Browsing by Author "Sun, Tao"

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    In Situ Quantification of Biological N2 Production Using Naturally Occurring 15N15N
    (American Chemical Society, 2019) Yeung, Laurence Y.; Haslun, Joshua A.; Ostrom, Nathaniel E.; Sun, Tao; Young, Edward D.; van Kessel, Maartje A.H.J.; Lücker, Sebastian; Jetten, Mike S.M.
    We describe an approach for determining biological N2 production in soils based on the proportions of naturally occurring 15N15N in N2. Laboratory incubation experiments reveal that biological N2 production, whether by denitrification or anaerobic ammonia oxidation, yields proportions of 15N15N in N2 that are within 1‰ of that predicted for a random distribution of 15N and 14N atoms. This relatively invariant isotopic signature contrasts with that of the atmosphere, which has 15N15N proportions in excess of the random distribution by 19.1 ± 0.1‰. Depth profiles of gases in agricultural soils from the Kellogg Biological Station Long-Term Ecological Research site show biological N2 accumulation that accounts for up to 1.6% of the soil N2. One-dimensional reaction-diffusion modeling of these soil profiles suggests that subsurface N2 pulses leading to surface emission rates as low as 0.3 mmol N2 m–2 d–1 can be detected with current analytical precision, decoupled from N2O production.
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    Stable isotope (C, N, O, and H) study of a comprehensive set of feathers from two Setophaga citrina
    (Public Library of Science, 2021) Deme, Samiksha; Yeung, Laurence Y.; Sun, Tao; Lee, Cin-Ty A.
    Oxygen, hydrogen, carbon and nitrogen stable isotopes were measured on a comprehensive sampling of feathers from two spring Hooded Warblers (Setophaga citrina) in Texas to evaluate isotopic variability between feathers and during molt. Isotopic homogeneity within each bird was found across all four isotopic systems, supporting the hypothesis that molt in these neotropical migrants is fully completed on the breeding grounds. This homogeneity suggests that the isotopic composition of a single feather is may be representative of the whole songbird. However, each bird was found to have one or two outlier feathers, which could signify regrowth of lost feathers after prebasic molt.