Boreal forests, which are located primarily in cold, high-latitude regions, are among the world’s largest carbon reservoirs, accounting for 30% of global soil carbon reserves. The role of the biggest storage is played by the humus layer of forests, which contains fallen leaves and other decomposed organic matter. However, as the authors of the study have suggested, this storage can be prone to crack formation under the influence of manganese, which is released into the atmosphere during metal smelting and fuel combustion, and which is then carried by the wind to settle in soils.
To test this hypothesis, the researchers conducted an experiment on two forest plantation plots in China’s Da Hinggan Range: in 2009, one plot of forest soil was seeded with manganese, while the other plot was left untouched. Fourteen years later, carbon content in the humus layer of the area fertilised with manganese was 13.3% lower compared to the control sample. The scientists believe that when manganese is released into soil, it stimulates the decomposition of organic matter, leading to the release of carbon dioxide stored therein. As a result, the concentration of manganese determines carbon content in the humus layer of forests.
However, uneven exchange of greenhouse gases is also typical for bogs, which retain CO2 while also emitting methane. Whereas methane emissions average 0.07 milligrams per hour per square metre in the upper parts of bogs, the average value reaches 11 milligrams per hour per square metre in the lower parts, as assessed by scientists from the Obukhov Institute of Atmospheric Physics RAS based on a study of the Mukhrinsky peat bog in Western Siberia. The vast difference is caused by, among other things, temperature differences between the “warmer” upper areas and the “colder” lower areas that are flooded with water: water warms up more slowly than air, which is why wet soils tend to have a lower temperature.
