Soil that has been buried under Earth's surface for thousands of years is rich in carbon contributing largely to global warming, a new study finds.
The findings are important because these long-buried stocks of organic carbon may have a significant effect on global climate change through processes like erosion, agriculture, deforestation, mining and other human activities.
"There is a lot of carbon at depths where nobody is measuring," said Erika Marin-Spiotta, lead author of the new study in a press statement. "It was assumed that there was little carbon in deeper soils. Most studies are done in only the top 30 centimeters. Our study is showing that we are potentially grossly underestimating carbon in soils."
For the study, researchers examined a soil known as Brady soil, which formed 15,000 and 13,500 years ago. According to the study report, this soil was buried by a vast buildup of windborne dust known as loess, beginning about 10,000 years ago when the glaciers that covered much of North America began to retreat.
Researchers clarified that the region where the Brady soil formed was not glaciated. However, the abrupt shift in climate, which was sparked by Northern Hemisphere's retreating glaciers resulted in the soil undergoing radical changes.
"Most of the carbon (in the Brady soil) was fire derived or black carbon," noted Marin-Spiotta. "It looks like there was an incredible amount of fire."
The study authors also found that organic matter from ancient plants had not fully decomposed, owing to the thick blanket of loess that had formed over them. Researchers also found that rapid burial helped the soil survive many biological processes that would have otherwise broken down carbon in the soil.
According to the researchers, the Brady soil is like a time capsule of a past environment. It provides environmentalists with an insight into how the environment underwent various climate shifts.
"The world was getting warmer during the time the Brady soil formed," said Mason. "Warm-season prairie grasses were increasing and their expansion on the landscape was almost certainly related to rising temperatures."
The study was funded by the National Science Foundation and the Wisconsin Alumni Research Foundation. Findings were published in the journal Nature Geoscience.
