Methane exchange in a boreal forest estimated by gradient method

Sundqvist, Elin; Mölder, Meelis; Crill, Patrick; Kljun, Natascha; Lindroth, Anders

doi:10.3402/tellusb.v67.26688

Cited by 19 publications

(9 citation statements)

References 60 publications

(73 reference statements)

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“…Other studies have reported daytime minima [49,103] in CH 4 fluxes. Sundqvist, Mölder [104] measured CH 4 fluxes in the Norunda forest with different gradient methods above the canopy and suggested that the observed daytime minima could be a result of plant uptake (as previously observed from branch chamber measurements by Sundqvist, Crill [105]) and that the observed nighttime maxima could be a result of larger nighttime footprints, with distant, wetter source areas (such as the clear-cut in this study) contributing more to the measured fluxes than during daytime.…”

Section: Diel Patterns Of Ch 4 and N 2 O Fluxessupporting

confidence: 78%

Impacts of Clear-Cutting of a Boreal Forest on Carbon Dioxide, Methane and Nitrous Oxide Fluxes

Vestin

Mölder

Kljun

et al. 2020

Forests

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The 2015 Paris Agreement encourages stakeholders to implement sustainable forest management policies to mitigate anthropogenic emissions of greenhouse gases (GHG). The net effects of forest management on the climate and the environment are, however, still not completely understood, partially as a result of a lack of long-term measurements of GHG fluxes in managed forests. During the period 2010–2013, we simultaneously measured carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes using the flux-gradient technique at two clear-cut plots of different degrees of wetness, located in central Sweden. The measurements started approx. one year after clear-cutting, directly following soil scarification and planting. The study focused on robust inter-plot comparisons, spatial and temporal dynamics of GHG fluxes, and the determination of the global warming potential of a clear-cut boreal forest. The clear-cutting resulted in significant emissions of GHGs at both the wet and the dry plot. The degree of wetness determined, directly or indirectly, the relative contribution of each GHG to the total budgets. Faster establishment of vegetation on the wet plot reduced total emissions of CO2 as compared to the dry plot but this was partially offset by higher CH4 emissions. Waterlogging following clear-cutting likely caused both plots to switch from sinks to sources of CH4. In addition, there were periods with N2O uptake at the wet plot, although both plots were net sources of N2O on an annual basis. We observed clear diel patters in CO2, CH4 and N2O fluxes during the growing season at both plots, with the exception of CH4 at the dry plot. The total three-year carbon budgets were 4107 gCO2-equivalent m−2 and 5274 gCO2-equivalent m−2 at the wet and the dry plots, respectively. CO2 contributed 91.8% to the total carbon budget at the wet plot and 98.2% at the dry plot. For the only full year with N2O measurements, the total GHG budgets were 1069.9 gCO2-eqvivalents m−2 and 1695.7 gCO2-eqvivalents m−2 at the wet and dry plot, respectively. At the wet plot, CH4 contributed 3.7%, while N2O contributed 7.3%. At the dry plot, CH4 and N2O contributed 1.5% and 7.6%, respectively. Our results emphasize the importance of considering the effects of the three GHGs on the climate for any forest management policy aiming at enhancing the mitigation potential of forests.

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Section: Diel Patterns Of Ch 4 and N 2 O Fluxessupporting

confidence: 78%

Impacts of Clear-Cutting of a Boreal Forest on Carbon Dioxide, Methane and Nitrous Oxide Fluxes

Vestin

Mölder

Kljun

et al. 2020

Forests

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“…Water table depth is a master variable that controls patterns of soil O 2 and redox potential in upland and wetland forests (Megonigal et al ., ), and strongly regulates rates of CH 4 consumption by upland soils (Topp & Pattey, ), CH 4 emission by wetland soils (Turetsky et al ., ), and CH 4 emissions by both wetland and upland tree stems (Pangala et al ., ; Terazawa et al ., ; Pitz et al ., ). Water table depth was a likely source of spatial variation in an upland boreal forest that appeared to be a net CH 4 sink when tree and soil fluxes were measured by small‐scale chambers, but a net source when measured by large‐scale micrometeorological methods (Sundqvist et al ., ). In this case, small areas of wet soils in the tower footprint may have been strong CH 4 sources.…”

