Variation in the acid-base parameters of automorphic loamy soils in the taiga and tundra zones of the Komi Republic

A database for the main genetic horizons of loamy automorphic soddy-podzolic, typical podzolic, gley-podzolic, and surface-gley tundra soils of the Komi Republic was developed on the basis of the available archive and literature data and unpublished results of the authors. The database included the following parameters: the pH_water and pH_KCl, the exchangeable and total acidity, and the degree of SEC saturation. All the parameters were characterized by normal distribution types. The variation coefficients V for the pH_water and pH_KCl were <10%. For the exchangeable and total acidities and the degree of SEC saturation, the V values varied among the soils and horizons in the range of 10–50%. The greatest differences in the acid-base properties of all the soils were revealed between the groups of organic horizons, the eluvial horizons, and the B horizon by the cluster analysis. Between the separate subtypes of podzolic soils, the maximum differences were observed in the organic and, to a lesser extent, eluvial horizons; the B horizons of the different soils in the taiga and tundra zones did not significantly differ in these terms. For the entire profiles, the highest similarity was found between the typical podzolic and gley-podzolic soils, which were more similar to the automorphic soils of the tundra zone than to soddy-podzolic soils.     

Correlations between different acidity forms in amorphous loamy soils of the tundra and taiga zones

Pair correlation coefficients (r) between the acidity parameters for the main genetic horizons of soddy-podzolic soils (SPSs), typical podzolic soils (TPSs), gley-podzolic soils (GPSs), and tundra surfacegley soils (TSGSs) have been calculated on the basis of a previously developed database. A significant direct linear correlation has been revealed between the pH_water and pH_KCl values in the organic and eluvial horizons of each soil, but the degree of correlation decreased when going from the less acidic SPSs to the more acidic soils of other taxons. This could be related to the fact that, under strongly acid conditions, extra Al³⁺ was dissolved in the KCl solutions from complex compounds in the organic horizons and from Al hydroxide interlayers in the soil chlorites. No significant linear correlation has been found between the exchangeable acidity (H _exch) and the activity of the [H]⁺ ions in the KCl extract (a(H⁺)_KCl) calculated per unit of mass in the organic horizons of the SPSs, but it has been revealed in the organic horizons of the other soils because of the presence of the strongest organic acids in their KCl extracts. The high r values between the H _exch and a(H⁺)_KCl in all the soils of the taiga zones have been related to the common source and composition of the acidic components. The correlation between the exchangeable and total (H _tot) acidities in the organic horizons of the podzolic soils has been characterized by high r values because of the common source of the acidity: H⁺ and probably Al³⁺ ions located on the functional groups of organic acids. High r values between the H _exch and a(H⁺)_KCl have been observed in the mineral horizons of all the soils, because the Al³⁺ hydroxo complexes occurring on the surface and in the interlayer spaces of the clay minerals were sources of both acidity forms.     

Psychrotolerant actinomycetes of plants and organic horizons in tundra and taiga soils

It has been revealed that in organic horizons and plants of the tundra and taiga ecosystems under low temperatures, actinomycetal complexes form. The population density of psychrotolerant actinomycetes in organic horizons and plants reaches tens and hundreds of thousands CFU/g of substrate or soil, and decreases in the sequence litters > plants > soils > undecomposed plant remains > moss growths. The mycelium length of psychrotolerant actinomycetes reaches 220 m/g of substrate. Application of the FISH method has demonstrated that metabolically active psychrotolerant bacteria of the phylum Actinobacteria constitute 30% of all metabolically active psychrotolerant representatives of the Bacterià domain of the prokaryotic microbial community of soils and plants. Psychrotolerant actinomycetes in tundra and taiga ecosystems possess antimicrobial properties.     

Psychrotolerant actinomycetes in soils of the tundra and northern taiga

Actinomycetes adapted to low-temperature conditions are present in the cold soils of the tundra and northern taiga in quantities comparable to mesophylic forms and dominate in the soil actinomycete complex. Actinomycetes isolated from cold soils were identified as Streptomyces. Most actinomycetes relate to psychrotolerant forms according to habitation temperature. Two of them are conditionally psychrophilic. Specific properties of the investigated populations were identified by multirespirometrical testing.     

