|LI, X - University Of Maryland|
|LANG, M.W. - Us Fish And Wildlife Service|
Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2016
Publication Date: 12/10/2016
Citation: Li, X., Mccarty, G.W., Lang, M., Ducey, T.F., Hunt, P.G., Miller, J.O. 2016. Topographic and physicochemical controls on soil denitrification potential in prior converted croplands located on the Delmarva Peninsula, USA. American Geophysical Union Fall Meeting,San Francisco, CA, December 14-18,2016. 2016 CDROM.
Technical Abstract: Topography and soil physiochemical characteristics exert substantial controls on denitrification in agricultural lands. In order to depict these controls at a landscape scale for decision support applications, metrics (i.e., proxies) must be developed based on commonly available geospatial data. In this study, we analyzed the combined effects of eleven topography and soil physiochemical factors, including three topographic attributes (relief, topographic wetness index, and positive openness), two soil texture indices (sand and clay), and six soil properties (soil moisture, pH, electrical conductivity, SOC, TN, and C:N ratio), on soil denitrification potential in three actively farmed crop fields that were converted from forested wetlands before 1986 (i.e., prior converted croplands). Denitrification potential was measured using denitrification enzyme activity (DEA) assays, which employed the acetylene inhibition method under two treatments – a non-nitrate and carbon limiting treatment to measure potential denitrification and a control treatment to measure the capacity for denitrification without soil amendment. Nitrate and carbon addition led to a doubling in DEA rates compared to the control treatment. Topography explained the greatest amount of variation in potential denitrification across the three sites. The relationship between topography and DEA may partly be explained through the relatively robust relationship between topography and soil moisture, texture, and carbon content. For DEA under the control treatment, soil electrical conductivity (EC) exhibited the highest correlation with denitrification capacity (i.e., r2 = 35%). Denitrification capacity and potential were higher in a dry year with low soil moisture, relative to an average year with high soil moisture, which may be caused by the substantial increase in soil EC in the dry year. However, DEA rates were less responsive to soil EC at sandy sites which tend to have low soil moisture. Results of this study suggested that the spatial-temporal variations of denitrification in these croplands were mainly caused by a complex interaction among topography, soil EC, and soil moisture. Topographic metrics derived from LiDAR data have potential to improve understanding of denitrification variability at a landscape scale.