Impacts of moisture, soil respiration, and agricultural practices on methanogenesis in upland soils as measured with stable isotope pool dilution

Brewer, Paul E.; Calderón, Francisco J.; Vigil, Merle F.; Fischer, Joseph C. von

doi:10.1016/j.soilbio.2018.09.014

Cited by 38 publications

(31 citation statements)

References 55 publications

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“…Soils can be net CH 4 sinks at surface level but could produce CH 4 at deeper depths 21 . We postulate that it is possible that tree roots might take up water from deep layers with dissolved CH 4 produced in deep anoxic layers or anoxic microsites 56,57 and bypass the surface methanotrophic layers in the soil 7 . Second, across certain days along the growing season we found temporal correlation at the 1-day period between CH 4 fluxes and SF, which directly links stem emissions with stem water transport and thus, with water coming from belowground in the transpiration stream.…”

Section: Discussionmentioning

confidence: 99%

Automated measurements of greenhouse gases fluxes from tree stems and soils: magnitudes, patterns and drivers

Barba

Poyatos

Vargas

2019

Sci Rep

125

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Tree stems exchange CO 2 , CH 4 and N 2 O with the atmosphere but the magnitudes, patterns and drivers of these greenhouse gas (GHG) fluxes remain poorly understood. Our understanding mainly comes from static-manual measurements, which provide limited information on the temporal variability and magnitude of these fluxes. We measured hourly CO 2 , CH 4 and N 2 O fluxes at two stem heights and adjacent soils within an upland temperate forest. We analyzed diurnal and seasonal variability of fluxes and biophysical drivers (i.e., temperature, soil moisture, sap flux). Tree stems were a net source of CO 2 (3.80 ± 0.18 µmol m −2 s −1 ; mean ± 95% CI) and CH 4 (0.37 ± 0.18 nmol m −2 s −1 ), but a sink for N 2 O (−0.016 ± 0.008 nmol m −2 s −1 ). Time series analysis showed diurnal temporal correlations between these gases with temperature or sap flux for certain days. CO 2 and CH 4 showed a clear seasonal pattern explained by temperature, soil water content and sap flux. Relationships between stem, soil fluxes and their drivers suggest that CH 4 for stem emissions could be partially produced belowground. High-frequency measurements demonstrate that: a) tree stems exchange GHGs with the atmosphere at multiple time scales; and b) are needed to better estimate fluxes magnitudes and understand underlying mechanisms of GHG stem emissions.

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Section: Discussionmentioning

confidence: 99%

Automated measurements of greenhouse gases fluxes from tree stems and soils: magnitudes, patterns and drivers

Barba

Poyatos

Vargas

2019

Sci Rep

125

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“…High CH 4 emission rates from wetland trees are evidence that mature trees also transport soil‐produced CH 4 (Table ). Less well established is the observation that CH 4 is produced in freely drained upland soils in anaerobic microsites (Von Fischer & Hedin, ; Brewer et al ., ). Mature upland trees may transport CH 4 produced in soil microsites or groundwater (Megonigal & Guenther, ), but this has not been demonstrated conclusively in situ .…”

Section: Tree Emissions Of Soil‐produced Ch4mentioning

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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“…To the best of our knowledge, isotope measurements of CH 4 stem fluxes have never been made in upland forests, but, in tropical floodplain forests, initial measurements suggest little and inconsistent differences between pore water and emitted δ 13 C of CH 4 (Pangala et al ., ). Simultaneous methanogenesis and methanotrophy in stem wood could be disentangled using a stable isotope pool dilution approach under laboratory conditions, a technique that has detected and quantified these simultaneous gross fluxes in upland soils (von Fischer & Hedin, ; Brewer et al ., ). Finally, isotopic labeling experiments would also be a useful approach to unravel the origin of CH 4 emitted from trees, as performed for CH 4 emissions from soils (Chowdhury & Dick, ) and lakes (Conrad et al ., ).…”

Section: Sources Of Ch4 Emissionsmentioning

confidence: 97%

“…It has been suggested that CH 4 produced in deep layers could bypass the soil methanotrophic layer via root transport (Megonigal & Guenther, ), highlighting the potential relevance of active transport by sap flow for stem emissions. Alternatively, trees may take up CH 4 from upland methanogenic microsites (von Fischer & Hedin, ; Yang & Silver, ; Brewer et al ., ) at relatively shallow depths, or directly from rhizosphere anoxic microsites (Baggs, ). On the other hand, as CH 4 and O 2 biogeochemical pathways are interrelated, the measurement of O 2 concentrations at different soil depths could provide valuable information on CH 4 production and oxidation.…”

Section: Sources Of Ch4 Emissionsmentioning

confidence: 99%

Methane emissions from tree stems: a new frontier in the global carbon cycle

et al. 2018

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Summary Tree stems from wetland, floodplain and upland forests can produce and emit methane (CH4). Tree CH4 stem emissions have high spatial and temporal variability, but there is no consensus on the biophysical mechanisms that drive stem CH4 production and emissions. Here, we summarize up to 30 opportunities and challenges for stem CH4 emissions research, which, when addressed, will improve estimates of the magnitudes, patterns and drivers of CH4 emissions and trace their potential origin. We identified the need: (1) for both long‐term, high‐frequency measurements of stem CH4 emissions to understand the fine‐scale processes, alongside rapid large‐scale measurements designed to understand the variability across individuals, species and ecosystems; (2) to identify microorganisms and biogeochemical pathways associated with CH4 production; and (3) to develop a mechanistic model including passive and active transport of CH4 from the soil–tree–atmosphere continuum. Addressing these challenges will help to constrain the magnitudes and patterns of CH4 emissions, and allow for the integration of pathways and mechanisms of CH4 production and emissions into process‐based models. These advances will facilitate the upscaling of stem CH4 emissions to the ecosystem level and quantify the role of stem CH4 emissions for the local to global CH4 budget.

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Impacts of moisture, soil respiration, and agricultural practices on methanogenesis in upland soils as measured with stable isotope pool dilution

Cited by 38 publications

References 55 publications

Automated measurements of greenhouse gases fluxes from tree stems and soils: magnitudes, patterns and drivers

Automated measurements of greenhouse gases fluxes from tree stems and soils: magnitudes, patterns and drivers

Methane production and emissions in trees and forests

Methane emissions from tree stems: a new frontier in the global carbon cycle

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