Preprints
https://doi.org/10.5194/egusphere-2024-1280
https://doi.org/10.5194/egusphere-2024-1280
14 May 2024
 | 14 May 2024
Status: this preprint is open for discussion.

Exploring micro-scale heterogeneity as a driver of biogeochemical transformations and gas transport in peat

Lukas Kohl, Petri Kiuru, Marjo Palviainen, Maarit Raivonen, Markku Koskinen, Mari Pihlatie, and Annamari Lauren

Abstract. Peat pore network architecture is a key determinant of water retention and gas transport properties, and has therefore been hypothesized to control redox conditions in and greenhouse gas emissions from peat soils. Yet, experimental proof of the impact of the pore network structure on biogeochemical reactions remains scarce. Here, we report on a 13C pulse-chase assay developed to functionally explain and visualize the cm-scale heterogeneity in greenhouse gas emissions in peat cores. We injected a 13C labeled substrate (13C2-acetate) at different depths in the peat cores and monitored its conversion into CO2 and CH4 and the subsequent transport to the core headspace. We then measured the pore network architecture of the same cores by X-ray microtomographic imaging and constructed the air-filled pore networks using pore network modeling. We found large heterogeneity among the replicate cores and injections, indicating the effects of cm-scale heterogeneity on biochemical processes and gas transport. This heterogeneity was largely present at the core (10 cm) and within-core (cm) scale heterogeneity whereas little additional variance occurred on the stand (>10 m) scale. Deeper injections resulted in a smaller faction of the label being converted to CO2 and this fraction being emitted more slowly from the peat cores. Greater peat air-filled porosity was and pore network metrics could not explain the fraction of label converted to CO2, but greater porosity as well as higher clustering coefficients and betweenness centrality were associated with slower CO2 emissions.

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Lukas Kohl, Petri Kiuru, Marjo Palviainen, Maarit Raivonen, Markku Koskinen, Mari Pihlatie, and Annamari Lauren

Status: open (until 25 Jun 2024)

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Lukas Kohl, Petri Kiuru, Marjo Palviainen, Maarit Raivonen, Markku Koskinen, Mari Pihlatie, and Annamari Lauren

Data sets

Exploring micro-scale heterogeneity as a driver of biogeochemical transformations and gas transport in peat - raw data and code Lukas Kohl https://doi.org/10.5281/zenodo.11088028

Lukas Kohl, Petri Kiuru, Marjo Palviainen, Maarit Raivonen, Markku Koskinen, Mari Pihlatie, and Annamari Lauren

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Short summary
We present an assay to illuminate heterogeneity of biogeochemical transformations within peat samples. For this, we injected isotope labelled acetate into peat cores and monitoring the release of label-derived gases, which we compared to microtomography images. The fraction of label converted to CO2 and the rapidness of this conversion was linked to injection depth as well as air-filled porosity. Pore network metric did not provide predictive power over compared to porosity alone.