1a. Objectives (from AD-416):
Assist NRCS to provide science-based data, results, and information to routinely inform conservation decisions affecting wetland ecosystems and the services they provide.
1b. Approach (from AD-416):
Participate in collaborative regional investigations to quantify wetlands ecosystem services across an alteration gradient in agricultural landscapes; interpret effects of conservation practices and programs, and the effectiveness (i.e., type, location, land treatment, design and/or management) of conservation practices on ecosystem services, and identify multiple-scale factors that influence the capacity for a wetland to provide nitrogen cycling ecosystem service. The Mitchell Ecology effort will be done via a grant focused on amphibian evaluations to consider potential connections with the conditions for and the level of denitrification.
3. Progress Report:
This research supports project objective 3: Develop practices and technologies that enhance denitrification with minimized nitrous oxide emissions in water table managed fields and wetlands. In the last several decades, there has been considerable effort to protect and restore wetlands throughout the USA. These efforts have required significant investment of both private and public funds. Accordingly, it has become important to document the effectiveness of this protection and restoration. This study for the Mid-Atlantic Region (MIAR) Wetland was part of the US Department of Agriculture Conservation Effects Assessment Project (CEAP). It assessed natural, converted, and hydrologically restored wetlands from Delaware to North Carolina. There were forty-eight total sites. Each site was sampled at 4 landscape elevations (wettest to driest) during three years. An assessment of soil denitrification was conducted as one component of the MIAR Wetland-CEAP using denitrification enzyme activity (DEA). DEA values varied significantly with relative elevation and management. All of the management types had regression coefficients for DEA and elevation greater than 0.90. The DEA response to nitrate addition varied significantly with relative elevation and management. Moreover, the percentage of denitrification as nitrous oxide was different with relative elevation and management. In all aspects of DEA, the restored wetlands were more similar to the natural wetlands than to the converted wetlands. Additionally, a subset of these 48 sites was used to determine microbial community structure by next-generation DNA sequencing, as well as measure greenhouse gas emissions via photoacoustic gas analysis. Sequencing analysis demonstrated that land use influenced community composition, with the major bacterial families found in different proportions amongst the three management types. Gas analysis revealed that natural wetlands had lower nitrous oxide gas fluxes compared to converted and restored wetlands. These findings reveal that while wetland conversion and restoration influences bacterial communities, it does not lead to increased production of greenhouse gases.