AUTHOR=Yin Chang , Fan Xiaoping , Yan Guochao , Chen Hao , Ye Mujun , Ni Liang , Peng Hongyun , Ran Wei , Zhao Yuhua , Li Tingqiang , Wakelin Steven A. , Liang Yongchao 

TITLE=Gross N2O Production Process, Not Consumption, Determines the Temperature Sensitivity of Net N2O Emission in Arable Soil Subject to Different Long-Term Fertilization Practices

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00745

DOI=10.3389/fmicb.2020.00745

ISSN=1664-302X

ABSTRACT=<p>Chronic amendment of agricultural soil with synthetic nitrogen fertilization and/or livestock manure has been demonstrated to enhance the feedback intensity of net N<sub>2</sub>O emission to temperature variation (i.e., temperature sensitivity, TS). Yet few studies have explored the relevance of changes in underlying gross N<sub>2</sub>O production and consumption processes toward explaining this phenomenon, in particular for the latter. Furthermore, the microbe-based mechanisms associated with the variation of N<sub>2</sub>O consumption process remain largely unexplored. To address this knowledge gap, a temperature- (15, 25, and 35°C) and moisture-controlled (50% water holding capacity) microcosm incubation experiment was established using an arable soil subject to long-term addition of synthetic fertilizer (NPK), a mixture of synthetic fertilizer with livestock manure (MNPK), or with no fertilizer treatment (CT). Over the incubation time period, the C<sub>2</sub>H<sub>2</sub> inhibition method was adopted to monitor reaction rates of gross N<sub>2</sub>O production and consumption; the population sizes and community structures of <italic>nosZ</italic>I- and <italic>nosZ</italic>II-N<sub>2</sub>O reducers were analyzed using quantitative PCR (Q-PCR) and terminal restriction fragment length polymorphism (T-RFLP). The results indicated that only NPK significantly increased the TS of net N<sub>2</sub>O emission, and gross N<sub>2</sub>O consumption process consistently occurred under all treatment combinations (temperature and fertilization) at each sampling time point. The responses of gross N<sub>2</sub>O production and consumption processes to temperature elevation exhibited fertilization- and sampling time-dependent pattern, and the higher net N<sub>2</sub>O production TS in the NPK treatment was underlain by its higher TS of gross production process and insensitivity of gross consumption process to temperature. The size and structure of <italic>nosZ</italic>II-N<sub>2</sub>O reducers, as well as the community structure of <italic>nosZ</italic>I-N<sub>2</sub>O reducers, were positively correlated with variation of gross N<sub>2</sub>O production and consumption rates across all fertilization regimes. <italic>NosZ</italic>II-N<sub>2</sub>O reducer abundance was less responsive to temperature change, and its community structure less susceptible to fertilization, as compared with <italic>nosZ</italic>I-N<sub>2</sub>O reducers. Overall, our results demonstrate that the TS of the gross N<sub>2</sub>O production process, not gross consumption, is the key step regulating the TS of net N<sub>2</sub>O production, and both <italic>nosZ</italic>I- and <italic>nosZ</italic>II-N<sub>2</sub>O clades are likely active N<sub>2</sub>O reducers in the tested soil.</p>