lateral migration of soil solid-phase material within a landscape-geochemical arena detected using...

ISSN 1064�2293, Eurasian Soil Science, 2013, Vol. 46, No. 10, pp. 983–993. © Pleiades Publishing, Ltd., 2013.Original Russian Text © A.N. Gennadiev, T.S. Koshovskii, A.P. Zhidkin, R.G. Kovach, 2013, published in Pochvovedenie, 2013, No. 10, pp. 1155–1166.

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INTRODUCTION

The study of the lateral migration processes relat�ing soils on different positions and uniting them into adynamic territorial system is one of the current tasks ingeographical�genetic soil science. The mechanicalmigration (transfer of material in the form of suspen�sions) frequently occupies the leading position interms of the transported volumes and manifestationintensity among the different migration forms ofpedogenesis products [6, 12]; however, experts in soilgenesis and geography pay less attention to it than tothe physicochemical and biogenic migrations. Themajor body of data on the lateral mechanical migra�tion of material was obtained by scientists studying soilerosion and is used for solving problems related to thedevelopment of relief forms, ravine networks, andriver�bed evolution [5, 7]. At the same time, assessingthe stability of the spatial soil combinations, revealingthe relationships between the soils of the differentlandscape�geochemical positions, and predicting thestatus of the soil cover under the effect of natural andtechnogenic factors are possible only at the consider�ation and parameterization of the lateral migration ofthe solid�phase soil material. Of special importance isthe quantification of the lateral transport of soil sus�pensions within integrated spatial geosystems: catch�ment basins or landscape�geochemical arenas, where

mutually related areas of dispersion, transit, and accu�mulation of the solid�phase products of pedogenesisare formed [6].

The aim of this work was to reveal the migrationand accumulation features of the soil solid�phasematerial within a small landscape�geochemical arenaand to analyze the effect of the lateral mass transfer onthe most informative soil properties and the soilcover’s structure in the catchment basin studied. Themagnetic tracer method was used for assessing the vol�umes and rates of the lateral migration of the solid�phase products of the pedogenesis on the selectedmodel territory.

METHODS AND OBJECTS

The magnetic tracer method has been developed bythe authors of this work, together with partners fromIllinois University, for more than ten years [2–4, 13–15]. The method is based on the quantification of thespherical magnetic particles (SMPs), which fall ontothe soil cover from the atmosphere, where they arriveat the combustion of coals and some other fuels [1].The period of the most intensive emission of SMPsinto the environment in the territory of Russia, as wellas in other industrially developed countries, corre�sponds to the last 100–150 years, because steam loco�

GENESIS AND GEOGRAPHY OF SOILS

Lateral Migration of Soil Solid�Phase Material within a Landscape�Geochemical Arena Detected

Using the Magnetic Tracer MethodA. N. Gennadiev, T. S. Koshovskii, A. P. Zhidkin, and R. G. Kovach

Faculty of Geography, Moscow State University, Moscow, 119991 RussiaReceived April 5, 2013

Abstract—Thorough studies of the lateral migration of the solid soil material and the large�scale mapping ofthe soil cover have been performed within a landscape�geochemical arena in the small catchment area of theLokna River basin (Tula oblast). Podzolized clay�illuvial agrochernozems are the predominant soils in thecatchment area. Nine soil types from four orders according to the 2004 soil classification have also beendescribed. The morphological analysis of the soil profile structures revealed their changes related to the lateralmigration of the solid�phase products of the pedogenesis. From the estimated reserves of the spherical mag�netic particles as tracers of the mass transfer, the accumulation and dispersion zones of the solid�phase mate�rial in the soil cover have been separated and conclusions about the genesis of these zones and their place inthe migration structure of the catchment basin have been drawn. The soil catenas within the landscape�geochemical arena have been classified in accordance with the migration intensity of the soil solid�phasematerial, the localization of deposits, and the degree of openness of the soil�geochemical conjugations. Theeffect of the lateral migration of the soil solid�phase material on the structure of the microarena soil cover andthe soil genetic profiles has been revealed.

