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Browsing by Author "Cummings, Angela R."

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    An Analysis of Palustrine Mitigation Wetlands in the Virginia Coastal Plain
    Cummings, Angela R. (Virginia Tech, 1999-05-13)
    In recent years, the success of wetland mitigation projects and their ability to function as natural systems has been questioned. This study was conducted (i) to characterize and examine differences between mitigation and natural wetlands, (ii) to examine differences in soil morphology along a wetness gradient in mitigation and natural wetlands, and (iii) to observe changes in mitigation wetlands with time. Site characteristics, including soil properties, hydrology, and vegetation, were analyzed for three mitigation-reference wetland pairs located in the Virginia Coastal Plain. Hydrologic regimes of mitigation areas, when compared to reference areas, generally showed larger differentials between seasonal high and low watertables. Mitigation areas, dominated by herbaceous vegetation, tended to be lower in C and N levels and higher in soil pH, and much higher in bulk density than the mature forested reference wetland. Initially low levels of C and N did not increase significantly over the five-year study period. Soils in the mitigation area were more uniform and considerably less differentiated when compared to those of the reference area. Testing for Fe(II) with alpha-alpha, dipyridyl dye solution produced mixed results, obtaining both positive and negative reactions to saturated samples. Oxidized rhizospheres, associated with active root channels in surface horizons, formed in less than ten years under the current hydrologic conditions. These features were more abundant and more prominent in areas saturated at or above the surface for longer periods of time. Overall, site differences between mitigation and reference areas are mainly due to construction practices and a lack of organic matter accumulation. Better design methods should incorporate the addition of organic amendments, with attempts to minimize soil compaction.
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    Evaluation of Methods to Calculate a Wetlands Water Balance
    Daniels, W. Lee; Cummings, Angela R.; Schmidt, Mike; Fomchenko, Nicole; Speiran, Gary K.; Focazio, Mike; Fitch, G. Michael (Virginia Center for Transportation Innovation and Research, 2000-08)
    The development of a workable approach to estimating mitigation site water budgets is a high priority for VDOT and the wetlands research and design community in general as they attempt to create successful mitigation sites. Additionally, correct soil physical, chemical and biological properties must be restored that are appropriate to the intended wetlands biota in order for the sites to function similar to a natural sites that they are replacing. The major objectives of this research program were to evaluate the currently recommended procedures for estimating wetland water balances and to characterize the soil and hydrologic regime present at natural and constructed sites and their interaction with wetlands biota. This report records our efforts to develop an estimated overall water budget at VDOT's Ft. Lee mitigation site along with a summary of our previous water budget studies at Manassas. Detail on supporting studies is also provided along with an overall summary of multi-year research results and implications. In this report, the terms water balance and water budget are used almost interchangeably. In our view, however, water budgets are developed by humans to interpret actual wetland water balances. It was concluded that the use of the Pierce (1993) approach for developing mitigation wetland water budgets is prone to a number of errors in surface water charging estimates and ET estimates via the Thornthwaite method. The Pierce approach is most appropriate for estimating water budgets in surface water driven emergent/shrub-scrub systems with little ground water flux that rely upon berms or other water control structures to detain and pond water over impermeable soils or strata. Additionally it was found that the development of soil redox features, particularly the quantity and distinctness of oxidized rhizospheres can be reliably used to interpret hydric soil development sequences in mitigation wetlands. However, the reestablishment of an appropriate mitigation site wetness regime to one that appears to meet jurisdictional wetness criteria will not always guarantee the success of desirable hydrophytic vegetation over time.