Referee Comment for Scaling and balancing carbon dioxide fluxes in a heterogeneous tundra ecosystem of the Lena River Delta

Abstract. Arctic tundra ecosystems are currently facing amplified rates of climate warming. Since these ecosystems store significant amounts of soil organic carbon, which can be mineralized to carbon dioxide (CO2) and methane (CH4), rising temperatures may cause increasing greenhouse gas fluxes to the atmosphere. To understand how net the ecosystem exchange (NEE) of CO2 will respond to changing climatic and environmental conditions, it is necessary to understand the individual responses of the processes contributing to NEE. Therefore, this study aimed to partition NEE at the soil–plant–atmosphere interface in an arctic tundra ecosystem and to identify the main environmental drivers of these fluxes. NEE was partitioned into gross primary productivity (GPP) and ecosystem respiration (Reco) and further into autotrophic (RA) and heterotrophic respiration (RH). The study examined CO2 flux data collected during the growing season in 2015 using closed-chamber measurements in a polygonal tundra landscape in the Lena River Delta, northeastern Siberia. To capture the influence of soil hydrology on CO2 fluxes, measurements were conducted at a water-saturated polygon center and a well-drained polygon rim. These chamber-measured fluxes were used to model NEE, GPP, Reco, RH, RA, and net primary production (NPP) at the pedon scale (1–10 m) and to determine cumulative growing season fluxes. Here, the response of in situ measured RA and RH fluxes from permafrost-affected soils of the polygonal tundra to hydrological conditions have been examined. Although changes in the water table depth at the polygon center sites did not affect CO2 fluxes from RH, rising water tables were linked to reduced CO2 fluxes from RA. Furthermore, this work found the polygonal tundra in the Lena River Delta to be a net sink for atmospheric CO2 during the growing season. The NEE at the wet, depressed polygon center was more than twice that at the drier polygon rim. These differences between the two sites were caused by higher GPP fluxes due to a higher vascular plant density and lower Reco fluxes due to oxygen limitation under water-saturated conditions at the polygon center in comparison to the rim. Hence, soil hydrological conditions were one of the key drivers for the different CO2 fluxes across this highly heterogeneous tundra landscape.

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Scaling and balancing methane fluxes in a heterogeneous tundra ecosystem of the Lena River Delta

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2018.06.026 ◽

2019 ◽

Vol 266-267 ◽

pp. 243-255 ◽

Cited By ~ 3

Author(s):

Norman Rößger ◽

Christian Wille ◽

Georg Veh ◽

Julia Boike ◽

Lars Kutzbach

Keyword(s):

River Delta ◽

Lena River ◽

Tundra Ecosystem ◽

Methane Fluxes ◽

Lena River Delta

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Scaling and balancing carbon dioxide fluxes in a heterogeneous tundra ecosystem of the Lena River Delta

Biogeosciences ◽

10.5194/bg-16-2591-2019 ◽

2019 ◽

Vol 16 (13) ◽

pp. 2591-2615 ◽

Cited By ~ 3

Author(s):

Norman Rößger ◽

Christian Wille ◽

David Holl ◽

Mathias Göckede ◽

Lars Kutzbach

Keyword(s):

