species colonizing the hummocks during the latter part of the growing season may be the
 cause of the discrepancy.

 Another possible reason for the difference comes to light when looking at the
 percent cover. The overburden hummocks in the Cargill wetland have much higher
 percent cover than do the Agrifos overburden hummocks. Combining the fact that
 vegetation is abundant with the low diversities shows that a few select species are
 dominating. This fact may also be attributed to the late construction of the hummocks.
 The organic hummocks in both the Agrifos and Cargill wetlands show higher percent
 cover when compared to the overburden hummocks. As stated previously, they may have
 higher nutrient availability and have higher soil moisture than the overburden hummocks,
 which is the likely cause of more vegetation cover. The values for diversity are similar
 for the organic hummocks in both wetlands. Similar soil conditions and nutrient
 availability likely exist for hummocks in both wetlands.

 Tree survivorship and growth from the wetlands can not be compared because of
 the lack of early stage data. Only initial data were available from the Cargill site, and no
 early numbers were available from Iluka site.


 VALUE OF HUMMOCKS IN WETLANDS

 The advantage of hummocks can be seen from the data shown in Table 5.2.
 Diversity indices are higher on the hummocks than off in all cases. The variation in
 micro-site hydrology found on the hummocks permits a wide variety of plants with
 different ranges of moisture requirements to establish themselves. The relatively uniform
 moisture found in the flat areas off the hummocks only allows growth of plants tolerant
 to high soil moisture and/or flooded conditions. These results substantiate those found by
 Sloan (1998) and Bukata (1999) in previous microtopography studies. Sloan found that
 species diversity increased with increased hummock frequency (rugosity) and expanded
 elevation ranges in lake and stream systems. Bukata found that constructed hummocks
 significantly contribute to the overall species richness and diversity of a constructed
 wetland. Species richness and diversity was higher on hummocks than areas between
 hummocks.

 Evenness numbers are higher off the hummocks in situations where there is a low
number of species. The Agrifos wetland has a high number of species living off the
hummocks and lower evenness than on the hummocks. The other two wetlands have
higher evenness off the hummocks and have fewer species growing off the hummocks.
The numbers are not dramatically different and might not indicate anything significant.
The soil moisture off the hummocks in the Iluka wetland and the water level in the
Cargill wetland were higher in relation to the hummocks than in the Agrifos. That fact
might explain why fewer species were growing off the hummocks and why they are
slightly more evenly distributed. Fewer plants were tolerant of the higher moisture
conditions in the Iluka and Cargill wetlands. Those that were tolerant had an even
distribution. In the Agrifos wetland, conditions were tolerated by more species, but some
species flourished where others did not.


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