Soil moisture may have key impact on carbon dioxide emission

7th May 2024 | Source: The Global Energy Association

The photo is sourced from glavagronom.ru

Soil moisture is the key factor affecting the gaseous interchange between atmosphere and soil: the higher it is, the more sensitive is soil breathing to temperature increase. On the contrary, drought results in significant decrease of access to nutrients for vital activity of soil biota leading to slow down of carbon dioxide emission into atmosphere. That was the conclusion of researchers from the Institute of physical, chemical and biological issues in soil sciences of Russian Academy of Sciences (RAS) based on the results of twenty-five-year-long study (published in Forests journal).

The study was performed starting from December 1997 until November 2021 in two ecosystems in the South of Moscow Region – in broad-leaved wood and mingled wood. The researchers measured the amount of carbon dioxide emitted by soil microorganisms and plant roots in the same sections of wood on a weekly basis. This was done by hermetically sealed cameras set up on the surface, where CO2 was accumulated. Gaseous samples were taken from the cameras at fixed intervals, and based on them the researchers calculated the CO2 concentration and soil breathing rate. Along with meteorological metrics these data reflected thermal sensitivity – soil breathing rate when the soil or ambient air temperature grew by ten degrees Celsius.

Long-term monitoring demonstrated that thermal sensitivity depends on soil moisture during the period of plant vegetation – the time of active growth of plants. Thus, in rainless years the temperature growth had a weaker catalytic impact on carbon dioxide emission compared to the normal or rainy years. At the same time, the biota in sandy loam soil (with low moisture-retention factor) were less sensitive to temperature growth compared to the biota in clay loam soil. And vice versa: the clays (capable of moisture retention even during the periods of extreme heat) provided water with dissolved nutrients to soil microorganisms. The resulted in the fact that thermal sensitivity of clay loam soil was less dependent on moisture conditions.

“Thus, we were able to demonstrate that moisture availability during the vegetation period is the key factor controlling the dependency of soil breathing on the temperature in forest ecosystems. Given the current trend of the climate getting more and more dry in many regions of Russia and globally, we can forecast that the emission of carbon dioxide from soil into atmosphere will be slowing down, and hence carbon sink into boreal (northern) forests and moderate ecosystems will be growing”, Russian Science Foundation is citing Irina Kurganova, Doctor of Biological Sciences, leader of the research.