Measuring the ‘farts’ of dead trees may not be something that comes to mind when first considering emissions of carbon dioxide into the atmosphere. It does need to be factored in, according to research by scientists at North Carolina State University.
Greenhouse gas (GHG) emissions from standing dead trees in coastal wetland forests – colloquially called “tree farts” – need to be accounted for when assessing the environmental impact of so-called “ghost forests, say the researchers.
“Even though these standing dead trees are not emitting as much as the soils, they’re still emitting something, and they definitely need to be accounted for,” said the study’s lead author Melinda Martinez, a graduate student in forestry and environmental resources at NC State.
“Even the smallest fart counts.”
Ghost forests in the Albemarle-Pamlico Peninsula in North Carolina are on the increase due to sea level rise.
Melinda Martinez explained:
“The transition from forest to marsh from these disturbances is happening quickly, and it’s leaving behind many dead trees. We expect these ghost forests will continue to expand as the climate changes.”
Using portable gas analyzers, researchers measured gases emitted by snags and from soils in each forest in 2018 and 2019. Overall average emissions from soils were approximately four times higher than average emissions from snags in both years. And while snags did not contribute as much as soils, researchers said they do contribute significantly to emissions.
“We started off this research wondering: Are these snags straws or corks?” said study co-author Marcelo Ardon, associate professor of forestry and environmental sciences at NC State.
“Are they facilitating the release from soils, or are they keeping the gases in? We think that they act as straws, but as a filtered straw. They change those gases, as the gases move through the snags.”
In addition to finding that soils emit more GHGs than snags, the work lays the foundation for the researchers’ ongoing work to understand the role snags are playing in emissions – whether they prevent emissions, like corks, or release them like straws. That is an area of future research they’re currently continuing to explore.
The study, “Drivers of Greenhouse Gas Emissions from Standing Dead Trees in Ghost Forests,” was published online in Biogeochemistry on May 10, 2021. Funding was provided by the National Science Foundation under grant DEB1713592 and a 2019 North Carolina Sea Grant/SpaceGrant Fellowship.