Abstract
Purpose
Microorganisms play important ecological roles in NO3 − pool production, e.g., through autotrophic nitrification (the oxidation of NH4 + to NO3 −) and heterotrophic nitrification (the oxidation of organic N to NO3 −). Previous studies have mainly focused on nitrifying microorganisms capable of autotrophic nitrification; however, the contribution of microorganisms to heterotrophic nitrification has not been well investigated. The aim of this study was to identify the contribution of fungi and bacteria to autotrophic nitrification and heterotrophic nitrification in a subtropical coniferous forest soil of China.
Materials and methods
A 15N tracing experiment was conducted in a subtropical forest soil, which was treated with CK (no antibiotics), cycloheximide (fungal inhibitor), and streptomycin (bacterial inhibitor), respectively. Soil was incubated at 25 °C with 60 % water holding capacity (WHC) for 144 h after being labeled with 15NH4NO3 or NH4 15NO3 at a 20 atom% 15N excess. Autotrophic and heterotrophic nitrification rates were calculated using a full process-based N cycle model.
Results and discussion
The net nitrification rates were negative in all treatments, ranging from −0.346 mg N kg−1 day−1 in the cycloheximide treatment to −0.179 mg N kg−1 day−1 in the streptomycin treatment. The autotrophic nitrification was almost negligible (only 0.001 mg N kg−1 day−1) in the soil from subtropical coniferous forest, while heterotrophic nitrification rate was 0.993 mg N kg−1 day−1. Streptomycin reduced heterotrophic nitrification rate by 22.1 %, while cycloheximide nearly completely inhibited this process.
Conclusions
Laboratory results showed that heterotrophic nitrification is a pivotal process producing NO3 − and that fungi rather than bacteria may dominate heterotrophic nitrification in the subtropical coniferous forest soil.
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Acknowledgments
The project was financially supported by the National Natural Science Foundation of China (41330744, 41301313, 41222005), Research Fund of State Key Laboratory of Soil and Sustainable Agriculture, Nanjing Institute of Soil Science, Chinese Academy of Science (0812201211), Outstanding Innovation Team in Colleges and Universities in Jiangsu Province, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
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Responsible editor: Jizheng He
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Zhu, T., Meng, T., Zhang, J. et al. Fungi-dominant heterotrophic nitrification in a subtropical forest soil of China. J Soils Sediments 15, 705–709 (2015). https://doi.org/10.1007/s11368-014-1048-4
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DOI: https://doi.org/10.1007/s11368-014-1048-4