Trees said missed sources of climate gases

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BRISTOL, England, Feb. 13 (UPI) -- Wetland trees are a significant but overlooked source of the greenhouse gas methane in the world's swamps and flooded forests, British researchers say.

While wetlands are a well-known and prolific source of atmospheric methane, ground-based measurements of methane have fallen well short of the quantities detected in tropical air by satellites, scientists at the University of Bristol.

They studied a forested peat swamp in Borneo to determine whether soil methane might be escaping to the atmosphere by an alternative route.

"Methane emissions normally are measured by putting sealed chambers on the ground to capture gas seeping or bubbling from the soil," said Sunitha Pangala, an Open University doctoral student whose work was supervised by Bristol researchers.

"We also enclosed tree stems in chambers and the results were surprising. About 80 percent of all methane emissions was venting through the trees."

A common adaptation in wetland trees, in which they enlarge porous structures in the trunks to take in oxygen, is also providing another route for soil gas to escape to the atmosphere, the researchers said.

"This work challenges current models of how forested wetlands exchange methane with the atmosphere," Open University researcher Vincent Gauci said. "Ground-based estimates of methane flux in the tropics may be coming up short because tree emissions are never included in field campaigns."