Wind as a Driver of Peat CO₂ Dynamics in a Northern Bog

Excess CO₂ accumulated in soils is typically transported to the atmosphere through molecular diffusion along a concentration gradient. Because of the slow and constant nature of this process, a steady state between peat CO₂ production and emissions is often established. However, in peatland ecosystems, high peat porosity could foster additional non-diffusive transport processes, whose dynamics may become important to peat CO₂ storage, transport and emission. Based on a continuous record of in situ peat pore CO₂ concentration within the unsaturated zone of a raised bog in southern Canada, we show that changes in wind speed create large diel fluctuations in peat pore CO₂ store. Peat CO₂ builds up overnight and is regularly flushed out the following morning. Persistently high wind speed during the day maintains the peat CO₂ with concentrations close to that of the ambient air. At night, wind speed decreases and CO₂ production overtakes the transport rate leading to the accumulation of CO₂ in the peat. Our results indicate that the effective diffusion coefficient fluctuates based on wind speed and generally exceeds the estimated molecular diffusion coefficient. The balance between peat CO₂ accumulation and transport is most dynamic within the range of 0-2 m s^-1 wind speeds, which occurs over 75% of the growing season and dominates night-time measurements. Wind therefore drives considerable temporal dynamics in peat CO₂ transport and storage, particularly over sub-daily timescales, such that peat CO₂ emissions can only be directly related to biological production over longer timescales.

The online version contains supplementary material available at 10.1007/s10021-024-00904-1.