Keywords: soil cover of small catchment basins, soil erodibility, mechanical migration of soil material

DOI: 10.1134/S1064229313100037

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motives were the first the main sources of SMPs. Weconfirmed this by the revealed increase in the concen�tration and average particle size in the close vicinity ofrailways [8]. On the local level, the SMPs that havearrived from the air are relatively uniformly dispersedon the surface of the soil cover. Their concentration inthe upper soil horizons is in the range of from tens tohundreds of milligrams per kilogram of soil. Under theeffect of the surface and soil runoffs, the magneticspherules move, together with other suspensions, inthe horizontal and vertical directions and mark thetransfer pathways of the solid�phase products of thepedogenesis. The quantitative assessment of the redis�tribution of the SMPs in the soils on slopes allowsdetermining the intensity and rate of the lateral migra�tion of the solid�phase soil material. The methodinvolves the magnetic separation of the soil material,the control of the changes in the magnetic susceptibil�ity of the soil under the impact of SMPs, and the directmicroscopic determination of the content of spherulesin the magnetic fraction of the soil. The identificationof the SMPs is performed using the diagnostic analysisbased on the revelation of their characteristic features(the shell structure, hollow structure, metallic luster,etc.) distinguishing them from a wide range of otherstrongly magnetic minerals at a magnification of 200–500 [9]. The volumes of the migrating soil material and

the time of their migration are calculated using thedeveloped procedures. A detailed description of themethod and examples of its use were reported earlier[2, 4, 13]. This is the first thorough study of an inte�grated catchment using this method.

A first�order catchment basin—a small landscape�geochemical arena in a tributary of the ChasovenkovVerkh ravine in the Plavsk district of Tula oblast—wasused as the key area. The temporary stream on theravine’s bottom flows into the Lokna River. The catch�ment area, together with the ravine network elements,is 96 ha. The catchment basin is drop�shaped; itslightly curves and is latitudinally oriented (Fig. 1).The catchment slopes are of southern, eastern, north�ern, and intermediate aspects.

In geomorphological terms, the small catchmentbasin is divided into several relief forms: (1) near�watershed convex surfaces with an inclination of 0° to1.5°; (2) gentle, slightly concave, completely plowedinterfluve slopes with an inclination of 1.5° in the upperpart to 4°–8° in the lower part; (3) completely grassedslopes of the ravine network with an inclination of 5°–6° to20°; and (4) the ravine’s bottom with an inclination of0.5°–3° and 10–25 m wide. A fallow plot was also sep�arated, which is located between the plowed gentleslopes and the grassed steep slopes of the ravine network;it is 5 to 40 m wide with an inclination of 5°–7°. This

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Fig. 1. Study object. A small catchment of a ravine tributary: (1) sampling points; (2) catenas; (3) catchment boundary; (4) plow�land, gentle slopes; (5) fallow land, slanting slopes; (6) meadow, steep ravine slopes; (7) meadow, ravine bottom; (8) catena num�ber, number of samples.


LATERAL MIGRATION OF SOIL SOLID�PHASE MATERIAL 985

plot was previously plowed and presently is occupiedby natural meadow associations; the plowing was sus�pended because of the intensive erosion and signifi�cant soil loss from the fertile layer. The total area of thegrassed soil is 12.7 ha, or 13.2% of the total catchmentarea. The beginning of the plowing of this territory isdated at the early 17 century. Two plowed fields arepresently located on the catchment area.

Within the small landscape�geochemical arena,74 soil profiles were described and soil samples weretaken from the plow (0� to 25�cm) and subsurface (25�to 50�cm) horizons. The soil sampling was performedin catenas with 25�m intervals. A total of 10 soil cate�nas coinciding with the predominant direction of thesurface water runoff were established, described, andtested in the catchment area.

The contents of the magnetic fraction and theSMPs were determined in the soil samples. The soilswere diagnosed according to the 2004 classification[10]; in some cases, the soil names in accordance withthe 1977 classification are also indicated for the com�pleteness of the information [11].

Podzolized clay�illuvial agrochernozems are thepredominant soils of the landscape�geochemicalarena. In addition, nine soil types from four orders ofthe 2004 classification were described [10]: humus�accumulative soils (clay�illuvial chernozems and clay�illuvial agrochernozems), texturally differentiatedsoils (gray, dark gray, and agrodark gray soils),agrozems (clay�illuvial agrozems and dark carbonate�accumulative agrozems), and stratozems (dark�humusstratozems, dark�humus stratozems on buried soil,and dark�humus agrostratozems on buried soil). A soilmap was composed for the catchment area (Fig. 2).

RESULTS AND DISCUSSION

The morphological analysis of the soil profile struc�tures revealed some of their changes related to the lat�eral migration of the solid�phase products of the pedo�genesis.

