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.     

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.     

Water-soluble low-molecular-weight organic acids in automorphic loamy soils of the tundra and taiga zones

The formation features of water-soluble low-molecular-weight organic acids (LMWOAs) in a zonal series of automorphic soils on loose silicate rocks from the middle taiga to the southern tundra (typical podzolic, gley-podzolic, and surface-gley tundra soils) were first revealed by gas chromatography mass spectrometry and gas-liquid chromatography. The content of LMWOAs varies within the range of 1–14 mg/dm³, which corresponds to 1–5% of the total carbon of the water-soluble soil organic matter. It has been shown that a subzonal feature of gley-podzolic soils in the northern taiga is the high content of LMWOAs, including primarily the strongest aliphatic hydroxyl acids. Possible mechanisms of their formation and accumulation in soils have been considered.     

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.     

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.     

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).     

Psychrotolerant actinomycetes on plant substrates of tundra and taiga ecosystems

Studies of tundra flowering plants and mosses on the Тaymyr Peninsula have determined the presence of thousands and tens of thousands of colony formation units of psychrotolerant actinomycetes in 1 g of vegetation substrate, which is smaller than the amount of mesophilic forms by one to two orders of magnitude. Incubation of plants at 5°C has shown very small taxonomical variety of actinomycetes. The actinomycete complex is represented by species of the genus Streptomyces, belonging to the sections and series Albus Albus and Cinereus Achromogenes, and by the genus Micromonospora.     

Automorphic taiga soils of the Sredneobskaya Lowland

The morphology of the profile, some chemical properties, and particle-size distribution of the automorphic soils developed from lacustrine-alluvial loamy-clayey deposits in the Sredneobskaya Lowland are considered. The soils of the West Siberian middle taiga zone remain poorly studied. A comparison of our data with data on podzolic soils in the northeastern part of European Russia and with diagnostic characteristics of the soil type of svetlozems included in the new classification system of Russian soils (2004) allows to argue that the studied soils cannot be classified as podzolic soils; most of them also do not fit the diagnostic criteria of svetlozems. The obtained data on the particle-size distribution in the studied soils do not agree with the concept of the sedimentation zonality in the West Siberian Plain.     

Microbial transformation of nitrogen compounds in middle taiga soils

The intensity of mineralization, nitrogen fixation, and denitrification in forest soils of the Karelian middle taiga ecosystems has been evaluated. Podzol-gleyish soil underlying a birch forest with gramineous plants and miscellaneous herbs was shown to have the highest nitrogen-fixing activity. The loss of gaseous nitrogen during denitrification was insignificant due to the low nitrifying activity of the soils named above. N₂O uptake by microorganisms was rather intensive in all the soils analyzed, and in illuvial-humo-ferric podzols underlying pine and spruce forests this process predominated. Podzolic sandy loam gley-like soil of a birch forest with gramineous plants and miscellaneous herbs had the highest potential for the mineralization of organic nitrogen; the rate of ammonification and nitrification in this soil was maximal.     

Microbial transformation of nitrogen compounds in soils of the southern taiga

The intensity of the processes of nitrogen mineralization, fixation, and denitrification was assessed in the high-moor peat gley, white-podzolic, pale-podzolic, burozem, low-moor peat, and soddy-gley soils of the Central Forest Biosphere Reserve (CFBR). The actual and potential activities of the nitrogen fixation and denitrification were determined using the gas-chromatographic method, and the intensity of the ammonification was determined using ion-selective electrodes. The maximum intensity of the nitrogen fixation was observed in the low-moor peat and soddy-gley soils, which are characterized by a high content of organic matter. High denitrification activity was found in the low-moor peat soil (0.31 nmol N₂O/g per h); this was determined by the excessive moistening of this soil. The processes of organic nitrogen mineralization were the most intensive in the upper (L and F) subhorizons of the litter.     

