Soil moisture as a key factor in carbon release from thawing permafrost in boreal forest

In this study, by quantifying the CO2, CH4 releases and the soil properties of moisture, SOC quantity and quality and microbial activities in a 239-day incubation experiment where the soil moisture was experimentally modified to simulate natural, drier and flooded condition, we tested the hypotheses 1) the C vulnerability in permafrost deposits would be higher than that in active layer soils; 2) C releases under aerobic conditions and their climate forcing would be greater than anaerobic condition, but aerobic C release would be constrained by drier condition; and 3) soil moisture would be the strongest factor influencing C release under aerobic condition, whereas anaerobic C release would be mostly related to microbial activities.本研究开展了一项为期239天的室内土壤培养实验，通过定量测定CO₂、CH₄的碳释放量，以及土壤湿度、土壤有机碳（Soil Organic Carbon, SOC）的数量与质量、微生物活性等参数，并在实验中通过人工调控土壤湿度以模拟自然、干旱及淹水三种环境条件，进而验证了三项假说：1）多年冻土沉积物中的碳脆弱性高于活动层土壤；2）有氧条件下的碳释放量及其气候强迫效应均强于厌氧条件，但干旱环境会抑制有氧碳排放；3）有氧条件下土壤湿度是影响碳释放的最关键因素，而厌氧碳排放则主要与微生物活性相关。