Podzolized clay�illuvial agrochernozems (developedpodzolized chernozems according to the 1977 classifi�cation) are the most prevalent soils within the studiedcatchment basin, where they occupy more than a thirdof the area (38%). Their distribution range confined tothe plowed area of the catchment basin occupies thenear�watershed and medium parts of the slopes in thenorthern half of the basin and borders the ravine’smouth as a narrow band. Within these areas, the incli�nation of the slopes does not exceed 3°. The profile ofthe soils includes the following horizons: PU–AU–(au + bi)el–(bi + au)el–BIe–BI–(BCAmc)–BC(ca).The plow horizon is 25–30 cm thick; the lower bound�ary of the dark�humus horizon, which includes theplow horizon, occurs at a depth of 30 to 60 cm (55 cmon the average). The thickness of the humus profile[AU + (au + bi); the upper part of the profile with ahumus content higher than 1%] is 60–70 cm. The upper

boundary of the calcareous horizon occurs at a depthof 100–105 cm; in some profiles, the calcareous hori�zon is not detected. The peculiar features of the soilprofile include the strong zoogenic turbation, espe�cially at the boundary between the humus and clay�illuvial horizons, manifested as mosaic humus mottlesof different ages; the clay�humus and clay films on thefaces of soil aggregates in the BI horizon; and the whit�ish powdering on most faces of the structural aggre�gates (10 to 40% of the face area). The soil structurevaries from crumb–coarse blocky in the PU horizon tomedium subangular blocky in the AU and (au + bi)horizons and angular blocky in the BI horizon. Thecarbonate neoformations consist of pseudomycelium.The degree of the soil erosion is low.

Clay�illuvial typical agrochernozems (developedleached chernozems according to the 1977 classifica�tion) occupy smaller areas than podzolized cher�nozems: about 10–13% of the study area. These soilsoccur on gently sloped (inclinations less than 1°)ridges at the northern and southern catchment basinboundaries; these soils are also described on the mid�dle slope of southwestern exposure. The system ofgenetic horizons in these soils is similar to that in pod�zolized clay�illuvial agrochernozems, except for thesignificantly lower development or absence of whitishpowdering. The reasons for the change of podzolizedclay�illuvial agrochernozems to clay�illuvial typicalagrochernozems (less prevalent) are not clear. Thiscould be related to the reduction of the descendingradial and soil lateral water flows because of the occur�rence on a slope or a leveled ridge, as well as to the fea�tures of the territory before its development, includingthe presence of steppificated zones before the clearingand plowing of the main forest areas. The degree oferosion of clay�illuvial typical agrochernozems is low.

Podzolized dark clay�illuvial agrozems (weaklyeroded podzolized chernozems) are confined to thepositions with the enhanced removal of soil materialbecause of its mechanical migration. They occupyabout 16% of the catchment area; the main rangesoccur in the middle part of a long slope in the westernpart of the plot and extend as a narrow band along theplowed zone in the southern half of the studied terri�tory. The profile of the soils analogous to that of pod�zolized clay�illuvial agrochernozems contains nodark�humus AU horizon (which is completely plowedand transformed to the PU horizon); the humus hori�zons are slightly thinner.

Dark clay�illuvial typical agrozems occupy 18% ofthe area. They occur in the lower part of the slope withan inclination of 2.5°–6° in the northern half of thecatchment area, in the gentle part of the slope beforethe plowed zone, and in the near�ravine part of thecatchment basin (with an inclination of 3.5°–4°).These soils also occur on the watershed positions inthe northeastern and southeastern parts of the studiedarea and on the ridge’s surface in the northern part ofthe catchment basin. The soil profile is slightly trun�

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cated; the dark�humus AU horizon is completely dis�placed by the agro�dark�humus PU horizon. Thetransitional (au + bi) horizon is 40–50 cm thick.

Dark carbonate�accumulative agrozems occupy theplowed steep lower parts of the slope of southern expo�sure (with an inclination of 6°–8°) and are character�ized by the highest manifestation of soil erosion; theyalso occur on the fallowed plot. The system of hori�zons is reduced to a PU(pa)–(bi + au)–BCAmc pro�file. The humus profile includes only the agro�dark�humus horizon; the calcareous horizon occurs near tothe surface (its upper boundary is at a depth of 30 cmcompared to 110 cm on the average for the entirecatchment basin). These soils occupy no more than1% of the total catchment area. Within the range ofthese soils, signs of the active lateral transfer of thesolid�phase products of the pedogenesis were noted inthe form of a gully network that remained after theerosion event in the summer of 2012. The gullies are

about 4 cm deep and 8–12 cm wide; 5 gullies per 10 malong the slope were recorded on the average. No sim�ilar gullies were found in other places of the catchmentarea.

The soil cover becomes more complex on thegrassed part of the catchment basin: on the slopes ofthe ravine network (6.2% of the basin’s area), on theravine’s bottom (2.2%), and on the fallowed plot(4.8%). Postagrogenic clay�illuvial chernozems anddark gray postagrogenic soils with an AUpa–AUe–BEL–BT horizon system were described on the fal�lowed area. The most eroded soils occur on the steep�est slopes within the fallowed area; postagrogenicmedium�shallow clay�illuvial agrozems with an AUpa–(bi + au)–BI–(BCAnc,mc) horizon system occurthere.

