New insight to the role of microbes in the methane exchange in trees: evidence from metagenomic sequencing

Abstract

Methane (CH 4 ) exchange in tree stems and canopies and the processes involved are among the least understood components of the global CH 4 cycle. Recent studies have focused on quantifying tree stems as sources of CH 4 and understanding abiotic CH 4 emissions in plant canopies, with the role of microbial in situ CH 4 formation receiving less attention. Moreover, despite initial reports revealing CH 4 consumption, studies have not adequately evaluated the potential of microbial CH 4 oxidation within trees. In this paper, we discuss the current level of understanding on these processes. Further, we demonstrate the potential of novel metagenomic tools in revealing the involvement of microbes in the CH 4 exchange of plants, and particularly in boreal trees. We detected CH 4 -producing methanogens and novel monooxygenases, potentially involved in CH 4 consumption, in coniferous plants. In addition, our field flux measurements from Norway spruce (Picea abies) canopies demonstrate both net CH 4 emissions and uptake, giving further evidence that both production and consumption are relevant to the net CH 4 exchange. Our findings, together with the emerging diversity of novel CH 4 -producing microbial groups, strongly suggest microbial analyses should be integrated in the studies aiming to reveal the processes and drivers behind plant CH 4 exchange.

Solar radiation drives methane emissions from the shoots of Scots pine

“…A brief summary of the CH 4 fluxes from Norway spruce shoots measured in 2020 was presented previously by Putkinen et al . (2021); however, so far, no thorough analysis of this dataset has been reported. Our data from 2019 or from the Scots pine measurements of 2020 have not been presented before.…”

“…Overall, there were 181 Scots pine, 53 Norway spruce and 55 empty chamber measurements made in 2019, and 205 Scots pine, 89 Norway spruce and 46 empty chamber measurements made in 2020. A brief summary of the CH 4 fluxes from Norway spruce shoots measured in 2020 was presented previously by Putkinen et al (2021); however, so far, no thorough analysis of this dataset has been reported. Our data from 2019 or from the Scots pine measurements of 2020 have not been presented before.…”

“…Vegetation has recently been recognized as an important component of the global cycle of methane (CH 4 ), a powerful greenhouse gas (Carmichael et al ., 2014). Plants, both woody and herbaceous, can contribute to the CH 4 exchange of different ecosystems via various pathways: soil‐derived CH 4 can be exported through stems (Pangala et al ., 2013, 2015; Barba et al ., 2019), CH 4 may be produced aerobically in foliage (Keppler et al ., 2006; Brüggemann et al ., 2009; Qaderi & Reid, 2009, 2011; Wang et al ., 2009; Fraser et al ., 2015; Martel & Qaderi, 2017, 2019), and it may be produced by microbial methanogenesis within core wood and potentially also other plant tissues (Yip et al ., 2019; Putkinen et al ., 2021). These fluxes, however, have not been incorporated into global CH 4 budgets as fundamental questions about the mechanisms, drivers and quantities of plant CH 4 emissions remain unaddressed (Saunois et al ., 2020).…”

“…Fluxes of CH 4 from the canopies of evergreen trees have only been reported in a handful of field studies. These results vary from small emissions early in the summer from Scots pine (Machacova et al ., 2016) to both small emissions and apparent uptake by Norway spruce in the summer (Putkinen et al ., 2021), and uptake in low light conditions late in the fall (Sundqvist et al ., 2012). It remains unknown how the high seasonal variations typical to the boreal climate affect the canopy CH 4 fluxes.…”

Advantage of conductive materials on interspecies electron transfer-independent acetoclastic methanogenesis: A critical review

“…Biomethane is produced solely by microbial methanogens, which belong to the archaea kingdom, yet precise microbial mechanisms of biomethane production are not fully understood [114,21]. A better knowledge of factors controlling biomethane emission would be useful both to improve industrial biomethane production, and to design techniques of land management that limit methane emission to the atmosphere [24,79,80,96]. This manuscript reviews the latest reports on mechanisms of methanogenesis by anaerobic fermentation.…”