Methane emissions may be driven by hydrogenotrophic methanogens inhabiting the stem tissues of poplar

We provide the raw stem and soil CH4 flux data from our recent study in New Phytologist. Out study highlights are as follows: • Living trees in forests emit methane (CH4) from their stems. However, the magnitudes, patterns, drivers, origins, and biogeochemical pathways of these emissions remain poorly understood. • We hypothesized that: 1) the stem and soil CH4 emission presented a typically seasonal tendency, which may be driven by the temperature and moisture and 2) the hydrogenotrophic methanogens dwelling in stem tissues could explain the CH4 emission from the stem. • We measured in situ CH4 fluxes in poplar stems and soils using static chambers and investigated the microbial communities of heartwood and sapwood by sequencing bacterial 16S, archaeal 16S, and fungal ITS rRNA genes. • The temporal variation of soil CH4 fluxes follows the same pattern as stem fluxes. CH4 emissions from poplar stems occurred throughout the sampling period. The mean CH4 emission rate was 2.65 mg·m−2·stem·d−1. However, soil could emit CH4 to atmosphere in summer but uptake CH4 from atmosphere in other seasons. The mean soil CH4 fluxes ranged from -0.48 mg·m–2·soil·d–1 on 15 November to 8.37 mg·m–2·soil·d–1 on 15 August. Stem CH4 emission rate increased significantly with air temperature, humidity, soil water content, and soil CH4 fluxes, but decreased with increasing sampling height. • The CO2 reduction and methylotrophic methanogenesis were the major methanogenic pathways in wood tissues. • Overall, stem CH4 emissions can originate directly from the internal tissues or co-occur from soils and stems. The co-existence of methanogens and methanotrophs within heartwood and sapwood highlights a need for future research in the microbial mechanisms underlying stem CH4 exchange with the atmosphere