The steep ravine slopes were never plowed. Graysoils with an AYrz–AYe–AEL1–AEL2–BEL–BT1–BT2 horizon system were developed on such slopes of

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Fig. 2. Soil map of the landscape�geochemical arena based on the results of the field soil�morphological studies: (1) soil profiles;(2) catchment boundary; (3) meadow (ravine slopes and bottom); (4) plowland, gentle slopes. Texturally differentiated soils:(5) gray typical, (6) dark gray typical and postagrogenic, (7) agrodark gray; clay�illuvial chernozems: (8) podzolized postagrogenicshallow, (9) deep and ultradeep typical; clay�illuvial agrochernozems: (10) podzolized medium deep, (11) typical medium�deep,(12) ultradeep humus�stratified; dark clay�illuviated agrozems: (13) podzolized low� and medium deep, (14) typical low� and mediumdeep, (15) medium�shallow postagrogenic; dark carbonate�accumulative agrozems: (16) medium�shallow micellar; stratified soils: (17)dark�humus postagrogenic stratozems, (18) dark�humus stratozems. The solid horizontals are at 5�m intervals.



northern exposure. The profile includes a gray�humusAY horizon and a humus�eluvial AEL horizon. Thesteep ravine slopes of southern exposure are occupiedby clay�illuvial typical chernozems (leached cher�nozems) with an increased thickness of the humus�accumulative horizon (to a depth of 100–110 cm).The accumulation of material is probably manifestedthere.

Humus�stratified soils—dark deep water�accumu�lative stratozems—are developed on the ravine’s bot�tom; they frequently occur on the buried meadow(hydrometamorphized) dark�humus soil. Its profile isusually as follows: AU–RU1–RU2–[AU]–[AU/Q(e)]–[Q]–[CQ]. Sometimes, podzolizationsigns appear in the middle part of the buried soil. Thestratozem area makes up about 4% of the total catch�ment area.

The particle�size distribution analysis of thedescribed soils (the upper dark�humus, agro�dark�humus, or humus�stratified horizons) shows that theircontent of physical clay (52–58%) corresponds to aclay loamy texture. Their content of the coarse silt(0.05–0.01 mm) fraction varies from 42 to 48%; thatof the clay fraction varies from 23 to 32%. The fine siltfraction makes up 13–20%, and the medium silt frac�tion 10–16%. The total content of fine, medium, andcoarse sand is insignificant: its content varies from 0.1to 0.7%. A tendency toward an increase in the contentof the clay fraction and a decrease in the content of themedium silt fraction is noted in the soils on the lowerparts of the slopes compared to their upper parts.

The particle�size distribution in the stratozemsoccurring on the ravine’s bottom was studied in moredetail. These soils are characterized by a lighter tex�ture: their content of physical clay is always lower than53% (with the average value for the entire catchmentarea being 55.2%), and the content of coarse siltexceeds 47%. The vertical distribution of the particle�size fractions in the profile of the stratozems reveals alightening of the texture down the profile. The contentof physical clay decreases to 49% at a depth of 90–105 cm;from a depth of 140 cm, the particle�size distributioncorresponds to a medium loamy texture. The contentof sand also increases down the profile up to 6% (at adepth of 240–250 cm).

The analysis of the origin of the dispersion and accu�mulation zones of the solid�phase soil material revealedby the magnetic tracer method. As was shown above, thelateral mechanical transfer of soil material is revealedby its morphogenetic study. The removal of materialresults in the erosion of soils; at the accumulation ofmaterial, stratified soil subtypes and stratozems areformed, as is shown on the soil map (Fig. 2). However,these data are insufficient for the parameterization ofthe soil erosion–aggradation processes, because theinitial thicknesses of the genetic horizons in the placeof the eroded soils are unknown, and the exact currentboundaries of the soil horizons are difficult to assessbecause of the zoogenic turbation of the soil profile.

The magnetic tracer method was used for the quantifi�cation of the lateral migration of the solid�phase prod�ucts of the pedogenesis within the landscape�geochemical arena.

