Soil Moisture but Not Warming Dominates Nitrous Oxide Emissions During Freeze–Thaw Cycles in a Qinghai–Tibetan Plateau Alpine Meadow With Discontinuous Permafrost

作者：Zhe Chen, Shidong Ge, Zhenhua Zhang, Yangong Du, Buqing Yao, Huichun Xie, Pan Liu, Yufang Zhang, Wenying Wang, Huakun Zhou · 发表于：Frontiers in Ecology and Evolution · 年份：2021 · DOI：10.3389/fevo.2021.676027 · 被引用次数：23 · 研究领域：Climate change and permafrost、Cryospheric studies and observations、Peatlands and Wetlands Ecology

Large quantities of organic matter are stored in frozen soils (permafrost) within the Qinghai–Tibetan Plateau (QTP). The most of QTP regions in particular have experienced significant warming and wetting over the past 50 years, and this warming trend is projected to intensify in the future. Such climate change will likely alter the soil freeze–thaw pattern in permafrost active layer and toward significant greenhouse gas nitrous oxide (N 2 O) release. However, the interaction effect of warming and altered soil moisture on N 2 O emission during freezing and thawing is unclear. Here, we used simulation experiments to test how changes in N 2 O flux relate to different thawing temperatures (T 5 –5°C, T 10 –10°C, and T 20 –20°C) and soil volumetric water contents (VWCs, W 15 –15%, W 30 –30%, and W 45 –45%) under 165 F–T cycles in topsoil (0–20 cm) of an alpine meadow with discontinuous permafrost in the QTP. First, in contrast to the prevailing view, soil moisture but not thawing temperature dominated the large N 2 O pulses during F–T events. The maximum emissions, 1,123.16–5,849.54 μg m –2 h –1 , appeared in the range of soil VWC from 17% to 38%. However, the mean N 2 O fluxes had no significant difference between different thawing temperatures when soil was dry or waterlogged. Second, in medium soil moisture, low thawing temperature is more able to promote soil N 2 O emission than high temperature. For example, the peak value (5,849.54 μg m –2 h –1 ) and cumulative emissions (366...