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

Large quantities of organic matter are stored in frozen soils (permafrost) within the Qinghai–Tibetan Plateau (QTP). The most QTP regions particular have experienced significant warming and wetting over past 50 years, this trend is projected to intensify future. Such climate change will likely alter soil freeze–thaw pattern permafrost active layer toward greenhouse gas nitrous oxide (N 2 O) release. However, interaction effect altered moisture on N O emission during freezing thawing unclear. Here, we used simulation experiments test how changes flux relate different temperatures (T 5 –5°C, T 10 –10°C, 20 –20°C) volumetric water contents (VWCs, W 15 –15%, 30 –30%, 45 –45%) under 165 F–T cycles topsoil (0–20 cm) an alpine meadow with discontinuous QTP. First, contrast prevailing view, but not temperature dominated large pulses events. maximum emissions, 1,123.16–5,849.54 ?g m –2 h –1 , appeared range VWC from 17% 38%. mean fluxes had no difference between when was dry or waterlogged. Second, medium moisture, low more able promote than high temperature. For example, peak value (5,849.54 ) cumulative emissions (366.6 mg treatment were five times two four higher respectively. Third, long-term cycles, patterns related moisture. treatments; contrary, treatments slowly increased until 80 cycles. Finally, could improve nitrogen availability, prolong release time, increase layer. Particularly, concentrated first 27 48 Overall, our study highlighted that events tend occur at lower temperature; number may enhance mineralization