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

土壤是一种至关重要的自然资源，其成功管理取决于监测和了解许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。为了促进我们对这些土壤过程的理解，本研究项目将结合联合收割机连续，高精度监测土壤孔隙空间的氧气，二氧化碳和氨气浓度，其中每一个都受到这些过程的影响，与计算机模型的发展。本科生谁认同代表性不足的群体将被招募参加这个研究项目。研究结果将有助于量化土壤作为碳源/汇，并为旨在养活不断扩大的全球人口的可持续土地管理实践提供信息，同时管理化肥造成的环境污染。这些结果将通过PI教授的课程以及同行评议的出版物传播。呼吸商（RQ，呼吸过程中消耗的每摩尔O2产生的CO2摩尔数）是我们目前无法在土壤中原位监测的代谢的基本指标。了解土壤群落RQ和影响其变异性的因素将有助于了解微生物代谢，控制自养和异养呼吸速率，并最终土壤碳循环。因此，本研究的目的是连续分离和原位监测土壤群落的RQ。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成分的影响。这些适应模型的有效性将使用受控实验室实验进行测试。下一步将是校准孔隙空间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选择以后的现场监测。为了准确确定RQ，需要该信息，因为除了呼吸消耗的O2之外，硝化还消耗O2。最后一步将是连续和原位测量CO2，O2和NH3浓度在自然土壤中使用市售的流通传感器耦合到定制的自动进样器。土壤湿度、土壤温度和相关气象变量的同时测量将伴随土壤气体监测。扩展的土壤物理模型和实验室土芯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。将调查草原和森林土壤中土壤群落RQ随时间和空间的变化。提高对土壤RQ自然变异性的认识将促进1）对土壤生物过程的理解，如土壤代谢如何在时间和空间上变化，以及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那些，该奖项反映了NSF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进行评估，被认为值得支持审查标准。

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.