Spatial and temporal variation of 13C-signature of methane emitted by a temperate mire ecosystem

<p>The net methane emission of any mire ecosystem results from a combination of biological and physical processes, including methane production by archaea, methane consumption by bacteria, and transport of methane from peat to the atmosphere. The complexity of spatial and temporal behavior of methane emission is connected to these.</p><p><sup>13</sup>C-signature of emitted methane offers us a further constraint to evaluate our hypothesis on the processes leading to the variation of methane emission rates. For example, assuming the spatial variation in methane emission rate at microtopographic scale is due to variation in trophic status or variation in methane consumption, will lead to differences in the relation of methane emission rate and its <sup>13</sup>C-signature, expressed as δ<sup>13</sup>C.</p><p>We have measured the methane emission rates and δ<sup>13</sup>C of emitted methane by six automated chambers at a poor fen ecosystem over two growing seasons. The measurements were conducted at Mycklemossen mire (58°21'N 12°10'E, 80m a.s.l.), Sweden, during 2019-2020. In addition, we measured atmospheric surface layer methane mixing ratios and δ<sup>13</sup>C to obtain larger scale <sup>13</sup>C-signatures by the nocturnal boundary-layer accumulation (NBL) approach. All δ<sup>13</sup>C-signatures were derived using the Keeling-plot approach.</p><p>The collected data shows spatial differences of up to 10-15 ‰ in 10-day averages of δ<sup>13</sup>C-signatures between different chamber locations. Temporal variations of 10-day average δ<sup>13</sup>C-signatures from most chamber locations reached over 5 ‰, while the temporal variation of NBL derived δ<sup>13</sup>C-signature was slightly lower.</p><p>The observed spatial variation in the δ<sup>13</sup>C-signature was somewhat systematic, indicating, especially in the middle of the summers, the main control of spatial variation of methane emission to be the trophic status. The temporal changes, measured at different locations, indicate spatial differences in the temporal dynamics at the microtopographic scale. The temporal behavior of larger scale NBL δ<sup>13</sup>C-signature does not fully correspond to the behavior of the chamber derived average δ<sup>13</sup>C-signature.</p>

Methane Emission from Palsa Mires in Northeastern European Russia

Measurement data on methane fluxes in the palsa mire ecosystem at the border of tundra and taiga zones in northeastern European Russia are presented. It was found for the first time that an intense methane flux from the surface of the permafrost mound (palsa) is determined by the spring thawing of the seasonally thawed horizon in the layer of 14–25 cm. During this period, the emission was 4–20 times higher than the summer values. In lichen communities of peat mounds, the CH4 sink prevailed during the summer-autumn period. The total methane flux in different parts of the mire in June–September varied from 0.18 to 16.5 kg CH4/ha. In general, the palsa mire emitted 81 kg CH4/ha per year to the atmosphere. The methane emission from the surface of peat mounds and hollows made up 20% and 80% of the annual flux, respectively.

Carbon dynamics and full carbon balance of a Northern mire ecosystem

<p>We present the Net Ecosystem Carbon Balance (NECB) of a Northern mire ecosystem for the period 2016-2019. The Mycklemossen peatland is located in the hemi-boreal region in the Southwestern part of Sweden and is classified as a fen with bog-like vegetation. The NECB was determined from eddy covariance (EC) measurements of carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) and continuous water discharge measurements with biweekly measurements of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and dissolved CH<sub>4</sub>. <br>We focus on the carbon dynamics of the Mycklemossen ecosystem during summer droughts and on its recovery during normal years. During 2016-2018, the annual precipitation was lower than the 30-year average while 2019 was a normal year in terms of weather conditions. 2018 sticks out as an extreme year with a severe drought and unusually high air temperature at Mycklemossen, as was the case in much of Northern and Central Europe.<br>The EC results indicate that Mycklemossen lost carbon during 2016-2018. While CH<sub>4</sub> emissions decreased, the mire became a strong source of CO<sub>2</sub> these years, especially 2018. There were also large losses of DOC during this period, which were further enhanced during 2019.</p>

Postglacial evolution of a small lake in the South Baltic coastal zone based on geochemical, pollen and subfossil Cladocera analysis

The paper presents sedimentary records acquired as part of the research on the coastal cliff located between 221.3 and 221.4 km of the Slovincian (Słowinskie) Coast near Debina. Palynological and subfossil Cladocera analysis of sediments combined with geochemical data proves the existence of varying environmental conditions that occurred depending on the climate fluctuation. The Debina reservoir was formed in the Late Glacial period. Mud and gyttja were deposited in an initially cold proglacial lake. Species of Cladocera identified in this period indicate a deeper oligotrophic reservoir. The end of the Late Glacial cooling inhibited the development of fauna in the reservoir. Climate change at the beginning of the Holocene improved the habitat conditions in the Debina paleolake, which is reflected in the growth of zooplankton biodiversity and enrichment of the aquatic pollen content. We distinguished three phases that illustrate the evolution of the studied aquatic-mire ecosystem. In the following periods, the trophic level in the reservoir increased and significant water-level fluctuations led to periodic transformations of reservoirs into peat bogs. Gradually, the water-level lowering and the intensification of eolian processes led to terrestrialization of the paleolake.

Multi-proxy reconstruction of mire development in the Poręby Wojsławskie ecosystem (Sandomierz Basin, southeastern Poland)

Multi-proxy analysis (sedimentological, palaeobotanical, geochemical data and results of radiocarbon dating) of the biogenic sediments from a small mire ecosystem in the Sandomierz Basin (SE Poland) is presented. The ecosystem contains a full hydroseral sequence from minerotrophic to ombrotrophic wetland. It is one of the few sites in this region which is so thoroughly investigated in terms of the palaeoenvironmental record. Changes in the water supply of the mire area, and consequently the changes in the plant and sediment succession, were well correlated with the regional tendencies in precipitation and temperature during the Late Glacial/Holocene transition and in the Holocene. Human impact is very well recorded in pollen diagram from the Subboreal period.