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Mosses of the genus Sphagnum are the dominant vegetation in most pristine peatlands in temperate and high‐latitude regions. They play a crucial role in carbon sequestration, being responsible for ca. 50% of carbon accumulation through their active participation in peat formation. They have a significant influence on the dynamics of CO2 emissions due to an efficient maximum potential photosynthetic rate, lower respiration rates, and the production of a recalcitrant litter whose decomposition is gradual. However, various anthropogenic disturbances and land use management actions that favor its reestablishment have the potential to modify the dynamics of these CO2 emissions. Therefore, the objective of this review is to discuss the role of Sphagnum in CO2 emissions generated in peatland ecosystems, and to understand the impacts of anthropogenic practices favorable and detrimental to Sphagnum on these emissions. Based on our review, increased Sphagnum cover reduces CO2 emissions and fosters C sequestration, but drainage transforms peatlands dominated by Sphagnum into a persistent source of CO2 due to lower gross primary productivity of the moss and increased respiration rates. Sites with moss removal used as donor material for peatland restoration emit twice as much CO2 as adjacent undisturbed natural sites, and those with commercial Sphagnum extraction generate almost neutral CO2 emissions, yet both can recover their sink status in the short term. The reintroduction of fragments and natural recolonization of Sphagnum in transitional peatlands, can reduce emissions, recover, or increase the CO2 sink function in the short and medium term. Furthermore, Sphagnum paludiculture is seen as a sustainable alternative for the use of transitional peatlands, allowing moss production strips to become CO2 sink, however, it is necessary to quantify the emissions of all the components of the field of production (ditches, causeway), and the biomass harvested from the moss to establish a final closing balance of C. [ABSTRACT FROM AUTHOR]

We present a reliable and robust open dynamic chamber for measuring greenhouse gas exchange in peatlands with minimal disturbance of the ground. This chamber, called the "skirt chamber", is based on a transparent plastic film placed above an open frame made of sparse interwoven wires and expanded around the base of the chamber below a steel chain that ensures contact to the ground, avoiding damage, trenching, and cutting vegetation. Gas exchange is determined using a portable gas analyzer from a mass balance in which the imperfect sealing of the chamber to the ground is quantified through the injection of a methane pulse. The method was tested on a pristine peatland dominated by Sphagnum magellanicum located on Navarino Island in the subantarctic Magellanic ecoregion in Chile. Our results indicate that the skirt chamber allowed the determination of methane fluxes and ecosystem respiration in about 20 min, with a limit of detection of 0.185 mg CH 4 m -2 h -1 and 173 mg CO 2 m -2 h -1 , respectively. We conclude that the skirt chamber is a minimally intrusive, fast, portable, and inexpensive method that allows the quantification of greenhouse gas emissions with high spatial resolution in remote locations and without delay. [ABSTRACT FROM AUTHOR]

Peatland open‐water pools can be net carbon (C) emitters within heterogeneous peatland ecosystems that are generally net C sinks. However, the intra‐ and inter‐regional patterns and drivers of CO2 and CH4 production, as well as their link with dissolved organic matter (DOM) quality and quantity, remain poorly understood. We analyzed a range of optical characteristics and chemical variables controlling DOM and CO2 and CH4 concentrations in peatland pools across two regions with contrasting geographical properties (i.e., climate, topography, morphometry, and vegetation cover) of eastern Canada and Chilean Patagonia. We found inter‐regional patterns in CO2, CH4 and DOM concentrations and composition that were coherent with patterns in mean annual temperature and precipitation, and vegetation cover. Cross‐regional patterns of CO2 and CH4 were driven by morphometry, vegetation cover, and protein‐like DOM composition, a proxy of high biological activity, whereas temporal variations of CO2 and CH4 concentrations were further influenced by seasonal changes in humic‐like DOM composition, dissolved organic carbon and nutrients (i.e., total phosphorus and total nitrogen) concentrations, as well as pH and oxygen levels. Our results suggest that geophysical constraints associated with local peat and pool characteristics as well as climate patterns are major drivers of DOM and greenhouse gases concentrations and the links between them in broadly distributed peatland pools. Key Points: Broad‐scale patterns in peatland pools dissolved organic matter (DOM) and CO2 were driven by vegetation cover and pool morphometryBroad‐scale patterns in CH4 were the most responsive among C‐species to long‐term climate averages across regionsProtein‐like DOM controls within‐pool greenhouse gases (GHG) concentrations across regions, while humic‐like DOM drives within‐site temporal GHG concentrations [ABSTRACT FROM AUTHOR]

Abstract: A fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (δ13C‐CH4) in surface waters was developed by applying a vacuum to a gas/liquid exchange membrane and measuring the extracted gases by a portable cavity ring‐down spectroscopy analyser (M‐CRDS). The M‐CRDS was calibrated and characterized for CH4 concentration and δ13C‐CH4 with synthetic water standards. The detection limit of the M‐CRDS for the simultaneous determination of CH4 and δ13C‐CH4 is 3.6 nmol L−1 CH4. A measurement precision of CH4 concentrations and δ13C‐CH4 in the range of 1.1%, respectively, 1.7‰ (1σ) and accuracy (1.3%, respectively, 0.8‰ [1σ]) was achieved for single measurements and averaging times of 10 min. The response time τ of 57 ± 5 s allow determination of δ13C‐CH4 values more than twice as fast than other methods. The demonstrated M‐CRDS method was applied and tested for Lake Stechlin (Germany) and compared with the headspace‐gas chromatography and fast membrane CH4 concentration methods. Maximum CH4 concentrations (577 nmol L−1) and lightest δ13C‐CH4 (−35.2‰) were found around the thermocline in depth profile measurements. The M‐CRDS‐method was in good agreement with other methods. Temporal variations in CH4 concentration and δ13C‐CH4 obtained in 24 h measurements indicate either local methane production/oxidation or physical variations in the thermocline. Therefore, these results illustrate the need of fast and sensitive analyses to achieve a better understanding of different mechanisms and pathways of CH4 formation in aquatic environments. [ABSTRACT FROM AUTHOR]