The informativeness of coefficients <Emphasis Type="Italic">a</Emphasis> and <Emphasis Type="Italic">b</Emphasis> of the soil line for the analysis of remote sensing materials

The coefficients of the soil line are often taken into account in calculations of vegetation indices. These coefficients are usually calculated for the entire satellite image, or are taken as constants without any calculations. In both cases, the informativeness of these coefficients is low and insufficient for the needs of soil mapping. In our study, we calculated soil line coefficients at 8000 lattice points for the territory of Plavsk, Arsen’evsk, and Chern districts of Tula oblast on the basis of 34 Landsat 5, 7, and 8 images obtained in 1985–2014. In order to distinguish between the soil line calculated for a given image and the soil line calculated for lattice points on the basis of dozens of multitemporal images, we suggest that the latter can be referred to as the temporal soil line. The temporal soil line is described by a classical equation: NIR = RED a + b, where a is its slope relative to the horizontal axis (RED), and b is the Y-axis (NIR) intercept. Both coefficients were used to create soil maps. The verification of the maps was performed with the use of data on 1985 soil pits. The informativeness of these coefficients appeared to be sufficient for delineation of eight groups of soils of different taxonomic levels: soddy moderately podzolic soils, soddy slightly podzolic soils, soddy-podzolic soils, light gray forest soils, gray forest soils, dark gray forest soils, podzolized chernozems, and leached chernozems. The b coefficient proved to be more informative, as it allowed us to create the soil map precisely on its basis. In order to create the soil map on the basis of the a coefficient, we had to apply some threshold values of the b coefficient. The bare soil on each of Landsat scenes was separated with the help of the mask of agricultural fields and the notion of the spectral neighborhood of soil line (SNSL).     

Maps of averaged spectral deviations from soil lines and their comparison with traditional soil maps

The analysis of 34 cloudless fragments of Landsat 5, 7, and 8 images (1985–2014) on the territory of Plavsk, Arsen’evsk, and Chern districts of Tula oblast has been performed. It is shown that bare soil surface on the RED–NIR plots derived from the images cannot be described in the form of a sector of spectral plane as it can be done for the NDVI values. The notion of spectral neighborhood of soil line (SNSL) is suggested. It is defined as the sum of points of the RED–NIR spectral space, which are characterized by spectral characteristics of the bare soil applied for constructing soil lines. The way of the SNSL separation along the line of the lowest concentration density of points on the RED–NIR spectral space is suggested. This line separates bare soil surface from vegetating plants. The SNSL has been applied to construct soil line (SL) for each of the 34 images and to delineate bare soil surface on them. Distances from the points with averaged RED–NIR coordinates to the SL have been calculated using the method of moving window. These distances can be referred to as averaged spectral deviations (ASDs). The calculations have been performed strictly for the SNSL areas. As a result, 34 maps of ASDs have been created. These maps contain ASD values for 6036 points of a grid used in the study. Then, the integral map of normalized ASD values has been built with due account for the number of points participating in the calculation (i.e., lying in the SNSL) within the moving window. The integral map of ASD values has been compared with four traditional soil maps on the studied territory. It is shown that this integral map can be interpreted in terms of soil taxa: the areas of seven soil subtypes (soddy moderately podzolic, soddy slightly podzolic, light gray forest. gray forest, dark gray forest, podzolized chernozems, and leached chernozems) belonging to three soil types (soddy-podzolic, gray forest, and chernozemic soils) can be delineated on it.     

Application of microbes to the soils of Siberian tree nurseries

The introduction of Trichoderma viride spores (10⁸ CFU per 1 cm²) essentially changed the structure of micromycetes in the soils of tree nurseries in Krasnoyarsk region. During the first 20 days, in the variants with dark gray forest soils and podzolized chernozems, the total number of fungi decreased by 3–4 and 1.5 times, respectively, as compared to that in the control plots. During the intense development of the introduced microbes, the species composition of the soil fungi changed considerably. The treatment of Scots pine seeds with metabolites of Trichoderma fungi, as well as Pseudomonas and Bacillus bacteria, in the form of water suspensions, biopreparations, and dry spores promoted an increase in the yield of seedlings and improve their morphometric parameters. At the end of the growing period, the treatment with Trichoderma and the biopreparation on its basis increased these parameters, on average, by 18–70%, and the treatment with bacteria increased the same parameters by 13–15%. The application of microbial preparations improved the phytosanitary state of the soils in the studied tree nurseries. The use of the strains of indigenous microorganisms might be feasible for solving bioremediation problems more successfully in particular regions.     

Dynamics of Soil Properties and Plant Composition during Postagrogenic Evolution in Different Bioclimatic Zones

The postagrogenic dynamics of acidity and some parameters of humus status have been studied in relation to the restoration of zonal vegetation in southern taiga (podzolic and soddy-podzolic soils (Retisols)), coniferous-broadleaved (subtaiga) forest (gray forest soil (Luvic Phaeozem)), and forest-steppe (gray forest soil (Haplic Phaeozem)) subzones. The most significant transformation of the studied properties of soils under changing vegetation has been revealed for poor sandy soils of southern taiga. The degree of changes in the content and stocks of organic carbon, the enrichment of humus in nitrogen, and acidity in the 0- to 20-cm soil layer during the postagrogenic evolution decreases from north to south. The adequate reflection of soil physicochemical properties in changes of plant cover is determined by the climatic zone and the land use pattern. A correlation between the changes in the soil acidity and the portion of acidophilic species in the plant cover is revealed for the southern taiga subzone. A positive relationship is found between the content of organic carbon and the share of species preferring humus-rich soils in the forest-steppe zone.     

