Soils with polygenetic profile as indicators of the climate evolution in vyatka prikamye

A.M. Prokashev, E.S. Soboleva, S.L. Mokrushin, R.R. Chepurnov

Vyatka State Humanities University,

amprokashev@gmail.com

A Variety of soils with polygenetic profile in Vytka Prikamye

In this paper soils with complex polygenetic profile are pedogenesis objects with preserved external morphological, and internal substantive signs of prolonged history of the formation. The external signs are difficult "non-standard" structure of soil bodies and individual genetic horizons due to the presence of: a) second (Ahh) and third (Vhh) residual relict humus horizons; b) buried humus ([A], [AG], peat [T]) horizons or buried organic materials (wood, detritus , etc); c) buried soil profiles. Similar phenomena were observed by us in the soils of southern taiga in watershed and valley landscapes of Vyatskoe Prikamye (VP) in the Kirov region and adjacent subjects of the Russian Federation.

To date, soils with the second (SH) and third (TH) humus horizons, as well with buried humus horizons, pedones, etc. have identified by the authors as a separate genus (with a complex history of development) among of a number of types and subtypes of automorphic, semi-hydromorphic and intra-zonal soils of southern taiga and mixed forests on different genetic groups of source rocks [Prokashev, 1999, 2006, 2009; Prokashev, Zhuykova Pakhomov, 2003; Tyulin, 1973, 1976; Tyulin, Rossohina, 1976; and others]. Among the latter, most typical on the territory of the VP are loamy clay sediments: cover noncalcareous and calcareous loam, eluvium of Permian rocks presented carbonate - clayey sediments (marl, calcareous clay, limestone), and ancient loamy clay alluvium of small rivers, recently released from the regime of floodplain sedimentation. Soil with SH were found solitary in the problematic drift clay loam surrounding "pugi" - sand and gravel hills of problematic genesis (Table 1).

The availability of such facilities in the VP is not accidental. It is caused by a number of reasons: first, specific geographical position of the region; secondly, the complex history of the modern landscapes formation on the late glacial - postglacial stages of the natural environment evolution; thirdly, this territory location in tectonically mobile zone - near Vyatka (Kazan- Kazhim) paleorift - submeridional fault in the crystalline basement of the platform, formed in the Precambrian and preserved seismic activity up to the present time.

These factors influenced to functioning and evolution of local geosystems and its components, including the development of pedosphere in VP. Together, it determined the shape of modern soil cover, which includes a very representative group with the signs of polygenesis mentioned above. Each of its is a result of certain factors, and possibly its combined product. It is reflected in the morphology and substantive properties of considered pedo-objects on the one hand, and allowed us to use its as an indicators of the natural environment evolution in the latter stages of the geological history, on the other hand. Let us consider the possible impact of the natural preconditions to the soils and its indicative role in deciphering the paleogeographic events in past eras.

Table 1. Soil groups with polygenetic profile of Vyatka Prikamye

Soil types and subtypes	Soil classes and subclasses
Automorphic soils with SHH and THH
Sod-podzolic with SHH and THH	On carbonate and noncarbonate loams
Sod-podzolic	On moraine loams
Sod-podzolic (Umbric Albeluvisols)	On ancient alluvium
Gray forest soils with dark and gray humus (Albic Luvisols)	On carbonate and noncarbonate loams
Intrazonal soil with SHH
Humic carbonate soils (Rhendzic Leptosols)	On Permian clayey marl (eluvium of limestone)
Semihydromorphic soil with SHH and THH
Humic gleyic soils (Mollic Gleysols)	On carbonate and noncarbonate loams
Gray forest gleyic soils with dark and gray humus (Albi-Endogleyic Luvisols)	On carbonate and noncarbonate loams and talus

VP is located near the main (between forest and steppe) landscape frontier of Russian plains. It determines increased gradients of natural condition changes in the latitudinal direction. These gradients are reinforced by the rise of continental climate in the east of EEP. It leads to convergence and even pinching some natural zones in the Pre-Urals. This determines the unstable state of conditions and factors of soil formation and, consequently, increased sensority and reflex of soils. Not coincidentally, S.I. Korzhinsky [1886, etc.] found the peculiar soil with problematic profile structure (which he called "second - podzolic") in soil- botanical expedition to the south of the Vyatka province. It served as one of the arguments put forward in favor of the concept of the onset of forest to steppe. Later V.V. Tyulin and M.V. Rossohina [1976 , etc.] made ​​the special study of the special kind of sod-podzolic soils with the second humus horizon on Chepetsk - Kilmez interfluve, that formed the basis of a regional concept of soil evolution. A further author research [Prokashev, 1999, 2006, 2009] showed that polygenesis signs of soil cover in VP have much broader manifestation than previously aware.

