论文摘要：

• 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 CH₄emissions were equivalent to c. 30–90% of the amount of CH₄consumed 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 CH₄can be produced.