湿地土壤有机碳与铁的交互作用及其对干旱的响应

As an important carbon sink globally, wetlands are vulnerable to drought induced by climate change and human activities. However, the response of wetland soil organic carbon (SOC) to drought and its underlying mechanisms are highly uncertain. Interactions between SOC and iron play an important role in governing the fate of SOC during wetland drought, but studies of their interaction mechanisms are constrained by the lack of sensitive analytical methods. This project proposes to employ highly sensitive and complementary techniques at the molecular level and aims to explore three key research questions: How does iron regulate the distribution and molecular composition of SOC in natural wetlands experiencing drought? Does iron oxidation contribute to the preservation of SOC (in particular, lignin)? How does iron transformation mediate the response of wetland SOC to drought? To address these questions, we propose to use biomarkers, nuclear magnetic resonance (NMR), and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) to examine the composition and origin of iron-protected SOC in natural wetlands witnessing various degrees of drought. We also propose to utilize water-table decline experiments in the field and redox incubation experiments in the laboratory. With in-tandem measurements of soil iron, enzyme activities, iron reduction/oxidation rates and genome sequencing, this project seeks to characterize chemical, microbial, redox and sorptive properties of typical wetland soils, to investigate the dynamics and coupling of wetland SOC components and iron during simulated soil redox changes, and to further elucidate the mechanisms of SOC-enzymes-iron interactions during wetland drought. Results from this project will provide molecular evidence on SOC-iron interactions and shed novel insights on the processes controlling SOC responses to drought in wetlands.

干旱正严重威胁着湿地的碳汇功能；而其土壤有机碳（SOC）对干旱的响应及机制极不明确。SOC与铁的交互作用直接影响湿地碳库对干旱的响应；但因缺乏灵敏的分析方法，其作用机制的研究尚不深入。本项目拟利用灵敏而互补的分子地球化学方法，回答三个科学问题：湿地铁氧化物与SOC的分子组成有何耦合关系？铁的氧化是否影响土壤碳（特别是木质素）的保存？铁转化如何调控湿地SOC对干旱的响应？针对这些问题，本研究拟利用生物标志物、核磁共振、傅立叶变换-离子回旋共振质谱、高通量测序等现代分析技术，揭示典型湿地干旱序列中被铁保护的SOC的分子组成及来源；利用野外水位控制及室内吸附/培养实验，结合微生物类群、酶活、铁的氧化/还原速率的测定，阐明SOC关键组分与铁转化的动态关系，厘清“SOC−酶−铁”在湿地干旱过程中的交互机理。结果有望为碳−铁耦合机制提供分子水平的解释，并为阐明湿地SOC对干旱的响应提供新颖的理论基础。