Carbon Dioxide ◽

Flood Plain ◽

Heterogeneous Surface ◽

Sink Strength ◽

Carbon Dioxide Fluxes ◽

Lena River ◽

Net Uptake ◽

Vegetation Class ◽

Lena River Delta ◽

Tundra Ecosystems

Abstract. The current assessments of the carbon turnover in the Arctic tundra are subject to large uncertainties. This problem can (inter alia) be ascribed to both the general shortage of flux data from the vast and sparsely inhabited Arctic region, as well as the typically high spatiotemporal variability of carbon fluxes in tundra ecosystems. Addressing these challenges, carbon dioxide fluxes on an active flood plain situated in the Siberian Lena River Delta were studied during two growing seasons with the eddy covariance method. The footprint exhibited a heterogeneous surface, which generated mixed flux signals that could be partitioned in such a way that both respiratory loss and photosynthetic gain were obtained for each of two vegetation classes. This downscaling of the observed fluxes revealed a differing seasonality in the net uptake of bushes (−0.89 µmol m−2 s−1) and sedges (−0.38 µmol m−2 s−1) in 2014. That discrepancy, which was concealed in the net signal, resulted from a comparatively warm spring in conjunction with an early snowmelt and a varying canopy structure. Thus, the representativeness of footprints may adversely be affected in response to prolonged unusual weather conditions. In 2015, when air temperatures on average corresponded to climatological means, both vegetation-class-specific flux rates were of similar magnitude (−0.69 µmol m−2 s−1). A comprehensive set of measures (e.g. phenocam) corroborated the reliability of the partitioned fluxes and hence confirmed the utility of flux decomposition for enhanced flux data analysis. This scrutiny encompassed insights into both the phenological dynamic of individual vegetation classes and their respective functional flux to flux driver relationships with the aid of ecophysiologically interpretable parameters. For comparison with other sites, the decomposed fluxes were employed in a vegetation class area-weighted upscaling that was based on a classified high-resolution orthomosaic of the flood plain. In this way, robust budgets that take the heterogeneous surface characteristics into account were estimated. In relation to the average sink strength of various Arctic flux sites, the flood plain constitutes a distinctly stronger carbon dioxide sink. Roughly 42 % of this net uptake, however, was on average offset by methane emissions lowering the sink strength for greenhouse gases. With growing concern about rising greenhouse gas emissions in high-latitude regions, providing robust carbon budgets from tundra ecosystems is critical in view of accelerating permafrost thaw, which can impact the global climate for centuries.

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The exchange of carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia

Biogeosciences Discussions ◽

10.5194/bgd-4-1953-2007 ◽

2007 ◽

Vol 4 (3) ◽

pp. 1953-2005 ◽

Cited By ~ 8

Author(s):

L. Kutzbach ◽

C. Wille ◽

E.-M. Pfeiffer

Keyword(s):

Carbon Dioxide ◽

Ecosystem Respiration ◽

Co2 Exchange ◽

River Delta ◽

Active Period ◽

Net Ecosystem Co2 Exchange ◽

Lena River ◽

Northern Siberia ◽

Gross Photosynthesis ◽

Lena River Delta

Abstract. The exchange fluxes of carbon dioxide between wet arctic polygonal tundra and the atmosphere were investigated by the micrometeorological eddy covariance method. The investigation site was situated in the centre of the Lena River Delta in Northern Siberia (72°22' N, 126°30' E). The study region is characterized by a polar and distinctly continental climate, very cold and ice-rich permafrost and its position at the interface between the Eurasian continent and the Arctic Ocean. The soils at the site are characterized by high organic matter content, low nutrient availability and pronounced water logging. The vegetation is dominated by sedges and mosses. The micrometeorological campaigns were performed during the periods July–October 2003 and May–July 2004 which included the period of snow and soil thaw as well as the beginning of soil refreeze. The main CO2 exchange processes, the gross photosynthesis and the ecosystem respiration, were found to be of a generally low intensity. The gross photosynthesis accumulated to –432 g m−2 over the photosynthetically active period (June–September). The contribution of mosses to the gross photosynthesis was estimated to be about 40%. The diurnal trend of the gross photosynthesis was mainly controlled by the incoming photosynthetically active radiation. During midday the photosynthetic apparatus of the canopy was frequently near saturation and represented the limiting factor on gross photosynthesis. The synoptic weather conditions strongly affected the exchange fluxes of CO2 by changes in cloudiness, precipitation and pronounced changes of air temperature. The ecosystem respiration accumulated to +327 g m−2 over the photosynthetically active period, which corresponds to 76% of the CO2 uptake by photosynthesis. However, the ecosystem respiration continued at substantial rates during autumn when photosynthesis had ceased and the soils were still largely unfrozen. The temporal variability of the ecosystem respiration during summer was best explained by an exponential function with surface temperature, and not soil temperature, as the independent variable. This was explained by the major role of the plant respiration within the CO2 balance of the tundra ecosystem. The wet polygonal tundra of the Lena River Delta was observed to be a substantial CO2 sink with an accumulated net ecosystem CO2 exchange of –119 g m−2 over the summer and an estimated annual net ecosystem CO2 exchange of –71 g m−2.

