Abstract—

The genesis of soils with the second humus horizon (SHH)—the most striking relict feature in the profiles of soddy-podzolic (Retisols) and gray (forest) soils (Luvisols)—is discussed. The Middle Holocene radiocarbon age of the SHH, its dark color, and the discrepancy of its properties and the properties of modern humus horizons of forest soils have specified the main issues in the study of SHH: the character of climate changes and shifts of the boundaries of natural zones in the Holocene and the reflection of these changes in the evolution of the soil profiles. We consider the history of studies, systematization, geographic distribution, and modern properties of the SHH. On the basis of the analysis of Holocene paleosols, we try to characterize the prototype of the SHH, to estimate its age, and to trace stages of its development in the Holocene. We have also tried to find analogous soils with the SHH outside of Russia. According to the accepted hypothesis, SHHs are residual paleoclimatogenic formations. Other hypotheses consider them as buried horizons, a result of paleohydromorphism, etc. Dark humic substances of SHHs were formed in the first half of the Holocene and are characterized by extremely high stability. This allows them to survive in the aggressive environment of the eluvial horizons of Retisols and Luvisols. Under the influence of biochemical and mechanical (tree uprooting) factors, SHHs are strongly transformed, which complicates their study. At the same time, well-preserved Chernozems and dark-colored Phaeozems buried under kurgans and other earthy structures and sediments make it possible to establish the prototype of the SHH and to trace its degradation in the late Holocene. Within the East European Plain, the thickness and age of the SHH vary in agreement with the hypothesis of the residual paleoclimatogenic genesis of this horizon. The validity of the hypotheses of the buried nature and hydrogenic origin of the SHH is discussed. At present, interest in soils with the SHH in Russia has somewhat weakened. In Central Europe and North America, soils with the SHH have not been studied, but research into the problem of relict chernozems is being actively pursued. In our opinion, the combination of these two types of objects and, accordingly, the directions of research can lead to more definite conclusions about the origin and evolution of soils with the SHH.

中文翻译：

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具有第二个腐殖质层的土壤、古黑土和森林与草原地区交界处的成土历史

摘要-

讨论了具有第二腐殖质层 (SHH) 的土壤的成因——这是草皮-灰化土 (Retisols) 和灰色（森林）土壤 (Luvisols) 剖面中最显着的残留特征。SHH的中全新世放射性碳年龄，其深色，以及其性质与现代森林土壤腐殖质层位性质的差异，明确了SHH研究的主要问题：气候变化特征和边界移动全新世自然带的变化以及这些变化在土壤剖面演变中的反映。我们考虑了 SHH 的研究历史、系统化、地理分布和现代特性。在对全新世古土壤分析的基础上，我们试图表征SHH的原型，估计其年龄，并追溯其在全新世的发展阶段。我们还尝试在俄罗斯以外寻找与 SHH 类似的土壤。根据公认的假设，SHHs 是残留的古气候形成层。其他假设认为它们是埋藏层位，是古水形作用等的结果。 SHHs的深色腐殖质形成于全新世前半期，具有极高的稳定性。这使它们能够在 Retisols 和 Luvisols 难以捉摸的恶劣环境中生存。在生化和机械（树木连根）因素的影响下，SHHs 发生强烈转化，这使他们的研究复杂化。同时，保存完好的黑钙土和深埋在库尔干岩和其他土质结构和沉积物下的暗色岩土使得建立 SHH 的原型并追踪其在全新世晚期的退化成为可能。在东欧平原内，SHH 的厚度和年龄的变化与该层位残余古气候成因的假设一致。讨论了SHH的掩埋性质和氢起源假设的有效性。目前，俄罗斯对 SHH 土壤的兴趣有所减弱。在中欧和北美，尚未研究具有 SHH 的土壤，但正在积极开展对残留黑钙土问题的研究。在我们看来，这两种类型的对象的组合，因此，