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气(O2)和二氧化碳(CO2)浓度已被用来得出全球陆地和海洋的碳汇。推导中的一个基本假设是，陆地和海洋通量的氧化比率(O2：CO2)是不同的。在这些估计中使用了固定的陆地碳汇的氧化比率(约1.1)。然而，微生物和根系呼吸的氧化比率及其时空变化是不确定的。因此，将土壤呼吸分为微生物组分和根部组分是困难的，到目前为止还没有令人满意的方法。该项目的目标是1)开发一种新的方法来连续和同时测量土壤中的CO2通量和O2通量，并计算微生物呼吸和根系呼吸的氧化比率；2)根据微生物呼吸和根系呼吸的不同氧化比率，开发一种新的方法来划分土壤呼吸。为了实现上述目标，将使用新开发的高频CO2和O2传感器同时测量CO2和O2通量，并将在实验室通过现场传感器测量和土壤碳化合物的化学提取来计算微生物和根系呼吸的氧化比率。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总呼吸分为根呼吸和微生物呼吸。通过探索氧化比率的变革性概念，这项工作将为碳循环提供新的见解，并可能塑造未来生物地球化学领域的研究。有关碳循环和氧循环的新信息将被纳入海洋生物实验室(MBL)提供的本科教学。它还将帮助制定研究生课程，并帮助培训通过MBL/布朗联合研究生项目进入布朗大学的研究生。该项目得出的结果将在国家会议上提出，并发表在科学文献上。

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.