Diagnostics of gleyzation upon a low content of iron oxides (Using the example of tundra soils in the Kolyma Lowland)

The matrix of iron (hydr)oxides exerts a decisive influence on the character of gleyzation. Upon a high content of iron (hydr)oxides, their reduction radically changes the horizon color from warm to cold hues, which is typical of soils on the Russian Plain. Upon the low content of iron (hydr)oxides, iron reduction takes place in phyllosilicates with minimal changes in the soil color. The cold hue of cryohydromorphic soils in the Kolyma Lowland is controlled by the color of the lithogenic matrix with a low content of iron (hydr)oxides. In this case, the soil color characteristics expressed in the Munsell notation or in the CIE-L*a*b* system are ineffective for diagnostic purposes. The colorimetric methods appear to be more efficient after the soil pretreatment with hydrogen peroxide, as the gleyed horizons turn green, while the nongleyed (and not overmoistened) horizons turn red. Physical methods (Mössbauer spectroscopy and magnetic susceptibility measurements) are more efficient for characterizing the properties of iron compounds in cryohydromorphic soils as compared with the methods of chemical extraction. Mössbauer spectroscopy proved to be highly efficient, as the iron oxidation index Fe³⁺/(Fe²⁺+Fe³⁺) decreases in the gleyed horizons. Chemical reagents (Tamm’s and Mehra-Jackson’s reagents) dissolve Fe-phyllosilicates and are not selective in soils with a low content of iron (hydr)oxides.     

Polycyclic aromatic hydrocarbons in tundra soils of the Komi Republic

The qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAHs) in tundra soils has been studied by gradient high-performance liquid chromatography. The differentiation of the PAHs in the soil profile is of clear accumulative character. The pool of polyarenes in the soils is determined by the cryogenesis processes and mainly consists of low-molecular-weight bi- to tetranuclear PAHs, the high-molecular-weight PAHs in the organic horizons make up no more than 20% of the total polyarenes in the soil, and penta- and hexanuclear structures are almost absent in the mineral layer.     

Transformation of properties of podzolic soils under development and cultivation in the middle taiga subzone (Komi Republic)

The results of long-term stationary studies on the properties of loamy soils under forest and plowland in the middle taiga subzone were summarized. Spatial and temporal changes in the morphology and physicochemical properties of agrosoddy-podzolic soils as compared to forest ones, the peculiar pedogenesis of the soils in automorphic positions and on the slopes, and the activation of gleying in these soils were discovered. The downward displacement of the eluvial horizon, the shift to a heavier texture of the arable layer due to the soil cultivation, the variation in the content of clay and silty particles in this layer depending on the duration and stability of the freezing periods, and the decrease in the removal of clay and most oxides in the developed soils were revealed. The removal of iron, aluminum, calcium, and magnesium oxides and the profile distribution of clay indicate the intensification of eluviation in the soils of mesodepressions. The long-term use of podzolic soils in agrocenoses resulted in the leveling of the humus reserves in the entire catena.     

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.     

Optimum conditions for extraction of Al,Fe, and Si from soils with acid oxalate

Abstract

Acid oxalate reagent was used at various concentrations, pH values, shaking times, and soil to solution ratios to find the optimum conditions for the extraction of Al, Fe, and Si from short‐range‐order materials in soils and stream‐bed deposits. The optimum conditions vary with the nature of the soil sample and its components. For most soils maximum amounts of Al, Fe, and Si were extracted with 0.15M acid oxalate reagent at pH 3.0 with a soil to solution ratio of 1:100 and shaking for 4 h in the dark at 20°C. Soils with more than 5% oxalate‐extractable Al or Fe require a 0.20M oxalate solution at pH 3.0 with a soil to solution ratio of 1:200.

