Date of Award
College of Science
Type of Degree
Dan K. Evans
Frank S. Gilliam
Jeffrey D. May
The construction of wetland mitigation sites to compensate for authorized losses is necessary under Section 404 of the Clean Water Act. Many mitigation sites have been determined to be unsuccessful. Monitoring of sites is necessary to determine if functions of natural wetlands have been replaced. Six mitigation sites in the Upper Scioto River watershed in central Ohio were chosen for study. Representative transects were established beginning in uplands adjacent to the wetlands (old field, OF), running through areas characterized by seasonal inundation (seasonally pooled, SP) and ending in permanent pools of inundation characterized by little or no vegetation (permanent pooled wetland – PW). Transects ranged between 60 and 110 meters, with between three and five per site. Vegetation was sampled by placing 1-meter square quadrats every 10 m along transects. Vegetation was identified and percent cover and frequency were collected to determine importance values. Soils were sampled to a depth of 10 cm along each transect and in each zone of OF, SP and PW. Extractable NO3- and NH4+ were determined before and after laboratory incubation to determine net nitrification and mineralization. Vegetation sampling determined a total of 121 species were present in the herbaceous layer of the wetlands, 37 of which were non-native. Of non-native species, eight are recognized as invasive. Aerial cover was at least 100 percent in most quadrats. Of the 15 dominant species at each site, all but one site contained between one and four non-hydropytic species (i.e. FACU or UPL/NI). In most sites, OF zones were dominated by upland species and SP and PW zones were dominated by hydrophytic species. Species from 12 genera present in study sites are recognized as valuable to wildlife as food sources. Calculation of Simpson’s Index resulted in a range of 0.056 – 0.172. Shannon-Weiner Diversity Index (H’) calculations ranged from 2.95 – 3.17. Floristic Quality Assessment Index scores ranged from 10.7 – 18. In OF plots, nitrification was 100 percent of mineralization in 2 sites (3.19 – 5.09 µg NO3- - N/g soil); the other four sites showed negative rates (-0.75 - -0.03 µg NO3- - N/g soil), thus indicative of immobilization. In SP plots, in two sites, the majority of mineralization occurred as ammonification (2.81 – 3.51 µg N/g soil), while the other sites displayed immobilization (-4.01 - -1.34 µg N/g soil). In PW plots, low to no levels of nitrification occurred, with the exception of one site (1.73 µg NO3- - N/g soil), the nitrification of which is likely attributed to the presence of an aerobic layer in inundated conditions. Almost all mineralization occurred in the form of ammonification (0.09 – 7.56 µg N/g soil). Canonical correspondence analysis indicated vegetation plays a more dominant role in allowing differentiation of sites, likely due to the variability of soil parameters studied. High percent cover of species and presence of diverse species indicate functions of sediment retention and wildlife habitat should be provided. While variable, soil data show processes of nitrification, ammonification and immobilization are occurring. Data collected will provide a baseline of these sites for further study to assess development of mitigation sites.
Wetland mitigation sites - Ohio.
Lawson, Desiree L., "An Analysis of Vegetation and Environmental Parameters at Mitigated Wetland Sites Located in the Upper Scioto River Drainage Basin, Central Ohio" (2004). Theses, Dissertations and Capstones. 704.