Publication Date:
2024-03-05
Description:
Arctic warming causes permafrost thaw and accelerates microbial decomposition of soil organic matter (SOM) to carbon dioxide (CO〈sub〉2〈/sub〉) and methane (CH〈sub〉4〈/sub〉). The determining factors for the ratio between CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 formation are still not well understood due to scarce in situ measurements, particularly in remote Arctic regions. We quantified the CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios of SOM decomposition in wet and dry tundra soils by using CO〈sub〉2〈/sub〉 fluxes from clipped plots and in situ CH〈sub〉4〈/sub〉 fluxes from vegetated plots. At the water‐saturated site, CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios decreased sharply from 95 at beginning of July to about 10 in August and September with a median of 12.2 (7.70–17.1; 25%–75% quartiles) over the whole vegetation period. When considering CH〈sub〉4〈/sub〉 oxidation, estimated to reduce in situ CH〈sub〉4〈/sub〉 fluxes by 10%–31%, even lower CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios were calculated (median 10.9–8.41). Active layer depth and soil temperature were the main factors controlling these ratios. Methane production was associated with subsoil (40 cm) temperature, while heterotrophic respiration was related to topsoil (5 cm) temperatures. As expected, CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios were substantially higher at the dry site (median 373, 292–500, 25%–75% quartiles). Both tundra types lost carbon preferentially in form of CO〈sub〉2〈/sub〉, and CH〈sub〉4〈/sub〉‐C represented only 0.27% of the dry tundra total carbon loss and 6.91% of the wet tundra total carbon loss. The current study demonstrates the dynamic of in situ CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios from SOM decomposition and will help improve simulations of future CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 fluxes from thawing tundra soils.
Description:
Plain Language Summary:
Global warming causes the thaw of the permanently frozen soil in Arctic regions, exposing soil organic matter (SOM) previously frozen to decomposition, increasing the emission of carbon dioxide (CO〈sub〉2〈/sub〉) and methane (CH〈sub〉4〈/sub〉), which are greenhouse gases. It is crucial to quantify the ratio of CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 produced because CH〈sub〉4〈/sub〉 has a stronger global warming potential than CO〈sub〉2〈/sub〉. We partitioned SOM decomposition into CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 formation (CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios) in wet and dry tundra soils on Samoylov Island, Northeastern Siberia, and we related these ratios to environmental variables. Deeper active layer, which is the topsoil layer that freezes and thaws annually, and higher subsoil (40 cm) temperature at the interface between the active layer and the permafrost, foster CH4 production and decrease CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios. Carbon was preferentially lost in form of CO〈sub〉2〈/sub〉 by the soils, but CH〈sub〉4〈/sub〉 had a larger contribution to the carbon loss in the wet tundra. Our study indicates that warming and deepening of the active layer can result in rising CH〈sub〉4〈/sub〉 production. Further understanding of in situ CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios from SOM decomposition will help improve simulations on future CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 fluxes from thawing tundra soils.
Description:
Key Points:
Topsoil (5 cm) warming increases the CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 production ratio, while warming of subsoil (40 cm) leads to lower CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 production ratios.
The CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 production ratio is associated with active‐layer depth (ALD) due to a direct effect of ALD on CH〈sub〉4〈/sub〉 production.
Carbon was preferentially lost in form of CO〈sub〉2〈/sub〉 at wet and dry sites, but CH〈sub〉4〈/sub〉 had a higher contribution at the wet tundra site.
Description:
Deutsche Forschungsgemeinschaft
http://dx.doi.org/10.13039/501100001659
Description:
Clusters of Excellence CliSAP
Description:
https://doi.pangaea.de/10.1594/PANGAEA.944841
Description:
https://doi.pangaea.de/10.1594/PANGAEA.944844
Keywords:
ddc:631.4
;
thaw depth
;
methanogenesis
;
heterotrophic respiration
;
chamber
;
greenhouse gases
;
active layer thickening
Language:
English
Type:
doc-type:article
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