Allophane is extracted by acid oxalate reagent after shaking for 2 h and it may be estimated from the 4 h oxalate‐extractable Si values. Ferrihydrite is extracted after shaking for 4 h, and it may be estimated from the oxalate‐extractable Fe values. Either sodium oxalate or ammonium oxalate may be used     

Impact of Al and Fe on the development of phenanthrene catabolism in soil

Purpose

Heavy metals often occur as co-contaminants with polycyclic aromatic hydrocarbons (PAHs) and reportedly have adverse effects on biodegradation. In this study, the development of ¹⁴C-phenanthrene mineralisation in soil co-contaminated with aged or freshly added Al or Fe amendment was assessed.

Materials and methods

¹⁴C-phenanthrene mineralisation was assessed using respirometry; respirometers incorporated a Teflon-lined screw-capped CO₂ trap containing 1-M NaOH within a glass scintillation vial. The production of ¹⁴CO₂ was assessed by the addition of Ultima Gold liquid scintillation fluid to the CO₂ traps and subsequent liquid scintillation counting. Enumeration of phenanthrene-degrading bacteria was achieved by counting the colony forming unit count using the spread plate method.

Results and discussion

This investigation considered the effects of Al and Fe (50, 100, 250 and 500 mg/kg) on ¹⁴C-phenanthrene biodegradation in soil over 63-day contact time. Fresh Al amendments at lower concentrations (50 and 100 mg/kg) stimulated phenanthrene catabolism (p <0.05) at t?=?21 and 42 days which may reflect an ‘Arndt–Schulz’ effect, but phenanthrene catabolism was significantly reduced (p <0.05) in 500 mg/kg aged Al this could be due to Al toxicity to phenanthrene degraders. Phenanthrene mineralisation was stimulated in the highest Fe concentration (500 mg/kg) in aged and fresh Fe amendments at t?=?21 days. This could be because Fe is an essential requirement for microbial growth.

Conclusions

The impact of Al or Fe on the catabolism of ¹⁴C-phenanthrene was dependent on incubation time and Al was more toxic than Fe to soil PAH catabolic activity. This could be because Al is a non-essential microbial requirement. Bioremediation of soils co-contaminated with PAH and heavy metal is a complex problem; therefore, studies on the impact of metals on PAHs biodegradation highlight the risks and biodegradation potential in contaminated soil.     

胶体悬液中白云母与铁铝氧化物表面双电层的相互作用

白云母是一种原生矿物,也是土壤中常见的层状硅酸盐矿物,其负电荷主要由四面体结构中的Al置换Si而来[1]。在通常的pH条件下,白云母带负电荷,可变电荷土壤中的铁、铝氧化物带正电荷。当白云母与铁、铝氧化物存在于同一悬液     

Formation of polycyclic aromatic hydrocarbons in northern and middle taiga soils

An integrated study of the qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAHs) in the atmospheric precipitation-soil-lysimetric water system was performed using high performance liquid chromatography. It was shown that the accumulation of low-molecular PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, and chrysene) in soils is due to the transformation of organic matter and the regional transport and deposition of PAHs with atmospheric precipitation on the underlying surface. High-molecular polyarenes (benz[b]fluoranthene, benz[k]fluoranthene, benz[a]pyrene, dibenz[a,h]anthracene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene) mainly result from the decomposition of soil organic matter.     

Transformation of nitrogen compounds in the tundra soils of Northern Fennoscandia

The transformation of organic nitrogen compounds in the soils of tundra ecosystems of Northern Fennoscandia has been studied under laboratory and natural conditions. Tundra soils contain significant reserves of total nitrogen, but they are poor in its extractable mineral and organic forms. The potential rates of the net mineralization and net immobilization of nitrogen by microorganisms vary among the soils and depend on the C: N ratio in the extractable organic matter and microbial biomass of soil. Under natural conditions, the rate of nitrogen net mineralization is lower than the potential rate determined under laboratory conditions by 6–25 times. The incubation of tundra soils in the presence of plants does not result in the accumulation of mineral nitrogen compounds either in the soil or in microbial biomass. This confirms the high competitive capacity of plants under conditions of limited nitrogen availability in tundra ecosystems.     

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...