Relative importance of landscape versus local wetland characteristics for estimating wetland denitrification...

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 (microg 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 NO₃ 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 NO₃, Soil Percent N, and Percent Agriculture) had significant (p<0.001, cum. r² = 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.