Gradual drying of permafrost peat decreases carbon dioxide production in drier peat plateaus but not in wetter fens and bogs
<p>Permafrost thawing of northern peatlands can cause the local collapse of peat plateaus into much wetter thermokarst bogs and fens, dominated by <i>Sphagnum</i> mosses and graminoids, respectively. However, permafrost thaw can also improve landscape drainage and, thus, lead to th...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-05-01
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| Series: | SOIL |
| Online Access: | https://soil.copernicus.org/articles/11/371/2025/soil-11-371-2025.pdf |
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| Summary: | <p>Permafrost thawing of northern peatlands can cause the local collapse of peat plateaus into much wetter thermokarst bogs and fens, dominated by <i>Sphagnum</i> mosses and graminoids, respectively. However, permafrost thaw can also improve landscape drainage and, thus, lead to the regional drying of peatlands. How gradual drying of these thawing permafrost peatlands affects the subsequent microbial production of carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) and nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) is uncertain because of landscape heterogeneity in moisture, peat quality, and vegetation. Here, we collected near-surface peat samples (5–20 <span class="inline-formula">cm</span>) from Alberta, Canada, across transects representing a thaw gradient from peat plateaus to a fen or bog. We incubated the samples for 2 weeks under either field moisture or under gradual drying to reduce moisture by <span class="inline-formula">∼</span> 80 %. Only the fen sites, which had high moisture and a high percentage of total N, produced <span class="inline-formula">N<sub>2</sub>O</span> (0.06–6.7 <span class="inline-formula">µg N<sub>2</sub>O-N</span> per gram of dry peat), but <span class="inline-formula">N<sub>2</sub>O</span> production was unaffected by the drying treatments. Peat <span class="inline-formula">CO<sub>2</sub></span> production was greatest from the fen and the youngest stage of the thermokarst bog, despite them having the most water-saturated field conditions, likely reflecting their more labile plant inputs and, thus, more decomposable peat. We found that <span class="inline-formula">CO<sub>2</sub></span> respiration was enhanced by drying at relatively wet sites like the fens and young bog but was suppressed by drying in relatively drier peat plateaus. Further, gradual drying increased <span class="inline-formula"><sup>13</sup>C</span>-<span class="inline-formula">CO<sub>2</sub></span> respiration, suggesting a possible shift to more decomposed, older <span class="inline-formula">C</span> being lost with peat drying. Thus, our study suggests that future peat <span class="inline-formula">CO<sub>2</sub></span> and <span class="inline-formula">N<sub>2</sub>O</span> production from peatlands will depend on whether peat plateaus thaw into fens or bogs and on their diverging responses of peat respiration to more moisture-limited conditions.</p> |
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| ISSN: | 2199-3971 2199-398X |