Effect of the biota diversity on the composition of low-molecular-weight water-soluble organic compounds in southern tundra soils

Water extracts from the organic horizons of southern-tundra loamy permafrost-affected soils (a surface-gleyed tundra soil, a surface-gleyed soddy tundra soil (Haplic Stagnosols (Gelic)), and a peaty tundra soil (Histic Cryosol (Reductaquic)) and their undecomposed moss layers have been analyzed. The total weight concentration of the cations (Ca²⁺, Mg²⁺, K⁺, and Na⁺) determined by the atomic absorption method reaches 20 mg/dm³ in the organic horizons and 40–90 mg/dm³ in the undecomposed moss layers. Potassium and calcium ions dominate in all the organic horizons (80–90% of the total weight); potassium ions prevail in the mosses (about 70%). The weight concentration of carbon in the water-soluble organic compounds is 0.04–0.07 g/dm³ in the organic horizons and 0.20–0.40 g/dm³ in the undecomposed moss layers. The content of low-molecular-weight organic compounds (alcohols, carbohydrates, and acids) identified by gas chromatography and chromatomass spectrometry is 1–30 mg/dm³ in the organic horizons of the soils and 80–180 mg/dm³ in the mosses, which does not exceed 26% of the total organic carbon in the extracts.     

Comparative characterization of humic acids from arable soils of the taiga, steppe, and semidesert zones

The parameters of the elemental composition, molecular weight distribution, infrared and proton spectroscopy, and hydrophilic-hydrophobic properties were determined for humic acids preparations isolated from arable horizons of soils from different natural zones (an ordinary chernozem, a soddy-podzolic soil, and a meadow sierozem). The general and specific properties of the humic acids from the three studied soils were revealed.     

Sulfate adsorption by variable charge soils: Effect of low-molecular-weight organic acids

Sulfate (SO₄ ^2–) movement and transport in soils has received considerable attention in recent years. In most soils, SO₄ ^2– coexists with a variety of natural organic compounds, especially organic acids. Studies were conducted to assess the effect of low-molecular-weight organic acids (eight aliphatic and five aromatic acids) on SO₄ ^2– adsorption by variable charge soils from Chile and Costa Rica. The effects of type of organic acid, pH, type of soil, and organic acid concentration were investigated. In one experiment, a 1.0 g soil sample was equilibrated with 25 ml 0, 0.5, 1.0, 2.0, 4.0, or 6.0 mM K₂SO₄ in 1 mM NaCl in the presence or absence of 5 mM citric acid. In the second set of experiments, the adsorption of 2 mM SO₄ ^2– in soils at pH 4 or pH 5 in the presence or absence of one of 13 organic acids at a concentration of 2 mM or 5 mM was studied. Results showed that citric acid significantly decreased SO₄ ^2– adsorption by the two soils. Sulfate adsorption decreased with increasing pH of the equilibrium solution. Aliphatic acids, with the exception of cis-aconitic acid, decreased the amount of SO₄ ^2– adsorbed by the two soils, with oxalic, tartaric, and citric acid showing the greatest effect. The differences in pH values of the equilibrium solutions in the presence and absence of organic acids were significantly, but negatively, correlated with the amount of SO₄ ^2– adsorbed, suggesting chemisorption of SO₄ ^2– and the release of hydroxide ions. The ionization fraction values of the organic acids at the equilibrium pH were correlated with the amounts of SO₄ ^2– adsorbed, suggesting that the protonation of surface hydroxyl groups of the mineral phase increased as the strength of the ionization of the acid increased, thus creating more positively charged surfaces. Received: 12 February 1997     

