including grass and wood chips. Organic matter decomposes much
more quickly in the presence of oxygen than in anaerobic conditions (Reddy and Patrick
1983). With little water in the wetland, oxygen was readily available to the exposed
organic hummocks. The damp, warm, oxygen rich conditions allowed aerobic bacteria to
break down the organic matter, decreasing the cross-sectional area. Erosion of all
hummocks from climatic conditions such as wind and rain may have been limited
because of the extremely dry conditions occurring during this growing season. Falling
raindrops have enormous kinetic energy, which, when contacting soils, can cause
movement of particles leading to erosion (Sharma and others 1993). Without much
rainfall, there was little potential for weathering from precipitation. Wind erosion may
also have been limited due to lower than normal wind speeds, the relative close proximity
of the hummocks to the surface of the ground, and the growth of wind breaking
vegetation like Typha spp. and Sesbania spp. Particle size of the soils may have been too
large for movement by low speed wind. The possibility exists that the erosion seen in the
Agrifos wetland is typical for the soil types chosen for the hummocks. Continued study
would show how these soils react during the development of the wetland.

 Based only on change in cross-sectional area, sand tailings hummocks appear to
be a good choice. However, having a pile of sand with nothing growing on it is not the
point of a hummock. Hummocks are supposed to provide conditions for vegetation
growth not found in other parts of a wetland. Availability of nutrients and soil moisture
contributes to determining vegetation growth.

 Sand and overburden are both highly mineral soils. Mineral soils generally have
high nutrient availability, meaning plants can easily utilize any nutrients present in the
soil (Mitsch and Gosselink 1993). Sand tailings are likely to be very low in nutrients due
to their structure consisting almost entirely of sand grains. Overburden likely contains
some phosphorus as its structure includes clays, sands, and organic matter. The available
nutrients lead to higher vegetation growth on the overburden hummocks than on the sand
hummocks even with the lack of water. Ground water and surface water contributing to
the wetland would contain some level of phosphate due to the abundance of phosphate in
central Florida. The water level in the wetland was very low however, and likely
provided little nutrient to the hummocks. Organic soils can have low nutrient availability
because many nutrients are tied up in organic form. Plants require inorganic forms for
uptake and use in photosynthesis. Availability depends on the degree of decomposition in
the organic soil. More decomposition means more available nutrients. The rapid
decomposition of organic hummocks makes more nutrients available to plants, seen as
the high percent cover in Table 5.1.

 Plants must also have available soil water for nutrient uptake and biological
processes. Organic soils have greater porosity and thus greater ability to hold water than


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