Standing Dead Trees are a Conduit for the Atmospheric Flux of CH4 and CO2 from Wetlands

Carmichael, Mary Jane; Helton, Ashley M.; White, Joseph C.; Smith, William K.

doi:10.1007/s13157-017-0963-8

Cited by 21 publications

(24 citation statements)

References 72 publications

(100 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They were, however, much lower than tropical Amazon floodplain tree CH 4 fluxes that were one to two orders of magnitude higher than our data (Pangala et al ., ). The only other published standing dead tree stem CH 4 emissions (600 μmol m −2 d −1 ), were from a restored coastal freshwater wetland of North Carolina (Carmichael et al ., ), which was similar to our dead stem fluxes (Fig. ).…”

Section: Discussionsupporting

confidence: 90%

“…It is conceivable that active rhizosphere O 2 transport near the root/sediment interface may attenuate CH 4 production and accumulation near the root interface, which may help explain the lower CH 4 fluxes from living tree stems. When tree mortality occurs, water is evacuated from the complex internal hydraulic channels within the trees, spanning from the roots to the atmosphere; leaving an array of empty internal cavities that facilitate upward (nonpressurized) diffusive gas transportation (Carmichael et al ., ). It is also plausible that a portion of the CH 4 flux from dead stems originates aboveground due to the chemical degradation of plant tissue (Keppler et al ., ), in situ methanogenesis from organic matter decomposition (Covey et al ., ; Wang et al ., ), or CH 4 from saprotrophic fungi (Mukhin & Voronin, ; Lenhart et al ., ).…”

Section: Discussionmentioning

confidence: 97%

See 1 more Smart Citation

Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality

et al. 2019

View full text Add to dashboard Cite

Summary Growing evidence indicates that tree‐stem methane (CH4) emissions may be an important and unaccounted‐for component of local, regional and global carbon (C) budgets. Studies to date have focused on upland and freshwater swamp‐forests; however, no data on tree‐stem fluxes from estuarine species currently exist. Here we provide the first‐ever mangrove tree‐stem CH4 flux measurements from >50 trees (n = 230 measurements), in both standing dead and living forest, from a region suffering a recent large‐scale climate‐driven dieback event (Gulf of Carpentaria, Australia). Average CH4 emissions from standing dead mangrove tree‐stems was 249.2 ± 41.0 μmol m−2 d−1 and was eight‐fold higher than from living mangrove tree‐stems (37.5 ± 5.8 μmol m−2 d−1). The average CH4 flux from tree‐stem bases (c. 10 cm aboveground) was 1071.1 ± 210.4 and 96.8 ± 27.7 μmol m−2 d−1 from dead and living stands respectively. Sediment CH4 fluxes and redox potentials did not differ significantly between living and dead stands. Our results suggest both dead and living tree‐stems act as CH4 conduits to the atmosphere, bypassing potential sedimentary oxidation processes. Although large uncertainties exist when upscaling data from small‐scale temporal measurements, we estimated that dead mangrove tree‐stem emissions may account for c. 26% of the net ecosystem CH4 flux.

show abstract

Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 97%

Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality

et al. 2019

View full text Add to dashboard Cite

show abstract

“…() demonstrated that transpiration‐driven CH 4 emissions varies with CO 2 concentration, humidity and other variables that affect stomatal conductance. Diffusive transport of soil‐produced CH 4 can continue after tree death, although net CH 4 consumption on standing dead trees has also been observed (Carmichael et al ., ).…”

Section: Tree Emissions Of Soil‐produced Ch4mentioning

confidence: 97%

Methane production and emissions in trees and forests

2019

View full text Add to dashboard Cite

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.

show abstract

“…White and Kaplan (2021) estimate that 19,480 km 2 of coastal forested wetlands have transitioned to other habitat types from 1986 to 2016, some of which were ghost forests at some point during the transition. Snags have the potential to transport soil produced CH 4 through the root and plant tissue cells to the atmosphere, but CH 4 emitted could also be produced internally due to decomposition (Carmichael and Smith, 2016;Carmichael et al, 2017). As the climate changes, ghost forests are projected to expand in area (Kirwan and Gedan, 2019), and therefore could emit a substantial amount of greenhouse gases to the local and regional carbon cycle (Martinez and Ardón, 2021).…”

Section: Introductionmentioning

confidence: 99%

Identifying Sources and Oxidation of Methane in Standing Dead Trees in Freshwater Forested Wetlands

Martinez

Ardón

Carmichael

2022

Front. Environ. Sci.

Self Cite

View full text Add to dashboard Cite

Wetlands are large sources of methane (CH4), therefore it is vital to understand the pathways, mechanisms, and sources to anticipate future positive feedbacks to climate change. Plant mediated transport of CH4 from sediment-borne gases is thought to be a major contributor in wetland ecosystems, though few studies have measured standing dead trees (snags). Snags are expected to become more common across the southeastern coast as marshes migrate into freshwater forested wetlands. In this study, our goal was to distinguish the main sources of CH4 being emitted from snags, that is, from soil or in situ origin. The δ2H and δ13C stable isotopic composition from various sources was sampled for source determination. We measured CH4 in various components: emissions from snag stem sides and the soil-atmosphere interface; and concentrations from snag trunk airspace at various heights from ground level (30, 60, and 120 cm), and soil porewater. Potential CH4 production and oxidation in tree cores from two heights (60 and 120 cm) was also measured to examine the potential for CH4 generation or oxidation in stems. We found that CH4 concentrations inside snags (∼10–200 ppm) were 2–50 times higher than atmospheric levels, and generally decreased with increasing stem height. The stable isotopes δ13C and δ2H showed an enrichment from porewater to soils and snag stems. δ13C enrichment of CH4 in snag stems suggests that CH4 is being oxidized as it moves through snags. The tree core vial incubations showed that very few cores produced small amounts of CH4 under anaerobic conditions (n = 5 out of 50), and very few cores oxidized CH4 under more aerobic conditions (n = 5 out of 50). It is possible that a small amount of CH4 is produced in-situ within the heartwood, but it is likely this depends on the density, porosity, and aeration of snags (degree of decay). Our results highlight that high concentrations of CH4 can persist within the heartwood of snags long after initial decay, and that CH4 emitted from snags is largely derived from deep wetland soils and oxidized during transport (via diffusion) throughout the stem of snags.

show abstract

Standing Dead Trees are a Conduit for the Atmospheric Flux of CH4 and CO2 from Wetlands

Cited by 21 publications

References 72 publications

Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality

Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality

Methane production and emissions in trees and forests

Identifying Sources and Oxidation of Methane in Standing Dead Trees in Freshwater Forested Wetlands

Contact Info

Product

Resources

About