Researchers find freeze–thaw processes have various effects on the Rs dynamics in different freeze–thaw stages

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  • Published: 2020-09-18
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Freezing and thawing action of the active layer plays a significant role in soil respiration (Rs) in permafrost regions. However, little is known about how the freeze–thaw processes affect the Rs dynamics in different stages of the alpine meadow underlain by permafrost in the Qinghai–Tibet Plateau (QTP).

Researchers in State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources of Chinese Academy of Sciences conducted continuous in situ measurements of Rs and freeze–thaw processes of the active layer at an alpine meadow site in the Beiluhe permafrost region of the QTP and divided the freeze–thaw processes into four different stages in a complete freeze–thaw cycle, comprising the summer thawing (ST) stage, autumn freezing (AF) stage, winter cooling (WC) stage, and spring warming (SW) stage. Researchers found that the freeze–thaw processes have various effects on the Rs dynamics in different freeze–thaw stages. The mean Rs ranged from 0.12 to 3.18µmolm2s1 across the stages, with the lowest value in WC and highest value in ST. Q10 among the different freeze–thaw stages changed greatly, with the maximum (4.91±0.35) in WC and minimum (0.33±0.21) in AF. Patterns of Rs among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative Rs to total Rs of a complete freeze–thaw cycle (1692.98±51.43gCO2m2) were 61.32±0.32%, 8.89±0.18%, 18.43±0.11%, and 11.29±0.11%, respectively. Soil temperature (Ts) was the most important driver of Rs regardless of soil water status in all stages. Our results suggest that as climate change and permafrost degradation continue, great changes in freeze–thaw process patterns may trigger more Rs emissions from this ecosystem because of a prolonged ST stage.

The study was published in The Cryosphere. Associate researcher WANG Junfeng is the first author; Prof. WU Qingbai is the corresponding author, who is also a doctoral supervisor at University of Chinese Academy of Sciences.