In samples taken from the plow soil horizons in tencatenas within the catchment basin, the content ofSMPs was determined, and their reserves were calcu�lated with consideration for the soil density at eachpoint of the 0� to 25�cm layer and for some sites in the25� to 50�cm layer. The obtained reserves of SMPswere mapped, and the field of the SMP reserves wascomposed by inverse distance weighted interpolationfor the 0� to 25�cm layer of soil in the landscape�geochemical arena. Its migration structure was deter�mined by the localization and proportions of the areaswith increased and decreased contents of SMPs,which were interpreted as dispersion (D) and accumu�lation (A) zones of soil material. Seven dispersionzones and nine accumulation zones were separated.For the quantification of the intensity of the lateralmigration and accumulation of the soil solid�phasematerial, the weighted average SMP reserve was calcu�lated for the catchment area, which was equal to3.2 g/m2 in the 0� to 25�cm layer. The soils were alsotested on three key plots located on watershed surfacesfor assessing the soil erosion–aggradation within thecatchment basin (30 samples). The average content ofSMPs on the least eroded surface is equal to 3.8 g/m2

in the 0� to 25�cm layer. The zones with significantexceeding of this value (by more than 0.5 units) wereconsidered as accumulation zones of the soil solid�phase material; the zones with the concentration ofSMPs lower than their average content on the leasteroded surface were considered as dispersion zones.The location and origin features of the dispersion andaccumulation zones of the soil solid�phase materialare described below (Fig. 3).

Zone D1 is located in the middle part of the ridge inthe northeastern area of the catchment basin. Theminimum reserve of SMPs in the soil among all thesampling points is observed there: 1.4 g/m2 in the 0� to25�cm layer. This zone occupies about 1 ha (1% of thecatchment area, which is 96 ha). The appearance ofthis zone is related to the location of the plot, whichrepresents a system of the intensive trilateral removalof the soil solid�phase material. The transitions withthe conjugated accumulation zones are characterizedby gradual changes in the concentrations of the SMPs.The soils described on this area belong to dark shallowclay�illuvial agrozems, which corresponds to theincreased erosion rate.

Zones D2 and D3 occupy near�watershed positionson long gentle slopes in the northwestern and south�western parts of the catchment basin. The decreases inthe SMP concentrations (2.3 and 2.6 g/m2 in the 0� to25�cm layer) are less manifested than in zone D1;however, the areas depleted of the tracer are signifi�cantly larger: 10–12 ha in total (or 11–13%). Thesedispersion zones are located on watersheds (inclina�

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tions less than 1.5°–2°), where the input of materialfrom higher positions is excluded and erosion (even ifinsignificant) is possible. The soils in zones D2 and D3are characterized by lower erosion signs: podzolizedmedium�thick clay�illuvial agrochernozems are devel�oped there.

In zone D4 located in the middle part of a longslope, the reserve of SMPs in the 0� to 25�cm layer is1.8 g/m2; i.e., it is lower than the mean for the catch�ment basin. The area of this dispersion zone makes upabout 6–7% of the catchment area. Its formation isrelated to the long length of the slope, which favors anincrease in the water flow [7]. The soils in this zone—podzolized shallow dark clay�illuvial agrozems—show erosion signs.

Zone D5, which is relatively large (about 5%), islocated in the middle part of a gentle near�mouthslope of northwestern exposure in the southeasternpart of the catchment basin. The reserve of magneticspherules in the 0� to 25�cm layer varies from 2.3 to2.6 g/m2. The formation factors of this dispersion zoneare the divergent cross shape of the slope and the rela�tively large inclinations of the soil surface (about 3°–4°).Dark medium�thick clay�illuvial agrozems with shal�lower humus profiles compared to the overlying pod�

zolized clay�illuvial agrochernozems were developedthere.

Zone D6 occupies about 4% of the area in the east�ern half of the catchment basin. It has the shape of aband 50–70 m wide that borders the plowland alongthe entire slope of southern exposure. The reserve ofSMPs is 2.4 g/m2. The zone is occupied by dark car�bonate�accumulative agrozems (soils with the mostmanifested erosion signs): the upper boundary of thecarbonate�illuvial horizon sometimes rises to a depthof 37–38 cm with the average occurrence depth of thehorizon being 100–110 cm; the thickness of thehumus horizon is only 25 cm with its average thicknessbeing 55–60 cm. Within the zone, the above�men�tioned gullies are developed; they also indicate a higherosion rate. The main formation factor of this zone isthe significant steepness of the slope (6°–7°, the max�imum for the plowed catchment area). On the steepestpart of the southern slope, where zone D6 is located,after the early snowmelt, the bare soil undergoes theintensive impact of melt water flowing from the stillsnow�covered more gentle slopes.

Zone D7 consists of separate fragments located inthe middle part of a relatively gentle slope of southernexposure. The concentration of SMPs in the zone

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(2.8 g/m2) is not the minimum, but the revelation ofthis zone is important for the more complete and ade�quate understanding of the migration structure of thelandscape�geochemical arena. The location of zoneD6 on a homogeneous slightly convex slope and itsconjugation with the accumulation zones of soil mate�rial located up and down the slope can be related to thehydrodynamic features of the surface runoff.

