Sizable carbon emission from the floodplain of Ob River

The Ob River floodplain is the second largest floodplain in the world. Despite its vast area, estimates of carbon (C) emissions from the Ob River floodplain are largely absent. Here we present seasonal C emission and water area extent from the main channel and the floodplain along a ~4 km reach in t...

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Bibliographic Details
Published in:Ecological Indicators
Main Authors: Ivan V. Krickov, Svetlana Serikova, Oleg S. Pokrovsky, Sergey N. Vorobyev, Artem G. Lim, Matthias B. Siewert, Jan Karlsson
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier 2021
Subjects:
Floodplain
Greenhouse gases
Ob river
Seasonal influences
Carbon emission
Ecology
QH540-549.5
ob river
permafrost
Online Access:https://doi.org/10.1016/j.ecolind.2021.108164
https://doaj.org/article/10f3c3374da8481d951da67e81f674d7
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Summary:The Ob River floodplain is the second largest floodplain in the world. Despite its vast area, estimates of carbon (C) emissions from the Ob River floodplain are largely absent. Here we present seasonal C emission and water area extent from the main channel and the floodplain along a ~4 km reach in the boreal zone of the Ob River. We found strong seasonality in water area extent of the Ob main channel (~1.8 km2) and floodplain (~3 km2) with water covering 34% of land during flood and subsequently declining to ~16% and ~14% during summer and autumn baseflow, respectively. The C emissions also varied seasonally over the open water period, ranging from −0.1 to 0.6 g C m−2 d−1 for the Ob main channel and from 0 to 9 g C m−2 d−1 for the floodplain. The dissolved organic carbon positively affected CO2 concentrations and fluxes in the floodplain during all seasons, whereas pH and oxygen concentration negatively impacted CO2 concentrations and fluxes. Some nutrients (ammonia and phosphate) positively correlated with CO2 and CH4 concentrations in summer. The total C emission from the study reach (1.8 km2 main channel, 3 km2 floodplain) during moderate flooding was 236 ± 51 tons C yr−1 (>99% CO2, <1% CH4) with the floodplain accounting for ~65%. The contribution of the floodplain to the net river C evasion may be even greater during years of high flooding and in northern regions of the Ob River basin, where floodplain soils are more C-rich and are underlain by permafrost, and in years with more extensive flooding.

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