ORE-CZ: Ecohydrological Controls on Soil Respiration and the Apparent Respiratory Quotient Across a Dynamic Storage Gradient

土壤中的碳含量超过植被和大气的总和，土壤呼吸描述了土壤碳通过植物根和微生物转移到大气中的过程。随着气温的升高和水分利用率的变化，土壤呼吸通量的变化对温室效应和未来变暖的幅度具有重要的潜在反馈作用。因此，该项目将利用由美国国家科学基金会资助的动态水临界区(CZ)专题组提供的土壤二氧化碳(CO2)和氧气数据来量化土壤呼吸的变异性和土壤产生的二氧化碳的去向，这些变化与土壤发育、植被和地形的变化有关，这些变化调节了典型的半干旱山地海拔和气候梯度的水可利用性。这项研究将支持加州州立大学CHICO的研究生和本科生的职业培训和学习经验，该大学是联邦指定的拉美裔服务机构(HSI)，主要是本科生，超过50%的学生是第一代大学生。“基岩到树顶”的CZ方法考虑了土壤、水、景观位置和地球表面生物之间的反馈。动态储水--具有中间停留时间的水--在降水事件之间维持CZ功能，对土壤呼吸和碳循环至关重要。因此，这项研究的主要目的是量化动态蓄水对土壤呼吸和表观呼吸商(ARQ)积分CZ函数的重要性，表观呼吸商(ARQ)决定了土壤产生的二氧化碳直接呼吸到大气中的程度，而土壤产生的二氧化碳通过入渗水横向或垂直输送到大气中。研究人员将具体检验以下假设：(1)土壤呼吸和ARQ将与根区动态储水量成正比，(2)动态储水量将与复杂地形相互作用，以确定土壤呼吸和ARQ在空间和时间上的变异性。由于研究活动将在多个流域重复和整合，因此将能够评估基于过程的信息的可转移性，从而更全面地了解CZ碳循环，这对半干旱山地生态系统的气候变化缓解潜力具有直接影响。该项目得到了HSI计划的共同资助，该计划旨在加强本科生STEM教育，扩大对STEM的参与，并建设HSIS的能力。考虑到HSIS的不同性质和背景，实现这些目标需要创新的方法来激励机构和社区的变革，并促进基础研究(I)关于参与式学生学习，(Ii)关于如何有效地多样化和增加对STEM的参与，以及(Iii)提高我们对如何在HSIS建设机构能力的理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Soils contain more carbon than vegetation and the atmosphere combined, and soil respiration describes the transfer of soil carbon to the atmosphere via plant roots and microbes. As air temperatures rise and water availability changes, changes in the soil respiration flux represent significant potential feedback to the greenhouse effect and the magnitude of future warming. Accordingly, this project will take advantage of soil carbon dioxide (CO2) and oxygen data provided by the NSF-funded Dynamic Water Critical Zone (CZ) Thematic Cluster to quantify the variability of soil respiration and the fate of soil-produced CO2 with respect to changes in soil development, vegetation, and topography that mediate water availability across representative semi-arid montane elevation and climatic gradients. The research will support career training and learning experiences for graduate and undergraduate students at California State University, Chico, which is a federally designated Hispanic-Serving Institution (HSI), a Primarily Undergraduate Institution, and where more than 50% of the student population are first generation college students. A “bedrock to treetop” CZ approach considers feedbacks between soil, water, landscape position, and living organisms at Earth’s surface. Dynamic water storage - water with intermediate residence times - sustains CZ function between precipitation events, and is critically important to soil respiration and carbon cycling. As a result, the main objective of this research is to quantify the importance of dynamic water storage to the integral CZ functions of soil respiration and the Apparent Respiratory Quotient (ARQ) that determines the degree to which soil-produced CO2 is respired directly to the atmosphere versus transported laterally or vertically with infiltrating water. The investigators will specifically test the hypotheses that (1) soil respiration and the ARQ will be proportional to the volume of dynamic water storage in the root zone, and (2) that dynamic water storage capacity will interact with complex terrain to determine the variability of soil respiration and ARQ over space and time. Because research activities will be replicated and integrated across multiple watersheds, they will allow for evaluation of the transferability of process-based information, toward a more comprehensive understanding of CZ carbon cycling with direct implications for the climate change mitigation potential of semi-arid montane ecosystems. This project was supported with co-funding of the HSI Program which aims to enhance undergraduate STEM education, broaden participation in STEM, and build capacity at HSIs. Achieving these aims, given the diverse nature and context of the HSIs, requires innovative approaches that incentivize institutional and community transformation and promote fundamental research (i) on engaged student learning, (ii) about what it takes to diversify and increase participation in STEM effectively, and (iii) that improves our understanding of how to build institutional capacity at HSIs.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.