Illuvial Horizons Research Articles

Rees and other critical raw materials in Cretaceous Mediterranean-type bauxite: The case of the Sardinian ore (Italy)

Mediterranean-type bauxite deposits in Sardinia formed during the Upper Cretaceous (Cenomanian–Turonian) due to the emergence of the south European margin of the Alpine Tethys in an area affected by monsoonal climate. The deposits were controlled by the structural frame formed in a transpressive tectonic regime and unconformably overlie carbonate rocks of different age and composition, which led to the formation of different bauxite types. In general, in the Sardinian bauxite deposits, boehmite is the main Al-phase, kaolinite is the main Si-rich mineral, and hematite as well as goethite are the Fe-rich phases. Secondary authigenic anatase and detrital rutile control the Ti contents. Eu/Eu* anomalies show that the bauxite types were derived from the Variscan basement. However, there are differences in Al2O3 and SiO2 contents, which suggest there was localised variability in the extent of epigenetic replacement of kaolinite by boehmite. R-mode factor analysis suggests that most critical raw materials (as defined by the devoted European Union working group), such as Sc, Ga, Nb, Hf, Ta, and W, covary with Al2O3 contents. In the Si-poor bauxite, these metals of economic interest are likely controlled by boehmite, whereas in the Si-rich bauxite they are mostly controlled by weathering-resistant minerals. Rare earth element (REE)-rich minerals, including fluorocarbonates and cerianite, are concentrated in the basal, illuvial horizon, especially in the silica-rich bauxite (ΣREE = 1006–2034 ppm). Cerianite formation required Ce oxidation, whereas fluorocarbonate formation involved mobilisation of trivalent REEs and further fluoride complexation. Both REE-rich mineral phases precipitated under alkaline pH conditions near to the carbonate bedrock. Our evaluation of the critical raw materials distribution in the Sardinian bauxite, coupled with the “economic importance” and “supply risk” parameters, indicate the ore contains large amounts of metals characterised by a “supply risk”, such as light and heavy REEs, and metals of “economic importance”, such as V and W. In this way, the Sardinian bauxite deposits could be reconsidered as a potential source of critical raw materials.

Redox-driven changes in organic C stabilization and Fe mineral transformations in temperate hydromorphic soils

Paddy soils experience long-term redox alternations affecting the interactions between the biogeochemical cycling of iron (Fe) and carbon (C). Differences in particle aggregation and soil organic matter (SOM) turnover are likely to both affect and be affected by the trajectory of Fe mineral evolution/crystallinity with redox fluctuations. We hypothesized that the legacy effects of redox cycling under paddy management affects particle aggregation, the distribution and mineralogy of Fe (hydr)oxides between particle-size fractions, and the interaction with SOM stabilization. Moreover, we expected underlying processes to be different in paddy eluvial and illuvial horizons, particularly due to the different inputs and redox conditions these horizons experience. To test these hypotheses, we evaluated the distribution of Fe species and organic C between different aggregate and particle-size fractions in topsoil (eluvial) and subsoil (illuvial) horizons of soils under long-term paddy and non-paddy management in NW Italy, as well as mineralogical changes in Fe phases by Fe K-edge Extended X-ray Adsorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Our findings indicate that although paddy topsoils are depleted in hydrous Fe oxides with respect to non-paddy soils, they can stabilize important amounts of C through mineral associations, particularly with finer particle-size fractions rich in less crystalline Fe phases. We also show that redox cycling can influence microaggregate stability and consequently the distribution of Fe phases and OC between intra and inter-microaggregate fractions. On the other hand, illuvial horizons under paddy management were enriched in short-range ordered hydrous Fe oxides and this contributed to enhanced microaggregate formation and C stabilization with respect to non-paddy subsoils.

