Abstract. 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). We 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. We 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 3.18 µmol m−2 s−1 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±51.43 g CO2 m−2) 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.
Freeze-thaw processes of active layer regulate soil respiration of alpine meadow in the permafrost region of the Qinghai-Tibet Plateau