SGER: An Experimental System to Study Belowground C Fluxes in Soils

陆地生态系统地下碳库和碳通量是全球变化研究的热点。 在全球范围内，土壤是一个重要的碳库，其碳含量超过大气。 这项建议侧重于两个关键过程，涉及地下碳，仍然相对知之甚少，即土壤呼吸和无机碳转化。 在很大程度上，这些过程的不确定性源于无法将生物过程（根和微生物呼吸）与非生物过程（气体运输和CaCO3转化）分开，以及难以原位测量根呼吸速率。 这些不确定性将通过建立模拟地下呼吸的人工根系来解决。 在拟议的项目中，将检验两个假设：1）降水事件后土壤呼吸的短期增加主要受地表微生物过程的调节，因为土壤扩散率、气体置换和根系呼吸速率的变化太慢，无法解释田间观察到的快速反应，2）CaCO3的沉淀和溶解直接取决于地下生物活性，因此主要发生在根表面周围。 该提案的核心是一种新型的人工根系系统，该系统将使用连接到CO2供应的穿孔管来构建。 通过调整CO2的流速，根系呼吸速率将被固定，并且已知该SGER奖的更广泛影响包括开发一种新方法，以更好地了解地下过程的机械学，该方法可应用于与陆地生态学相关的广泛问题。 这项研究补充了沙漠研究所正在进行的研究，并将提高其研究能力。 该实验系统可以作为一个重要的工具，教学生在异质环境中的气体传输的基础知识，并帮助学生了解生物和物理过程之间的相互作用。 将支持一名研究生从事该项目。

Belowground carbon pools and fluxes in terrestrial ecosystems have received much attention in global change research. Globally, soils are a significant carbon pool containing more carbon than the atmosphere. This proposal focuses on two key processes involving belowground carbon that are still relatively poorly understood, viz. soil respiration and inorganic carbon transformations. Uncertainties with regard to these processes originate, in large measure, from the inability to separate biotic processes (root and microbial respiration) from abiotic processes (gas transport and CaCO3 transformations) and difficulties in measuring root respiration rates in situ. These uncertainties will be addressed by building an artificial root system simulating belowground respiration. In the proposed project two hypotheses will be tested: 1) short-term increases in soil respiration after precipitation events are predominantly regulated by surface microbial processes because changes in soil diffusivity, gas displacement and root respiration rates are too slow to account for rapid responses as observed in the field, and 2) CaCO3 precipitation and dissolution are directly dependent on belowground biological activity and will therefore predominantly occur around root surfaces. The heart of this proposal is a novel artificial root system, which will be constructed using perforated tubing connected to a CO2 supply. By adjusting the flow rate of CO2, the root respiration rates will be fixed and known Broader impacts of this SGER award include the development of a novel approach to obtain a better mechanistic understanding of belowground processes that can be applied to a wide range of questions relevant to terrestrial ecology. The study complements ongoing research at the Desert Research Institute and will enhance its research capabilities. The experimental system can act as an important tool for teaching students fundamentals of gas transport in heterogeneous environments and help students understand the interaction between biological and physical processes. One graduate student will be supported to work on this project.