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Scaling and balancing carbon dioxide fluxes in a heterogeneous tundra ecosystem of the Lena River Delta

10.5194/bg-2019-10 ◽

2019 ◽

Cited By ~ 1

Author(s):

Norman Rößger ◽

Christian Wille ◽

David Holl ◽

Mathias Göckede ◽

Lars Kutzbach

Keyword(s):

Carbon Dioxide ◽

Flood Plain ◽

Heterogeneous Surface ◽

Sink Strength ◽

Carbon Dioxide Fluxes ◽

Lena River ◽

Flux Data ◽

Vegetation Class ◽

Lena River Delta ◽

Tundra Ecosystems

Abstract. The current assessments of the carbon turnover in the Arctic tundra are subject to large uncertainties. This problem can (inter alia) be ascribed to both the general shortage of flux data from the vast and sparsely inhabited Arctic region, as well as the typically high spatiotemporal variability of carbon fluxes in tundra ecosystems. Addressing these challenges, carbon dioxide fluxes on an active flood plain situated in the Siberian Lena River Delta were studied during two growing seasons with the eddy covariance method. The footprint exhibited a heterogeneous surface, and the mixed flux signal associated therewith could extensively be decomposed: respiratory loss and photosynthetic gain were not only modelled for the overall footprint, but also for each of two vegetation classes. This downscaling of the observed fluxes unveiled a differing seasonality in the net uptakes of bushes (0.89 μmol m−2 s−1) and sedges (0.38 μmol m−2 s−1) in 2014. That discrepancy, which was concealed in the net signal, resulted from a comparatively warm spring in conjunction with an early snow melt and a varying canopy structure. Thus, the representativeness of footprints may adversely be affected in response to prolonged unusual weather conditions. In 2015, when air temperatures on average corresponded to climatological means, both vegetation class-specific flux rates were of similar magnitude (0.69 μmol m−2 s−1). A comprehensive set of measures (e.g. phenocam) approved the reliability of the partitioned fluxes, and hence confirmed the utility of the flux decomposition for enhanced flux data analysis. This scrutiny encompassed insights into both the phenological dynamic of individual vegetation classes, plus their respective functional flux to flux driver relationships with the aid of ecophysiologically interpretable parameters. For the purpose of comparison with other sites, the decomposed fluxes were employed in a vegetation class area-weighted upscaling that was based on a classified high-resolution orthomosaic of the flood plain. In this way, robust budgets that take the heterogeneous surface characteristics into account were estimated. In relation to the average sink strength of various Arctic flux sites, the flood plain constitutes a distinctly stronger carbon dioxide sink. Roughly 42 % of this net uptake, however, was on average offset by methane emissions lowering the sink strength for greenhouse gases. With growing concern about rising greenhouse gas emissions in high-latitude regions, providing robust carbon budgets from tundra ecosystems is critical in view of the thawing permafrost, whose released carbon can impact the global climate for centuries.

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The exchange of carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia

Biogeosciences ◽

10.5194/bg-4-869-2007 ◽

2007 ◽

Vol 4 (5) ◽

pp. 869-890 ◽

Cited By ~ 70

Author(s):

L. Kutzbach ◽

C. Wille ◽

E.-M. Pfeiffer

Keyword(s):

