From: Stanford School of Earth, Energy & Environmental Sciences
Published May 1, 2017 01:31 PM

Shunned by microbes, organic carbon can resist breakdown in underground environments, Stanford scientists say

The soils and sediments beneath our feet can contain an astonishing amount of carbon – more than in all of the world’s plants and the atmosphere combined – and represents a significant potential source of the greenhouse gas carbon dioxide.

In a new study, Stanford scientists have uncovered a previously unknown mechanism that explains why microbes sometimes fail to break down all the plant and animal matter, leaving carbon underfoot. Understanding where, and how long, this buried organic matter lingers is crucial for scientists and policymakers to better predict and respond to climate change.

“Our picture of how organic matter is broken down in soils and sediments is incomplete,” said study lead author Kristin Boye, an associate staff scientist at the Stanford Synchrotron Radiation Lightsource at the SLAC National Accelerator Laboratory and former postdoctoral scholar at Stanford’s School of Earth, Energy & Environmental Sciences. “With this study, we are gaining new insights into the mechanisms of carbon preservation in low- or no-oxygen subterranean environments.”

In oxygen-starved places such as marshes and in floodplains, microorganisms do not equally break down all of the available organic matter, the study shows. Instead, carbon compounds that do not provide enough energy to be worthwhile for microorganisms to degrade end up accumulating. This passed-over carbon, however, does not necessarily stay locked away below ground in the long run. Being water soluble, the carbon can seep into nearby oxygen-rich waterways, where microbes readily consume it.

Continue reading at: Stanford School of Earth, Energy & Environmental Sciences

Image: A new study uncovered a previously unknown mechanism that explains why microbes sometimes fail to break down buried plant and animal matter. Above, the field site in the floodplains in the upper Colorado River Basin where soil samples were taken. (Image credit: John Bargar)

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