Campeau A, He H, Riml J, Humphreys E, Dalva M, Roulet N
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
Department of Geography, McGill University, Montreal, Canada.
Ecosystems. 2024;27(5):621-635. doi: 10.1007/s10021-024-00904-1. Epub 2024 May 23.
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.
The online version contains supplementary material available at 10.1007/s10021-024-00904-1.
土壤中积累的过量二氧化碳通常通过沿浓度梯度的分子扩散输送到大气中。由于这个过程缓慢且持续，泥炭地二氧化碳产生与排放之间常常会建立一个稳定状态。然而，在泥炭地生态系统中，高泥炭孔隙度可能会促进额外的非扩散传输过程，其动态变化可能对泥炭地二氧化碳的储存、传输和排放具有重要意义。基于对加拿大南部一个高位沼泽非饱和带内原位泥炭孔隙二氧化碳浓度的连续记录，我们发现风速变化会导致泥炭孔隙二氧化碳储量出现大幅的昼夜波动。泥炭地中的二氧化碳在夜间积累，并在次日清晨被定期排出。白天持续的高风速使泥炭地中的二氧化碳浓度维持在接近周围空气的水平。夜间，风速降低，二氧化碳产生速率超过传输速率，导致泥炭地中二氧化碳积累。我们的结果表明，有效扩散系数随风速波动，且通常超过估计的分子扩散系数。泥炭地二氧化碳积累与传输之间的平衡在风速0 - 2米/秒范围内最为动态，这一风速范围在生长季节中出现超过75%的时间，并且主导夜间测量。因此，风驱动了泥炭地二氧化碳传输和储存的显著时间动态变化，特别是在亚日时间尺度上，以至于泥炭地二氧化碳排放仅在较长时间尺度上才能直接与生物产生相关。
在线版本包含可在10.1007/s10021-024-00904-1获取的补充材料。