Section: Trees In Forest Ch4 Budgetsmentioning

confidence: 97%

Methane production and emissions in trees and forests

2019

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Forest ecosystem methane (CH 4 ) research has focused on soils, but trees are also important sources and sinks in forest CH 4 budgets. Living and dead trees transport and emit CH 4 produced in soils; living trees and dead wood emit CH 4 produced inside trees by microorganisms; and trees produce CH 4 through an abiotic photochemical process. Here, we review the state of the science on the production, consumption, transport, and emission of CH 4 by living and dead trees, and the spatial and temporal dynamics of these processes across hydrologic gradients inclusive of wetland and upland ecosystems. Emerging research demonstrates that tree CH 4 emissions can significantly increase the source strength of wetland forests, and modestly decrease the sink strength of upland forests. Scaling from stem or leaf measurements to trees or forests is limited by knowledge of the mechanisms by which trees transport soil-produced CH 4 , microbial processes produce and oxidize CH 4 inside trees, a lack of mechanistic models, the diffuse nature of forest CH 4 fluxes, complex overlap between sources and sinks, and extreme variation across individuals. Understanding the complex processes that regulate CH 4 source-sink dynamics in trees and forests requires cross-disciplinary research and new conceptual models that transcend the traditional binary classification of wetland vs upland forest.

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“…While chamber measurements usually found that the soil acted as a sink for atmospheric CH 4 , the latter studies have shown that boreal forests are net sources of CH 4 , contributing about 7.5% to the global CH 4 emissions (Bergamaschi et al., ; Sinha et al., ). These emissions could not be attributed to light‐dependent CH 4 production by the vegetation as no differences were observed between day and night time emissions (Bergamaschi et al., ; Sundqvist et al., ). Based on our results we hypothesize that CH 4 emissions from moss could be in part contributing to the observed CH 4 emissions in boreal forests.…”

Section: Discussionmentioning

confidence: 99%

“…Hence, these soils were regarded to be net CH 4 sinks (Conrad, 1996;LeMer & Roger, 2001). However, quantification of CH 4 emissions (DoCarmo, Keller, Dias, DeCamargo, & Crill, 2006;Machacova et al, 2016;Sinha, Williams, Crutzen, & Lelieveld, 2007;Sundqvist, M€ older, Crill, Kljun, & Lindroth, 2015) and remote sensing methods (Frankenberg, Meirink, VanWeele, Platt, & Wagner, 2005) showed large uncertainties in CH 4 fluxes from forest ecosystems (Bergamaschi et al, 2007;Frankenberg et al, 2005), challenging the perceived role of forests as net CH 4 sinks.…”

Section: Introductionmentioning

confidence: 99%

Methane emission from feather moss stands

Kanaparthi

Reim

Martinson

et al. 2017

Global Change Biology

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Data from remote sensing and Eddy towers indicate that forests are not always net sinks for atmospheric CH . However, studies describing specific sources within forests and functional analysis of microorganisms on sites with CH turnover are scarce. Feather moss stands were considered to be net sinks for carbon dioxide, but received little attention to their role in CH cycling. Therefore, we investigated methanogenic rates and pathways together with the methanogenic microbial community composition in feather moss stands from temperate and boreal forests. Potential rates of CH emission from intact moss stands (n = 60) under aerobic conditions ranged between 19 and 133 pmol CH h gdw . Temperature and water content positively influenced CH emission. Methanogenic potentials determined under N atmosphere in darkness ranged between 22 and 157 pmol CH h gdw . Methane production was strongly inhibited by bromoethane sulfonate or chloroform, showing that CH was of microbial origin. The moss samples tested contained fluorescent microbial cells and between 10 and 10 copies per gram dry weight moss of the mcrA gene coding for a subunit of the methyl CoM reductase. Archaeal 16S rRNA and mcrA gene sequences in the moss stands were characteristic for the archaeal families Methanobacteriaceae and Methanosarcinaceae. The potential methanogenic rates were similar in incubations with and without methyl fluoride, indicating that the CH was produced by the hydrogenotrophic rather than aceticlastic pathway. Consistently, the CH produced was depleted in C in comparison with the moss biomass carbon and acetate accumulated to rather high concentrations (3-62 mM). The δ C of acetate was similar to that of the moss biomass, indicating acetate production by fermentation. Our study showed that the feather moss stands contained active methanogenic microbial communities producing CH by hydrogenotrophic methanogenesis and causing net emission of CH under ambient conditions, albeit at low rates.

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Methane exchange in a boreal forest estimated by gradient method

Cited by 19 publications

References 60 publications

Impacts of Clear-Cutting of a Boreal Forest on Carbon Dioxide, Methane and Nitrous Oxide Fluxes

Impacts of Clear-Cutting of a Boreal Forest on Carbon Dioxide, Methane and Nitrous Oxide Fluxes

Methane production and emissions in trees and forests

Methane emission from feather moss stands

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