The flow of (melt or rain) water, which starts fromthe watershed, is gradually saturated with suspendedparticles (due to the eroding action of the near�bottomstreams and raindrops), which are involved in themigration processes. The content of particles sus�pended in the flow increases down the slope andbegins to exceed the transport capacity of the flow. Thesuspensions are partly deposited at some distance fromthe watershed and form a mechanical barrier for thesurface runoff. Down the slope, the erosion is againintensified and the soil material is involved in the waterflow down to the new accumulation zone [5]. A wavystructure of alternating accumulation and dispersionzones is thus formed.

The described formation mechanism of the mate�rial accumulation and removal zones is observed onlyon the slopes with increased intensities of the lateralmechanical migration of the soil material. On theslopes with low migration activities; small inclina�tions; and, hence, low flow velocities, such processesare less manifested. The wavy cyclic erosion–aggrada�tion process of the soil material within catena 1 isshown in Fig. 5.

The obtained data on the increased content ofSMPs in the upper 25�cm thick soil layer (compared tothe average value for the catchment area) can be inter�preted as evidence for the accumulation of soil mate�rial due to its mechanical migration or no loss. Theabsence of material loss (or its minimum manifesta�tion) can be a reason for the increased concentrationsof SMPs in the below�described zones A8 and A9 andthe accumulation of material in zones A1–A7. Addi�tional data on the content of the SMPs in the 25� to50�cm layer were used in some cases at the separationof the accumulation zones.

Zones A1 and A2 form a vast region of accumulationof soil material in the plowed part of the catchmentbasin (about 8–9% of the catchment area). They arelocated in a cup�shaped depression on the plowedslope adjacent to the ravine’s head. The reserve ofSMPs in the 0� to 25�cm layer is 4.3–4.7 g/m2. Sus�pended sediments are brought here from the slopes ofthree exposures. Therefore, their deposition results inthe formation of stratified soil subtypes and stra�tozems; the thickness of the aggraded humus horizonsincreases to 110–170 cm.

Zones A3 and A4 of soil material accumulation, eachof which occupies about 2–3% of the catchment area,belong to intraslope accumulation types. They occuron the same slope, where they alternate with erosionzones D6 and D7, to which they are geneticallyrelated; their formation mechanism is describedabove. The deposition of the suspended sediments inthese zones is also marked by a small increase in thethickness of the humus horizons; the reserve of SMPs

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in zones A3 and A4 varies from 4.0 to 4.6 g/m2 in the0� to 25�cm layer and from 2.0 to 4.0 g/m2 in the 25�to 50�cm layer (in the nonaggraded soils, the reserve ofmagnetic spherules in the 25� to 50�cm layer is 0.9–1.2 g/m2).

Accumulation zones A5 and A6 are located on steepunplowed slopes of the ravine adjacent to its bottom(the mean inclinations are 12°–17° and, sometimes,up to 20°). They occupy 3–4% of the catchment area.These accumulation zones are well identified by thedenser natural grasses with a poorer floristic composi�tion. The reserve of SMPs is close to the reference val�ues (3.7–4.4 g/m2) in the 0� to 25�cm layer andreaches 4.7 g/m2 in the 25� to 50�cm layer. The accu�mulation of soil material in these zones is due to thepresence of a dense plant cover with a large projectivecover area (up to 90–100%) and a high degree of turf�ness. The described steep ravine slopes are usually nearthe boundary of a plowland located at the edge of asteep slope. The dense vegetation on the slope acts asa barrier abruptly increasing the surface roughness andreducing the velocity of the flow moving from theplowland and saturated with suspended soil particles.The soil profiles penetrated chernozems with signifi�cantly higher thicknesses of the humus and transi�tional horizons (80–130 cm compared to the averagethickness of 60 cm).

Zone A7 is one of the main accumulation zoneswithin the catchment area; it is located on the ravine’sbottom. The bottom occupies 2–3% of the catchmentarea. The accumulation of material on the ravine’sbottom is due to its subordinated geochemical posi�

tion, small inclinations (0.5° to 3°) reducing thevelocity of the arriving flows, and the high degree ofturfness hampering the formation of secondary chan�nels. Stratozems—soils with a thick aggraded humus�stratified horizon—are formed there. Six profiles andeight drill cores were described for the ravine’s bottomwith the determination of the thickness of theaggraded profile part. In the samples taken at differentdepths, the lower boundary of the SMP distributionwas determined by the magnetic tracer method. Thethickness of the aggraded soil layer during the deposi�tion of the SMPs was 90 cm in the upper part, 130 cmin the middle part, and 150 cm in the lower part of theravine. The content of magnetic spherules at the lowerboundary of their distribution in the soil profile is 3–4 mg/kg.

