A synthesis of <i>Sphagnum</i> litterbag experiments: initial leaching losses bias decomposition rate estimates
<p>Our knowledge of the magnitude and controls of <i>Sphagnum</i> decomposition rates is derived to a large extent from litterbag experiments that do not explicitly consider initial leaching losses. Previous research on vascular plants suggests that decomposition rate (<span cla...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-01-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/417/2025/bg-22-417-2025.pdf |
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| Summary: | <p>Our knowledge of the magnitude and controls of <i>Sphagnum</i> decomposition rates is derived to a large extent from litterbag experiments that do not explicitly consider initial leaching losses. Previous research on vascular plants suggests that decomposition rate (<span class="inline-formula"><i>k</i><sub>0</sub></span>) estimates from litterbag experiments are biased when initial leaching losses (<span class="inline-formula"><i>l</i><sub>0</sub></span>) are ignored. In contrast, the magnitude and variability of <span class="inline-formula"><i>l</i><sub>0</sub></span> for <i>Sphagnum</i> litterbag experiments are not well known, and it is therefore also not known how much <i>Sphagnum</i> <span class="inline-formula"><i>k</i><sub>0</sub></span> estimates are biased. As <i>Sphagnum</i> is the main peat-forming species in many northern peatlands, and biases in <span class="inline-formula"><i>k</i><sub>0</sub></span> estimates can propagate and amplify in long-term peatland models, minimizing such bias is necessary for accurate predictions of peat accumulation.</p>
<p>We present a meta-analysis of 15 <i>Sphagnum</i> litterbag studies to estimate initial leaching losses (<span class="inline-formula"><i>l</i><sub>0</sub></span>), to analyze how much <i>Sphagnum</i> <span class="inline-formula"><i>k</i><sub>0</sub></span> estimates are biased when the decomposition model ignores initial leaching losses and to analyze how much the variance in <span class="inline-formula"><i>k</i><sub>0</sub></span> estimates increases due to initial leaching losses even when they are estimated by the decomposition model.</p>
<p>Average <span class="inline-formula"><i>l</i><sub>0</sub></span> estimates range between 3 mass-% to 18 mass-%, and average <span class="inline-formula"><i>k</i><sub>0</sub></span> estimates range between 0.01 to 1.16 yr<span class="inline-formula"><sup>−1</sup></span>. Simulations and models fitted to empirical data indicate that ignoring initial leaching losses leads to an overestimation of <span class="inline-formula"><i>k</i><sub>0</sub></span>. An error analysis suggests that <span class="inline-formula"><i>k</i><sub>0</sub></span> and <span class="inline-formula"><i>l</i><sub>0</sub></span> can be estimated only with relatively large errors because of limitations in the design of most available litterbag experiments. Sampling the first litterbags shortly after the start of the experiments allows more accurate estimation of <span class="inline-formula"><i>l</i><sub>0</sub></span> and <span class="inline-formula"><i>k</i><sub>0</sub></span>. We also estimated large <span class="inline-formula"><i>l</i><sub>0</sub></span> (<span class="inline-formula">>5</span> mass-%) for only air-dried samples, which could imply that <i>Sphagnum</i> litterbag experiments with dried litter are unrepresentative for natural decomposition processes in which <span class="inline-formula"><i>l</i><sub>0</sub></span> may be smaller according to leaching experiments with fresh litter.</p>
<p>We conclude that comparing results of litterbag experiments between experimental treatments and between studies and accurately estimating decomposition rates may only be possible if initial leaching losses are explicitly considered.</p> |
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| ISSN: | 1726-4170 1726-4189 |