Assessment of the relationships between the distribution of soil horizons and the climatic parameters

The influence of 15 parameters of atmospheric and soil climates on the distribution of 12 genetic soil horizons (humus, eluvial, illuvial, and metamorphic) in the soils of Russian plains was studied. Quantitative characteristics of the relationships between these climatic parameters and the distribution of soil horizons were estimated by the rank correlation method. The initial dataset was prepared with the use of digitized maps in the MapInfo program. The results of our study made it possible to estimate the climatic parameters with respect to their impact on the formation of soil horizons. The difference between precipitation and potential evaporation, evaporation, and bulk atmospheric moistening of the soils proved to be the most significant climatic parameters affecting the distribution of soil horizons. These characteristics reflect the redistribution of moisture under the influence of temperature factors. The weakest correlation with the distribution of soil horizons was found for the index characterizing the depth of penetration of temperatures >10°C into the soils.     

Cartographic analysis of the distribution of saline soils in Russia depending on some climatic parameters

The subdistrict zoning map distinguishes 27 subjects of the Russian Federation, 109 municipal districts, and 142 districts and subdistricts along the latitude line at 53°44′ N in Russia. Among them, soil salinization is observed in 13 subjects of the Russian Federation, 39 municipal districts, and 41 districts and subdistricts. The total length of the transect is 6354 m. The relationship between the distribution of saline soils and climatic parameters has been analyzed in the districts and subdistricts of the subdistrict zoning map. Information about soil salinity has been borrowed from the Soil Salinization Map of Russia (2003) and some regional salinization maps (Khakassia, Barguzin Depression). Climate is the main factor affecting the distribution of soil salinity. Among the analyzed climatic parameters, the Ivanov wetting coefficient (WC) best describes the relationship between climate and soil salinity. The share of saline soils in a district is inversely proportional to the WC value. The degrees of drainage and dissection of the area limit the effect of climate on soil salinity. It is proposed to subdivide the relief into three groups depending on the degree of dissection in order to correct the calculations of relationship between WC and soil salinity. With consideration for relief features, the relationship between soil salinity and WC is represented by a segment of the coordinate plane with WC as the ordinate and the share of saline soils as the abscissa. The segment is limited by two lines corresponding to the maximum and minimum soil salinities at given WC values. The use of the limiting equations allows predicting, with a high probability, the presence and distribution area of saline soils at a given latitude at 0.85 ≥ WC ≥ 0.5.     

美国土壤Salic层研究

The taxonomic hierarchy and nationwide distribution of soils with a salic horizon were studied using the USA Natural Resources Conservation Service Soil Survey Geographic (SSURGO) Database to provide a more holistic view of the role of soil-forming factors in pedogenesis than from isolated case studies.Soils with a salic horizon occupied an area of 11 000 km2,i.e.,0.1% of land area in the contiguous USA.These soils occur narrowly in three great groups(Aquisalids,Haplosalids and Halaquepts),11 subgroups,and 97 soil series.Soils with a salic horizon commonly had a mesic (50% of soil series) or thermic (19%) soil-temperature class,an aquic (89%) soil-moisture class,a mixed mineral class (79%),a calcareous (52%)reaction class,a superactive (59%) cation exchange activity class,and a fine (24% of soil series),fine-loamy (24% of soil series),or fine-silty (19% of soil series) particle-size class.Soils with a salic horizon were concentrated in the Basin and Range Province of western USA.The key pedogenic processes leading to the development of salic horizons were salinization,gleization,and calcification,with some evidence for argilluviation and silicification.     

Diagnostic horizons in the Russian soil classification system

The analysis of the responses of users of the substantive-genetic Russian soil classification system revealed some problems concerning the genetic (diagnostic) horizons. Applying horizons is essential since soil diagnostics are based on their identification and their combinations in soil profiles. In the recent Russian system, there are many diagnostic horizons, and their recognition is not always easy. This review is aimed at displaying the main elements and the genetic essence of the horizons, as well as the reasons to choose the diagnostic criteria and parameters for most of them. The horizons are grouped into genetic sets, and the specific properties of the horizons are emphasized, as well as the differences between the horizons and the feasibility to introduce new horizons. A rough comparison of the diagnostic horizons in the Russian and WRB systems revealed the considerable similarity of the taxa, whose definitions depend on the presence of the diagnostic horizons: these are the orders and soil reference groups, respectively.     

Mercury in humus horizons of soils in the Transbaikal region

The total mercury content has been determined in gray forest soils, chernozems, chestnut soils, and in different parent materials in the Transbaikal region. The mercury content is below the clarke value in the intrusive, effusive, and alluvial soil-forming rocks (0.004–0.024 mg/kg). In the humus horizons of the soils, it reaches 0.011–0.026 mg/kg, which is higher than the clarke value for the pedosphere. The mean background content of mercury in the soils of the Transbaikal region is 0.018 mg/kg. No significant positive correlation between the mercury content and the humus content of the soils has been revealed.     

