淡水恢复工程对黄河三角洲湿地土壤碳排放的影响机制

Carbon emissions in coastal wetlands affected by anthropogenic activities are a global research project. However, the changes of soil CO2 and CH4 after wetlands degradation or restoration measures still need further investigations. Typical tidal salt marshes, degraded salt marshes, restored wetlands with freshwater inputs and degraded wetlands without freshwater inputs are chosen as sampling sites to investigate the influences of sulfate reduction on soil CO2 and CH4 emissions. Simultaneously, the spatial and seasonal characteristics of soil CO2 and CH4 emissions after wetlands degradation and freshwater inputs, and the controlling effect of sulfate concentrations on carbon emissions would be revealed in this project. With the application of 35S isotope tracer technique, the seasonal variations of sulfate reduction rates and their contributions to anaerobic metabolism and carbon emission would be clarified. Furthermore, the incubation experiments would explore the role of sulfate reduction played in aerobic and anaerobic mineralization of soil organic carbon and the response mechanism of carbon emissions to the inputs of sulfate. The results provide deep insights to the influencing mechanism of wetland degradation and freshwater inputs on carbon emissions and guidelines for restoration of degraded wetlands, which are theoretically and practically meaningful to the protection of coastal wetlands ecosystems.

气候变化背景下湿地土壤碳排放研究是全球重点研究课题，但是目前关于淡水恢复工程对湿地土壤CO2和CH4排放影响的研究还比较少。本项目以黄河三角洲淡水恢复湿地、退化湿地和天然芦苇盐沼为研究样地，探究淡水恢复工程对湿地土壤碳排放的影响，揭示三种湿地土壤碳排放的季节变化特征。通过硫35同位素示踪技术等，阐明淡水恢复对硫酸盐还原速率、铁离子还原速率和产甲烷潜力的影响特征，探究三种厌氧代谢途径对厌氧碳代谢和土壤碳排放的影响。通过室内模拟实验，阐释湿地土壤碳排放响应淡水输入的微生物机制。研究结果有利于深入理解淡水恢复对湿地碳排放的影响，可以为受损湿地修复提供指导，对于保护滨海湿地生态系统具有重要的理论和实践意义。

淡水恢复是一种重要的退化湿地修复方式，其对湿地生态系统的影响受到广泛关注。在全球气候变化和湿地退化的背景下，研究淡水恢复工程对湿地土壤碳排放的影响对于湿地修复策略的选择以及实现碳中和、碳达峰的目标具有重要意义。但现有研究较少关注淡水恢复工程对湿地土壤碳排放的影响机制。本研究选择淡水恢复芦苇湿地、潮汐芦苇湿地、非淹水芦苇湿地和盐地碱蓬湿地为研究样地，采集了气体样品、土壤样品和植物样品，并开展了室内模拟实验。本研究探究了淡水输入对湿地土壤CO2和CH4排放速率的影响，发现淡水输入在一定程度上提高了CH4的排放，对CO2排放的影响相对弱一些。本研究揭示了淡水输入对三种厌氧碳矿化途径的影响，发现淡水输入提高了土壤产甲烷潜力，但对硫酸盐还原和铁离子还原过程影响不明显。本研究通过模拟实验发现，淡水输入后，盐地碱蓬湿地土壤CO2排放速率低于非淹水芦苇湿地和潮汐芦苇湿地。但淡水输入后，潮汐芦苇湿地土壤CH4排放速率高于非淹水芦苇湿地和盐地碱蓬湿地。通过宏基因组测序技术发现淡水输入明显改变了土壤微生物群落，降低了非淹水芦苇湿地土壤基因数目但提高了潮汐芦苇湿地和盐地碱蓬湿地土壤基因的数目，对土壤酶活和代谢功能也具有一定影响。同时，本研究发现，淡水输入提高了芦苇的生物量和土壤含水率，改变了土壤盐分和质地。淡水输入对土壤真菌、细菌和古菌群落的多样性和丰度具有不同影响，改变了三种微生物群落的群落组成。相关成果对于深入了解淡水恢复对滨海湿地的生态影响提供有效依据，对于深入了解湿地储碳功能及碳排放的动态变化提供进一步的理论支撑，可以为退化湿地修复策略选择提供指导，也将为实现碳中和和碳达峰也提供理论基础。