Multi-year effect of wetting on CH<sub>4</sub> flux at taiga–tundra boundary in northeastern Siberia deduced from stable isotope ratios of CH<sub>4</sub>
<p>The response of <span class="inline-formula">CH<sub>4</sub></span> emission from natural wetlands due to meteorological conditions is important because of its strong greenhouse effect. To understand the relationship between <span class="inline-formu...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/16/755/2019/bg-16-755-2019.pdf |
| Summary: | <p>The response of <span class="inline-formula">CH<sub>4</sub></span> emission from natural wetlands due to
meteorological conditions is important because of its strong greenhouse
effect. To understand the relationship between <span class="inline-formula">CH<sub>4</sub></span> flux and
wetting, we observed interannual variations in chamber <span class="inline-formula">CH<sub>4</sub></span> flux, as
well as the concentration, <span class="inline-formula"><i>δ</i><sup>13</sup>C</span>, and <span class="inline-formula"><i>δ</i>D</span> of
dissolved <span class="inline-formula">CH<sub>4</sub></span> during the summer from 2009 to 2013 at the
taiga–tundra boundary in the vicinity of Chokurdakh (70<span class="inline-formula"><sup>∘</sup></span>37<span class="inline-formula"><sup>′</sup></span> N,
147<span class="inline-formula"><sup>∘</sup></span>55<span class="inline-formula"><sup>′</sup></span> E), located on the lowlands of the Indigirka River in
northeastern Siberia. We also conducted soil incubation experiments to
interpret <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> and <span class="inline-formula"><i>δ</i>D</span> of dissolved <span class="inline-formula">CH<sub>4</sub></span>
and to investigate variations in <span class="inline-formula">CH<sub>4</sub></span> production and oxidation
processes. Methane flux showed large interannual variations in wet areas of
sphagnum mosses and sedges
(36–140 mg <span class="inline-formula">CH<sub>4</sub></span> m<span class="inline-formula"><sup>−2</sup></span> day<span class="inline-formula"><sup>−1</sup></span> emitted). Increased
<span class="inline-formula">CH<sub>4</sub></span> emission was recorded in the summer of 2011 when a wetting
event with extreme precipitation occurred. Although water level decreased
from 2011 to 2013, <span class="inline-formula">CH<sub>4</sub></span> emission remained relatively high in 2012,
and increased further in 2013. Thaw depth became deeper from 2011 to 2013,
which may partly explain the increase in <span class="inline-formula">CH<sub>4</sub></span> emission. Moreover,
dissolved <span class="inline-formula">CH<sub>4</sub></span> concentration rose sharply by 1 order of magnitude
from 2011 to 2012, and increased further from 2012 to 2013. Large variations
in <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> and <span class="inline-formula"><i>δ</i>D</span> of dissolved <span class="inline-formula">CH<sub>4</sub></span> were
observed in 2011, and smaller variations were seen in 2012 and 2013,
suggesting both enhancement of <span class="inline-formula">CH<sub>4</sub></span> production and less significance
of <span class="inline-formula">CH<sub>4</sub></span> oxidation relative to the larger pool of dissolved
<span class="inline-formula">CH<sub>4</sub></span>. These multi-year effects of wetting on <span class="inline-formula">CH<sub>4</sub></span> dynamics
may have been caused by continued soil reduction across multiple years
following the wetting. Delayed activation of acetoclastic methanogenesis
following soil reduction could also have contributed to the enhancement of
<span class="inline-formula">CH<sub>4</sub></span> production. These processes suggest that duration of water
saturation in the active layer can be important for predicting <span class="inline-formula">CH<sub>4</sub></span>
emission following a wetting event in the permafrost ecosystem.</p> |
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| ISSN: | 1726-4170 1726-4189 |