Droughts are recognized to impact global biogeochemical cycles. However, the implication of desiccation on in-stream carbon (C) cycling is not well understood yet. We subjected sediments from a lowland, organic rich intermittent stream to experimental desiccation over a 9-week-period to investigate temporal changes in microbial functional traits in relation to their redox requirements, carbon dioxide (CO₂) and methane (CH₄) fluxes and water-soluble organic carbon (WSOC). Concurrently, the implications of rewetting by simulated short rainfalls (4 and 21 mm) on gaseous C fluxes were tested. Early desiccation triggered dynamic fluxes of CO₂ and CH₄ with peak values of 383 and 30 mg C m⁻² h⁻¹ (mean ± SD), respectively, likely in response to enhanced aerobic mineralization and accelerated evasion. At longer desiccation, CH₄ dropped abruptly, likely because of reduced abundance of anaerobic microbial traits. The CO₂ fluxes ceased later, suggesting aerobic activity was constrained only by extended desiccation over time. We found that rainfall boosted fluxes of CO₂, which were modulated by rainfall size and the preceding desiccation time. Desiccation also reduced the amount of WSOC and the proportion of labile compounds leaching from sediment. It remains questionable to which extent changes of the sediment C pool are influenced by respiration processes, microbial C uptake and cell lysis due to drying-rewetting cycles. We highlight that the severity of the dry period, which is controlled by its duration and the presence of precipitation events, needs detailed consideration to estimate the impact of intermittent flow on global riverine C fluxes.

干旱被认为会影响全球生物地球化学循环。然而，干燥对流中碳（C）循环的影响尚不清楚。我们对来自低地、富含有机质的间歇性溪流的沉积物进行了为期 9 周的实验干燥，以研究微生物功能特征的时间变化与其氧化还原需求、二氧化碳 (CO ₂ ) 和甲烷 (CH ₄ ) 通量和水溶性有机碳 (WSOC)。同时，测试了模拟短时间降雨（4 和 21 毫米）的再润湿对气态 C ​​通量的影响。早期干燥触发 CO ₂和 CH _{4 的}动态通量，峰值分别为 383 和 30 mg C m ^-2  h ^-1（平均值±标准差），分别可能是对有氧矿化增强和加速逃避的反应。在更长的干燥时间，CH ₄突然下降，可能是因为厌氧微生物特征的丰度减少。CO ₂通量稍后停止，表明有氧活动仅受随时间延长干燥的限制。我们发现降雨增加了 CO _{2 的}通量，受降雨量大小和先前的干燥时间调节。干燥还减少了 WSOC 的数量和从沉积物中浸出的不稳定化合物的比例。由于干燥-再润湿循环，呼吸过程、微生物 C 吸收和细胞裂解对沉积物 C 库的变化影响到何种程度仍然存在疑问。我们强调，干旱期的严重程度受其持续时间和降水事件的存在控制，需要详细考虑以估计间歇性流量对全球河流 C 通量的影响。