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- Title
Interpreting the temperature-induced response of ammonia oxidizing microorganisms in soil using nitrogen isotope fractionation.
- Authors
Seok-In Yun; Hee-Myong Ro; Woo-Jung Choi; Gwang-Hyun Han
- Abstract
Purpose: Although nitrification plays a key role in the fate of soil nitrogen (N) under global warming, little information is available for the nitrifiers' response to changing temperatures. Nitrogen isotope fractionation associated with nitrification can be a proxy of nitrifiers' sensitivity to changing temperature. We hypothesized that the temperature-induced balance between the transport of substrate NH into the microbial cell (supply) and the intracellular NH oxidation (consumption) governs the intracellular NH concentration and then affects nitrification rates and associated isotope fractionations. This study was conducted to understand the microbial response of NH oxidation to changing temperatures by examining the effect of changing temperature on nitrification rate and apparent isotope fractionation. Materials and methods: A batch aerobic incubation was conducted with a sandy loam soil over 150 days at three different soil temperatures: 10, 20, and 30°C. After applying ammonium sulfate, we analyzed the temporal variations in the concentrations and the isotopic compositions of soil inorganic N and calculated nitrification rates and isotope fractionation factors. Results and discussion: Net nitrification rate increased with increasing soil temperature, while apparent isotope fractionation factors decreased. The increased net nitrification rate was attributable to both an increase in NH transport across cell membranes and an increase in intracellular enzymatic activity. Meanwhile, the decreased apparent isotope fractionation suggested that NH oxidation rate became faster than NH transport rate, resulting in a decrease in intracellular NH concentrations. Conclusions: Although intracellular NH transport and oxidation were not directly measured in this study, it is concluded that NH oxidation is more sensitive to increasing temperature than NH transport judging from the apparent N isotopic fractionation associated with NH concentration changes (mainly by nitrification) under different temperature regimes.
- Subjects
SOIL microbiology; NITROGEN isotopes; MICROBIAL cell cycle; SOIL composition; NITRATES; SOIL temperature; NITRIFICATION
- Publication
Journal of Soils & Sediments: Protection, Risk Assessment, & Remediation, 2011, Vol 11, Issue 7, p1253
- ISSN
1439-0108
- Publication type
Article
- DOI
10.1007/s11368-011-0380-1