EAGER SitS: Studying soil biotic and abiotic processes through continuous, high-precision monitoring of soil CO2 an O2 concentrations

土壤是一种重要的自然资源，其成功管理取决于监测和了解众多地下生物和非生物过程的能力。这些过程，如矿物风化和碳氮循环，直接影响土壤健康。为了提高我们对这些土壤过程的认识，本研究项目将结合对土壤孔隙空间中受这些过程影响的氧气、二氧化碳和氨气浓度的连续、高精度监测，并开发一个计算机模型。本研究项目将招募来自代表性不足群体的本科生参与。研究结果将有助于量化土壤作为碳源/汇的作用，并为可持续土地管理实践提供信息，旨在养活不断增长的全球人口，同时管理肥料造成的环境污染。这些结果将通过PI教授的课程以及同行评议的出版物进行传播。呼吸商（RQ，呼吸过程中消耗的每摩尔氧气产生的二氧化碳的摩尔数）是新陈代谢的基本指标，目前我们无法在土壤中进行现场监测。了解土壤群落RQ及其变异的影响因素将有助于了解微生物代谢，控制自养和异养呼吸速率，最终实现土壤碳循环。因此，本研究项目的目标是对土壤群落的RQ进行连续分离和原位监测。该研究项目的第一步将是扩展现有的土壤物理和化学模型，以量化扩散和气水交换对土壤气体组成的影响。这些经过调整的模型的有效性将通过受控的实验室实验进行检验。下一步将是校准孔空间NH3和O2浓度，作为硝化作用的衡量标准，使用实验室培养的土壤进行后期的现场监测。准确测定RQ需要这些信息，因为除了呼吸作用消耗的氧气外，硝化作用还消耗氧气。最后一步将是连续和原位测量自然土壤中的CO2， O2和NH3浓度，使用市售的流量传感器与定制的自动进样器耦合。同时测量土壤湿度、土壤温度和相关气象变量将伴随土壤气体监测。扩展土壤物理模型和实验室土壤核心校准将用于解释扩散，水-气交换和硝化作用，以确定土壤群落RQ。研究了草地和森林土壤群落RQ的时空变化规律。提高对土壤RQ自然变异性的理解将促进1)对土壤生物过程的理解，例如土壤代谢如何在时间和空间上变化；2)生物和非生物过程之间的相互作用，例如驱动化学风化和碳酸钙溶解/沉淀的过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Soils are a vital natural resource, the successful management of which depends on the ability to monitor and understand numerous belowground biotic and abiotic processes. These processes, such as mineral weathering and carbon and nitrogen cycling, directly affect soil health. In order to advance our understanding of these soil processes, this research project will combine continuous, high precision monitoring of soil pore space oxygen, carbon dioxide, and ammonia gas concentrations, each of which are affected by these processes, with the development of a computer model. Undergraduate students who identify with underrepresented groups will be recruited to participate in this research project. The research results will help to quantify soils as a carbon source/sink and inform sustainable land management practices aimed at feeding the expanding global population while managing environmental contamination from fertilizers. These results will be disseminated through courses that the PI teaches, in addition to peer-reviewed publications.The respiratory quotient (RQ, moles of CO2 produced per mole of O2 consumed during respiration) is a fundamental indicator of metabolism that we currently cannot monitor in-situ in soils. Learning about soil community RQ and the factors that affect its variability will help to understand microbial metabolisms, controls on autotrophic and heterotrophic respiration rates, and ultimately soil carbon cycling. Therefore, the goal of this research project is to isolate continuously and monitor in-situ the RQ of the soil community. The first step of this research project will be to expand existing soil physics and chemistry models to quantify the effects of diffusion and gas-water exchange on soil gas composition. The effectiveness of these adapted models will be tested using controlled laboratory experiments. The next step will be to calibrate pore space NH3 and O2 concentrations as a measure of nitrification, using laboratory incubations of soils selected for later field-monitoring. This information is required for accurate determination of RQ, because nitrification consumes O2 in addition to that consumed by respiration. The final step will be to measure continuously and in-situ CO2, O2, and NH3 concentrations in natural soils using commercially-available flow-through sensors coupled to a custom-built autosampler. Simultaneous measurement of soil moisture, soil temperature, and relevant meteorological variables will accompany the soil gas monitoring. The expanded soil physics model and the laboratory soil core calibrations will be used to account for diffusion, water-gas exchange and nitrification in order to determine soil community RQ. Variation in soil community RQ through time and space in grassland and forest soils will be investigated. An improved understanding of natural variability in soil RQ will advance 1) understanding of soil biotic processes, such as how metabolisms in soil change temporally and spatially, and 2) the interaction between biotic and abiotic processes, such as those that drive chemical weathering and calcium carbonate dissolution/precipitation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.