Fig. 2. Contents of silt and clay in sod-podzolic and gray forest soils with complex organic profile of Vyatka Prikamye

The factional group composition of humus (FGCH) - is one of the most accessible and informative biochemical methods in the practice of evolutionary genetic studies of soil. Fundamental provisions of this method can be reduced to the following positions: a) zonal soils of humid acidic forest landscapes (and arid alkaline desert and semi-desert landscapes) are characterized by fulvate or humate - fulvate type of humus with domination of fulvous humic acids (HA) of fraction HA1 (ГК1) (associated with Fe and Al), or low content of black HA of fraction HA2 (ГК2) (associated with Ca) as part of the humate and with the prevalence of mobile and aggressive fractions of fulvic acids (FA1 and FA1a) (ФК1 and ФК1а) among fulvic components; b) zonal soil of moderately moist and semiarid neutral forest-steppe and steppe landscapes have humate or fulvic - humate type of humus with the dominance of black humic acid of fractions GA2 and GA3 (associated, respectively, with Ca and clay minerals) in the absence or with very little content of fulvous humic acids of fraction GA1 as part of the humate part and mobile and aggressive fractions of fulvic acids among fulvic components.

Fig. 3a. The humus composition of sod-podzolic soils with complex organic profile of Vyatka Prikamye

Fig. 3b. The humus composition of gray forest gray humus soils with complex organic profile of Vyatka Prikamye

The tested soils with polygenetic profile of VP exhibit fundamental differences in FGCH that lead to the following regularities (Fig. 3):

- Firstly, the smallest amount in residual SH (TH) horizons humins or insoluble residue among all genetic horizons;

- Secondly, the significant differences of humate's degree of horizons AY and AElh (AUh), which judging by the relative Cga / Cfa reach values ​​about 2.5 -4 in bottom of its, that is 2-3 times or more surpass this parameter for the upper humus horizon;

- Thirdly, black HA (compared with fulvous HA) increase in the composition of humates in SHH. Black HA are significant in sod-podzolic soils and especially in the gray forest gray humus soils, whereas fulvous fraction of HA can completely absent in dark humus subtype;

- Fourth, the reduction in the SHH of humates Ca (up to its complete transformation into a brown HA in case of leaching of Ca) is most noticeable in sod-podzolic soils and is clearly latched by morphologically degradation of organic substance (OS) of these horizons.

Coaly - gray color of SH and TH horizons is explained by the humate composition of OS with high optical density of the HA as aromatic compounds. The humus content is much less compared to the upper humus horizons.

These biochemical features served as one of the main arguments in favor of the concept of the complex formation's history of the humus - accumulative thickness of these soils. Two stages are singled out in history of formation. First, accumulative (eutrophic) stage of developmental evolution was occurring in other, less humid than at present, natural conditions, close to the forest-steppe. The formation of relatively developed humus horizons happened in this stage. It corresponds to the total power of the modern and the second (third) humus horizons.

Subsequently eutrophic stage was replaced to mesotrophic (in the south part of VP) and to the oligotrophic (in the north part of VP) stage of heritable evolution with elements of erasing that corresponds to a boreal landscape position. It leds to the differentiation of previously single humus horizon into two: the top, it corresponds to the new bioclimatic situation and lower (SHH), the residual, which has become a relic in the changed circumstances. OS was updated in the first of its that corresponds to subtaiga (south) and southern taiga (north) factors of pedogenesis with formation of less humate humus of MODER type. The residual humus horizon gone out of the sphere of active bioturnover. Humification processes are dramatically weakened or completely stopped. It has been replaced by a degradation of preformed OS with selective destruction primarily least stable - fulvic - components. As a result, this led to a decrease of total humus content with a simultaneous increase of the relative humate's degree, until the above-mentioned values ​​which are not specific for any of the currently known modern soil types. The increase of relative humate's degree was accompanied by darkening of SH and TH horizons, despite of the reduction in the amount of OS.