Influence of climatic conditions and soil properties on 137Cs vertical distribution in selected Chilean soils

Long-term downward distribution of global fallout ¹³⁷Cs was studied in different soil types, in natural and semi-natural environments of four Chilean climatic zones. The ¹³⁷Cs soil content showed an exponential decrease with depth; relaxation depth ranged from 0.9 cm in the polar climate environment up to 6.8 cm in the mesothermal warm summer one. In the Antarctic and Westpatagonic ecosystems the long freezing periods delayed the ¹³⁷Cs leaching. In temperate and tropical climate zones, primarily the rates of annual rainfall and volume of coarse soil pores control the radionuclide's distribution in the soil profiles.     

Acidity in organic horizons of arctic soils on the Barents Sea coast

Parameters of water and KCl extracts from organic horizons of arctic soils on the coast of Khaipudyr Bay of the Barents Sea, in which the values of pH are 3.8–4.3 and 2.7–3.5, respectively, have been compared. It has been found that the content of water-extractable organic carbon is 0.2–0.5 g/dm³; the contents of low-molecular-weight carbohydrates and acids are 1–24 and 6 mg/dm³, respectively, and the content of Fe³⁺ ions is 1–4 mmol/dm³. The increase in the ionic strength of solution reduces the extraction efficiency of total organic carbon in 1.2 times and that of acids and carbohydrates in 3 times on the average at the simultaneous increase in the content of iron ions in the liquid phase in 7–15 times. It has been shown that organic acids and iron compounds are the main sources of acidity in salt extracts from organic soil horizons. The low contents of Ca²⁺ and Mg²⁺, which participate in the neutralization of acids, favor the high acidity of the studied horizons.     

Assessment of the functional state of soils in Moscow Zoo on the basis of microbiological parameters

The functional state of soils in the Moscow Zoo was assessed on the basis of the indices of intensity of the main biological processes. Studies of the carbon and nitrogen cycles in the soils, the soil enzyme activity, the microbial biomass, and the functional diversity of soil microorganisms (using the method of multisubstrate testing) were performed in aviaries, open-air animal enclosures, and on public parts of the Moscow Zoo. Against the background of relatively favorable physical properties of the soils (soil density and soil air, water, and temperature regimes), their biological activity was very low. The highest values of the biological activity were found in the soils of enclosures with the white-tailed gnu (Connochaetes gnou) and the cassowary (Casuarius casuarius). No significant differences in the biological activity of the soils within the aviaries and animal enclosures and on the public territories were found.     

Modeling of the development of humus horizons in soils of Crimea

Current approaches to the simulation of pedogenesis processes in time are considered. Models for the formation of humus horizon on parent rocks of different genesis in Crimea are presented. Formation rates of humus horizons have been determined, which allows developing the remediation strategies for mining dumps of mineral deposits in Crimea.     

Microstructure of genetic horizons in automorphic soils of the Timan Ridge

Data are presented on the physicochemical composition and specific macro-, meso- and micro-morphological features of automorphic soils formed on silty loams in the northern and middle taiga subzones of the Timan Ridge. These soils have a texture-differentiated profile and are well aggregated, which is manifested at all levels of structural organization of the soil mass. The morphological structure of the middle soil horizons is characterized by the presence of specific nongleyed cryometamorphic horizon CRM. Its formation is due to the development of long-term seasonal cryogenic processes in relatively deep (up to 40 cm) light and medium loam deposits under conditions of the northern and middle taiga subzones. The processes of cryometamorphism, combined with Al-Fe-humus and textural differentiation, result in the formation of podzolic, iron-illuvial, cryometamorphic, and textural horizons (O-E-BF-CRM-BT). The textural horizons have a set of micromorphological features indicating that recent clay illuviation is a weak process.     

The effect of petrocalcic horizons on the content and distribution of organic carbon in a Mediterranean semiarid landscape

Petrocalcic horizons are frequent in soils of semiarid landscapes. A survey of SIC and SOC contents made in Southern Spain in a pilot area with well defined geomorphological surfaces showed that topsoils overlying petrocalcic horizons are almost twice as rich in SOC as soil of similar depth without petrocalcic horizons. This could be due to impedance to root penetration, changes in redox potential and soil water availability caused by the presence of indurated crust. Soil age, on the contrary, seems not be an essential factor, since only a short time is required to reach a steady state in SOC in comparison to the time span available for soil formation on the different geomorphic surfaces.     