Impact of podzolization on lamellae transformation in sandy soils in a temperate climate – A case study from southern Poland

Lamellae occur in Podzols around the world, mostly in illuvial horizons and parent material, while in eluvial horizons they are often absent or very rare. While many studies have been conducted on lamellae origins, there has been little research focused on their transformation in the soil profile, including the disappearance of lamellae in the course of soil formation. Some studies show that the transformation of lamellae toward physical degradation over time occurs frequently. However, there still exists a lack of studies on lamellae transformation in soils occurring in similar environmental conditions, formed from the same parent material, and varying only in terms of type of dominant soil-forming process. The main aims of this study were: (1) to determine the mechanism of lamellae transformation in sandy soils in a moderately humid climate in southern Poland in relation to progressing podzolization and (2) to compare lamellae transformation mechanisms in well-developed sandy soils affected and not affected by podzolization. The obtained results indicate that soil lamellae commonly occur in the sandy soils of southern Poland – and are characterized by very diverse morphology as well as diverse physical and chemical properties. Soil lamellae exhibit a higher content of fine fractions, iron, aluminum and total organic carbon compared with interlamellae. Soil lamellae are affected by different mechanisms of transformation that depend on their position in the soil profile, predominant soil-forming process, and stage of soil development. Soil lamellae in the upper part of initial sandy soils are mainly transformed by mechanical degradation related to bioturbation. Mechanical degradation of soil lamellae due to clay translocation as well as chemical degradation due to dissolution of iron compounds occur in the upper part of well-developed sandy soils in which podzolization takes place and the eluvial horizon is well-developed. Mechanical degradation of soil lamellae due to bioturbation and clay translocation occurs in the upper part of well-developed sandy soils, which do not exhibit podzolization. Soil lamellae occurring in the lower part of initial and well-developed sandy soils develop progressively due to the illuviation and accumulation of clay and iron compounds as well as lack of biological activity.

Intra-Soil Milling for Stable Evolution and High Productivity of Kastanozem Soil

The long-term field experiment on the Kastanozem showed that the standard moldboard plowing to a depth of 22 cm (control), chiseling to a depth of 35 cm, and three-tier plowing (machine type PTN–40) to a depth of 45 cm was incapable of providing a stable soil structure and aggregate system. The transcendental Biogeosystem Technique (BGT*) methodology for intra-soil milling of the 20–45 cm layer and the intra-soil milling PMS–70 machine were developed. The PMS–70 soil processing provided the content of 1–3 mm sized aggregate particle fraction in the illuvial horizon of about 50 to 60%, which was 3-fold higher compared to standard plowing systems. Soil bulk density reduced in the layer 20–40 cm to 1.35 t m−3 compared to 1.51 t m−3 in the control option. In the control, the rhizosphere developed only in the soil upper layer. There were 1.3 roots per cm2 in 0–20 cm, and 0.2 roots per cm2 in 20–40 cm. The rhizosphere spreads only through the soil crevices after chilling. After three-tier plowing (PTN–40), the rhizosphere developed better in the local comfort zones of the soil profile between soil blocks impermeable for roots. After intra-soil milling PMS–70, the rhizosphere developed uniformly in the whole soil profile: 2.2 roots per cm2 in 0–20 cm; 1.7 roots per cm2 in 20–40 cm. Matric water potential was higher, soil salinization was lower, and the pH was close to neutral. Soil organic matter (SOM) content increased to 3.3% in 0–20 cm and 2.1% in 20–40 cm compared to the control (2.0% in the 0–20 cm soil layer and 1.3% in the 20–40 cm layer). The spring barley yield was 53% higher compared to the control. The technology life cycle profitability was moldboard 21.5%, chiseling 6.9%, three-tier 15.6%, and intra-soil milling 45.6%. The new design of the intra-soil milling machine provides five times less traction resistance and 80% increased reliability, halving energy costs.

Patterning total mercury distribution in coastal podzolic soils from an Atlantic area: Influence of pedogenetic processes and soil components

