Rapid bark-mediated tree stem methane transport occurs independently of the transpiration stream in Melaleuca quinquenervia

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This electronic data available here was used to write the manuscript titled: Rapid bark-mediated tree stem methane transport occurs independently of the transpiration stream in Melaleuca quinquenervia, which was accepted in New Phytologist (27/10/2023). A summary of the research findings in this publication are: • Tree stem methane emissions are important components of lowland forest methane budgets. The potential for species-specific behaviour among co-occurring lowland trees with contrasting bark characteristics has not been investigated. • We compare bark-mediated methane transport in two common lowland species of contrasting bark characteristics (Melaleuca quinquenervia featuring spongy/layered bark with longitudinally-continuous airspaces and Casuarina glauca featuring hard/dense common bark) through several manipulative experiments. • Firstly, the progressive cutting through M. quinquenervia bark layers caused exponential increases in methane fluxes (~3 orders of magnitude), however sapwood-only fluxes were lower, suggesting that upward/axial methane transport occurs between bark layers. Secondly, concentrated methane pulse injections into exposed M. quinquenervia bark, revealed rapid axial methane transport rates (1.42 mm/s), which were further supported through lab-simulated experiments (1.41 mm/s). Lab-simulated radial CH4 diffusion rates (through bark) were ~20-times slower. Finally, girdling M. quinquenervia stems caused a near-instantaneous decrease in methane flux immediately above the cut. In contrast, girdling C. glauca displayed persistent, though diminished, methane fluxes. • Overall, the experiments revealed evidence for rapid ‘between-bark’ methane transport independent from the transpiration stream in M. quinquenervia, which facilitates diffusive axial transport from the rhizosphere and/or sapwood sources. This contrasts with the slower, radial ‘through-bark’ diffusive-dominated gas transportation in C. glauca.

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