SPATIAL VARIATION IN WETLAND SOIL PROPERTIES AS INFLUENCED BY HYDROLOGY AND ELEVATION IN A COASTAL WETLAND OF LAKE ONTARIO

Variations in wetland soil properties are interrelated to site hydrology and landscape elevation. These variations are also linked to biomass production and species diversity. The Ellison Park wetland is a delta-type coastal wetland covering over 423 acres at the southern end of the Irondequoit Bay in an urban area adjacent to Rochester, NY. The wetland extends for about 3 km with a main channel and secondary channels through the wetland. The marshes are bordered by steep hillsides. Soils and sediments include sands, particularly along the main channel levees and silts in low relief areas. The resulting levees are up to 1 m higher than the bottom of the adjacent channel. In downstream sections of the wetland, these levees diminish in height as the channel moves through the wetland and are essentially absent. Five 60 m transects spaced 10 m apart were surveyed for elevation and soil sampling. Soil samples were analyzed for particle size distribution by laser diffraction and for soil chemical properties including organic matter content, pH, nitrogen and trace element content. Most physical and chemical properties correlate well with changes in elevation along a transect. Elevation was found to vary 0.61 meters across the site from a levee on the south end of a large meander to where the ground surface sloped into the stream at the north end of the site. Median particle size was found to range from 70.8 um to 19.5 um. Variation in median particle size exhibit good correlation with elevation with an r2 value of 0.78. Furthermore, samples may be divided into three groups, levee, slope and low relief areas. The levee samples have an average median particle size of 60.8 +/- 6.6 um while the low relief areas have a value of 30.6 +/- 5.3 um. The intervening slope area is not distinguishable from the low relief area. Organic matter (OM) content as measured by loss on ignition ranges from 1.7 to 11.6 wt.%. As expected, OM content correlates well with percent nitrogen and pH values. The OM content of the soil also correlates well with elevation. The coarser grained levees having lower OM content than the low relief areas. Elemental analyses including major elements and trace elements (Pb, Zn, Mn, Cu) do not show as strong a correlation with elevation as does OM, N and pH. Biomass production and species diversity are also linked to landscape position in the study area.