Soils are the main Hg reservoir in the terrestrial ecosystems where it is deposited via wet or dry deposition and litterfall. Once on the soil surface, different biogeochemical routes will determine the fate of Hg and the role of terrestrial ecosystems as a Hg source or sink. The specific chemical and physical characteristics of Podzols and podzolic soils contribute to the accumulation of Hg in their illuvial horizons, avoiding its leaching to groundwater. The geographical location, state of pedogenesis, soil age, abundance of carrier phases and physical properties can affect the presence and distribution of Hg in soils. Therefore, understand and relate these factors with the behavior of Hg in Podzols and podzolic soils is key to define the role of this type of soil in the terrestrial Hg cycle. In this work, ten podzolic soil profiles were collected in an Atlantic coastal forest area of Portugal and analyzed for the main physico-chemical properties and Hg content to assess the influence of the intensity of podzolization in the Hg depth distribution. Three different patterns of Hg distribution in the studied Podzols, depending on the predominance of atmospheric deposition or the intensity of podzolization, have been defined. The pattern I showed the maximum Hg contents in the surface A horizons (12.9–23.5 µg kg−1), pattern II exhibited the highest peaks in the subsurface illuvial horizons (2.3–17.3 µg kg−1) and pattern III presented an even distribution of Hg through the soil profile. We found that dissolved organic matter (DOM) is the main carrier of Hg in the A and E horizons, whereas metal(Al, Fe)-humus complexes and/or oxyhydroxides contribute to immobilizing Hg in the illuvial horizons (Bh, Bs and Bhs). The principal component regression (PCR) analysis predicted satisfactorily the Hg distribution through soil organic matter and Al and Fe oxyhydroxides. The Hg immobilized in the subsurface layers of Podzols is retained in the long term, avoiding its migration to other components of terrestrial ecosystems where it could cause serious environmental damage such as groundwater and superficial waters.

Using stable nitrogen isotope to indicate soil nitrogen dynamics under agricultural soil erosion in the Mun River basin, Northeast Thailand

Soil erosion has threatened food security by decreasing the area of arable lands and disturbing soil nutrient cycling, especially nitrogen (N) cycling. However, there is still a challenge to indicate soil N dynamics by N stable isotope composition (δ15N) under an erodible environment. In the present study, the six soil sites from forest lands and agricultural lands were selected to collect soil samples in the Mun River basin, the largest agricultural region in Thailand. The contents of soil organic nitrogen (SON), C/N ratios, and δ15N values of SON in soil profiles were analyzed to identify soil N transformation processes under agricultural soil erosion. Moreover, the relationships of SON and δ15N with soil erodibility K factor were determined by linear regression analysis. Fine particles in the paddy land were largely lost under intensive soil erosion during a short-term abandonment (1 ~ 5 years). Agricultural soil erosion has reduced SON content by 3.8 ~ 4.9 times. The δ15N values of SON in the paddy soils ranged from –5‰ to 5‰, which was attributed to the application of manure and synthetic fertilizer and the δ15N fractionations in the alteration processes of the redox environment. In the abandoned paddy lands, δ15N values of SON in the soils above the illuvial horizon were 4‰ higher than those in the soils below the horizon. The results indicated the discrepant soil N processes at the two soil layers, i.e., soil N mineralization in the upper layer produces 15N-depleted inorganic N and leads to 15N enrichment in organic residues; the inorganic N was leached into the lower layer and re-assimilated by microbes, resulting in 15N-depleted SON. The results suggest that agricultural soil erosion significantly reduces soil N level. However, microbial re-assimilation of inorganic N in the deep soils can mitigate soil N loss.

Thermophysical Properties of Chernozem Soils Growing Ornamental Plants in Summer

Currently, there is no data on the transfer of heat and moisture of arboretum soils that grow such ornamental plants as Meyer lilac (Syringa meyeri), rowan “Alaya” (Sorbus aucuparia), and dwarf thuja “Danica” (Thuja occidentals). We experimentally determined that the thermophysical qualities of chernozems in lilac plantations changed with the water regime in the growing season. The sample maximum values of volumetric heat capacity and thermal conductivity were observed in the dense illuvial horizon. The sample minimums were registered in the AB transition horizon. Thermal diffusivity was the highest at the lowest humidity. In rowan plantations, the moisture content in transitional and illuvial horizons AB and B changed insignificantly. Such moisture distribution corresponds to the slope aspect and the features of rowan. The thermophysical coefficients also slightly fluctuated in rowan plantations, especially in the underlying horizons AB and B. The same horizons displayed the sample maximum of thermal diffusivity. It corresponded to the moisture content of capillarity disruption (MCCD from now onward). MCCD is a value lying between the minimal water potential of soil and the Briggs-Shantz wilting coefficient. It denotes the water content, at which moisture mobility and conductivity sharply decrease. In thuja plantations, the indexes of volumetric heat capacity and thermal conductivity in the upper soil horizon were minimal. In the illuvial horizon, these indexes were 42% and 12% higher, respectively. However, the uniform distribution of moisture in the soils that grow thuja has equalized thermal diffusivity in the AB and B horizons. Overall, the soil profile of rowan plantations contained less moisture than that of lilac and thuja plantations. Therefore, the volumetric heat capacity and thermal conductivity were lower, since they corresponded to the soil moisture content.

