Preprints
https://doi.org/10.5194/egusphere-2024-271
https://doi.org/10.5194/egusphere-2024-271
19 Feb 2024
 | 19 Feb 2024
Status: this preprint is open for discussion.

Patterns and drivers of organic matter decomposition in peatland open-water pools

Julien Arsenault, Julie Talbot, Tim R. Moore, Klaus-Holger Knorr, Henning Teickner, and Jean-François Lapierre

Abstract. Peatlands pools are unvegetated, inundated depressions that cover up to 30 % of the surface of many temperate and boreal peatlands and that are net carbon (C) sources within C-accumulating ecosystems. The emission of carbon dioxide (CO2) and methane (CH4) from peatland pools comes from the degradation of organic matter (OM) that comprise the surrounding matrix. It is, however, not clear how decomposition rates in pools, which define their function and distinguish them from other aquatic ecosystems, vary spatially and what mechanisms drive these variations. We quantified rates of OM decomposition from fresh litter at different depths in six pools of distinct morphological characteristics in a temperate ombrotrophic peatland using litterbags of Sphagnum capillifolium and Typha latifolia over a 27-month period and measured potential CO2 and CH4 production of pool sediments in laboratory incubations. Rates of decomposition were faster for T. latifolia than S. capillifolium and, overall, faster at the pool surface and decreased with increasing depth. Pool sediment chemistry was variable among pools and drove the production of CH4 and CO2 from sediments, with decreasing CO2 production with increasing OM humification and decreasing CH4 production with increasing nitrogen-to-phosphorus ratio. Both CH4 and CO2 production from pool sediments were higher in the 1 m deep pools, but similar in the shallow < 1 m and the > 1.5 m deep pools. Our results show that OM decomposition in peatland pools is highly variable and related to OM chemistry, but decomposition depends primarily on the environmental conditions in which it occurs, with differences in both fresh litter and pool sediment decomposability as a function of decreasing O2 concentrations, light, and temperature with increasing depth in the pools.

Julien Arsenault, Julie Talbot, Tim R. Moore, Klaus-Holger Knorr, Henning Teickner, and Jean-François Lapierre

Status: open (until 25 Apr 2024)

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Julien Arsenault, Julie Talbot, Tim R. Moore, Klaus-Holger Knorr, Henning Teickner, and Jean-François Lapierre
Julien Arsenault, Julie Talbot, Tim R. Moore, Klaus-Holger Knorr, Henning Teickner, and Jean-François Lapierre

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Short summary
Peatlands are among the largest carbon sinks on the planet. Peatland features such as open-water pools however emit more carbon than they accumulate because of higher decomposition than in the peat. With this study, we show that the rates of decomposition vary among pools and are mostly driven by the environmental conditions in pools rather than by the nature of the material to decomposition. This means that changes in pool number or size may modify the capacity of peatland to accumulate carbon.