Thermal Stability of Soil Organic Matter in Postagrogenic Luvic Phaeozems

• Published in: Eurasian soil science 2023-12, Vol.56 (Suppl 2), p.S139-S146
• Main Authors: Filimonenko, E. A., Uporova, M. A., Arbuzova, E. A., Konstantinov, A. O., Kurganova, I. N., Kuzyakov, Ya. V.
• Format: Article
• Language: English
• Subjects: Calorimetry; Carbon content; Carbon sequestration; Deciduous forests; Depth; Differential scanning calorimetry; Dokuchaev Youth Readings; Earth and Environmental Science; Earth Sciences; Forest soils; Geotechnical Engineering & Applied Earth Sciences; Microorganisms; Organic matter; Organic soils; Oxidation; Soil; Soil depth; Soil layers; Soil organic matter; Soil resistance; Soil stability; Soils; Stability; Thermal stability; Thermogravimetry
• ISSN: 1064-2293; 1556-195X
• DOI: 10.1134/S1064229323602263

The efficiency of carbon sequestration in abandoned soils depends on the stability of accumulated organic matter. The resistance of soil organic matter (SOM) of postagrogenic dark gray forest soils ( Luvic Phaeozems ( Aric, Cutanic, Densic )) in the subtaiga deciduous forest to microbial decomposition was estimated by soil respiratory activity. The thermal stability of SOM was determined by thermogravimetry and differential scanning calorimetry methods. Based on the increase of SOM thermal stability according to the rising temperature, four pools were separated in the SOM: thermally labile (thermal oxidation occurs at temperatures from 200 to 380°С), stable (380–460°С), overstable (460–520°С), and persistent (520–600°С). The thermally labile pool predominated in the SOM (58% on average) in the soil layer 0–30 cm. As soil depth increased, total portion of thermally stable pools (380–600°C) in the SOM increased and accounted for 63% on average at the depth of 70–100 cm. The temperature, at which thermal oxidation of half of the organic matter is reached (T 50 ), was the indicator of SOM thermal stability. In the soil layer 0–30 cm T 50 equaled to 362 ± 4°С, and in the soil layer 30–100 cm to 408 ± 4°С, and this reflected the increase with depth of the portion of thermally stable pools in the SOM. It was found that respiratory activity of abandoned soils decreased, as thermal stability, estimated by the ratio of the resistant pool to the labile pool, increased in SOM.