The Influence of the Relief and Granulometric Composition of the Arable and Illuvial Horizons of Sod-Podzolic Soil on the Formation of Physical and Chemical Properties and Productivity of Culture

The article presents research results on the water physical properties of sod-podzolic soils forming from binomial deposit sediments. The authors show that the granulometric composition of water-glacial deposits and the depth of the underlying rocks of sod-podzolic soils have adverse agrophysical properties. These properties affect crop productivity as a result of soaking crops in the autumn-winter period and a healthy moisture deficit in the vegetation period. The authors show the dependence of organic matter content, water-physical quantities on the range of particles of physical clay. The authors draw a clear differentiation of water physical properties along the profile of sod-podzolic soils.

ВОДНЫЙ РЕЖИМ ЧЕРНОЗЕМА ВЫЩЕЛОЧЕННОГО ПОД ОБЛЕПИХОЙ НА ЛИМАНАХ ГЛУБОКОГО НАПОЛНЕНИЯ

In the humus horizons, the productive moisture reserves in the chernozem in the middle of the slope did not differ much from the moisture reserves at its top. At the same time, in the transition layer of the SUN in the second half of summer, they were significantly higher. This difference also occurred in the soilforming rock. In the lower part of the slope, the meter-long layer of the soil layer contained a greater amount of moisture, which helped to reduce its deficit during the entire growing season. This was especially noticeable in the illuvial horizon and the soil-forming rock. In the second half of the growing season, the ELVs here remained higher than on the upper elements of the slope. In conclusion, it should be noted that only humus-accumulative horizons of Ap+AB needed irrigation with different irrigation norms, depending on the location of sea buckthorn plantations on the slope and the characteristics of their vegetation.

The impact of pine self-afforestation on podzolization process in semi-natural grassland areas of Volyn Polissya (Ukraine)

Background. Several theories have been proposed to explain the podzolization process. Currently, the role of organic matter in both weathering and immobilization in the illuvial horizon is clearly stated. The origin of soil organic matter and, accordingly, the various mechanisms of its influence on the soil material, create the basis of these theories. We assume that in the base-poor sandy soils under rich herbaceous vegetation with a well developed sod layer, the process of podzolization may also depend on CO2 soil formation agent . Materials and Methods. Four localities along a Pinus sylvestris L. self-afforestation chronosequence with pine stands of 10, 20, 40 yrs and an adjacent semi-natural grassland area were investigated in order to determine the patterns of podzolization process on sandy glacial till deposits. Soil pH, exchangeable base, soil cation exchange capacity, total content of soil organic carbon, amorphous Fe, Si and Al and total contents of Al, Fe, Mn, Zn, Cd, Pb, Cu, Co, Ni, Na, K were determined. Statistical analysis of the results was performed using LibreOffice for Linux. Results. During the pine succession, a previously well differentiated into horizons podzolic soil under the grassland vegetation community gradually degrades. Previously well-defined albic and spodic diagnostic horizons disappear, the soil profile becomes more acidic, the soil organic carbon, the base cation content and the base cation saturation decrease, the leaching rate of aluminium and iron increases. Secondary podzolization features in the soil profiles were detected 40 years after the onset of afforestation. The podzolization has not been intensive enough to develop fully fledged albic and spodic diagnostic horizons over such a short period. Conclusions. Based on the obtained soil morphological, physical and chemical properties, three most important agents of podzolization are proposed as principal for the studied area. The main gent under pine forest is fulvic acids that are produced during coniferous litter decomposition. Low molecular weight organic acids and carbon dioxide produced to the rhizosphere by roots and a root associated microbiota are mainly involved in the podzolization process under the grassland ecosystem.