Carbon Dioxide ◽

Ecosystem Respiration ◽

Co2 Exchange ◽

River Delta ◽

Active Period ◽

Net Ecosystem Co2 Exchange ◽

Lena River ◽

Northern Siberia ◽

Gross Photosynthesis ◽

Lena River Delta

Abstract. The exchange fluxes of carbon dioxide between wet arctic polygonal tundra and the atmosphere were investigated by the micrometeorological eddy covariance method. The investigation site was situated in the centre of the Lena River Delta in Northern Siberia (72°22' N, 126°30' E). The study region is characterized by a polar and distinctly continental climate, very cold and ice-rich permafrost and its position at the interface between the Eurasian continent and the Arctic Ocean. The soils at the site are characterized by high organic matter content, low nutrient availability and pronounced water logging. The vegetation is dominated by sedges and mosses. The micrometeorological campaigns were performed during the periods July–October 2003 and May–July 2004 which included the period of snow and soil thaw as well as the beginning of soil refreeze. The main CO2 exchange processes, the gross photosynthesis and the ecosystem respiration, were found to be of a generally low intensity. The gross photosynthesis accumulated to −432 g m−2 over the photosynthetically active period (June–September). The contribution of mosses to the gross photosynthesis was estimated to be about 40%. The diurnal trend of the gross photosynthesis was mainly controlled by the incoming photosynthetically active radiation. During midday, the photosynthetic apparatus of the canopy was frequently near saturation and represented the limiting factor on gross photosynthesis. The synoptic weather conditions strongly affected the exchange fluxes of CO2 by changes in cloudiness, precipitation and pronounced changes of air temperature. The ecosystem respiration accumulated to +327 g m−2 over the photosynthetically active period, which corresponds to 76% of the CO2 uptake by photosynthesis. However, the ecosystem respiration continued at substantial rates during autumn when photosynthesis had ceased and the soils were still largely unfrozen. The temporal variability of the ecosystem respiration during summer was best explained by an exponential function with surface temperature, and not soil temperature, as the independent variable. This was explained by the major role of the plant respiration within the CO2 balance of the tundra ecosystem. The wet polygonal tundra of the Lena River Delta was observed to be a substantial CO2 sink with an accumulated net ecosystem CO2 exchange of −119 g m−2 over the summer and an estimated annual net ecosystem CO2 exchange of −71 g m−2.

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Subrecent Spore-Pollen Spectra and Modern Vegetation from the Lena River Delta, Russian Arctic

Сибирский экологический журнал ◽

10.15372/sej20170407 ◽

2017 ◽

Keyword(s):

River Delta ◽

Russian Arctic ◽

Lena River ◽

Lena River Delta

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Short-term climate and vegetation dynamics in Lena River Delta (northern Yakutia, Eastern Siberia) during early Eocene

Palaeoworld ◽

10.1016/j.palwor.2021.09.006 ◽

2021 ◽

Author(s):

Olesya V. Bondarenko ◽

Nadezhda I. Blokhina ◽

Tatiyana A. Evstigneeva ◽

Torsten Utescher

Keyword(s):

Vegetation Dynamics ◽

River Delta ◽

Early Eocene ◽

Eastern Siberia ◽

Short Term ◽

Lena River ◽

Lena River Delta

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The Rock Magnetic Portrait of the Devonian Section of Stolb Island (Lena River Delta)

Doklady Earth Sciences ◽

10.1134/s1028334x2111009x ◽

2021 ◽

Vol 501 (1) ◽

pp. 906-911

Author(s):

D. V. Metelkin ◽

A. I. Chernova ◽

V. A. Vernikovsky ◽

N. E. Mikhaltsov ◽

V. V. Abashev

Keyword(s):

River Delta ◽

Lena River ◽

Lena River Delta

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Sentinel-1 SAR Interferometry for Surface Deformation Monitoring in Low-Land Permafrost Areas

Remote Sensing ◽

10.3390/rs10091360 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1360 ◽

Cited By ~ 22

Author(s):

Tazio Strozzi ◽

Sofia Antonova ◽

Frank Günther ◽

Eva Mätzler ◽

Gonçalo Vieira ◽

...

Keyword(s):

Time Series ◽

Surface Displacement ◽

Deformation Monitoring ◽

In Situ Measurements ◽

River Delta ◽

Sar Interferometry ◽

The Arctic ◽

Lena River ◽

Lena River Delta

Low-land permafrost areas are subject to intense freeze-thaw cycles and characterized by remarkable surface displacement. We used Sentinel-1 SAR interferometry (InSAR) in order to analyse the summer surface displacement over four spots in the Arctic and Antarctica since 2015. Choosing floodplain or outcrop areas as the reference for the InSAR relative deformation measurements, we found maximum subsidence of about 3 to 10 cm during the thawing season with generally high spatial variability. Sentinel-1 time-series of interferograms with 6–12 day time intervals highlight that subsidence is often occurring rather quickly within roughly one month in early summer. Intercomparison of summer subsidence from Sentinel-1 in 2017 with TerraSAR-X in 2013 over part of the Lena River Delta (Russia) shows a high spatial agreement between both SAR systems. A comparison with in-situ measurements for the summer of 2014 over the Lena River Delta indicates a pronounced downward movement of several centimetres in both cases but does not reveal a spatial correspondence between InSAR and local in-situ measurements. For the reconstruction of longer time-series of deformation, yearly Sentinel-1 interferograms from the end of the summer were considered. However, in order to infer an effective subsidence of the surface through melting of excess ice layers over multi-annual scales with Sentinel-1, a longer observation time period is necessary.

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