干湿交替对若尔盖泥炭湿地关键碳过程的影响

The effect of extreme climate change on the key process of carbon sequestration is not clear although peatland is an important carbon pool in the world. The carbon dynamic of Zoigê alpine peatland with drying-wetting cycles due to extreme climate change is studied. By using stable carbon isotope labeling and tracing in situ and in incubation experiment, we aim to explore the effect of drying-wetting cycles on carbon dynamic of the plant - soil (water) - litter system, to reveal the mechanism of drying-wetting cycles on key carbon process, to confirm the effect of drying-wetting cycles on carbon emissions and carbon sink, to clarify the priming effect and its mechanism of litter and drying-wetting cycles on carbon emissions, to evaluate the carbon balance of Zoigê peatland with different intensities of drying-wetting cycles. This study will help us understand the dynamic of carbon sequestration and emission in alpine peatland with global climate change. The results will provide the basis for the perfection and development of wetlands ecosystem carbon model in theory,and provide the foundation for the negotiation of climate change and wetlands protection in practice.

作为全球重要的碳储存库，泥炭湿地对极端气候变化的响应及其机理尚不清楚。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，基于野外原位模拟和室内培养实验，采用稳定性碳同位素标记和示踪技术，探讨极端气候变化引起的干湿交替循环对泥炭湿地植物-土壤（水）-枯落物系统碳库动态的影响；揭示湿地生态系统关键碳过程对干湿交替的响应机制；阐明干湿交替对泥炭湿地碳排放及碳源汇功能的影响；揭示干湿交替及枯落物对泥炭土碳排放的激发效应及其机制；量化评估不同干湿交替强度下若尔盖泥炭湿地碳平衡动态。研究结果将有助于深入认识气候变化下高寒泥炭湿地碳固持与碳排放动态，理论上可为湿地生态系统碳循环模型的完善和发展提供依据，实践上可为湿地保护与管理纳入气候变化谈判提供基础支持。

降水模式变化对高寒湿地生态系统关键碳过程的影响及其机理尚不清楚。本项目以若尔盖高寒湿地为研究对象，基于野外连续四年原位模拟实验、室内多次培养实验，应用稳定性碳同位素标记和示踪技术，系统研究了降水模式变化引起的土壤干湿交替循环对高寒湿地植物生长、枯落物分解、CO2和CH4排放、有机质分解的激发效应等关键碳过程，估算了降水量和降水频率变化对土壤碳平衡的影响。结果表明，自然降水量下降低降水频率（延长降水间隔）显著降低了若尔盖湿地植物群落的物种丰富度，增加了群落生物量，增加了土壤有机碳和可溶性有机碳的含量，增加了表层土壤的硝态氮含量而降低了氨态氮含量。降水量和降水频率变化对深层土壤团聚体稳定性的影响更大。实验期间，高寒湿地生态系统温室气体排放的年际间波动较大，整体上表现为碳汇。枯落物添加均对土壤有机质分解产生了正激发效应，降低降水频率减少了CO2激发效应，而水量和频率对CH4激发效应没有显著影响。总体上，降水模式变化尤其是降水间隔延长对高寒湿地碳过程影响较大。本项目研究结果有助于深入认识降水模式变化下高寒湿地碳固持与碳排放动态，为高寒湿地生态系统保护与管理提供了参考价值。