低分子量有机酸对促进可变电荷土壤中铝溶解的影响

Low-molecular-weight （LMW） organic acids exist widely in soils and play an important role in soil processes such as mineral weathering, nutrient mobilization and A1 detoxification. In this research, a batch experiment was conducted to examine the effects of LMW organic acids on dissolution of aluminum in two variably charged soils, an Ultisol and an Oxisol. The results showed that the LMW organic acids enhanced the dissolution of A1 in the two investigated soils in the following order： citric 〉 oxalic 〉 malonic 〉 malic 〉 tartaric 〉 salicylic 〉 lactic 〉 maleic. This was generally in agreement with the magnitude of the stability constants for the Al-organic complexes. The effects of LMW organic acids on Al dissolution were greater in the Ultisol than in the Oxisol as compared to their controls. Also, the accelerating effects of citric and oxalic acids on dissolution of A1 increased with an increase in pH, while the effects of lactic and salicylic acids decreased. Additionally, when the organic acid concentration was less than 0.2 mmol L-I, the dissolution of A1 changed Iittle with increase in acid concentration. However, when the organic acid concentration was greater than 0.2 mmol L^-1,the dissolution of A1 increased with increase in acid concentration. In addition to the acid first dissociation constant and stability constant of Al-organic complexes, the promoting effects of LMW organic acids on dissolution of A1 were also related to their sorption-desorption equilibrium in the soils.     

Genesis and classification position of automorphic soils developed from mantle loams in the northern taiga of European Russia

Automorphic loamy soils of the northern taiga and forest-tundra zones in the northeastern part of European Russia are characterized. These soils are diagnosed by the presence of a paragenetic system of the podzolic (often, with gley features) and iron-illuvial horizons combined with a specific cryometamorphic CRM horizon. The podzolic horizon is considerably impoverished in the total and oxalate-extractable iron and slightly impoverished in aluminum and clay in comparison with the iron-illuvial horizon. A distinctive feature of the cryometamorphic horizon is its fine angular blocky, ooidal, or granulated structure in the dry state and curdled cryogenic structure in the wet state. The soil profile is relatively weakly differentiated with respect to the contents of clay and sesquioxides. The genesis of these soils is related to a combination of the gley-Al-Fe-humus mobilization, migration, and illuvial accumulation of substances and the cryogenic structuring. According to the new Classification and Diagnostic System of Russian Soils, these soils fit the criteria of iron-illuvial svetlozems in the order of cryometamorphic soils. In the studied area, these soils are found together with texture-differentiated gley-podzolic soils having the Bt horizon and belonging to the order of texture-differentiated soils.     

低分子量有机酸对可变电荷土壤铝活化动力学的影响

从动力学角度研究了几种低分子量有机酸对2种酸性土壤中铝的活化和活化铝在土壤固/液相之间分配的影响。结果表明:对于络合能力弱的醋酸和乳酸,主要通过质子作用活化铝,且活化作用明显小于盐酸。而络合能力较强的苹果酸、草酸和柠檬酸,主要通过络合作用促进铝的释放,且这种作用随有机酸根阴离子络合能力的增强而增加。在氧化铁含量较高的砖红壤中,苹果酸、草酸和柠檬酸通过专性吸附增加土壤表面负电荷,从而增加土壤交换态铝;但在氧化铁含量较低的红壤中,草酸和柠檬酸主要通过形成可溶性铝络合物降低交换态铝。活化铝在土壤固/液相间的分配主要决定于溶液中有机阴离子与土壤固相表面对铝离子的竞争。醋酸和乳酸活化的铝主要以交换态铝存在;而草酸和柠檬酸活化的铝主要以有机酸-铝络合物存在于溶液中,特别是在氧化铁低的红壤中,这将促进铝在土壤-水体中的迁移。     

Effect of low-molecular-weight organic acids on Cl- adsorption by variable charge soils

Low-molecular-weight (LMW) organic acids exist widely in soils and have been implicated in many soil processes.The objective of the present paper was to evaluate effect of two LMW organic acids, citric acid and oxalic acid, on Cl^- adsorption by three variable charge soils, a latosol, a lateritic red soil and a red soil, using a batch method. The results showed that the presence of citric acid and oxalic acid led to a decrease in Cl- adsorption with larger decreases for citric acid. Among the different soils Cl- adsorption in the lateritic red soil and the red soil was more affected by both the LMW organic acids than that in the latosol.     