A study of argillic horizons in some soils in Morocco

Whether some soils observed in Morocco prior to the 1966 conference on Mediterranean soils held in Madrid had argillic horizons was the subject of active discussions. Textural differences between A- and B-horizons were obvious. Consequently, individual horizons of a number of profiles were sampled for micromorphological study. No clay films were observed in thin sections representing the B-horizons free in carbonate. Peds had pressure faces and internal striations in the matrix. Microchurning and swelling and shrinking are believed to have obliterated evidence of clay illuviation in the B-horizons, but clay coatings were observed at greater depth in well-developed B_ca-horizons.     

Soil horizons as the basis for classification of alluvial soils

The horizons of different types in alluvial soils of central Russia are compared with respect to their morphological characteristics using the method of dendrograms. It is argued that diagnostic soil horizons should clearly reflect in their properties the character of pedogenic processes and, thus, be the basis for classification of alluvial soils. Overall, seven types of soil horizons are suggested as diagnostic horizons for flood-plain soils of the Russian Plain.     

Records of climatic changes in the carbonate profiles of Russian Chernozems

The carbonate profiles of Chernozems bear important information on soil processes and can be successfully used for paleoenvironmental reconstruction. In the Northern Caucasus region, Russia, carbonate profiles of Chernozems were compared under anthropogenic (irrigation) and natural changes of moisture regime. The results for irrigation served as the basis for understanding the response to natural climatic changes. A soil chronosequence, consisting of soils buried under archaeological mounds dated to >5000, 3800–4000 and 1600–1700 BP and modern surface soils, was studied in a similar way. The soils buried >5000 and 3800–4000 BP had distinctive migrational and segregational carbonate accumulations (CAs). The migrational forms occurred in the surface horizons and contained 89–92% calcite with the highest dissociation temperatures. In the soils buried 1600–1700 BP the carbonate profile was clearly defined in terms of migrational CAs; they occurred only in the deeper horizons, had no clear boundaries and were diffused throughout the soil mass. In the modern surface soils the migrational CAs have almost disappeared, and the segregational CAs have the largest halos of recrystallised carbonates. The values of δ¹³C for CAs in the soils buried >5000 and 3800–4000 BP were lighter than in the soils buried 1600–1700 BP and the modern surface soils (−10.6‰ to −9.9‰ and −9.6‰ to −8.8‰, respectively). We conclude that the climate of the region during the second half of the Holocene changed from relatively dry and warm in the Atlantic period (>5000 BP) to more humid and cooler in the early Subboreal (5000–4000 BP). Since 4000 BP the climatic conditions have remained relatively stable with some changes in moisture regime resulting from human activities in recent centuries.     

Micromorphometric features of pore space in the plow horizons of loamy soils

A computer-based analysis of thin sections has been applied to study pore space in the plow horizons of loamy soils in European Russia and Ukraine. Differences in the morphology of soil macro-and mesopores are shown. It is argued that agrogenic impacts result in the convergence of the shape and orientation of macropores in plowed loamy soils of the forest, forest-steppe, and steppe zones. At the same time, this convergence is not observed for the soil mesopores.     

Temporal denitrification patterns in different horizons of two riparian soils

The dynamics of biological denitrification in riparian soil is still poorly understood. We studied the spring‐time pattern of denitrifying enzyme activity (DEA) and the rate of denitrification (DNT) in two hydromorphic riparian soils, one a mollic Gleysol and the other a terric Histosol. The average DEA ranged from 73 to 1232 ng N g^?1 hour^?1, and DNT ranged from 4 to 36 ng N g^?1 hour^?1. Both DEA and DNT diminished with increasing depth in both soil types. This decrease corresponded to a decrease in total and K₂SO₄‐extractable organic carbon and K₂SO₄‐extractable mineral nitrogen. The DEA and DNT differed in their dynamics. The former had no evident pattern in subsurface horizons but increased with temperature at the end of spring in surface and structural horizons. The DNT diminished as the soil dried in the mollic Gleysol when the water table fell. In the terric Histosol, the water table was still too high at the end of spring to affect the DNT. The results suggest that the vertical pattern of denitrification is related to that of organic carbon content. This organic carbon content determines biological activity and the supply of carbon and nitrous oxides. In biologically active horizons temperature drives the dynamics of DEA, whereas soil moisture drives the dynamics of DNT. Our results show the importance of the dynamic soil–water relationship in controlling denitrification within the riparian zone.     

