反硝化剂的组成和活性变化主导了N2O排放的CO2刺激。,Environmental Science & Technology

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反硝化剂的组成和活性变化主导了N2O排放的CO2刺激。
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2019-09-09 , DOI: 10.1021/acs.est.9b02983
Yunpeng Qiu , Yu Jiang , Lijin Guo ₁ , Lin Zhang , Kent O. Burkey ₂ , Richard W. Zobel , S. Chris Reberg-Horton , H. David Shew , Shuijin Hu

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升高的大气CO ₂（eCO ₂）通常会增加土壤N ₂ O的排放量，但其基本机理仍不清楚。一种假设表明，N ₂ O的高排放可能源于CO ₂增强地下植物碳（C）分配所引起的反硝化作用增加。然而，仍然缺乏直接的证据说明在eCO ₂下N ₂ O排放，植物C分配和反硝化微生物之间的联系。我们研究了eCO ₂对植物C分配给根及其相关的丛枝菌根真菌及其对N _2的影响的影响。在存在两个不同的氮源（铵态氮（NH ₄⁺ -N）和硝态氮（NO ₃^-- N））的情况下，O排放和反硝化微生物。我们的研究结果表明，N个输入的形式为主ECO的影响₂在N个₂ O排放：ECO ₂显著提高了氮肥₂与NO O排放₃^- -N输入而与NH没有效果_4个⁺ -N输入。ECO ₂增加的植物生物量N多用NH ₄⁺ -N比NO ₃^- -N输入，有可能降低NH下有效氮微生物访问₄⁺ –N输入和/或在NO ₃^– –N输入下导致更高的N ₂ O排放。在NO ₃^– –N输入下，eCO ₂增强了根和菌根氮的吸收，并增加了N ₂ O的排放。此外，在NO ₃^– –N输入下eCO ₂增强N ₂ O排放的同时，土壤反硝化器群落组成发生了变化，有利于生产N ₂ O（nir K型和nir S型）而不是N ₂ O-。消耗（号Z型）反硝化菌。这些结果加在一起表明eCO ₂模拟氮₂ O排放主要是通过改变植物氮偏好赞成NH的₄⁺过度NO ₃^-和从而刺激反硝化细菌土壤和他们的活动。这些发现表明，通过消除土壤反硝化微生物及其活动的eCO ₂刺激，对N源的有效管理可以减轻N ₂ O的排放。

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Shifts in the Composition and Activities of Denitrifiers Dominate CO2 Stimulation of N2O Emissions

Elevated atmospheric CO₂ (eCO₂) often increases soil N₂O emissions, but the underlying mechanisms remain largely unknown. One hypothesis suggests that high N₂O emissions may stem from increased denitrification induced by CO₂ enhancement of plant carbon (C) allocation belowground. However, direct evidence illustrating linkages among N₂O emissions, plant C allocation, and denitrifying microbes under eCO₂ is still lacking. We examined the impact of eCO₂ on plant C allocation to roots and their associated arbuscular mycorrhizal fungi and its subsequent effects on N₂O emissions and denitrifying microbes in the presence of two distinct N sources, ammonium nitrogen (NH₄⁺–N) and nitrate nitrogen (NO₃^––N). Our results showed that the form of the N inputs dominated the effects of eCO₂ on N₂O emissions: eCO₂ significantly increased N₂O emissions with NO₃^––N inputs but had no effect with NH₄⁺–N inputs. eCO₂ increased plant biomass N more with NH₄⁺–N than with NO₃^––N inputs, likely reducing microbial access to available N under NH₄⁺–N inputs and/or contributing to higher N₂O emissions under NO₃^––N inputs. eCO₂ enhanced root and mycorrhizal N uptake and also increased N₂O emissions under NO₃^––N inputs. Further, eCO₂ enhancement of N₂O emissions under NO₃^––N inputs concurred with a shift in the soil denitrifier community composition in favor of N₂O-producing (nirK- and nirS-type) over N₂O-consuming (nosZ-type) denitrifiers. Together, these results indicate that eCO₂ stimulated N₂O emissions mainly through altering plant N preference in favor of NH₄⁺ over NO₃^– and thus stimulating soil denitrifiers and their activities. These findings suggest that effective management of N sources may mitigate N₂O emissions by negating the eCO₂ stimulation of soil denitrifying microbes and their activities.

更新日期：2019-09-10

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