РЕЖИМ ВЛАЖНОСТИ ПОЧВЫ И ЕГО РЕГУЛИРОВАНИЕ ПРИ СОДЕРЖАНИИ ТРАВЯНОГО ПОКРОВА ПОЛЯН И ЛУЖАЕК В ДЕНДРАРИИ

Glades and lawns beautify any forest-park area, and therefore, when developing them, it is necessary to take into account the size and configuration, relief, path net-work, placement of shrubs and tree species as well as the quality of the grass cover. In small recreation areas or in arboretums, it is advisable to create lawns, not glades. It should be emphasized that there is practically no infor-mation on the processes of the formation of moisture con-tent regimes in soil profiles under glades or lawns in an arboretum. Therefore, the study of moisture accumulation and movement in the genetic horizons of chernozem is a topical issue. It follows from the analysis of the actual data that in early June 2014there was a significant moistening of the humus horizon of the chernozem under the grass cover. But at the end of the month, the amount of available moisture dropped sharply and continued to decrease in July and August. This caused soil moisture deficit that could only be met by irrigation. The year of 2016 was gen-erally wetter although in May the moisture content in the upper humus horizon was low. The drop of moisture con-tent in chernozem continued until mid-June when available moisture decreased to unsatisfactory values. From the end of June, regular rainfall has dramatically increased the available moisture that remained very good until the end of the growing season. As a result, a significant deficit of available moisture was observed only in late May and early June. In June 2017, the available moisture in the humus-accumulative horizon was satisfactory. But in the illuvial horizon, the moisture reserves were evaluated as good and irrigation was not required. Thus, for the research period only in 2014 it was required to irrigate the chernozem soil profile in the glade under grass cover.

ВЛАГООБЕСПЕЧЕННОСТЬ ТРАВЯНИСТОГО ПОКРОВА В УСЛОВИЯХ ДЕНДРАРИЯ И ЕЕ ОСОБЕННОСТИ

From the analysis of the actual data, it follows that at the beginning of June 2014, there was a significant moistening of the humus horizon of Chernozem under the grass cover. But at the end of the month, the amount of available moisture decreased sharply and continued to decrease during July and August. This led to a shortage of water reserves, which could only be compensated by irrigation. 2016 was generally wetter, although the moisture content in the upper humus horizon was low when it emerged from winter in may. The drop in humidity in Chernozem continued until mid-June, when the ELVs decreased to unsatisfactory values. Since the end of June, regular precipitation has dramatically increased the available moisture reserves, remaining very good until the end of the growing season. As a result, a significant deficit of productive moisture was observed only in late may and early June. In June 2017, the productive moisture reserves in the humus-accumulative horizon were satisfactory. But in the illuvial horizon, the moisture reserves were estimated to be good, which did not require irrigation.

ОЦЕНКАУСЛОВИЙПРОИЗРАСТАНИЯНАСАЖДЕНИЙ ОБЛЕПИХИ ПРИ ЛИМАННОМ ОРОШЕНИИ

Sea-buckthorn grows well on slope lands that are high-ly drained and lack stagnant water. The optimum soil mois-ture content for sea-buckthorn corresponds to 70% of the lowest moisture capacity. Under continuous soil moisture deficit, the leaf surface area decreased, the fruits were poorly set as a result of ovary drop during the first half of the growing season, and berry size decreased. In this re-gard, the study of the water regime of the soil under sea-buckthorn plantations the possibility of its regulation re-mained quite topical. The available moisture in the humus horizons of chernozem in May 2004 corresponded to a satisfactory level. At the end of summer, the moisture con-tent of the chernozem decreased to unsatisfactory state. As a result, the plants experienced water deprivation throughout the growing season. Naturally, the need arose for irrigation, especially in June and August with irrigation rates of 490 and 280 t per m3, respectively. In the underly-ing horizons, the soil moisture deficit was weaker. In the humus horizons, the available moisture in the chernozem in the middle of the slope did not differ much from the mois-ture content at its top. At the same time, in the transitional BC layer in the second half of summer, the available mois-ture content was significantly higher. This difference was also found in the parent rock. In the lower part of theslope, the one-meter soil layer contained a greater amount of moisture which contributed to the decrease of its deficit during the entire growing season. This was especially no-ticeable in the illuvial horizon and parent rock. In the sec-ond half of summer,the available moisture content here remained higher than in the upper slope sites. In conclu-sion, it should be noted that only humus-accumulative hori-zons A (arable) + AB needed irrigation with different irriga-tion rates depending on the location of the sea-buckthorn plantations on the slope and their growth features.