Copper and zinc sorption on some B horizons of Quebec soils

Abstract

The sorption of Cu and Zn on soils, as a function of pH, is important to an understanding of their mobility in the soil solution and their availability for plant nutrition. Copper and Zn sorption as a function of the pH were measured for six B horizons of two Orthic Humic Gleysols, two Orthic Humo‐Ferric Podzols, one Orthic Dystric Brunisol and one Orthic Sombric Brunisol. The results show that: 1) for the same amount of metal in solution and the same pH, more Cu is sorbed than Zn and 2) there is a maximum of sorption at or just above pH 5.00 and a large decrease as pH decreases.

During the pH‐dependent sorption of Cu and Zn on six B horizons of Quebec soils, it was found that ions were released into solution thus altering the charge generated by the soil at low pH and the sorption behavior of Cu and Zn. The solid phase most likely to control the level of ions in solution is believed to be the amorphous and oxide forms of Al and Fe. The dissolution of these metal oxide or hydrous oxide materials also releases cations adsorbed on, or occluded in, the amorphous material.     

The effect of acidity on the distribution and symbiotic efficiency of rhizobia in Lithuanian soils

The distribution and symbiotic efficiency of nodule bacteria Rhizobium leguminosarum_bv. trifolii F., Sinorhizobium meliloti D., Rhizobium galegae L., and Rhizobium leguminosarum bv. viciae F. in Lithuanian soils as dependent on the soil acidity were studied in the long-term field, pot, and laboratory experiments. The critical and optimal pH values controlling the distribution of rhizobia and the symbiotic nitrogen fixation were determined for every bacterial species. The relationship was found between the soil pH and the nitrogen-fixing capacity of rhizobia. A positive effect of liming of acid soils in combination with inoculation of legumes on the efficiency of symbiotic nitrogen fixation was demonstrated.     

Polycyclic aromatic hydrocarbons in different forest soils: Mineral horizons

The objective of this study was to assess the behavior of PAH in mineral soil horizons of different forest soils (Allersdorf, All: Inceptisol, mull humus type; Geisberg, Geis: Entisol, mull; Hohe Matzen, HoM: Spodosol, mor). At the mor site, the highest PAH loading was observed in the forest floor (HoM L to Oh, ΣX 20 PAH: 829 g ha^?1), whereas at the mull sites the humified mineral soil horizons were the main sink for PAH (All aAxh, Σ 20 PAH: 522 g ha^?1). In all soils, there was a significant PAH translocation into subsoil horizons (Σ 20 PAH in the subsoil: 76–195 g ha^?1). In order to delineate possible transport mechanisms, double-logarithmic relationships were established between the translocation of the distinct PAH from the surface soil to the subsoil and the PAH's K_ow values. The data suggested that transport of low-molecular PAH into the subsoil was primarily a function of the water solubility of each compound. In the biologically active All and Geis soils, high-molecular PAH were translocated independently from their K_ow value, and particle-bound transport probably by soil burrowing animals was assumed to control translocation of the penta- and hexacyclic PAH. In contrast, at HoM transfer of high-molecular PAH increased with increasing hydrophobicity, suggesting dissolved organic matter (DOM)-mediated transport of PAH. Fractionation of soil into a floatable fraction and into sand- (20–2000 μm), silt- (2–20 μm), coarse clay- (0.2–2 μm), and fine claysized (< 0.2 μm) separates revealed that more than 80% of the PAH loading could be assigned to silt- and coarse clay-sized separates, irrespective of the soil's texture (loamy sand to silty clay loam). Silt generally showed the highest C_org?related PAH concentrations. PAH profiles (relative proportion of each PAH on the sum of 20 PAH) revealed increasing proportions of high-molecular, more refractory PAH from the floatables and the sand-sized separates to the finer particles, corresponding with an increasing degree of SOM alteration in the same direction. At HoM, depth gradients of high-molecular PAH suggested co-transport of penta- and hexacyclic PAH with DOM and subsequent co-sorption selectively to the silt- and coarse-clay sized separates of the Bsh horizon.     

Disintegration of the clay fraction in the eluvial horizons of some Danish podzolized soils

Abstract

Using sequential extractions, total elemental analysis, and X‐ray diffraction, we have investigated the impact of the podzolization process on component composition of the clay fraction in the eluvial horizons of eight more or less podzolized Danish soils. The results indicate that podzolization is highly aggressive towards all clay components in the eluvial horizons eventually leading to their disintegration. The 2:1 layer silicate clay minerals, illite and chlorite, are first transformed into other 2:1 layer silicate clay minerals. After passing through a microcrystalline phase high in Si but low in Al, Fe, Mg, and K, they finally disintegrate completely. Even gibbsite and kaolinite disintegrate under the aggressive conditions, caused among other things by the presence of dissolved complex forming organic molecules in these horizons. Application of lime and fertilizers seems to be able to reverse the process in case of the 2:1 layer silicate clay minerals.