Preprints
https://doi.org/10.5194/egusphere-2024-1739
https://doi.org/10.5194/egusphere-2024-1739
26 Jun 2024
 | 26 Jun 2024
Status: this preprint is open for discussion.

Underestimation of Anaerobic Decomposition Rates in Sphagnum Litterbag Experiments by the Holocene Peatland Model Depends on Initial Leaching Losses

Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr

Abstract. The Holocene Peatland Model (HPM) is a widely applied model to understand and predict long-term peat accumulation. Here, we test whether the HPM can predict decomposition of available Sphagnum litterbag data along a gradient from oxic to anoxic conditionsand estimate parameter values from the litterbag data.

Large uncertainties in available litterbag data allow predictions of the HPM to fit decomposition rates estimated from litterbags by adjusting initial leaching losses and decomposition rates estimated from the litterbag data within the range of their uncertainties. Specifically, with standard parameter values, the HPM assumes larger initial leaching losses and smaller decomposition rates than estimated from the litterbag data alone. Therefore, improved tests of the HPM rely on future litterbag experiments that allow a more accurate estimation of initial leaching losses and decomposition rates.

When estimating HPM parameters from the litterbag data and assuming smaller initial leaching losses, our analysis indicates that the HPM with standard parameter values underestimates anaerobic decomposition rates for several species and assumes a too steep decrease of decomposition rates from oxic to anoxic conditions. This may be caused by not considering effects of water table fluctuations on aerobic and anaerobic decomposition rates.

Whether the discrepancies are reproducible and the estimated parameter values may be an easy fix to account for effects of water table fluctuations in long-term predictions needs further investigation. Based on previous sensitivity analyses of the HPM, the updated parameter estimates can cause differences in predicted 5000 year C accumulation up to 100 kg m−2.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr

Status: open (until 30 Aug 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr

Data sets

Peatland Decomposition Database (1.0.0) Henning Teickner and Klaus-Holger Knorr https://zenodo.org/records/11276065

Model code and software

Compendium of R code and data for "A Synthesis of Sphagnum Litterbag Experiments: Initial Leaching Losses Bias Decomposition Rate Estimates" and "Underestimation of Anaerobic Decomposition Rates in Sphagnum Litterbag Experiments by the Holocene Peatland Model Depends on Initial Leaching Losses" Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr https://zenodo.org/records/11472955

Interactive computing environment

hpmdpredict: Predictions with model HPMe-LE-peat-l0 from Teickner et al. (2024) Henning Teickner and Klaus-Holger Knorr https://zenodo.org/records/11339733

Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr

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Short summary
The Holocene Peatland Model (HPM) is a widely used peatland model to understand and predict long-term peatland dynamics. Here, we test whether the HPM can predict Sphagnum litterbag decomposition rates from oxic to anoxic conditions. Our results indicate that decomposition rates change more gradually from oxic to anoxic conditions and may be underestimated under anoxic conditions, possibly because the effect of water table fluctuations on decomposition rates is not considered.