The creation and/or restoration of wetlands is an important strategy for controlling the release of reactive nitrogen (N) via denitrification, but there can be tradeoffs between enhanced denitrification and the production of nitrous oxide (N2 O), a potent greenhouse gas. A knowledge gap in current understanding of belowground wetland N dynamics is the role of gas transfer through the root aerenchyma system of wetland plants as a shortcut emission pathway for N2 O in denitrifying wetland soils. This investigation evaluates the significance of mass transfer into gas-filled root aerenchyma for the N2 O budget in wetland mesocosms planted with Sagittaria latifolia Willd. and Schoenoplectus acutus (Muhl. ex Bigelow) Á. Löve & D. Löve. Dissolved gas tracer push-pull tests with N2 O and the nonreactive gas tracers helium, sulfur hexafluoride, and ethane were used to estimate first-order rate constants for gas transfer into roots and microbial N2 O reduction and thereby disentangle the effects of root-mediated gas transport from microbial metabolism on N2 O balances in saturated soils. Root-mediated gas transport was estimated to account for up to 37% of overall N2 O removal from the wetland soils. Rates of microbial N2 O reduction varied widely based on the organic matter content of the soil media and served as a key control on the fraction of N2 O that transferred into roots. This research identifies transport through root aerenchyma as a potential shortcut pathway for N2 O emission from wetland soils and sediments and indicates that this process should be considered in both measurements and mechanistic modeling of belowground wetland N dynamics.

中文翻译：

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一氧化二氮从孔隙水中向湿地植物根系通气组织的传质动力学

湿地的创建和/或恢复是控制通过反硝化作用释放活性氮 (N) 的重要策略，但在增强反硝化作用和一氧化二氮 (N2 O)（一种强效温室气体）的产生之间可以进行权衡。目前对地下湿地氮动力学理解的一个知识空白是通过湿地植物根系通气组织系统的气体转移作为 N2 O 在反硝化湿地土壤中的捷径排放途径的作用。本研究评估了在种植有 Sagittaria latifolia Willd 的湿地中宇宙中 N2 O 收支的质量转移到充满气体的根通气组织的重要性。和 Schoenoplectus acutus (Muhl. ex Bigelow) Á。爱 & D. 爱。使用 N2 O 和非反应性气体示踪剂氦气、六氟化硫、和乙烷用于估计气体转移到根部和微生物 N2O 还原的一级速率常数，从而解开根系介导的气体传输对饱和土壤中 N2O 平衡的微生物代谢的影响。据估计，根系介导的气体传输占湿地土壤中 N2 O 总去除量的 37%。微生物 N2 O 减少的速率因土壤介质的有机质含量而异，并且是控制转移到根部的 N2 O 比例的关键。该研究将通过根系通气组织的运输确定为湿地土壤和沉积物中 N2 O 排放的潜在捷径，并表明在地下湿地 N 动力学的测量和机械建模中应考虑这一过程。