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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-320
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-320
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 13 Sep 2019

Submitted as: research article | 13 Sep 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Maize root and shoot litter quality controls short-term CO2 and N2O emissions and bacterial community structure of arable soil

Pauline Sophie Rummel1, Birgit Pfeiffer1,2, Johanna Pausch3, Reinhard Well4, Dominik Schneider2, and Klaus Dittert1 Pauline Sophie Rummel et al.
  • 1Division of Plant Nutrition and Crop Physiology, Department of Crop Science, University of Göttingen, Germany
  • 2Institute of Microbiology and Genetics, Dept. of Genomic and Applied Microbiology, University of Göttingen, Germany
  • 3Agroecology, Faculty for Biology, Chemistry, and Earth Sciences, University of Bayreuth, Germany
  • 4Thünen Institute, Climate-Smart Agriculture, Braunschweig, Germany

Abstract. Chemical composition of root and shoot litter controls decomposition and, subsequently, C availability for biological nitrogen transformation processes in soils. While aboveground plant residues have been proven to increase N2O emissions, studies on root litter effects are scarce. This study aimed (1) to evaluate how fresh maize root litter affects N2O emissions compared to fresh maize shoot litter, (2) to assess whether N2O emissions are related to the interaction of C and N mineralization from soil and litter, and (3) to analyze changes in soil microbial community structures related to litter input and N2O emissions.

To obtain root and shoot litter, Maize plants (Zea mays L.) were cultivated with two N fertilizer levels in a greenhouse and harvested. A two-factorial 22-day laboratory incubation experiment was set up with soil from both N levels (N1, N2) and three litter addition treatments (Control, Root, Root+Shoot). We measured hourly CO2 and N2O fluxes, analyzed soil nitrate and water extractable organic C (WEOC) concentrations, and determined quality parameters of maize litter. Bacterial community structures were analyzed using 16S rRNA gene sequencing.

Maize litter quality controlled NO3 and WEOC availability and decomposition related CO2 emissions. High bioavailability of maize shoot litter strongly increased CO2 and N2O emissions, while emissions induced by maize root litter remained low. We identified a strong positive correlation between cumulative CO2 and N2O emissions, supporting our hypothesis that litter quality affects denitrification by creating plant litter associated anaerobic microsites. The interdependency of C and N availability was validated by analyses of regression. Moreover, there was a strong positive interaction between soil NO3 and WEOC concentration resulting in much higher N2O emissions, when both NO3 and WEOC were available. A significant correlation was observed between total CO2 and N2O emissions, the soil bacterial community composition and the litter level, showing a clear separation of Root+Shoot samples of all remaining samples. Bacterial diversity decreased with higher N level and higher input of easily available C. Altogether, changes in bacterial community structure reflected degradability of maize litter with easily degradable C from maize shoot litter favoring fast growing C cycling and N reducing bacteria of the phyla Actinobacteria, Chloroflexi, Firmicutes and Proteobacteria.

Pauline Sophie Rummel et al.
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Pauline Sophie Rummel et al.
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Short summary
Chemical composition of plant litter controls C availability for biological N transformation processes in soil. In this study, we showed that easily degradable maize shoots stimulated microbial respiration and mineralization leading to high N2O formation in litter associated hotspots. A higher share of slowly degradable C compounds and lower concentrations of water soluble N restricted N2O emissions from maize roots. Bacterial community structure reflected degradability of maize litter.
Chemical composition of plant litter controls C availability for biological N transformation...
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