Date Awarded


Document Type


Degree Name

Master of Science (M.Sc.)


Virginia Institute of Marine Science


Created wetlands are often limited in soil organic matter, usually a long-term product of ecosystem succession. Although many studies have tested the effect of adding organic material to these systems, few if any, have quantified the effect of various loadings of organic matter in created wetlands. The goal of this study was to determine how vegetation composition, standing crop biomass, woody vegetation development, and ecosystem gas exchange varied in a created freshwater wetland along a gradient of soil organic carbon (0 to 336 Mg ha-1 loading rates). Plot surface elevation varied positively with OM loadings, suggesting that inundation/aeration may modify OM effects. Soil nutrients (C, N, C:N, and P) also positively correlated with loading rate. Vegetation measurements suggested an overall similarity of plant assemblage composition and biomass regardless of loading rate, and a slight increase in tree size with loading rate. Gross primary production and net ecosystem exchange were weakly positively and negatively correlated with loading rate, respectively. Respiration was strongly positively correlated with loading rate, and was likely the controlling factor of CO2 gas flux among treatments. Soil nutrient values and vegetation composition, as well as ecosystem gas flux balance appear to be the best parameters upon which to base an organic matter loading rate decision. In this study, adding an organic matter amendment between LR 2 (56 Mg ha-1) and 3 (112 Mg ha-1) seems most appropriate, and may provide a “jumpstart” for the created non-tidal wetlands while also minimizing changes in surface elevation due to the added bulk material.



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