EAPSI: Constraining the Isotope Effect of Denitrification to Improve Global Models of N Fluxes

该项目将使用模型来量化通过反硝化作用（氮循环的关键组成部分）从土壤中流失的氮量。量化反硝化是很重要的，因为反硝化过程中产生的气体会导致空气质量差，损害人体健康。此外，由于氮限制了植物的生长能力，量化它将有助于更好地预测碳储量。反硝化几乎不可能直接测量，因此，开发一个准确的模型是至关重要的。该项目将在澳大利亚联邦科学与工业研究组织（CSIRO）进行，由王颖平博士指导。该合作提供了对CSIRO专业知识和计算能力的访问。反硝化作用从生态系统中去除生物可利用的氮(N)，使其成为对生物圈氮平衡的重要控制，对空气质量、人类健康和气候变化都有影响。尽管它很重要，但对全球土壤反硝化通量的估计仍然高度不确定。主要的挑战在于直接测量反硝化的气态副产物和缩放这一复杂的微生物过程。受经验同位素证据约束的基于过程的模型已经成为帮助克服这些挑战的一种方法。然而，这种方法的稳健性受到对反硝化同位素表达的不完全理解以及它在已知控制因素（如碳和硝酸盐有效性以及土壤湿度和温度）中的变化方式的限制。该项目将确定反硝化的同位素表达如何在一系列环境控制下变化，并将这些数据纳入反硝化模型。最终，该模型将被纳入CASA-CNP，这是由CSIRO的科学家开发的陆地碳固存营养限制的全球模型。这将减少碳封存预测中的一个关键不确定性。该奖项由美国国家科学基金会和澳大利亚科学院共同资助，隶属于东亚和太平洋暑期研究所项目，支持一名美国研究生进行暑期研究。

This project will use modeling to quantify the amount of nitrogen lost from soils through denitrification, a key component of the nitrogen cycle. Quantifying denitrification is important because the gases produced during denitrification cause poor air quality that damages human health. Also, because nitrogen limits the ability of plants to grow, quantifying it will allow for better predictions about carbon storage. Denitrification is nearly impossible to measure directly, and as such, developing an accurate model is essential. This project will be conducted at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia under the mentorship of Dr. Ying-Ping Wang. The collaboration provides access to the expertise and computing capacity at CSIRO. Denitrification removes biologically available nitrogen (N) from ecosystems, making it an important control over the biosphere's N balance, with implications for air quality, human health, and climate change. Despite its importance, estimates of the global soil denitrification flux remain highly uncertain. Major challenges lie in directly measuring the gaseous by-products of denitrification and scaling this complex microbial processes. Process-based models constrained by empirical isotopic evidence have emerged as a method to help overcome these challenges. However, the robustness of this method is limited by incomplete understanding of isotopic expression of denitrification and how it varies across known controls, such as carbon and nitrate availability and soil moisture and temperature. The project will determine how the isotopic expression of denitrification varies across a range of environmental controls and will incorporate this data into models of denitrification. Ultimately this model will be incorporated into the CASA-CNP, the global model of nutrient limitations on terrestrial carbon sequestration developed by scientists at CSIRO. This will reduce a key uncertainty in predictions of carbon sequestration. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a US graduate student and is jointly funded by NSF and the Australian Academy of Science.