Within the landscape�geochemical arena, zoneswith increased reserves of SMPs were separated, whichare located on eluvial or transeluvial positions ratherthan on geochemically subordinated positions. Theseare zones A8 and A9. They are located on convex near�watershed ridge�shaped surfaces in the northern andsouthern parts of the catchment, respectively; thesezones occupy about 5% of the catchment area. Theirformation is not related to the accumulation of soilmaterial brought from higher hypsometric positions; itis rather due to the low�intensity erosion within theirlimits and the more intensive mechanical migration ofthe material from the adjacent dispersion zones.Therefore, high reserves of SMPs remained in zonesA8 and A9 (4.8–5.0 g/m2 in the 0� to 25�cm layer).

4

2

0

–2

–4

–6

–8

–10

I II III

t/ha per year

1 2 3 4 5 6 7 8 9 10

Fig. 5. Parameters of the lateral migration of the soil solid�phase material in the studied catenas: (1–10) catena numbers; (I) accu�mulation of soil material within the arable part of the slope; (II) transfer of soil material within the arable part of the slope;(III) removal of soil material beyond the arable part of the slope.



Podzolized agrochernozems characterized by mini�mum erosion signs were described there.

In general, the location of the accumulation anddispersion zones revealed by the magnetic tracermethod coincides with the described areas of erodedand aggraded soils. However, no complete quantitativecoincidence between the results of the different meth�ods is observed in some cases.

In particular, the most intense erosion (when about20–30% of the soil is lost) sometimes corresponds tothe lower but not minimum reserves of SMPs (e.g.,zone D6). This situation can be explained by the dif�ferent durations of the erosion–accumulation pro�cesses, which are characterized by the magnetic tracermethod and the soil�morphological method. Theplowing of lands in this region began at least many tensof years before the construction of railways.

In other cases, in the zones of intensive accumula�tion (e.g., zone A6, where the layer of 15–30 cm isaggraded), the reserve of SMPs in the tested 0� to25�cm layer is not the maximum; sometimes, it islower than the initial reserve on the watershed area,although it exceeds the average value for the catch�ment area. In these cases, the inversion of the SMPcontent is usually observed in the soil profile, when thelower (25� to 50�cm) layer contains more magneticspherules than the upper (0� to 25�cm) layer. This isrelated to the fact that material can be brought fromthe dispersion zones, where the topsoil layer is alreadylost and material from the horizons initially depletedof magnetic spherules is involved in the mechanicalmigration. Similar cases are illustrated at the compar�ison of the SMP distribution curves in different soil layers(Fig. 4). At most sampling points within the catchmentbasin, the reserve of SMPS in the 25� to 50�cm layer isabout half that in the 0� to 25�cm layer.

Classification of the soil�geochemical catenas basedon the lateral migration parameters of the soil solid�phase material. The separated dispersion and accumu�lation zones of the soil material are genetically conju�gated with one another and represent a component ofthe migration structure of the landscape�geochemicalarena. Another component includes the classificationof the soil catenas occurring within the catchmentbasin. The classification was performed with the use ofthe work of Gennadiev and Zhidkin [8] based on theconsideration for (a) the mechanical migration rate ofthe soil material within the catenas, (b) the degree oftheir openness (i.e., the assessment of the portion ofthe material’s removed beyond the catena’s limits),and (c) the localization of the areas of the soil mate�rial’s accumulation on the slope. For the classificationof the soil catenas, the volumes of the soil materialinvolved in the mechanical migration within each cat�ena were calculated (Fig. 5). The calculation wasbased on the comparison of the SMP reserves at thesampling points with those in the reference plots; theerosion rate was calculated on the average for the last

100 years. The detailed calculation procedure wasreported earlier [2, 3, 8].

The studied catenas within the catchment basinwere found to significantly differ according to the pro�posed criteria: most of them have different character�istics (table). Five catenas were classified as hypody�namic (the migration rate is <5 t/ha per year) and open(the portion of the material removed beyond the cat�ena is 50 to 85%). According to the location of theaccumulation zones within the plowed slope part, theupper�accumulative catena (the accumulation zonesare located in the upper third of the plowed slopepart), two middle�accumulative catenas (one or severalaccumulation zones are located in the middle part ofthe slope), and two lower�accumulative catenas (theaccumulation zones are mainly located in the lowerpart of the slope) are separated. In addition, hypody�namic half�open catenas (the portion of materialremoved beyond the catena is lower than 59% of thetotal transported soil material); upper� and middle�accumulative catenas; two mesodynamic ultraopen cat�enas, including an exoaccumulative catena (i.e., nosignificant accumulation zones were revealed) and anupper�accumulative catena; and a mesodynamic openexo�accumulative catena were distinguished.

