EAGER: Differentiating Heterotrophic and Root Respiration Through Concurrent Measurement of CO2 and O2 Fluxes in Soils

同时测量大气中的氧（O2）和二氧化碳（CO2）浓度已被用来计算全球陆地和海洋的碳汇。推导中的一个基本假设是，陆地通量和海洋通量的氧化比率（O2:CO2）是不同的。在这些估算中使用了陆地碳汇的固定氧化比（约1.1）。然而，微生物和根呼吸的氧化比及其时空变化是不确定的。因此，将土壤呼吸分解为微生物和根组分是困难的，迄今为止还没有令人满意的方法。本项目的目标是：1)开发一种新的方法来连续和同时测量土壤中CO2通量和O2通量，并计算微生物呼吸和根呼吸的氧化比；2)开发一种基于微生物呼吸和根呼吸两种过程不同氧化比的土壤呼吸划分新方法。一项实地研究将在马萨诸塞州中部的哈佛森林进行，这是一个长期生态研究地点。为了实现上述目标，将使用新开发的高频CO2和O2传感器同时进行CO2和O2通量测量，并通过原位传感器测量和实验室土壤碳化合物的化学提取来计算微生物和根呼吸的氧化比。微生物呼吸和根呼吸之间的不同氧化比率将被用来将土壤呼吸总量划分为根呼吸和微生物呼吸。通过探索氧化比的变革性概念，这项工作将为碳循环提供新的见解，并有可能塑造生物地球化学领域的未来研究。海洋生物实验室（MBL）将把有关碳和氧循环的新信息纳入本科教学。它还将帮助制定研究生课程，并帮助培训通过MBL/Brown联合研究生项目进入布朗大学的研究生。从这个项目中得出的结果将在国家会议上提出，并在科学文献中发表。

Concurrent measurement of atmospheric oxygen (O2) and carbon dioxide (CO2) concentrations have been used to derive the global terrestrial and ocean carbon sinks. A basic assumption in the derivation is that the oxidative ratios (O2:CO2) are distinct for terrestrial and ocean fluxes. A fixed oxidative ratio (approximately 1.1) of the terrestrial carbon sink was used in these estimations. However, the oxidative ratios of microbial and root respiration and their spatial and temporal variations are uncertain. Partitioning of soil respiration into microbial and root components is therefore difficult and there are no satisfactory methods available to date. The objectives of this project are 1) to develop a novel method to continuously and concurrently measure CO2 fluxes and O2 fluxes in soils, and calculate the oxidative ratios of microbial respiration and root respiration; and 2) to develop a novel method to partition soil respiration into microbial respiration and root respiration based on the different oxidative ratios for the two processes.A field study will be conducted at the Harvard Forest in central Massachusetts, a Long Term Ecological Research site. To address the above objectives concurrent CO2 and O2 flux measurements will be made with newly developed high-frequency CO2 and O2 sensors and the oxidative ratios for microbial and root respiration will be calculated with both in situ sensor measurement and chemical extraction of soil carbon compounds in the laboratory. The different oxidative ratios between microbial respiration and root respiration will be used to partition total soil respiration into root and microbial respiration.By exploring the transformative concept of the oxidative ratio, the work will provide new insight into the carbon cycle, and potentially shape future research in the field of biogeochemistry. New information on the carbon and oxygen cycles will be incorporated into undergraduate teaching provided by the Marine Biological Laboratory (MBL). It will also help shape graduate curricula and help training graduate students enrolled at Brown University through the joint MBL/Brown graduate program. The results drawn from this project will be presented at national meetings and published in the scientific literature.