Redox-driven changes in water-dispersible colloids and their role in carbon cycling in hydromorphic soils

Redox fluctuations in hydromorphic soils can influence ecosystem functions by altering the cycling of organic carbon (OC) and other elements in both the aqueous and solid phases throughout the soil profile. Most studies focusing on the mobility of dissolved OC in rice paddy soils have often disregarded the contribution of colloidal particles. We provide a detailed chemical and size-related characterization of water-dispersible soil colloids and their depth distribution in two soil profiles under long-term temperate paddy and non-paddy management, by asymmetric flow field-flow fractionation. Anoxic conditions enhanced colloid dispersion with a preferential release of the finer colloid fractions (5 and 4-fold increase in the < 30 nm and 30–240 nm fractions, respectively). The mobility of OC-rich, iron (Fe) and aluminium (hydr)oxide and aluminosilicate colloids along the soil profile was probably responsible for their depletion in the topsoil and a corresponding accumulation in the deeper illuvial horizons compared to the non-paddy soil. However, the release, percolation and subsequent reoxidation of Fe2+ was also shown to be a plausible mechanism leading to the formation of fine colloids in the subsoil. Redox-driven changes in colloid distribution were also linked to the differences in OC and pedogenetic Fe stocks in these two agro-ecosystems.

Діагностика процесів елювіально-ілювіальної диференціації профілю в грунтах Передкарпаття

Elementary soil processes, as components of the soil-forming process, play an important role in the formation of morphological and genetic features of soils and are used for their genetic diagnosis. Eluvial-illuvial differentiation of the background profile for Precarpathian soils is due to the passage of processes from the group of eluvial, in particular podzolization, silting and gley-eluvial. The diagnostic criteria for these processes remain controversial and need further development. The article provides some justifications for their objectivity and reliability in identifying individual processes of soil formation and the results of establishing the genetic consequences of their passage. The formation of clay cutanes in the illuvion is considered to be an important sign of lessivage, but the presence of one and a half oxides may also indicate the passage of the processes of podzolization and in-soil clay forming According to another criterion - the presence of "optically oriented clays" in the illuvion is difficult to establish their migration path and the intensity of the lessivage process. Increasing the value of the ratio of silt content to the content of physical clay in the illuvial horizons compared to the eluvial horizons does not allow to distinguish the processes of podzolization and lessivage, and the same ratio in the illuvial horizon compared to the parent rock - lessivage and clay forming. Changes within the profile of the mineral part of the soil, which are reflected by the molecular ratios of SiO2:Al2O3 and eluvial-accumulative coefficients of aluminum, the values of silt and aluminum losses, also the profile distribution of montmorillonite are important criteria for the separation of loess and podzolization and indicate the decisive role of the latter in the formation of the profile differentiation of the soils of Precarpathians. Important criteria for gley-eluvial processes are higher losses from the upper podzolic illuminated of Fe2O3 layer than Al2O3, an increase in the molecular ratio of Al2O3:Fe2O3, the ratio of losses of Fe2O3 and Al2O3, also increase the criterion SiO2:Fe2O3/SiO2. Complementing the national system of parameters for the diagnosis and classification of soils with criteria that are characteristic of the substantive-genetic approach according to the WRB requires further study.

