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Abstract <p>New data on the soils of the Mondy Basin—the most arid and coldest basin of the Tunka system, with the most contrasting environmental conditions and poorly studied soil cover—are reported. The arrangement of the humus profile is characterized, organic matter organization is assessed at the micromorphological level, and profile variations in the total organic carbon or TOC and δ<sup>13</sup>C are determined for five soil sections under the most typical plant communities on similar parent rocks to assess the effect of the bioclimatic conditions on the dynamics of soil organic matter. The main soil cover components in the Mondy Basin are palevye (pale) and cryoaridic soils, as well as the transitional soils that combine the features of taiga and steppe pedogenesis in their profile and reflect the dynamic character of the landscape boundaries. The differences in the micromorphology of soil organic horizons suggest a higher productivity of the phytocenoses and the activity of biota involved in the processing of organic matter of the litter in palevye and cryoaridic soils under larch forests as compared with steppe cryoaridic soils. Differences in the organization and transformation characteristics of organic matter observed at the microscale are well correlated with the intraprofile distribution patterns of total organic carbon and δ<sup>13</sup>C. As compared with the forest soils, the steppe soils of the Mondy Basin display an increased linear regression slope between log-transformed C<sub>org</sub> and δ<sup>13</sup>C down the profile. This suggests a low intensity of the carbon turnover determined by a low productivity of phytocenoses, a low biological activity of cryoaridic soils, a slow transformation of plant residues under conditions of dry growing season, and a short period of optimum temperature and humidity combination. The middle-profile horizons of the studied soils often contain a considerable amount of organic matter in the micromass and certain pedofeatures (humus–clayey and, to a lesser degree, carbonate coatings), which makes it possible to consider these horizons as part of the humus profile.</p>

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Specific Isotopic (δ13C) and Micromorphological Features of the Organic Matter in Soils of the Mondy Basin (Eastern Sayan Mountains)

  • 期刊论文

  • 发表日期：

    2025年6月23日

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  • V. A. Golubtsov,
  • A. A. Cherkashina,
  • M. A. Bronnikova

摘要

Abstract

New data on the soils of the Mondy Basin—the most arid and coldest basin of the Tunka system, with the most contrasting environmental conditions and poorly studied soil cover—are reported. The arrangement of the humus profile is characterized, organic matter organization is assessed at the micromorphological level, and profile variations in the total organic carbon or TOC and δ13C are determined for five soil sections under the most typical plant communities on similar parent rocks to assess the effect of the bioclimatic conditions on the dynamics of soil organic matter. The main soil cover components in the Mondy Basin are palevye (pale) and cryoaridic soils, as well as the transitional soils that combine the features of taiga and steppe pedogenesis in their profile and reflect the dynamic character of the landscape boundaries. The differences in the micromorphology of soil organic horizons suggest a higher productivity of the phytocenoses and the activity of biota involved in the processing of organic matter of the litter in palevye and cryoaridic soils under larch forests as compared with steppe cryoaridic soils. Differences in the organization and transformation characteristics of organic matter observed at the microscale are well correlated with the intraprofile distribution patterns of total organic carbon and δ13C. As compared with the forest soils, the steppe soils of the Mondy Basin display an increased linear regression slope between log-transformed Corg and δ13C down the profile. This suggests a low intensity of the carbon turnover determined by a low productivity of phytocenoses, a low biological activity of cryoaridic soils, a slow transformation of plant residues under conditions of dry growing season, and a short period of optimum temperature and humidity combination. The middle-profile horizons of the studied soils often contain a considerable amount of organic matter in the micromass and certain pedofeatures (humus–clayey and, to a lesser degree, carbonate coatings), which makes it possible to consider these horizons as part of the humus profile.