Radiocarbon dating is one of the most compelling arguments in favor of the concept of relic nature of OS in SH and TH horizons and polygenetic properties of these soils in VP. Dozens of age determinations of HA in upper and lower humus horizons of different types of zonal and intra-zonal soils with problematic genesis (specified previously in Table. 1) have been producing during our long-term studies (Prokashev, 1999, 2006, 2009, etc.). In all cases, we obtained similar values ​​of radiocarbon dates for the same type of genetic horizons, which allow to talk with a high degree of confidence about the objectivity of this method, on the one hand, and we can declare about the common direction of the pedogenesis's processes in automorphic (and semihydromorphic) soils in postglacial stage of evolution of the natural environment in VP, i.e. for the period 10 thousand years ago, on the other hand (Table 2).

Table 2. The age of humic acids in soils with complex organic profile of Vyatka Prikamye

The cut, №	Horizon, the depth of the sample, cm	The faction of HA	Age 14С, years	Laboratory sample number
Sod-podzolic soils
Я-1	АY 5–14	HA1	600±90	ЛУ-1502
		HA2	1580±180	ЛУ-1501
		HA3	2590±140	ЛУ-988
	Elh 15–25	HA1	5580±140	ЛУ-994
		HA2	6600±430	ЛУ-993
		HA3	6740±300	ЛУ-984
	Вh 35–50	HA1	5530±160	ЛУ-995
		HA3	7630±390	ЛУ-985
С-8	АElh 17–25	HA1	6230±100	ЛУ-997
		HA2	8360±370	ЛУ-991
		HA3	8900±390	ЛУ-987
К-28	АY 5–13	HA1	340±60	ЛУ-4512
		HA2	560±50	ЛУ-4513
		HA3	730±80	ЛУ-4514
	АElh 15–27	HA1	6240±80	ЛУ-4511
		HA2	6660±70	ЛУ-4509
		HA3	6800±80	ЛУ-4510
Gray forest gray humus soils
В-18	AElh 25–32	HA3	6950100	ЛУ-3880
У-27	AElh 40–50	HA2	551060	ЛУ-4636
		HA3	6440120	ЛУ-4637
Gray forest dark humus gleyic soils
М-13	PU 0–26	HA1	68060	ЛУ-4515
		HA2	126060	ЛУ-3878
		HA3	147070	ЛУ-3879
М-17	AUhg 26–36	HA3	6650  150	ЛУ-3877
	Bh 85–105	HA3	7140  1500	ЛУ-4623
В-40	Вh 100-120	HA3	733080	ЛУ-5389

These data correlate closely with study materials of factional and group humus composition. It clearly shows: first, the qualitative differences in radiocarbon age of OS between upper and the lower humus horizons, that gives good reason for statement about polygenetic structure of organic profile and all profiles of these soils in VP; secondly, SH and TH horizons have the relic nature and HA age of 9-5,5 thousand years ago regardless of the depth that correspond to early post-glacial stages, namely the stage of the Boreal -Atlantic Holocene; thirdly, the sharp change in direction of pedogenesis with the change of soil accumulative stage on accumulative - eluvial in the second half of the Holocene about 5,5-5 thousand years ago, that is, starting with subboreal stage (5-2,5 thousand years ago) right up to subatlantic stage (2,5-0 thousand years ago) or until the present time; fourth, conformity in the HA age of the upper horizon to average time of carbon residence (mrt index) in the humus horizons, within the sphere of active bioturnover and free exchange of CO2 between atmospheric and biospheric, and ultimately pedosferic reservoirs (less than one thousand years).

The last statement illustrates most tellingly by the radiocarbon data for AY horizon of the cut K- 28, where the HA3 fraction showed the age 730 years and partly for the same horizon in the cut Я -1, where the HA1 fraction has age 600 years. However, we cannot pay attention to the fact that fractions HA2 and HA3 from the same horizon are significantly more ancient, arised about 1.5-2.5 thousand years. This may be due to two main possible reasons: a) it has residual nature of the Atlantic stage, although the nature was rejuvenated; b) partial ploughing of relict humus horizon AElh into the former topsoil at previous stages of agricultural development of south - western part VP where the cut Я -1 is laying now under mature (conditionally virgin) forest. In any case, it evidences indirect about different rates of update a various HA fractions of relic humus in a modern setting with rapid formation of predominantly fulvous HA in new horizons AY. It associates with Fe and Al.