Evidence for an alternative concept of the Finow soil formation

Paleosols can widely be used as chronometric markers, and the so-called Finow soil is reported to be a supraregional marker in the sandy deposits in northern central Europe and Siberia. The Finow soil is thought to be associated with pedogenesis between the Allerød and the Younger Dryas with subsequent fossilization by eolian activity. The formation of the 5- to 15-cm-thick brownish Finow soils is often explained by brunification and some minor illuviation of clay. Although the Finow soil has been described at several distant sites, the lack of an entire soil sequence consisting of a topsoil and a subsoil recently raised doubts about the formation of the Finow soil.We present a micromorphological approach together with grain size analysis from two sites in northeastern Germany (Glashütte and Jänschwalde in Brandenburg) and one site in Poland (Błędno) where purported Finow soils have been reported and were dated in earlier studies to investigate the processes that led to the formation of the Finow soil.Our findings show that the three studied Finow soils are characterized by clay migration, rather than brunification, and that the Finow soils are situated below well-drained sandy deposits at hydrological barriers. Whereas at Glashütte, the soil organic matter of an Usselo soil acts as a hydrological barrier, at Jänschwalde and Błędno, changes in the granulometry of the sandy deposits presumably act as a hydrological barrier. At Jänschwalde, the illuvial horizon is the least developed of the three sites and the eluvial horizon has a depth of only 40 cm, but at Glashütte, the Finow soil below the 330-cm-thick sandy deposit shows extensive features of clay illuviation. Hence, we propose that the thickness of the eluvial horizon strongly influences the degree of clay illuviation in the Finow soil. Further, we propose that due to the well-drained character of the sandy substrates, the formation of the Finow soil is limited to the supply of clay for the clay migration rather than being time limited. Therefore, the clay illuvial features of the Finow soil are indicative of neither the suggested pre-Holocene soil development nor of the lack of the eluvial and topsoil horizons of the supposedly truncated Finow soil due to late Quaternary soil erosion or landscape activity. Indeed, the clay illuviation that causes the formation of the Finow soil can visually accentuate sedimentological changes, but because the clay illuviation is a post-sedimentary process, the indicative potential of the Finow soil is site specific. Hence, we conclude that the use of the Finow soil as a supraregional chronometric or pedostratigraphic marker should be avoided.

Soil properties influencing Hg vertical pattern in temperate forest podzols

Mercury content of twelve podzols from NW Spain was studied to elucidate the main soil properties involved in the Hg accumulation of these soils. The highest average Hg concentrations (HgT) were found in the Bh and Bs horizons (64 and 105 μg kg−1), whereas the lowest occurred in the E horizons (15 μg kg−1). Moderate values of HgT were obtained for the A and C horizons (38 and 52 μg kg−1). The Hg enrichment factors revealed that the predominant origin of Hg in these soils is the atmosphere instead of the parent material. As it was shown by the PCA performed (which explained 82% of the variance of the data), the main soil characteristics involved in the pedogenetic processes of the studied podzols are organic matter and Al and Fe compounds. The stepwise linear regressions made described between 54% and 84% of the predicted Hg depending on the soil horizon. Besides a complex ensemble of biogeochemical reactions involved in the balance between input and outputs of Hg, the most influencing variable in the A horizons was organic C, moderate stability Al-humus complexes in the E horizons, Fe-humus complexes and pHw in the Bh horizons, Al-humus compounds in the Bs horizons and crystalline Al and Fe compounds in the C horizons. Therefore, Hg is mobilized from the A and E horizons bound to dissolved organic matter and precipitated in the illuvial horizons due to the saturation of the organic matter with metals. The immobilization of Hg in the subsuperficial horizons of podzols leads to different environmental benefits derived from the removal of Hg from the A horizons, more exposed to climate-induced and land use/cover changes that could potentially modify the dynamics of Hg in those superficial horizons.

Mid-Holocene soil water and vegetation in the Xi’an area of the southern Chinese Loess Plateau

This paper investigates mid-Holocene palaeo-vegetation and soil water in the Xi’an area of the southern Chinese Loess Plateau (CLP). A well-dated (8.5–6.0 ka BP and 5.0–3.1 ka BP) loess-palaeosol (unit S0) was logged, sampled and analyzed at four sites in the Xi'an area of the southern CLP, from which we report soil micromorphological (type and occurrence of root pores), particle size and geochemical data (CaCO3 and Sr concentration) to: (i) infer changes in soil water content, (ii) infer the limits of gravity water and the types of hydrologic cycle, and (iii) reconstruct the palaeovegetation. Numerous woody plant root holes were identified (2–4 mm diameter) within the illuvial horizon underlying palaeosol S0, the morphology of which is consistent with those produced by woody plants. The clay-rich argillic horizon of palaeosol S0 was found to contain high concentrations of kaolinite, which in concert with the geochemical indices, indicates that soil gravity water attained a depth of 2.2–2.8 m, whilst soil water content was ~20–25%. This implies that pedogenic processes at this site were more intense during the mid- compared to late Holocene loessic soils elsewhere on the CLP, and ultimately attests to relatively wet climatic conditions (e.g. up to 800 mm yr−1 rainfall), the hydrologic cycle type of precipitation-soil water-groundwater, and the vegetation of deciduous broad-leaved forest. We propose that combined analyses of root-channel morphology and mobile element geochemistry can be used to infer changes in palaeo-hydrology and ultimately, the strength of the Asian Summer Monsoon.