Factors of the development of taiga and tundra soils with differentiation of Fe and Al oxides in the profile

Statistical data on the bulk contents of iron and aluminum oxides in iron-depleted and iron-enriched horizons of a wide range of taiga and tundra soils were compared. It was found that the soils could be arranged into the following sequence characterized by an increase in the relative contribution of iron oxides and a decrease in the relative contribution of aluminum oxides to the differentiation of sesquioxides in the soil profiles: sandy podzols—soddy-podzolic soils—loamy micropodzols and iron-illuvial svetlozems—cryogenic ferruginated gleyzems. It was concluded that the bleaching of eluvial horizons and the depletion of sesquioxides from them, as well as the accumulation of sesquioxides in the illuvial horizons, are controlled by different processes in different soils. In sandy podzols, the differentiation of sesquioxides is due to the Al-Fe-humus podzolization; in loamy micropodzols and iron-illuvial svetlozems, due to the redox-Al-Fe-humus podzolization; in podzolic and soddy-podzolic soils, due to the selective podzolization and lessivage; and, in cryogenic ferruginated gleyzems, due to the reduction-oxidation processes.     

Artificial and natural radionuclides in soils of the southern and middle taiga zones of Komi Republic

Specific activities of artificial (¹³⁷Cs, ⁹⁰Sr) and natural (⁴⁰К, ²³²Th, ²²⁶Ra) radionuclides in background soils of southern and middle taiga of Komi Republic have been estimated with consideration for the landscape-geochemical features of the territory. It has been shown that their accumulation and migration in soils are determined by the following factors: position in relief, texture, and organic matter content. No anomalous zones with increased contents of radionuclides in soils have been revealed.     

Morphometric profiles of pore space in loamy soils of the forest and steppe zones of European Russia

A computer-based image analysis of vertically oriented thin sections was applied to study changes in the shape and orientation of fine soil macropores (d = 0.2−2.0 mm) in the profiles of soddy-podzolic soils and typical (migrational-mycelial) chernozems. Generalization of the obtained morphometric data was based on the theory of mereology, a scientific discipline studying the structure (part-whole relationships) of classified objects. As a first approximation, generalized data characterized archetypes of morphometric porespace profiles of the studied soils. The archetype of the pore-space profile of the soddy-podzolic soil consists of four components (meronyms) corresponding to the humus-accumulative, eluvial, textural (clay-illuvial), and transitional to the parent material (BC) horizons. Sharp boundaries between the upper horizons specify sharp changes in the studied meronomic indices of the shape and orientation of soil pores. The pore-space profile of the migrational-mycelial chernozem consists of two major components: specific pores in the granular dark-humus (AU) horizon and complex pore space of the BCA and BCca horizons that are poorly differentiated with respect to the shape and orientation of their fine macropores despite clear genetic differences between these horizons. Pore-space patterns in the lower (transitional to the parent material) horizons of the studied soils are characterized by the high degree of similarity (>75%). Pore-space patterns in the upper horizons of the studied soils are different; the level of their similarity does not exceed 24–41.5%. The results obtained in this study hold promise in the use of morphometric characteristics of the pore space in separate genetic soil horizons as meronyms composing archetypes of the pore-space profiles of different soils. Such archetypes may be used for diagnostic purposes as reference pore-space profiles of the particular types of soils.     

Structural features of tundra and taiga soil humic acids according to IR EXPERT analytical system data

Journal of Soils and Sediments - The purpose of this work is to identify the most probable structural fragments of the tundra and the taiga soil humic acids on the basis of computer analysis of...     

Changes in the organic matter of taiga soils during the natural reafforestation after cutting in the middle taiga of the Komi Republic

It has been shown that the distribution features of the hydrophilic and hydrophobic fractions of humic substances (HSs) in the upper genetic horizons of undisturbed podzolic soils and litho-barrier podzols are similar. The concentrations of the separate HS fractions in the mineral horizons are largely determined by the soil mineralogy. In forest litters of secondary phytocenoses developed after the cutting of spruce forests, an increase in the content of hydrophilic compounds has been observed on loamy deposits at a decrease in the portion of lignin-like organic compounds. An increase in the portion of Al-Fe-humus compounds has been revealed in the mineral soil horizons of secondary phytocenoses. It has been proposed to use the degree of hydrophilicity (D _H ) for characterizing the features of the organic matter in taiga soils. An increase in the content of the fractions of occluded organic matter and that bound to minerals (density of 1.6–2.2 g/cm³) has been observed in the eluvial horizons of a young cutover area.     