The formula "soils are mirror and memory of a landscape" has become the one of the leading paradigms in soil genetic studies. It helps to explain many unclear (with actualistic positions) soil properties and form an objective perspective about the direction of the processes of pedogenesis and the level of soil stability in the event of a change of soil formation ecology. Soils and pedo- lito-sediments with residual and buried humus or detritus horizons are very convenient objects for paleogeographic and, in particular, paleoclimatic reconstructions [Alifanov, 1985; Gennadiev, 1990; Dergacheva, 1984, 1998; Karavayeva, Cherkinskaya, Goriachkin, 1986; Ivanov, Alexandrovskiy, 1984; Makeev, 2012 ; Memory of soil ... , 2008; Sokolov, Targulian, 1976; Targulian, 1982; Targulian, Alexandrovskiy, 1987; Khotinskiy, 1977; Chendev, 2004; and others].

The residual humus horizons are soil organic mineral phenomena occurring within the upper accumulative-eluvial or accumulative and the middle and lower texture part of the profile below modern horizons A1 (AY , AU), Ap (PY, PU). These phenomena owe its origin to earlier, the previous stages of pedogenesis which generally more favorable for the processes of accumulative nature (humification, humus accumulation, etc.). Its transition to a new a relic state is not the result of self-development or burial of soil. It happened due to more or less abrupt change of bioclimatic conditions, tectonic or hydrological regime of the territory. The type of pedogenesis was changed from accumulative to accumulative-eluvial or eluvial.

Residual humus horizons (with varying degrees of preservation, ranging from a few cm up to 50-100 cm or more) are found within the accumulative - eluvial and texture series of profiles, depending from the type of soil. At the same time, horizons of Ah type are confined to the accumulative - eluvial or accumulative series. In virgin soils it has sustained position in the profile - at the level from 10-15 to 40-50 cm or more. Often it tapers out in many areas due to uneven degree of development at the time of its formation or due to late differentiated overlay of eluvial processes.

These horizons are preserved to a much lesser extent due to machining and soil erosion in farmland soils of VP. In recent decades, there is a progressive reduction of soil areas with complex organic profile and transforming into soil with relic horizons of broken ground. Residual horizons of Bhh type confined to the middle and lower parts of the soil profiles at depths ranging from 30-40 to 100 cm or more. It has sporadic distribution and is commonly found in soils of low watershed hypsometric level or in subordinate geomorphological positions of high interfluves. It often bears traces of waterlogged (gleification etc.).

Understanding of the composition of soil with residual humus horizon is given in table. 2.

Table 2. Structure of soils with polygenetic profile in Vyatka Prikamye

Indices of soil types and subtypes	Structure of profiles
Soils with relict residual humus horizons
Sod-podzolic (Umbric Albeluvisols)	О + АY + Ahh + (ElB) + Bt + BC + C(ca)
	О + АY + Ahh + (ElB) + (Bhh) + Bt + BC + C(ca)
	О + АY + (El) + Ahh + (ElB) + (Bhh) + Bt + BC + C(ca)
Gray forest soils with gray humus (Albic Luvisols)	О + АY + AYhh + (ElB) + Bt + BC + C(ca)
Gray forest soils with dark humus (Albic Luvisols)	О + АU + AUhh + (Bhh) + Bt + BC + C(ca)
	О + АU + AUhh + (AUBhh) + (Bhh) + Bt + BC + C(ca)
Humic carbonate soils (Rhendzic Leptosols)	О (Ap) + AUhh + (MCA) + B(Bca) + BCca + Cca
Humic gleyic soils (Mollic Gleysols)	О + АU + A Elhh + (ElB) + (Bhhg) + Btg + BCg + C(ca)
	О + АU + (АUhh) + (Bhhg) + Btg + BCg + C(ca)
Gray forest gleyic soils with dark humus (Albi-Endogleyic Luvisols)	О + АU + AUhh + (AUBhh) + (Bhhg) + Btg + BCg + C(ca)
Alluvial sod soils (Haplic Fluvisols)	А0 + АU + (AUBhh) + (Bhhg) + Bg + BCg + C(ca)

Note. O - organogenic; AY - gray humus; AU - dark humus;

Ap - tillable; AY (U) hh - second humus; AUBt - dark humus, transition;

Bt - texture; Bhh - third humus; BC - the transition to the parent rock; C - parent rock; MCA - indigenous limestone rock; ca - carbonates; g - gleyic.