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

土壤所含的碳比植被和大气的总和还要多，土壤呼吸描述了土壤碳通过植物根系和微生物转移到大气中。随着气温的升高和水资源的变化，土壤呼吸通量的变化代表着对温室效应和未来变暖幅度的重要潜在反馈。因此，该项目将利用NSF资助的动态水临界区（CZ）专题集群提供的土壤二氧化碳（CO2）和氧气数据，以量化土壤呼吸的变化和土壤产生的CO2的命运，土壤发育，植被和地形的变化，介导了代表性的半干旱山地海拔和气候梯度的水供应。这项研究将支持职业培训和学习经验的研究生和本科生在加州州立大学，奇科，这是一个联邦指定的西班牙裔服务机构（HSI），一个私立本科院校，其中超过50%的学生人口是第一代大学生。一个“从基岩到树梢”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。动态水储存-中间停留时间的水-维持降水事件之间的CZ功能，对土壤呼吸和碳循环至关重要。因此，本研究的主要目的是量化的重要性，动态水存储的积分CZ功能的土壤呼吸和表观呼吸商（ARQ），决定在何种程度上土壤产生的CO2直接呼吸到大气中与横向或垂直运输的渗透水。研究人员将专门测试以下假设：（1）土壤呼吸和ARQ将与根区动态水储存量成比例，（2）动态水储存量将与复杂地形相互作用，以确定土壤呼吸和ARQ随空间和时间的变化。由于研究活动将在多个流域复制和集成，它们将允许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，直接影响半干旱山地生态系统的气候变化缓解潜力。该项目得到了HSI计划的共同资助，该计划旨在加强本科STEM教育，扩大STEM的参与，并建立HSI的能力。实现这些目标，鉴于HSIs的多样性和背景，需要创新的方法，激励机构和社区转型，促进基础研究（i）参与学生学习，（ii）关于如何有效地使STEM多样化和增加参与，以及（iii）该奖项反映了NSF的法定使命，并被认为值得支持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。

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.