Soil properties and microbial abundance explain variations in N2O fluxes from temperate steppe soil treated with nitrogen and water in Inner Mongolia, China
2021
Zhang, Jiaqi | He, Pei | Liu, Yinghui | Du, Wei | Jing, Haichao | Nie, Cheng
Microbe-mediated soil nitrification and denitrification processes affect the variations in soil N₂O fluxes. Researchers are concerned about how the abundances of nitrifiers and denitrifiers and the N₂O fluxes from temperate semi-arid grassland soil vary as nitrogen (N) and water inputs vary. In this study, we report the results from a field experiment that was set up in a temperate semi-arid grassland area in northern China in May 2017. In August 2018, we collected samples to investigate how a range of physical, chemical and biological characteristics of soil, including the pH, moisture, dissolved organic carbon content (DOC) and available N content, N₂O fluxes, and the abundances of ammonia oxidizers and denitrifiers in the soil, changed after N (4 g N·m⁻²·year⁻¹ NH₄NO₃) and water (112.5 mm·year⁻¹) were added over a period of 1 year. We analyzed the abundances of AOA amoA, AOB amoA, nirS, nirK and nosZ using quantitative PCR. We found that the soil N₂O emissions were negatively affected by the water additions, but were not affected by the N additions. We also found that the AOA amoA and nosZ genes responded positively to the N additions. Watering had a positive effect on the nirS gene abundance, while N additions and water together intensified the effect of only water on the nirS gene abundance. The nirS gene abundance, soil pH, and DOC content explained 46.1%, 20.1% and 12.0% of the variations in the soil N₂O fluxes, respectively. These results provide improved insights into how microorganisms affect N cycling, and may be used to help predict how soil N₂O fluxes might change in the future, as N deposition and precipitation change.
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