Wind as a Driver of Peat CO Dynamics in a Northern Bog.

UNLABELLED

Excess CO 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 CO 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 CO storage, transport and emission. Based on a continuous record of in situ peat pore CO 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 CO store. Peat CO builds up overnight and is regularly flushed out the following morning. Persistently high wind speed during the day maintains the peat CO with concentrations close to that of the ambient air. At night, wind speed decreases and CO production overtakes the transport rate leading to the accumulation of CO 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 CO accumulation and transport is most dynamic within the range of 0-2 m s wind speeds, which occurs over 75% of the growing season and dominates night-time measurements. Wind therefore drives considerable temporal dynamics in peat CO transport and storage, particularly over sub-daily timescales, such that peat CO emissions can only be directly related to biological production over longer timescales.

SUPPLEMENTARY INFORMATION

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