Features of soil thermophysical properties of the southern variant of ravine biogeocenoses of the Ukrainian steppe zone

Thermophysical properties are an important characteristic of the general condition of soils, which determine the peculiarities of the distribution of heat flow in them. Today studies of thermophysical properties of soils, including the steppe zone of Ukraine, are practically not performed. This determines the relevance of the work, which is devoted to establishing the characteristics of the thermal properties of various soils. As a result of the study of thermal diffusivity, heat capacity and thermal conductivity of soils of northern and southern exposures, as well as the thalweg of the Voyskovoy Bayrak (located near the village of Voyskovoe Solonyansky district of Dnipropetrovsk region), it was found that the most important soil factors particles of physical clay and organic matter content. It was found that the eluvial horizons of the chernozem of the forest of the northern exposure differ in the reduced values ​​of heat capacity and thermal conductivity in comparison with the illuvial horizons. Eluvial horizons of forest-meadow soil of thalweg are characterized by increased values ​​of thermal diffusivity and thermal conductivity, as well as reduced values ​​of heat capacity compared to illuvial horizons. Eluvial horizons of forest chernozem of southern exposure are characterized by lower values ​​of thermal diffusivity, heat capacity and thermal conductivity compared to illuvial horizons. The most significant boundary between eluvial and illuvial horizons in terms of thermophysical properties is characteristic of the chernozem of forest southern exposure, which is manifested in a sharp increase in the values ​​of thermophysical properties in the first illuvial horizon. Cluster analysis revealed that the most similar in terms of thermal diffusivity are forest chernozems of southern and northern exposures, and in terms of heat capacity and thermal conductivity – forest chernozems of northern exposure and forest-meadow soil of thalweg ravine.

Landscape change and occupation history in the Central Russian Upland from Upper Palaeolithic to medieval: Paleopedological record from Zaraysk Kremlin

Paleosol-sedimentary sequences encountered in the settlements with long occupation history could provide a unique insight into the trends of landscape development and human-environment interaction over long time scales. We studied paleosols exposed by the excavations in the Kremlin of Zaraysk (Central European Russia) which were formed during the late Pleistocene and the Holocene and contain archaeological materials spanning from Upper Palaeolithic till late Medieval. Archaeological findings and numerous radiocarbon dates provide a reliable time frame for paleopedological record which we extracted from paleosols using macro- and micromorphological observations as well as physical and chemical properties and paleobotanical indicators (phytolith assemblages). The basal layer without archaeological materials presents signs of soil formation which resemble Bryansk fossil soil developed in the second half of Marine Isotope Stage (MIS) 3. The overlying archaeological stratum - one of the Gravettian cultural layers is linked to the paleosol level known as Zaraysk soil. Its age is estimated at 16 ka BP. Macro- and micromorphological features point to moderate dark humus accumulation, anthropogenic compaction and cryogenic processes at the final stages of paleopedogenesis. Poorly sorted heterogeneous composition of the mineral material with a large proportion of sand grains indicates colluvial origin of the paleosol parent material. The overlying sorted silty deposit supposes contribution of windblown material to its formation. We associate cryogenic and eolian processes at the end and after Zaraysk soil development with the cold intervals at the end MIS 2, presumably with the Oldest and Younger Dryas. The complete profile of Luvisol/Grey Forest Soil with eluvial and illuvial horizons and relict dark humus morphons is developed within the silty unit. This soil indicates long-term natural pedogenesis under first steppe and then deciduous forest vegetation during major part of the Holocene. The topsoil however is formed by clear plough horizon which points to cultivation started in the Middle Ages. Sharp boundary separates the buried Luvisol from the overlying cultural layer-Technosol developed after building of Zaraysk Kremlin in the 16th century. Technosol presents a mixture of natural soil with construction materials, especially limestone fragments. Soil units, both natural and affected by humans, are not separated one from another by an unaltered C horizon, so soil-forming processes from the upper soils penetrate into the underlying ones forming a multistory pedocomplex.