Paradigm shift: giant underestimated source of natural CO2 discovered

Giant underestimated source of natural CO2 discovered

It is scientifically recognized that soil is the most important source of carbon dioxide produced by forests. And CO2, in turn, is a by-product of life in it. However, a new study from the University of Texas changes the view. The scientists showed that CO2 can form deep underground in cracks in rocks, and that source can account for up to 29% of daily CO2 emissions, depending on the season. It does not mean that open landscapes emit more CO2.

But in general, such discovery will allow a better study of climate change models. Latent CO2 is produced in rocks by the absorption of water by deep tree roots. Thus, tree roots and microbial communities can be a new source of CO2, and cracks in bedrock can be a source of CO2.

A researcher Danielle Rempe of UT Jackson's School of Geosciences is confident that the scientists seemed on the verge of a paradigm shift, when soils may not be considered the only key player in CO2 production. It has transition zones of bedrock, which is extremely difficult to process.

The scientists used special tools to take the samples, and the samples themselves were taken from a hillside in northern California. The tool used showed that the area turned out to be an active site for CO2 production.

There is a large source under the soil layer, and when the researchers obtained the first measurements of the concentration profiles, they were surprised by the results. Analysis of thousands of samples taken between 2017 and 2019 showed that CO2 stocks are constantly moving.

During the dry season, they end up in the soil layers, from where they are released into the atmosphere. And during the rainy season, when groundwater rose to the surface and filled cracks, CO2 moved under the soil, from where it was then released into the air.

At the same time, almost 50% of CO2 was dissolved in water. The discovery is of great importance, if only because the scientists were able to determine for the first time exactly where the ongoing weathering of rocks on the hillside occurs.

Reference: “Carbon Dioxide Production in Bedrock Beneath Soils Substantially Contributes to Forest Carbon Cycling” by Alison K. Tune, Jennifer L. Druhan, Jia Wang, Philip C. Bennett and Daniella M. Rempe, 27 November 2020, JGR Biogeosciences. DOI: 10.1029/2020JG005795