Chemical composition of organic matter in a deep soil changed with a positive priming effect due to glucose addition as investigated by 13C NMR spectroscopy |
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| Affiliation: | 1. College of Resources and Environmental Sciences, Northeast Agricultural University, Harbin 150030, China;2. Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing 210042, China;3. Department of Animal, Plant and Soil Science, AgriBio, Centre for AgriBioscience, La Trobe University, Melbourne Campus, Victoria 3086, Australia;4. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China;1. School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China;2. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China;1. National Engineering Laboratory for Improving Fertility of Arable Soils, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China;2. Key Laboratory of Mollisols Agroecology, National Field Observation and Research Station of Hailun Agroecosystems, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, PR China;3. Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Blvd, Norfolk, VA 23529, USA |
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| Abstract: | Fresh organic carbon becomes more accessible to deep soil following losses of surface soil and deep intentional incorporation of crop residues, which can cause the priming effect and influence the quality and quantity of SOC in deep soil. This study determined the priming effect due to addition of water-dissolved 13C-labeled glucose (0.4 g C kg−1 soil) to a soil taken from 1.00 to 1.20 m depth. The changes in chemical compositions of SOC in soils without (G0) and with (G0.4) glucose addition during a 31-d incubation were investigated with solid-state 13C cross polarization/total sideband suppression (13C-CP/TOSS) and CP/TOSS with dipolar dephasing nuclear magnetic resonance (NMR) techniques. No glucose remained in the soil after 21 days of incubation, with 48% being completely mineralized into CO2 emission and 52% being incorporated into SOC. The native SOC was decomposed by 0.23% more in G0.4 than in G0. The NMR spectra demonstrated that both labile and recalcitrant organic compounds in SOC changed during the incubation, but in different manners in G0 and G0.4. During the incubation, the -(CH2)n-abundance in G0 did not change over time, but in G0.4 it decreased from Day 0 to Day 21 and then increased from Day 21 to Day 31, suggesting shifts of soil microbial communities only in G0.4. After the incubation, in G0 the abundances of ketones/aldehydes and nonpolar alkyl C increased, but those of aromatic C–C and protonated O-alkyl C (OCH) decreased; In G0.4, the abundances of NCH and protonated O-alkyl C (OCH) increased, but those of nonpolar alkyl C and nonprotonated aromatic C–O and ketones/aldehydes decreased. Such inconsistent changes in recalcitrant compounds between G0 and G0.4 indicated that glucose addition likely primed the decomposition of aromatic C–O and suppressed the formation of ketones/aldehydes. We have demonstrated for the first time that the priming effect of SOC decomposition in the deep soil was involved with larger notable changes in both labile and recalcitrant structures of native SOC due to glucose addition compared with that without glucose addition. |
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| Keywords: | Priming effect Deep soil Soil organic carbon Dipolar dephasing |
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