Water table and vegetation shape peatland CO2 and CH4 fluxes with water table modulating temperature sensitivity

Peatland rewetting can reduce CO 2 loss but increase CH 4 emissions. How vegetation shapes this trade‐off and how the water table modifies temperature sensitivity remain unclear. We analysed 14,643 observations from 285 peatland sites. CH 4 emissions increased more steeply with rising water‐table level (WTL) under graminoid dominance, while the pattern of declining ecosystem respiration differed between vegetation classes. Combined CO 2 ‐equivalent emissions (GHGE; respiration + CH 4 at GWP 100 = 28) declined by 73.9% as WTL rose from 60 cm below to 15 cm above the peat surface and were still declining at the wet end of the analysed range. The decline persisted under GWP 20 , although the magnitude of the decline above the peat surface depended strongly on the CH 4 weighting. The within‐site analysis further showed that apparent CH 4 temperature sensitivity (Q 10 ) increased by 14.9% per 10 cm rise in WTL (95% CI 6.9%–23.5%), whereas respiration Q 10 showed no detectable WTL dependence. A supplementary comparison within non‐graminoid‐dominated bogs showed that fitted CH 4 Q 10 increased with WTL where graminoids were present and decreased where graminoids were absent or negligible. Under +3°C warming, fixing CH 4 Q 10 at its value at WTL = −10 cm gave a predicted warming multiplier that was 24.7% larger at WTL = −63 cm and 11.8% smaller at +20 cm than the WTL‐dependent formulation. These results suggest that assessments of peatland rewetting under warming should consider both vegetation differences in emission responses and the WTL dependence of CH 4 temperature sensitivity.