Natural 13C Abundance in the Organic Matter of Water-Stable Aggregates of Haplic Chernozem under Contrasting Land Uses

Artemyeva, Z.S.; Zazovskaya, E.P.; Zasukhina, E.S.; Tsomaeva, E.V.

Авторы: Artemyeva Z.S., Zazovskaya E.P., Zasukhina E.S., Tsomaeva E.V.
Журнал: Eurasian Soil Science
Том: 56
Номер: 3
Год издания: 2023
Издательство: Maik Nauka/Interperiodica Publishing
Местоположение издательства: Russian Federation
Первая страница: 294
Последняя страница: 305
DOI: 10.1134/s1064229322602323
Аннотация: Natural 13C abundances in different organic matter (OM) pools in the water-stable macro- andfree microaggregates of Haplic Chernozem under contrasting land uses (steppe and long-term bare fallow)are described. The 13C fractionation at individual stages in the formation of OM pools is relatively constantregardless of the level of soil structural organization. The proposed conceptual scheme, allowing for quantification of the carbon (C) fluxes in the system of aggregate/OM pool, illustrates this assertion. As is shown,the main C fluxes in the OM pools go from the free OM (LFfr) to the residue fraction (Res) through microaggregates within water-stable aggregates (mWSAs), the components of which are the occluded OM (LFocc)and clay fraction (Clay). With a high degree of probability, C migrates from macroaggregates (WSAma) to freemicroaggregates (WSAmi). However, a higher probability of the C flux from the mWSA into the Res as compared with the direct C fluxes from the LFocc and Clay supports the hypothesis that the Res is to a greaterdegree represented by pieces/fragments (50–1 μm in size) of disintegrated mWSAs. Regardless of the size,the WSAs contain labile OM (as the components of mWSAs) along with LFfr (only in macroaggregates) andstable OM (Res). The labile OM (LFocc and Clay) within WSAmi displays a lower degree of microbial transformation (a “lighter” isotopic signature) compared to that in WSAma, which is a result of its better “physical”protection against microbial attacks. However, the most stable OM pool, concentrated in the Res withinWSAmi, is enriched in 13C as compared with that in WSAma. Considering that the Res determines the totalisotopic composition of C in WSAs, the OM of free microaggregates is generally characterized by a higherdegree of microbial processing compared to that of macroaggregates. Free microaggregates are pieces of disintegrated macroaggregates.
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