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从土壤中流失的氮素的数量，反硝化作用是氮循环的关键组成部分。量化反硝化很重要，因为反硝化过程中产生的气体会导致空气质量差，损害人类健康。此外，由于氮限制了植物的生长能力，量化氮将使人们能够更好地预测碳储量。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。该项目将由澳大利亚联邦科学与工业研究组织(CSIRO)在王英平博士的指导下进行。通过协作，可以获得CSIRO的专业知识和计算能力。反硝化作用从生态系统中去除生物有效氮(N)，使其成为生物圈N平衡的重要控制因素，并对空气质量、人类健康和气候变化产生影响。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扩大这一复杂的微生物过程的规模。受经验同位素证据约束的基于过程的模型已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不完全理解反硝化的同位素表达以及它如何在已知的控制措施中变化的限制，例如碳和硝酸盐的有效性以及土壤水分和温度。该项目将确定反硝化作用的同位素表达如何在一系列环境控制措施中发生变化，并将这些数据纳入反硝化作用模型。最终，这个模型将被纳入CASA-CNP，这是CSIRO的科学家开发的关于陆地碳封存的养分限制的全球模型。这将减少碳封存预测中的一个关键不确定性。该奖项根据东亚和太平洋夏季学院计划，支持一名美国研究生的暑期研究，由NSF和澳大利亚科学院联合资助。

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.