It follows from the above that the factional group composition and an age of OS may well correspond with the concept of "a soil is memory of a landscape" and serve as a reliable indicator of the evolution of investigated soils. Judging by the geography of soils with complex organic profile in VP, conception implies wider distribution of dark colored (accumulative or eutrophic) stage of pedogenesis in the early and middle Holocene. The northern borders of this stage reached the Cheptsa river valley within areas of carbonate and noncarbonate covering loams, and clay eluvium, marl clay, and in some cases limestone eluvium in places of exit Permian rocks to the surface.

The dark humus stage in early-middle Holocene time has not became apparent on more poorer rocks of light granulometric composition. Soils with relict phenomena are not typical here. The question of the formation of dark-colored soils to north from the Cheptsa river is also problematic, because the presence of soils with obvious signs of polygenesis is not detected there. If conditions favorable for the accumulation type of soil formation existed in the first half of the Holocene, at the present time it should probably not have remained even at relatively rich source rocks due to modern more boreal climate with domination of wash water regime and eluvial processes in northern parts of southern taiga and in the middle taiga subzone of VP.

Special consideration should be paid to the character of the environment of VP in the first half of Holocene. The most common view is the advance forest steppe landscapes to north. However, the regional paleogeographic materials obtained M.M. Pakhomov with colleagues give evidence of the predominance while bleached pine- birch forests with limited presence of broad-leaved trees [Zhuykova Pakhomov, Prokashev, 2000; Prokashev, Zhuykova, Pakhomov, 2003]. It corresponds to the forest-steppe landscapes of West Siberian type that can be explained by quite northerly position of Vyatka-Kama province, compared to the center of European part of Russia.

The question of the typical accessories of dark humus soils in Boreal- Atlantic time of its formation is not less interesting. From the standpoint of the concept of actualism and soil archaeological materials for the more southerly forest-steppe regions of Russian plain [Alexandrovskiy, 1985; Alexandrovskiy, Alexandrovskaya, 2005] the most likely hypothesis is about belonging of these soils: a) to the gray forest gray (and dark) humus subtype in the north of polygenetic soil's area that is occupied now sod- podzolic soils with SH horizons and b) to the gray forest dark humus subtype - in the south of the area, where types of soil of the same name is currently found, but it has a special kind - sod- podzolic similar.

The distinctive feature of the latter from the typical soils is a relic nature of the bottom of once united humus thickness, with a predominance of the degradation processes of metamorphism its OS. Essentially, gray forest soils of VP are only partly relevant to the modern complex of soil-forming factors. Figuratively speaking, it gradually drifts towards the forest soils of the subtaiga and southern taiga (sod- podzolic) since the second half of the Holocene.

The question of the carbonate's degree of rocks at the time of formation of the ancient soils with polygenetic soil profiles is also noteworthy. Whether was it the same everywhere on the same type of rocks, such as covering loam or initially it was varied and was weakening until the complete lack in the north part of VP? Or these differences are consequence of humidity increase in the same direction of climate on the stage of heritable evolution with elements of erasing? However, this aspect is beyond the theme developed in this lecture.

Thus, the set of methods listed above can reveal predominantly conservative behavior of investigated soils and its paleogeographic significance in the spirit of paradigm "soil is memory". Nevertheless, cognitive moments of marginal nature related to the paradigm of "soil is life" occurred in the analysis of the composition and age of humus horizon AY (AU). Together, it allows to form a more complete picture of the natural environment and soil history in VP.

