Tree stem methane emissions from subtropical lowland forest (Melaleuca quinquenervia) regulated by local and seasonal hydrology

Jeffrey, Luke C.; Maher, Damien T.; Tait, Douglas R.; Euler, Sebastian; Johnston, Scott G

doi:10.1007/s10533-020-00726-y

Cited by 40 publications

(53 citation statements)

References 61 publications

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“…In order to detect MOB activity, we monitored methane concentrations and isotope fractionation in methaneinoculated gas-tight bottles containing freshly collected Melaleuca quinquenervia bark samples from three different sites (see Supplementary Methods). Because the heavier 13 C-CH 4 isotope contains slightly stronger bonds, MOB preferentially consume 12 C-CH 4 , thereby triggering isotopic fractionation. Two laboratory time series experiments both revealed clear methane consumption coupled to δ 13 C-CH 4 enrichment (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…If MOB are a ubiquitous feature within the bark of methane emitting trees, our conceptual understanding of the global methane cycle may need revision. However, as the M. quinquenervia bark structure represents an ideal methane transport medium 12 and a potentially unique habitat for MOB communities, further work on a variety of tree species featuring more common dense and woody bark substrates is required to determine the generalisability of these findings. Future work in this frontier research area should also focus on (i) constraining MOB importance and magnitude of MOB in mitigating methane emissions from trees, (ii) investigating MOB ecophysiology through metagenomic, imaging and cultivation studies and (iii) determining MOB spatial and geographical distribution from tree scale to global scale, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Isotope time series inoculation experiment. The headspace concentration of CH 4 and δ 13 C-CH 4 of the inoculated bark bottles, the neutralised bark bottles and blanks were sampled using a CRDS with a sensitivity of 5 ppb + 0.05% of reading for 12 C and 1 ppb + 0.05% of reading for 13 C (Picarro, G2201-i). At 3 to 24 hourly intervals (increasing with experiment duration), a 60 mL gas sample of 101 ppm CH 4 was injected into the bottle septum using a long syringe needle, whilst simultaneously mixing and removing 60 mL of gas sample via a second and short syringe needle.…”

Section: Methodsmentioning

confidence: 99%

“…With an estimated three trillion trees on Earth 7 and reforestation/afforestation promoted as viable climate change mitigation strategies [8][9][10][11] , a mechanistic understanding of the processes driving and moderating methane emission from trees is of critical importance. Freshwater wetland trees typically emit much higher rates of methane 5,12,13 than their mangrove 14 and upland forest counterparts [15][16][17][18][19] . This is because the poorly drained, carbon-rich soils typical of freshwater wetland forests are favourable for methanogenesis.…”

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confidence: 99%

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Bark-dwelling methanotrophic bacteria decrease methane emissions from trees

et al. 2021

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Tree stems are an important and unconstrained source of methane, yet it is uncertain whether internal microbial controls (i.e. methanotrophy) within tree bark may reduce methane emissions. Here we demonstrate that unique microbial communities dominated by methane-oxidising bacteria (MOB) dwell within bark of Melaleuca quinquenervia, a common, invasive and globally distributed lowland species. In laboratory incubations, methane-inoculated M. quinquenervia bark mediated methane consumption (up to 96.3 µmol m−2 bark d−1) and reveal distinct isotopic δ13C-CH4 enrichment characteristic of MOB. Molecular analysis indicates unique microbial communities reside within the bark, with MOB primarily from the genus Methylomonas comprising up to 25 % of the total microbial community. Methanotroph abundance was linearly correlated to methane uptake rates (R2 = 0.76, p = 0.006). Finally, field-based methane oxidation inhibition experiments demonstrate that bark-dwelling MOB reduce methane emissions by 36 ± 5 %. These multiple complementary lines of evidence indicate that bark-dwelling MOB represent a potentially significant methane sink, and an important frontier for further research.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Bark-dwelling methanotrophic bacteria decrease methane emissions from trees

et al. 2021

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“…Although a higher proportion of methanogens to methanotrophs in inner and more anoxic parts of the tree diameter cannot be excluded, it is likely that soil sediment methanogens, rather than tree‐dwelling methanogens, sustain the high measured tree stem CH 4 emissions of this study (maximum flux recorded was 332 mmol m −2 d −1 ; Fig. 2), which represented some of the highest reported tree stem fluxes to date (Pangala et al ., 2017; Jeffrey et al ., 2020a; Sjögersten et al ., 2020). Furthermore, the maximum lower stem [CH 4 ] measured (10 411 and 149 ppm for Melaleuca and Casuarina , respectively) were c .…”

