Relative Importance of Landscape Versus Local Wetland Characteristics for Estimating Wetland Denitrification Potential

Abstract

Wetlands can be significant sinks for N r , via denitrification. There is a lack of understanding about factors controlling denitrification. Research suggests that hydrology, geomorphology, and nitrogen loading are dominant controls. We compared site-scale characteristics with denitrification enzyme activity (DEA) in wetlands along gradients of drainage basin land use to explore the relative importance of landscape and site-scale factors for determining denitrification potential. DEA rates ranged between 0.01-1.69 (μg N gdw −1 hr −1 ), with most sites falling at the lower end. Sites with higher DEA rates had higher percentages of soil carbon and nitrogen, concentrations of soil extractable NO 3 and percent loss on ignition. Sites with upstream agricultural activity had higher DEA rates than more natural sites, but there existed a wide range of DEA rates along both agricultural and urban land gradients. When multiple site and landscape-scale explanatory factors were compared to DEA rates, two site and one landscape scale characteristic (Soil NO 3 , Soil Percent N, and Percent Agriculture) had significant (p<0.001, cum. r 2 = 0.77) correlations with DEA rates. Our results suggest that DEA is controlled mainly by local-scale site characteristics with more work needed to determine the interdependencies and relative importance among these and potentially related landscape-scale factors.

Ditching Nutrients: Roadside Drainage Networks are Hotspots for Microbial Nitrogen Removal

“…Our results showed a muted effect of land use type on ditch dissimilatory NO 3 − reduction processes and microbial community structure, suggesting that roadside ditch construction and management results in homogenization. Urbanization and agricultural intensification affect biogeochemical processes in streams and wetlands by altering the magnitude and composition of nutrient delivery (Arango et al, 2007;Coble et al, 2019;Inwood et al, 2007;Mulholland et al, 2008;Parr et al, 2015;Russell et al, 2018), but we did not observe differences in soil properties that would indicate changes in nutrient vailability across land use types. Rather, denitrification potential in forested ditches was less than half that in urban and agricultural ditches, an effect that appeared to be mediated through a combination of changes in key microbial taxa and management practices rather than soil physicochemical characteristics.…”

Denitrification and associated nitrous oxide and carbon dioxide emissions from the Amazonian wetlands

“…Sixth, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two natural processes for NO − 3 reduction. In their review, Rütting et al (2011) stated that DNRA competition for NO − 3 should be considered for some ecosystems which do not include aquatic ecosystems. They added that more studies are needed for terrestrial aquatic ecosystems based on Burgin and Hamilton (2007).…”

Soil Characteristics and Hydromorphological Patterns Control Denitrification at the Floodplain Scale

“…This method determines the denitrification potential (DP), which is defined as the amount of nitrous oxide (N 2 O) and dinitrogen (N 2 ) released from soil within a given time period after enrichment with nitrate and carbon and anaerobic incubation in the presence of acetylene (Groffman et al, 1999). This method has been proven to work when comparing soils and ecosystems (Groffman et al, 2006;Felber et al, 2012;Russell et al, 2019) and allows the soil DP to be estimated at the landscape level. Parameters leading to bias are adjusted to be as low as possible, by using the AIT modified by Kaden et al (2020), which addresses a time series analysis of rewetting as this is likely to strongly affect denitrification.…”