Physico-chemical properties, as already mentioned, disclose actual soil properties, corresponding to the current stage of pedogenesis. The most informative of its can be considered in the Table. 3. These data (presented as an example on isolated cuts) conform with conclusion about the overlap of degradation processes of organic and mineral phase of these soils with polygenetic profile in the final stages of evolution.

Table 3. Physicochemical properties of soils with complex organic profile of Vyatka Prikamye

Horizon, the depth of the sample, cm	рН		Нг	Са¨ +Мg¨	Са¨	Мg¨	E	V, %	Accumulation Са+Mg (%)		H˙+ Al¨˙	H˙	Al¨˙
	Н2О	КСI	mEq /100 g								mEq /100 g
Sod-podzolic soils: The cut С-8
O 0-2	5,4	4,6	43,0	31,8	26,0	5,8	74,8	42		+39	1,14	0,64	0,50
OА 2-5	5,0	4,0	49,5	27,8	23,2	4,6	77,3	36		+21	1,15	0,26	0,89
АY 5-17	5,3	3,9	10,2	5,7	4,2	1,5	15,9	36		–75	1,75	0,02	1,75
АЕlh 17-25	5,9	4,2	6,4	8,4	6,9	1,5	14,8	57		–63	0,30	0,01	0.29
Вt1 25-35	5,8	4,0	6,1	16,8	13,0	3,8	22,9	73		–27	1,09	0,05	1,04
Вt1 40-50	5,7	3,9	6,8	19,5	14,7	4,8	26,3	74		–15	1,54	0,11	1,43
Вt2 60-70	5,8	3,9	6,3	21,1	15,6	5,5	27,4	77		–8	1,36	0,09	1,27
ВС 90-100	5,8	4,0	5,4	22,3	16,3	6,0	27,7	80		–3	0,94	0,09	0,85
С 135-145	6,1	4,1	3,9	22,9	16,3	6,6	26,8	85		0	0,42	0,03	0,39
Gray forest gray humus soils: The cut У-27
PY 0-30	6,8	5,5	2,5	14,9	13,1	4,3	17,4	86		–35	–	–	–
AElh 30-35	6,3	5,1	3,6	12,1	10,6	5,1	15,7	77		–47	–	–	–
AElh 45-50	6,4	5,2	3,2	11,6	10,0	4,8	14,8	78		–40	–	–	–
ElB 55-65	7,1	5,4	1,6	15,3	13,5	3,4	16,9	91		–33	–	–	–
Bt1 75-85	7,2	5,4	1,7	17,5	15,0	4,2	19,2	91		–23	–	–	–
Bt2 93-103	7,1	5,2	1,9	22,5	20,1	4,3	24,4	92		–1	–	–	–
C 115-125	6,7	4,8	2,3	22,4	20,1	4,6	24,7	91		–2	–	–	–
C 135-145	6,4	4,6	2,5	22,8	20,3	5,0	25,3	90		0	–	–	–
C 175-185	6,8	5,0	1,9	26,6	25,1	3,4	28,5	93		–	–	–	–

As can be seen from the indices of the exchange, and partly hydrolytic acidity, it indicates to medium and strong acid reaction in sod-podzolic and medium in gray forest soils. For this reason, profiles and especially its accumulative - eluvial series had leached from the exchange ions of Ca and Mg. Saturation coefficient of bases in soils of sod- podzolic type is very small. However, there are obvious fundamental difference between both types for eluviation level. It can be illustrated by the presence of significant amounts of the Al ion in composition of the exchange acidity. In general, the actual properties indicate to more rapid degradation of polygenetic sod-podzolic soils in comparison with gray forest at the present stage of its evolution. History of its formation and further development can be represented in the following diagram (Fig. 4).

I - Ancient holocene soil (pre-boreal time 11-9 thousand years ago);

II - Early middle holocene soil (boreal-atlantic time, 9-5,5 thousand years ago);

III - Late holocene soil (subboreal - subatlantic time 5,5-0,2 thousand years ago);

IV - Modern soil with complex organic profile;

V - Soil with complex organic profile in the future (after 1-2 thousand years).