|MILLER, JARROD - Former ARS Employee|
|LANG, MEGAN - University Of Maryland|
|HUNT, PATRICK - Retired ARS Employee|
|FENSTERMACHER, DANIEL - University Of Maryland|
|RABENHORST, MARTIN - University Of Maryland|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2015
Publication Date: 4/27/2015
Citation: Ducey, T.F., Miller, J.O., Lang, M.W., Szogi, A.A., Hunt, P.G., Fenstermacher, D.C., Rabenhorst, M.C., McCarty, G.W. 2015. Soil physicochemical conditions, denitrification rates, and nosZ abundance in North Carolina Coastal Plain restored wetlands. Journal of Environmental Quality. 44(3):1011-1022.
Interpretive Summary: Over the past 100 years, wetland areas have been converted for agricultural and urban use. Unfortunately, wetlands provide a number of ecological benefits, and their destruction can have major economic and environmental impacts. To counter the loss of wetlands, United States policy has instituted a “No Net Loss” measure. The Conservation Effects Assessment Project (CEAP) is aimed at examined the effectiveness of conservation practices, and develop management practices to ensure continued environmental quality standards for agriculture. Under the CEAP program, we examined a total of nine sites in the North Carolina coastal plain. The sites were comprised of a series of hydrologically-restored wetlands, currently existing wetlands (natural wetlands), and wetlands that were drained to use for agricultural purposes (converted wetlands). We measured physicochemical parameters, denitrification enzyme activity (DEA) rates, and abundances of the gene (nosZ) responsible for the reduction of nitrous oxide, a potent greenhouse gas. Results indicated that there exists an agricultural legacy in the restored wetland sites. While some parameters seemed to resemble natural wetlands, others were still similar to the converted sites. For denitrification enzyme activity and nosZ gene abundances, values were lower in restored wetlands, than they were for both natural and converted sites. This potentially indicates that while restored wetland microbial communities have not recovered after hydrological restoration of those sites, they do not result in higher greenhouse gas emissions.
Technical Abstract: Ever since the United States adopted a national policy of wetland “No Net Loss”, a variety of measures have been aimed at restoring wetland biogeochemical function to former wetland areas. Nitrogen is a key element controlled by properly functioning wetlands, particularly when they are located adjacent to agricultural operations. Removal of nitrogen by the process of denitrification results in the conversion of nitrate to either molecular nitrogen or the green house gas nitrous oxide. Production of these gases is contingent on a variety of factors, including the physicochemical makeup of the soil, as well as the microbial communities which reside therein. The study reported here focused on a total of nine sites located in North Carolina, and looked at the comparison of hydrologically restored wetlands to naturally occurring wetland sites, as well as prior converted wetland sites currently under management for agricultural purposes. All sites were located within the Mid-Atlantic Region (MIAR) Wetland Conservations Effects Assessment Project (CEAP). Physicochemically, restored wetland sites shared characteristics of both natural and prior converted (PC) sites. Denitrification enzyme activity (DEA) rates varied based on relative elevation, but when compared to the other two managements trended lower in restored wetland sites. At the lowest relative elevation, complete denitrification in restored wetlands was 2.76 micrograms of nitrous oxide per kilogram of soil per hour, as compared to 4.10 micrograms of nitrous oxide per kilogram of soil per hour and 3.61 micrograms of nitrous oxide per kilogram of soil per hour for natural and PC sites respectively. Abundance of nosZ, the gene that encodes for nitrous oxide reductase, saw statistically significant decreases in the restored wetland sites. The results indicate that while hydrological restoration has resulted in changes to physicochemical properties, and microbial enzymatic function and community structure, the restored sites have yet to approximate their natural wetland counterparts.