RUDN University soil scientist showed how waterlogging of soils due to climate change increases the greenhouse effect

The main cause of global climate change is the increase in the concentration of carbon dioxide. It accumulates in the atmosphere and retains heat, the planet does not have time to cool down and turns into a “greenhouse” — a greenhouse effect occurs. Carbon dioxide is produced not only by people, even the soil “breathes” — carbon, which is contained in the earth as part of various compounds, comes out in the form of carbon dioxide and increases the temperature. Because of warming, glaciers are melting, permafrost is thawing — as a result, soil moisture increases. Until now, it was not known how increasing humidity would affect the amount of carbon dioxide that is released from the soil. To find out, the soil scientist from RUDN studied soil samples of the Tibetan highlands, where the temperature rises three times faster than the global average.

“Despite the fact that soil drainage accelerates the mineralization of carbon in the soil and the release of carbon dioxide, increasing humidity does not necessarily lead to the opposite effect — to slow down the mineralization and release of carbon dioxide. To find out this, we investigated how these processes take place in wetland and meadow soils with contrasting biochemical properties,” Yakov Kuzyakov, Doctor of Biological Sciences, Head of the Center for Mathematical Modeling and Design of Sustainable Ecosystems of the RUDN University.

Soil scientists took samples of meadow and swamp soil and determined which substances contain carbon-undecayed plant residues or decomposed biomass. Then the meadow soil was saturated with water up to 70% of the amount that it could hold as much as possible. Marsh soil, on the contrary, was drained, withstanding 95 days at 25 ℃. Then the soil scientists from RUDN University again measured the carbon content in the samples and calculated how much the release of carbon dioxide changed with a change in humidity.

It turned out that in both cases, carbon dioxide was released more intensively. The reason for this is considered by soil scientists to be the original composition of carbon in the samples. In swamp soil, carbon is mainly contained in the composition of plant residues that have not yet decomposed. The carbon of meadow soil is mainly in the already decomposed biomass, soil enzymes work more actively in it. As a result, in swamp soil, high humidity inhibits carbon mineralization and the release of carbon dioxide. In meadow soil, the opposite happens — saturation with water further activates mineralization and the release of carbon dioxide.

“We showed that the decomposition of soil carbon in water-filled soil depended on the initial fraction of plant and microbial residues. Our work speaks to the importance of the biochemical nature in regulating the decomposition of carbon. We have come to the conclusion that both drainage of wetlands and waterlogging of meadows increase carbon mineralization (measured as CO2 release),” Yakov Kuzyakov, Head of the Center for Mathematical Modeling and Design of Sustainable Ecosystems RUDN.

The findings prove that protecting meadow soils from waterlogging will help curb the release of carbon dioxide and slow warming. Otherwise, there is a chain reaction-an increase in the greenhouse effect will lead to even greater global warming, increase waterlogging of meadows, and so on.

The results are published in Soil Biology and Biochemistry.