Six feet underground, a new approach to global warming

A researcher at Washington State University discovered that a quarter of the carbon in the soil is bound to minerals up to six feet below the surface. The discovery opens up a new opportunity to treat the element as it continues to warm the Earth's atmosphere.

A hitch: Most of this carbon is concentrated deep in the world's rainforests, and they will not sequester as much as global temperatures continue to rise.

Marc Kramer, an associate professor of environmental chemistry at WSU Vancouver, is inspired by new data from soils around the world to describe how water dissolves organic carbon and drives it deep into the soil. where it is physically and chemically related to minerals. Kramer and Oliver Chadwick, a soil scientist at the University of California at Santa Barbara, estimate that this industry retains about 600 billion tonnes of carbon. That's more than twice the carbon added to the atmosphere since the beginning of the industrial revolution.

Scientists still need to find a way to take advantage of this discovery and move some of the extra carbon from the atmosphere into the subsoil, but Kramer says the soils can easily hold back more. For starters, a new understanding of the industry is "a breakthrough" in our understanding of how carbon goes underground and stays there, he said.

"We know less about the soils of the Earth than about the surface of Mars," said Kramer, whose work appears in the newspaper Nature Climate change. "Before we can begin to think about storing carbon in the soil, we really need to understand how it does it and how likely it is to stay in. This discovery highlights a major breakthrough in our understanding."

This study is the first global assessment of the role soil plays in dissolved organic carbon and the minerals that help store it. Kramer analyzed soil and climate data from the Americas, New Caledonia, Indonesia, and Europe. He drew on more than 65 sites sampled at a depth of six feet from the National Network of Environmental Observatories funded by the National Science Foundation.

"These data show the kind of great science you can do when you have a national ecological observatory," Kramer said. On the one hand, they let researchers build a map on a global scale of this pathway of carbon accumulation in soils.

Comparing different ecosystems, Kramer found that wet environments hold much more carbon than dry ones. In desert climates, where rain is scarce and water evaporates easily, reactive minerals retain less than 6% of the soil's organic carbon. Dry forests are not much better. But moist forests can contain up to half of their total carbon bound by reactive minerals.

Moist forests tend to be more productive, with thick layers of organic matter from which water will leach carbon and transport it to minerals up to six feet below the surface.

"This is one of the most persistent mechanisms of our carbon accumulation," said Kramer.

But if it is unlikely that climate change will directly affect the deep carbon associated with minerals, it can also influence the path by which carbon is buried. Indeed, the distribution system depends on the water to extract carbon from the roots, dead leaves and other organic matter near the surface and push it deep into the soil, where it s & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; Will attach to iron and aluminum rich minerals to form strong bonds.

If near-surface temperatures are hot, there may be less water flowing through the soil, even if the amounts of precipitation remain the same or increase. Evaporation and respiration of plants can lose a greater amount of water that falls, making less water available to move carbon for long-term storage.

Explore further:
Researcher sees huge carbon sink in soil minerals

More information:
Marc G. Kramer et al., Climate-related thresholds in the retention of reactive minerals in soil carbon on a global scale. Nature Climate change (2018). DOI: 10.1038 / s41558-018-0341-4