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Soils as a Recording System: Recent and Inherited Soil Memory
V. TARGULIAN, Institute of Geography, Russian Academy of Sciences, Staromonetny, 29, Moscow 109017, Russia.
Soil is distinct from other exogenic geosystems due to its ability to generate and accumulate in situ the solid products of pedogenesis within the immobile and unrenewable infomatrix. Pedogenesis is perceived as a record of memory of soil forming factors and processes throughout the soil’s life. Soils have characteristic palimpsest-like record formed in situ, which sharply differs from the book-like record of sediment sequences. The clearest information is recording within monogenetic soils that have had sufficient time for development. However, in nature we deal mainly with polygenetic soils complicated by relict features inherited from earlier periods. All soils features could be subdivided according to their genesis, rates of formation, relict or recent nature. The main bearers of soil memory (humus, secondary minerals, peds, cutans, pores, etc.) are discussed in respect of how long they take to form and how deep they occur. The completeness on the records depends of the soil’s age and is complicated by partial truncation and burial. Various types of climate-led soil evolution are discussed: the erasing, developing, inheriting and superimposing types. Three models of such evolution are analysed: with gradual increase; gradual decrease and frequent fluctuations of the temperature and moisture. The main trend of Cenozoic climate change resulted in a combination of the second and third models and increased of the role of inherited exogenic materials at each stage of soil’s evolution. Holocene input into exogenic mantle on present land surface had been relatively small and this mantle consists mainly of mineral materials inherited from Pre-Holocene pedogenesis, weathering and sedimentation. Holocene soil evolution contributes to the polygenetic present-day soil mantle of the world. The so-called “zonal” soils on the present land surface are rarely monogenetic records of present environment and cannot be used directly as keys to understand the paleosols and their paleoenvironments. Present-day soils must also be read and decoded as multilayered memories combining the inherited and recent futures.
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