Bogs release more carbon when they’re alkaline
Researchers from Yonsei University, led by Prof. Hojeong Kang, performed four experiments to understand how peatland pH levels affect the production of dissolved organic carbon (DOC). “It’s important to understand DOC release because we are finding higher concentrations of DOC in rivers worldwide. This affects both our drinking water sources and the environment,” said Prof. Kang, explaining the importance of their study.
Professor Kang and his colleagues first compared seven peak bogs with different pH. Next, they manipulated pH in the field for four years, treating one site with an alkaline solution and another site with an acidic solution. The third experiment took place in the lab, where researchers altered pH and temperature of peat soil with originally neutral pH. Finally, they treated peat soil samples with phenol oxidase, an enzyme that is important in decomposing peat and causing DOC release. The results of all these experiments showed that increasing pH caused phenol oxidase to increase, a connection that is affected by temperature (the enzyme was more active when soil was warmer). Additionally, certain soil bacterial species and fungi became more abundant under higher pH. This increase in specific microbes coincided with higher phenol oxidase activity and eventually more DOC production.
Prof. Kang explains that raising pH has an immediate positive effect on phenol oxidase already in soil, triggering DOC leaching into the surrounding environment. Decreasing soil acidity also has a long-term effect, changing bacterial composition in favour of species that produce phenol oxidase. “We found a new mechanism for how acid soils cause DOC release, and it’s through the action of an enzyme produced by soil microbes,” says Prof. Kang.
This study thus provides evidence for a link between soil pH and DOC production, highlighting the importance of soil microbes. These findings should prove very useful for efforts to deal with DOC leaching into aquatic ecosystems and sources of our drinking water.
Updated in Dec 2018
Professor Cheolmin Park
Professor Jung Hyun Kim