干湿交替下水氮耦合对若尔盖高寒湿地土壤碳库稳定性的影响

The effect of climate change on the stability of carbon pool is not clear although peatland is an important carbon pool in the world. The stability of carbon pool of Zoigê alpine peatland with water and nitrogen coupling with drying-rewetting cycles due to extreme climate change is studied. By using stable carbon isotope labeling and tracing and solid-state nuclear magnetic resonance spectroscopy technique in situ and in incubation experiment, we aim to explore the effect of drying-wetting cycles and nitrogen deposition on carbon dynamic of the plant - soil system, to confirm the effect of drying-wetting cycles and nitrogen deposition on carbon sequestration potentiality, to clarify the priming effect and its mechanism of drying-wetting cycles and nitrogen deposition on carbon emissions, to evaluate the stability of soil carbon pool with water and nitrogen coupling according to the physical protection and chemical structures of soil carbon. This study will help us understand the dynamic of carbon sequestration and stability in alpine peatland with global climate change. The results will provide the basis for the perfection and development of alpine wetlands ecosystem carbon model in theory, and provide the foundation for the assessment and trade of carbon sink with climate change and wetlands protection in practice.

作为全球重要的碳储存库，泥炭湿地及其与气候变化的关系一直是碳循环研究的难点和前沿领域。降水和氮沉降变化显著改变泥炭湿地碳过程，但是水氮耦合对高寒泥炭湿地土壤碳库稳定性的作用及其机理尚不清楚。本项目瞄准此国际前沿热点，以若尔盖高寒泥炭湿地为研究对象，采用稳定性碳氮同位素标记示踪和固态核磁共振波谱技术，基于野外原位实验和室内培养实验，阐明若尔盖高寒湿地植物-土壤系统碳动态对水氮耦合的响应；阐明水氮耦合对高寒湿地土壤碳固持潜力的影响；揭示水氮耦合对泥炭土碳排放的激发效应并探讨其机制；采用土壤碳的物理保护和化学结构等多指标量化评估水氮耦合对泥炭湿地土壤碳库稳定性的影响。研究结果将有助于深入认识气候变化下高寒泥炭湿地土壤碳固持与碳库稳定性，理论上可为高寒湿地生态系统碳循环模型的完善和发展提供依据，实践上可为气候变化下高寒湿地保护与管理以及湿地碳汇扩增和评估交易提供支持。

作为全球重要的碳储存库，高寒湿地碳库及其稳定性对气候变化的响应及其机理尚不清楚。本项目依托若尔盖高寒湿地，基于连续4年的野外原位模拟实验和室内培养实验，采用稳定性碳同位素标记示踪技术，系统分析了降水/水位变化与氮沉降对高寒湿地植物生长、土壤碳组分、CO2和CH4排放、光合碳分配和有机质的激发效应等关键碳过程的影响，综合评估了降水变化和水位变化与氮沉降对土壤碳稳定性的影响。结果表明，自然降水量下，降低降水频率减少了群落物种丰富度，但对群落生物量的影响依赖于施氮量，土壤有机碳和可溶性有机碳含量有所增加，而土壤CO2和CH4排放变化较为复杂。水位波动降低了木里苔草生物量的积累，也降低了系统净碳吸收，但负激发效应（实验期内）增强，即抑制了CO2和CH4的激发效应，有利于原有土壤有机碳库的保护。土壤团聚体稳定性分析也证实了这一点。氮沉降则有利于木里苔草生物量积累和净碳吸收。水位波动可通过提高团聚体物理保护作用以及稳定性化学结构碳的比例，增强碳稳定性，但会受到外源碳输入和氮沉降的调控。降水变化和水位波动与氮沉降均对高寒湿地碳吸收和碳排放具有显著影响，但对土壤矿物结合碳和铁结合碳没有显著影响。本项目研究结果有助于深入认识水氮耦合对高寒湿地土壤有机碳稳定性的影响及其物理化学机制，为高寒湿地的管理和保护提供了科学参考。