The exoaccumulative catena type, where the accu�mulation of material within the plowed slope part isalmost absent, is typical for catena 6 on the near�topslope in the western part of the catchment basin andcatena 10 on the near�mouth slope of northern expo�sure. In the former case, the absence of accumulationzones is related to the long slope length, thus increas�ing the transfer of the suspended material by waterflows; in the latter case, it is related to the location ofthe catena’s portion on the near�ridge slope (see thedescription of zone D5). The upper�accumulativetype includes catenas 3, 8, and 9, the upper links ofwhich are confined to the leveled slightly concave seg�ments of the slope. The middle�accumulative catenatype is manifested on the convex slope of southernexposure (catenas 1 and 2); a wavy alternation of accu�mulation (A4, A5) and erosion (D6, D7) zones areobserved there; another middle�accumulative catenaoccupies the near�top slope of eastern exposure (cat�ena 5). The accumulation of material in the lower linksof the catena�soil conjugations (within the plowedslope part) is noted in catenas 4 and 7. According tothe leveling data, no increase in the slope inclinationoccurs in the lower part of catena 7. In catena 4, theaccumulation of soil material in the lower part of theslope occurs in the background of the increasing slopeinclination (to 4°). The accumulation on plowedslopes of increased inclination can be related to theretention of the soil material at the boundary betweenthe fields. During some time, the catchment area hasadditional separation into arable fields, whose bound�aries passed closely to those of the revealed accumula�tion zones.

992


GENNADIEV et al.

CONCLUSIONS

The lateral mechanical transfer of soil material isrevealed by its morphogenetic study. The removal ofmaterial determines the formation of soils with differ�ent degrees of erosion; stratified soil subtypes and stra�tozems are formed at the accumulation of material.However, these data are insufficient for the parameter�ization of the soil erosion–aggradation processes,because the initial thicknesses of the genetic horizonsin the place of the eroded soils are unknown. The mag�netic tracer method was used for the quantification ofthe lateral migration of the solid�phase products of thepedogenesis within the studied catchment basin.

This method allowed separating the spatial disper�sion and accumulation zones of the soil material,which are genetically conjugated with one another andrepresent a component of the migration structure ofthe landscape�geochemical arena. It was revealed thatthe manifestations of the dispersion and accumulationzones in the catchment area are of multifactor nature:the zones can be located on the upper, middle, andlower parts of the slopes; on the near�watershed (near�ridge) surfaces; and on the slopes of different expo�sures. The origin of these zones is due to the summaryeffect of the slope’s length and the exposure, the sur�face’s shape and inclination, the spatial conjugationstructure of the zones, the variability of the carryingcapacity of the water flow, etc. The total area of therevealed dispersion zones makes up 35% of the catch�ment basin; the accumulation zones occupy 26% ofthe catchment area. The transit�buffer area occupies39% of the catchment basin. The area proportions ofthe different functional zones characterize the specificmigration structure of the landscape�geochemicalarena.

The second component of the migration structureof the landscape�geochemical arena included the for�malized system of soil catenas within the landscape�

geochemical arena. The soil catenas characterizingthe arena include different combinations of soil slopeconjugations according to the manifestations of thelateral migration of the solid�phase products of thepedogenesis. However, they can be classified with con�sideration for (a) the mechanical migration rate of thesoil material within the catenas, (b) the degree of theiropenness (i.e., the assessment of the portion of mate�rial removed beyond the catena limits), and (c) thelocalization of the zones of the soil material’s accumu�lation on the slope.

The next step in the development of the describedmethod and approach should involve the classificationof different landscape�geochemical arenas accordingto the manifestations of the lateral migration of thesolid�phase soil material within their limits.

ACKNOWLEDGMENTS

This work was supported in part by the RussianFoundation for Basic Research, project no. 13�05�00098�a and by the President's grant to support youngscientists MK�1221.2012.5.

REFERENCES

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Classification of the catenas according to the mechanical migration of the soil material

Soil migration rate, t/ha per year

Portion of soil material removed beyond theconjugation limits

Localization of the soil accumulation zones

exoaccumu�lative

upper�accu�mulative

middle�accumu�lative

low�accumula�tive

Hypodynamic (<5) Ultraopen (>85%) – – – –

Open (50–85%) – 3 1, 5 4, 7

Half�open (<50%) – 8 2 –

Mesodynamic (5–10) Ultraopen (>85%) 6 9 – –

Open (50–85%) 10 – – –

Half�open (<50%) – – – –

Hyperdynamic (>10) Ultraopen (>85%) – – – –

Open (50–85%) – – – –

Half�open (<50%) – – – –

A dash indicates there no catenas meeting the classification criteria.



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Translated by K. Pankratova

lateral migration of soil solid-phase material within a landscape-geochemical arena detected using...

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