Methane emissions from the trunks of living trees on upland soils.

Upland forests are traditionally thought to be net sinks for atmospheric methane ( CH₄). In such forests, in situ CH₄ fluxes on tree trunks have been neglected relative to soil and canopy fluxes., We measured in situ CH₄ fluxes from the trunks of living trees and other surfaces, such as twigs and soils, using a static closed-chamber method, and estimated the CH₄ budget in a temperate upland forest in Beijing., We found that the trunks of Populus davidiana emitted large quantities of CH₄ during July 2014-July 2015, amounting to mean annual emissions of 85.3 and 103.1 μg m⁻² h⁻¹ on a trunk surface area basis on two replicate plots. The emission rates were similar in magnitude to those from tree trunks in wetland forests. The emitted CH₄ was derived from the heartwood of trunks. On a plot or ecosystem scale, trunk CH₄ emissions were equivalent to c. 30-90% of the amount of CH₄ consumed by soils throughout the year, with an annual average of 63%., Our findings suggest that wet heartwoods, regardless of rot or not, occur widely in living trees on various habitats, where CH₄ can be produced. [ABSTRACT FROM AUTHOR]