Spatial and Spectral Relationships Between Field-measured Denitrification Gas Fluxes and Soil Properties
1985
Folorunso, O. A. | Rolston, D. E.
The relationship of the spatial variability of field-measured denitrification gas fluxes to the variability of physical and chemical soil properties affecting denitrification were investigated in order to better understand the denitrification process in the field. The values of N₂O, N₂, and CO₂ fluxes, soil-water content, soil temperature, water soluble organic C, and NO⁻₃ were determined from four transects, each with 36 observations, in a Yolo loam (Typic Xerorthents) field site. Spectral analysis indicated the presence of spatial cycling of some parameters. Cospectra and coherency spectra were used to establish relationships between variables in the frequency domain. Spectra of N₂O + N₂ flux gave evidence that denitrification was cycling with a period of 4 to 5 m for some of the strips. Spectra of soil-water content (0–0.15 m depth) showed that soil-water content was also cycling at a period of about 5 m. Spectra of other variables showed less consistent cycling. Cospectra of N₂O flux vs. most variables provided evidence of both positive and negative correlations over different frequency ranges. The cyclic nature of the soil-water content in the surface soil appears to be the primary cause of cycling of the denitrification gas flux at a period of 4 to 5 m. Cycling of water soluble organic C at periods different from that of water content also caused some periodic behavior in denitrification gas fluxes. Without using spectral and coherency techniques, standard correlation or regression methods would have provided little evidence of significant causal effects on denitrification.
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