Denitrification plays a critical role in regulating ecosystem nutrient availability and anthropogenic reactive nitrogen (N) production. Its importance has inspired an increasing number of studies, yet it remains the most poorly constrained term in terrestrial ecosystem N budgets. We censused the peer-reviewed soil denitrification literature (1975 to 2015) to identify opportunities for future studies to advance our understanding despite the inherent challenges in studying the process. We found that only one-third of studies reported estimates of both nitrous oxide (N2 O) and dinitrogen (N2 ) production fluxes, often the dominant end products of denitrification, while the majority of studies reported only net N2 O fluxes or denitrification potential. Of the 236 studies that measured complete denitrification to N2 , 49% used the acetylene inhibition method; 84% were conducted in the laboratory; 81% were performed on surface soils (0-20 cm depth); 75% were located in North America and Europe; and 78% performed treatment manipulations, mostly of N, carbon, or water. To improve understanding of soil denitrification, we recommend broadening access to technologies for new methodologies to measure soil N2 production rates, conducting more studies in the tropics and on subsoils, performing standardized experiments on unmanipulated soils, and using more precise terminology to refer to measured process rates (e.g., net N2 O flux or denitrification potential). To overcome the greater challenges in studying soil denitrification, we envision coordinated research efforts based on standard reporting of metadata for all soil denitrification studies, standard protocols for studies contributing to a Global Denitrification Research Network, and a global consortium of denitrification researchers to facilitate sharing ideas, resources, and to provide mentorship for researchers new to the field.

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回首展望：土壤反硝化研究的愿景

反硝化在调节生态系统养分可用性和人为活性氮 (N) 生产方面发挥着关键作用。它的重要性激发了越来越多的研究，但它仍然是陆地生态系统 N 预算中约束最差的术语。我们对经过同行评审的土壤反硝化文献（1975 年至 2015 年）进行了普查，以确定未来研究的机会，以促进我们的理解，尽管研究该过程存在固有挑战。我们发现只有三分之一的研究报告了对一氧化二氮 (N2 O) 和二氮 (N2) 生产通量的估计，这通常是反硝化的主要最终产品，而大多数研究仅报告了净 N2 O 通量或反硝化潜力。在测量完全反硝化至 N2 的 236 项研究中，49%采用乙炔抑制法；84% 在实验室进行；81% 在表层土壤（0-20 厘米深度）上进行；75% 位于北美和欧洲；78% 的人进行了处理操作，主要是 N、碳或水。为增进对土壤反硝化作用的理解，我们建议扩大获取测量土壤 N2 生产率的新方法的技术，在热带和底土上开展更多研究，对未经处理的土壤进行标准化实验，并使用更精确的术语来指代测量过程率（例如，净 N2 O 通量或反硝化潜力）。为了克服土壤反硝化研究中的更大挑战，我们设想了基于所有土壤反硝化研究元数据标准报告的协调研究工作，