CH4 production and emissions from the upper parts of tree trunks in cool-temperate upland forest

Trees, typically large trees in upland forests, emit CH4 produced in their trunk by methanogenic archaea. In this case, the spatial variability of emissions can be more complicated than when tree trunks act as a passive conduit for CH4 produced in the soil. However, due to poor accessibility, CH4 emissions from the trunk above 3 m, where a researcher cannot reach without a ladder, scaffold, or crane, have not been well studied. In this study, we investigated vertical patterns of CH4 emissions, internal CH4 concentration, production, and copy number of the methanogenic archaeal gene mcrA at 6 different heights up to 12 m above ground, in six trees of three species in a cool-temperate upland forest., We targeted 6 mature trees from 3 species in a cool-temperate upland mixed forest. We measured variables at 6 different heights per 1 individual.
Trunk CH4 flux was measured by the dynamic closed chamber method. A polypropylene chamber, with a measuring area of 37 cm2 on average and a volume of 695 mL, including the cell of the analyser and tubing, was attached to the trunk with neutral seal putty. A lid connected to a portable trace gas analyser (Li-7810, LICOR, Lincoln, USA) with two 6-mm-diameter, 2-m-long PTED tubes was used to close the chamber during the measurement. The trunk CH4 flux was calculated from the changes in the CH4 molar fraction in the closed system measured every second during four minutes of chamber closure. Trunk CH4 flux was expressed not only in per unit area (nmol m-2 s-1), but also in the entire trunk circumference per unit length of trunk (nmol 0.1 m-1 s-1) to compare it to internal CH4 production rate.
CH4 concentration inside the trunk was measured after th..., , # CH4 production and emissions from the upper parts of tree trunks in cool-temperate upland forest

Dataset DOI: [10.5061/dryad.7m0cfxq61](10.5061/dryad.7m0cfxq61)

## Description of the data and file structure

All the experiments were conducted in a cool-temperate upland mixed forest in Ashiu Experimental Forest of Kyoto University (35.34 N, 135.76 E)  in Kyoto, Japan. 6 mature trees of 3 species were selected, and variables were measured at 6 heights per individual. Using a crane truck, we investigated vertical patterns of CH4 emissions, internal CH4 concentration, and production and copy number of the methanogenic archaeal gene *mcrA*.

Trunk CH4 flux was measured by the dynamic closed chamber method. A polypropylene chamber was attached to the trunk with neutral seal putty. A lid connected to a portable trace gas analyser (Li-7810, LICOR, Lincoln, USA) was used to close the chamber during the measurement. The trunk CH4 flux was calculated from the changes in the CH4 concentration i...,