Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in the permafrost region of the Qinghai–Tibet Plateau

• Published in: The Cryosphere
• Main Authors: Wang, Junfeng, Wu, Qingbai, Yuan, Ziqiang, Kang, Hojeong
• Format: Text
• Language: English
• Published: 2020
• Subjects: permafrost
• Online Access: https://doi.org/10.5194/tc-14-2835-2020; https://tc.copernicus.org/articles/14/2835/2020/

Freezing and thawing action of the active layer plays a significant role in soil respiration ( R s ) in permafrost regions. However, little is known about how the freeze–thaw processes affect the R s dynamics in different stages of the alpine meadow underlain by permafrost in the Qinghai–Tibet Plateau (QTP). We conducted continuous in situ measurements of R s 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. We found that the freeze–thaw processes have various effects on the R s dynamics in different freeze–thaw stages. The mean R s ranged from 0.12 to 3.18 µ mol m −2 s −1 across the stages, with the lowest value in WC and highest value in ST. Q 10 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 R s among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative R s to total R s of a complete freeze–thaw cycle ( 1692.98±51.43 g CO 2 m −2 ) were 61.32±0.32 %, 8.89±0.18 %, 18.43±0.11 %, and 11.29±0.11 %, respectively. Soil temperature ( T s ) was the most important driver of R s 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 R s emissions from this ecosystem because of a prolonged ST stage.