The elemental composition and amphiphilic properties of humic acids in southern taiga soils

This paper gives the characteristics of the elemental composition and amphiphilic properties of humic acids (HAs) extracted from different horizons of the most typical soils in the Central Forest Biosphere Reserve (CFBR, the Tver Oblast). An attempt at characterizing some properties of the structure of HAs is made based on the data of the elemental composition. The data on amphiphilic properties enable one to reveal whether components that are capable of migration are present.     

Influence of low-molecular-weight organic acids on the solubilization of phosphates

A range of low-molecular-weight organic acids were identified in rhizosphere soil, leaf litter, and poultry manure compost. Laboratory and greenhouse experiments were carried out to examine the effects of seven low-molecular-weight organic acids on phosphate adsorption by soils, and the solubilization and plant uptake of P from soil pre-incubated with monocalcium phosphate and North Carolina phosphate rock. Acetic, formic, lactic (monocarboxylic), malic, tartaric, oxalic (dicarboxylic), and citric (tricarboxylic) acids were used in the study. The addition of organic acids decreased the adsorption of P by soils in the order tricarboxylic acid>dicarboxylic acid>monocarboxylic acid. The decreases in P adsorption with organic acid addition increased with an increase in the stability constant of the organic acid for Al (logK _Al). Organic acids extracted greater amounts of P from soils meubated with both monocalcium phosphate and phosphate rock than water did. Although more phosphate was extracted by the organic acids from monocalcium phosphate — than from phosphate rock — treated soils in absolute terms, when the results were expressed as a percentage of dissolved phosphate there was little difference between the two fertilizers. The amount of P extracted by the organic acids from both fertilizers increased with an increase in logK _Al values. The addition of oxalic and citric acids increased the dry matter yield of ryegrass and the uptake of P in soils treated with both fertilizers. The agronomic effectiveness of both fertilizers increased in the presence of organic acids and the increase was greater with the phosphate rock than with the monocalcium phosphate. The results indicated that organic acids increase the availability of P in soils mainly through both decreased adsorption of P and increased solubilization of P compounds.     

低分子量有机酸对土壤磷活化影响的研究

研究两种低分子量有机酸（柠檬酸和苹果酸）对土壤磷活化影响,并用修正的Hedley法测定土壤磷活化前后磷组分的变化。结果表明,低分子量有机酸能持续活化土壤磷,活化强度随低分子量有机酸浓度的增大而增强,并且柠檬酸活化土壤磷的能力强于苹果酸。低分子量有机酸能促进作物有效态无机磷组分（H2O-P和NaHCO3-Pi）的释放;同时还促进有机磷组分（NaHCO3-Po和NaOH-Po）的矿化。在低分子量有机酸浓度达到0.5 mmol/L以上时,其对土壤磷组分的活化量的顺序为:NaOH-Pi HCl-P NaHCO3-Pi H2O-P,即铁铝结合态磷 钙结合态磷 作物有效态磷。低分子量有机酸活化土壤磷的过程中伴有大量铁、铝释放,且铁或铝的释放量与磷活化量之间显著正相关（P0.05）。说明铁、铝结合态磷是低分子量有机酸活化土壤磷的主要磷源,并且其活化机制可能与铁、铝结合态磷的螯合溶解有关。     

Soil carbon pools in tundra and taiga ecosystems of northeastern Europe

The mean pools of soil carbon were determined for the first time for twelve soil groups (according to the World Reference Base for Soil Resources, 2006) on four test plots with the use of the high-resolution (Landsat and QuickBird) satellite imagery, original field data on more than 200 soil profiles, and literature data included in the soil database. Three test plots belonged to the ecotone between tundra and forest-tundra zones, and the fourth plot characterized the middle taiga zone. Spatial distribution patterns of soil carbon in different soil subgroups and genetic horizons were characterized for the areas with the mosaic soil and vegetation covers. The mean soil carbon content for the first three test plots in permafrost area was estimated at 39.5 kg C/m², including 28.7 kg C/m² in the upper soil meter. The mean soil carbon pool of the taiga plot reached 16.7 kg C/m² (0–100 cm).