14:45 〜 15:00
[MIS05-17] Greenhouse gas fluxes from typical ecosystems of polygonal tundra in the Lena River Delta (North-Eastern Siberia, Russia)
キーワード：methane, carbon dioxide, carbon balance, emission, wetlands, terrestrial ecosystems
Greenhouse gas emissions on Samoylov Island have been monitored since 1998 [Hubberten et al., 2003]. Currently, extensive data on methane fluxes from polygonal tundra have been collected at different scales. The seasonal dynamics of these fluxes within the vegetation period had been investigated, as had the influence of various environmental factors and vegetation cover. This study makes it possible to continue the existing series of observations and to assess the current state of the ecosystem influenced by climate change. Besides, previous works have paid negligible attention to the measurements of carbon dioxide fluxes by the static chamber method, as well as to the daily dynamics of greenhouse gas fluxes.
Samoylov Island is located in the southern central Lena River Delta (72.37º N, 126.50º E) and characterized by a continuous permafrost distribution of considerable thickness (400-600 m). Field studies were conducted in the summers of 2023 and 2024 on typical polygonal microrelief elements. Methane and carbon dioxide fluxes were measured by dark static chamber method with a portable gas analyzer LI-COR LI-7810 (LI-COR Biosciences, USA). In 2023, the diurnal flux monitoring was conducted over a period of 7 days at two wet low-center polygons and an elevated dry poligon rim, with several measurements made at four ponds. In 2024, fluxes were measured during two weeks at three wet low-center polygons, one dry high-center polygon and one polygon rim (points were selected according to [Sachs et al., 2008]). Additionally, the study included a one-day measurement period at three ponds/lakes, corresponding to different stages of the polygonal landscape degradation.
This study revealed the strong diurnal dynamics of methane and carbon dioxide fluxes from the wet low-center polygons. It is the first time this has been observed on Samoylov Island by the static chamber method. At different sites, the diurnal amplitude of methane flux variations ranged from 0.3 to 2.2 mgCH4 m-2 h-1. The study noted diurnal variability in carbon dioxide fluxes at wet low-center polygons, high-center polygon, and polygon rims, with an amplitude ranging from 239 to 593 mgCO2 m-2 h-1 up to 839 mgCO2 m-2 h-1 for the rim in 2023.
Wet low-center polygons emit the largest amount of methane (2.6-3.5 mgCH4 m-2 h-1). Intermediate fluxes were observed in polygon centers with lower water table levels (1.0-1.4 mgCH4 m-2 h-1). The smallest average methane fluxes from 0.01 to 0.1 mgCH4 m-2 h-1 were measured in the dry microrelief elements, i.e. rims and high-center polygon. Methane fluxes from ponds and lakes varied widely from 0.1 to 1.3 mgCH4 m-2 h-1 and were independent of the number of polygons that constituted the studied water body. The highest carbon dioxide fluxes were observed in wet low-center polygons with mean values ranging from 208 to 415 mgCO2 m-2 h-1, and the lowest fluxes were measured on pond surfaces (3-37 mgCO2 m-2 h-1). Average carbon dioxide fluxes from rims and high-centered polygon varied from 150 to 193 mgCO2 m-2 h-1.
The study confirms that in order to obtain representative emission assessments from the polygonal tundra, it is necessary to consider the diurnal variability of greenhouse gas fluxes. The elevated greenhouse gas emissions from the wet low-center polygons in comparison to ponds and lakes underscores the substantial role of these ecosystems in Samoylov Island's greenhouse gas emissions.
This work was supported by the Russian Science Foundation (project no. 22-47-04408) and state task of IAP RAS (theme no. 1024100700065-0-1.5.10).
References
Hubberten H.-W. et al. The Russian-German research station Samoylov, Lena Delta - A key site for polar research in the Siberian Arctic // Polarforschung. 2003. 73(2/3), 111-116.
Sachs T. et al. Environmental controls on ecosystem-scale CH4 emission from polygonal tundra in the Lena River Delta, Siberia // Journal of Geophysical Research. 2008. 113, 1-12.
Samoylov Island is located in the southern central Lena River Delta (72.37º N, 126.50º E) and characterized by a continuous permafrost distribution of considerable thickness (400-600 m). Field studies were conducted in the summers of 2023 and 2024 on typical polygonal microrelief elements. Methane and carbon dioxide fluxes were measured by dark static chamber method with a portable gas analyzer LI-COR LI-7810 (LI-COR Biosciences, USA). In 2023, the diurnal flux monitoring was conducted over a period of 7 days at two wet low-center polygons and an elevated dry poligon rim, with several measurements made at four ponds. In 2024, fluxes were measured during two weeks at three wet low-center polygons, one dry high-center polygon and one polygon rim (points were selected according to [Sachs et al., 2008]). Additionally, the study included a one-day measurement period at three ponds/lakes, corresponding to different stages of the polygonal landscape degradation.
This study revealed the strong diurnal dynamics of methane and carbon dioxide fluxes from the wet low-center polygons. It is the first time this has been observed on Samoylov Island by the static chamber method. At different sites, the diurnal amplitude of methane flux variations ranged from 0.3 to 2.2 mgCH4 m-2 h-1. The study noted diurnal variability in carbon dioxide fluxes at wet low-center polygons, high-center polygon, and polygon rims, with an amplitude ranging from 239 to 593 mgCO2 m-2 h-1 up to 839 mgCO2 m-2 h-1 for the rim in 2023.
Wet low-center polygons emit the largest amount of methane (2.6-3.5 mgCH4 m-2 h-1). Intermediate fluxes were observed in polygon centers with lower water table levels (1.0-1.4 mgCH4 m-2 h-1). The smallest average methane fluxes from 0.01 to 0.1 mgCH4 m-2 h-1 were measured in the dry microrelief elements, i.e. rims and high-center polygon. Methane fluxes from ponds and lakes varied widely from 0.1 to 1.3 mgCH4 m-2 h-1 and were independent of the number of polygons that constituted the studied water body. The highest carbon dioxide fluxes were observed in wet low-center polygons with mean values ranging from 208 to 415 mgCO2 m-2 h-1, and the lowest fluxes were measured on pond surfaces (3-37 mgCO2 m-2 h-1). Average carbon dioxide fluxes from rims and high-centered polygon varied from 150 to 193 mgCO2 m-2 h-1.
The study confirms that in order to obtain representative emission assessments from the polygonal tundra, it is necessary to consider the diurnal variability of greenhouse gas fluxes. The elevated greenhouse gas emissions from the wet low-center polygons in comparison to ponds and lakes underscores the substantial role of these ecosystems in Samoylov Island's greenhouse gas emissions.
This work was supported by the Russian Science Foundation (project no. 22-47-04408) and state task of IAP RAS (theme no. 1024100700065-0-1.5.10).
References
Hubberten H.-W. et al. The Russian-German research station Samoylov, Lena Delta - A key site for polar research in the Siberian Arctic // Polarforschung. 2003. 73(2/3), 111-116.
Sachs T. et al. Environmental controls on ecosystem-scale CH4 emission from polygonal tundra in the Lena River Delta, Siberia // Journal of Geophysical Research. 2008. 113, 1-12.