Tiny Fungi Play Big Role in Levels of Carbon in the Environment

Tiny fungi that play a role in the storage and release of carbon from plants have been overlooked in myriad studies of carbon and its effect on the environment, according to new research which suggest the tiny organism plays a big part in the global carbon cycle.

These microscopic mycorrhizal fungi live on plant's roots and play a major role in how much carbon is stored and released by the plants, according to scientists, who say the role of these tiny organisms has gone unreported in global climate models.

"Natural fluxes of carbon between the land and atmosphere are enormous and play a crucial role in regulating the concentration of carbon dioxide in the atmosphere and, in turn, Earth's climate," said lead study author Colin Averill, a graduate student in the College of Natural Sciences at University of Texas in Austin. "This analysis clearly establishes that the different types of symbiotic fungi that colonize plant roots exert major control on the global carbon cycle, which has not been fully appreciated or demonstrated until now."

Boston University biologist Adrien Finzi, who participated in the research, said the work is not only relevant to climate models and predictions of future atmospheric greenhouse gas levels, "but also challenges the core foundation in modern biogeochemistry that climate exerts major control over soil carbon pools."

The role of soil must not be overlooked when modeling for greenhouse gas emissions, the researchers report, as soil contains more carbon than both the atmosphere and vegetation combined. Therefore, the researchers argue, accurate models of future climate depend on a complete understanding of how carbon cycles between land and air.

"This study is showing that trees and decomposers are really connected via these mycorrhizal fungi, and you can't make accurate predictions about future carbon cycling without thinking about how the two groups interact. We need to think of these systems holistically," Averill said.

There are two major types of these mycorrhizal fungi, ecto- and ericoid mycorrhizal (EEM) fungi and arbuscular mycorrhizal (AM) fungi.

"EEM fungi produce nitrogen-degrading enzymes, which allows them to extract more nitrogen from the soil than the AM fungi extract," UT Austin explained in a news release. "The EEM fungi allow the plants to compete with the microbes for available nitrogen, thus reducing the amount of decomposition and lowering the amount of carbon released back into the atmosphere.

By examining soil data from around the world, the researchers were able to determine that when plants are in a symbiotic relationship with EEM fungi, the soil contains 70 percent more carbon per unit of nitrogen than in soil where AM fungi are dominant.

The study is scheduled for publication this week in the journal Nature.