Significant Global Methane Emissions from Tree Stems

Understanding the global patterns and magnitudes of methane (CH4) fluxes in terrestrial ecosystems and the underlying processing driving these fluxes is crucial for climate change mitigation. However, knowledge of the global CH4 emissions from tree stems and soil, as well as the influences of various biotic and abiotic conditions remain limited. Here, we compiled a comprehensive dataset consisting of 2,373 in situ observations of CH4 fluxes, including 2,255 from soil and 118 from tree stems. Using this dataset, we evaluated the environmental controls of soil and tree stem CH4 fluxes, and utilized machine learning techniques to upscale the global distribution and estimate global emissions. The results indicated that CH4 fluxes in terrestrial ecosystems were largely driven by vegetation characteristics and their interaction with soil moisture and water table dynamics. The estimated annual emissions of terrestrial ecosystems were 173.81 Tg CH4 yr−1 (152.46–203.02 Tg CH4 yr−1), with 139.85–176.21 Tg CH4 yr−1 emitted by soil and 12.61–26.81 Tg CH4 yr−1 emitted by tree stems. The findings underscored the unignorable CH4 emissions from tree stems.The full dataset for publications used in our machine learning model and the global CH4 budget in terrestrial ecosystems from soils and tree stems at a 10 km resolution generated using machine learning (Figure 5 and Figure 6) are available.