Section: Discussionmentioning

confidence: 99%

Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests

et al. 2021

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Summary Knowledge regarding mechanisms moderating methane (CH4) sink/source behaviour along the soil–tree stem–atmosphere continuum remains incomplete. Here, we applied stable isotope analysis (δ13C‐CH4) to gain insights into axial CH4 transport and oxidation in two globally distributed subtropical lowland species (Melaleuca quinquenervia and Casuarina glauca). We found consistent trends in CH4 flux (decreasing with height) and δ13C‐CH4 enrichment (increasing with height) in relation to stem height from ground. The average lower tree stem δ13C‐CH4 (0–40 cm) of Melaleuca and Casuarina (−53.96‰ and −65.89‰) were similar to adjacent flooded soil CH4 ebullition (−52.87‰ and −62.98‰), suggesting that stem CH4 is derived mainly by soil sources. Upper stems (81–200 cm) displayed distinct δ13C‐CH4 enrichment (Melaleuca −44.6‰ and Casuarina −46.5‰, respectively). Coupled 3D‐photogrammetry with novel 3D‐stem measurements revealed distinct hotspots of CH4 flux and isotopic fractionation on Melaleuca, which were likely due to bark anomalies in which preferential pathways of gas efflux were enhanced. Diel experiments revealed greater δ13C‐CH4 enrichment and higher oxidation rates in the afternoon, compared with the morning. Overall, we estimated that c. 33% of the methane was oxidised between lower and upper stems during axial transport, therefore potentially representing a globally significant, yet previously unaccounted for, methane sink.

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Climate change mitigation and improvement of water quality from the restoration of a subtropical coastal wetland

Iram

Maher

Lovelock

et al. 2022

Ecological Applications

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Coastal wetland restoration is an important activity to achieve greenhouse gas (GHG) reduction targets, improve water quality, and reach the Sustainable Development Goals. However, many uncertainties remain in connection with achieving, measuring, and reporting success from coastal wetland restoration.We measured levels of carbon (C) abatement and nitrogen (N) removal potential of restored coastal wetlands in subtropical Queensland, Australia. The site was originally a supratidal forest composed of Melaleuca spp. that was cleared and drained in the 1990s for sugarcane production. In 2010, tidal inundation was reinstated, and a mosaic of coastal vegetation (saltmarshes, mangroves, and supratidal forests) emerged. We measured soil GHG fluxes (CH 4 , N 2 O, CO 2 ) and sequestration of organic C in the trees and soil to estimate the net C abatement associated with the reference, converted, and restored sites. To assess the influence of restoration on water quality improvement, we measured denitrification and soil N accumulation. We calculated C abatement of 18.5 Mg CO 2Àeq ha À1 year À1 when sugarcane land transitioned to supratidal forests, 11.0 Mg CO 2Àeq ha À1 year À1 when the land transitioned to mangroves, and 6.2 Mg CO 2Àeq ha À1 year À1 when the land transitioned to saltmarshes. The C abatement was due to tree growth, soil accumulation, and reduced N 2 O emissions due to the cessation of fertilization. Carbon abatement was still positive, even accounting for CH 4 emissions, which increased in the wetlands due to flooding and N 2 O production due to enhanced levels of denitrification.Coastal wetland restoration in this subtropical setting effectively reduces CO 2 emissions while providing additional cobenefits, notably water quality improvement.

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Tree stem methane emissions from subtropical lowland forest (Melaleuca quinquenervia) regulated by local and seasonal hydrology

Cited by 40 publications

References 61 publications

Bark-dwelling methanotrophic bacteria decrease methane emissions from trees

Bark-dwelling methanotrophic bacteria decrease methane emissions from trees

Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests

Climate change mitigation and improvement of water quality from the restoration of a subtropical coastal wetland

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