Cartographic Assessment of Soil Diversity in Russia

The paper describes approaches assessing the diversity of soils in Russia, as well as algorithms for quantitatively assessing the differentiation of soil bodies and covers. To assess soil diversity (or the degree of differentiation of parent rock materials into soil bodies and soil covers), two indices have been introduced: the vertical differentiation index (Ird) and the spatial lateral differentiation index (Ild (red)). These indices were computed based on the soil cover structure shown on the Soil Map of the Russian Federation on a scale of 1: 2.5 M within the spatial framework of the Map of Soil-Ecological Zoning of the Russian Federation on a scale of 1: 2.5 M. Based on the data obtained, the most complex soil covers and soil profiles on plains were identified at the boundary of the Boreal and Subboreal geographical belts in the zones of soddy-podzolic soils (umbric albeluvisols/umbric podzols) of the southern taiga and gray forest soils (albic luvisols/luvic greyic phaeozems) of deciduous forests characterized by widespread occurrence of dynamically mature soils, as well as in mountainous soil provinces of the Altai and Caucasus.     

Application of the Spectral Neighborhood of Soil Line Technique to Analyze the Intensity of Soil Use in 1985–2014 (by the Example of Three Districts of Tula Oblast)

The technique of separation of the spectral neighborhood of soil line (SNSL) makes it possible to perform quantitative estimates of the intensity of agricultural land use. This is achieved via calculation of the frequency of occurrence of bare soil surface (BSS). It is shown that the frequency of occurrence of BSS in 1984–1994 was linearly related to the soil type within the sequence of soddy strongly podzolic, soddy moderately podzolic, soddy slightly podzolic (Eutric Albic Glossic Retisols (Loamic, Aric, Cutanic, Differentic, Ochric)); light gray forest (Eutric Retisols (Loamic, Aric, Cutanic, Differentic, Ochric)), gray forest (Eutric Retisols (Loamic, Aric, Cutanic, Ochric)), and dark gray forest soils (Luvic Retic Greyzemic Phaeozems (Loamic, Aric)); podzolized chernozems (Luvic Greyzemic Chernic Phaeozems (Loamic, Aric, Pachic)) and leached chernozems (Luvic Chernic Phaeozems (Loamic, Aric, Pachic)). The intensity of exploitation of the least and most fertile soils in this sequence comprised 28 and 48%, respectively. In the next decade (1995–2004) the relationship between the type of soil and the intensity of its exploitation drastically changed; the intensity of exploitation of the leas and most fertile soils comprised 14 and 43%, respectively. Nearly a half of agricultural lands in the zones of soddy-podzolic and gray forest soils were abandoned, because the cultivation of the soils with the natural fertility below that in the podzolized chernozems became economically unfeasible under conditions of the economic crisis of the 1990s. The spatiotemporal relationships between the character of the soil cover and the intensity of exploitation of the agricultural lands manifest themselves by the decreasing frequency of occurrence of BSS from leached chernozems to soddy strongly podzolic soils and from 1985 to 2014.     

Assessment of soil tolerance toward contamination with black oil in the south of Russia on the basis of soil biological indices: A model experiment

The effect of soil contamination with black oil added in amounts of 0.1, 0.5, 1.0, 2.5, 5, 10, 25, and 50% of the soil mass on the biological properties of ordinary and leached vertic chernozems, brown forest soils, and gray sands in the south of Russia was studied in a model laboratory experiment. It was shown that the soil contamination causes a drop in the catalase and dehydrogenase activities, the cellulolytic capacity, the number of Azotobacter bacteria, and the characteristics of the plant germination. The ordinary and vertic chernozems were more tolerant toward the contamination than the gray sands and brown forest soils. The changes in the biological soil properties in dependence on the degree of the soil contamination differed considerably for the soils with different properties (the chernozems, brown forest soil, and gray sands) and were similar for the soils with similar properties (the ordinary and vertic chernozems). One soil (the brown forest soil) could be more tolerant toward the contamination than another soil (the gray sands) at a given concentration of black oil (<2.5%) and less tolerant at another concentration of black oil (>2.5%). The ecologically safe levels of the soil contamination with black oil do not exceed 0.7% in the ordinary chernozems, 0.3% in the compact chernozems, 0.1% in the brown forest soils, and 0.06% in the gray sands.     

Effect of the physicochemical parameters of soils on the biological availability of natural and radioactive zinc

The relationship between the main physicochemical properties of soils and the accumulation of natural Zn and ⁶⁵Zn radionuclide has been studied, and the capacity of soils to limit the mobility of the element in the soil–plant system has been assessed. The contribution of each of the selected soil state parameters to the accumulation of zinc by barley has been determined, and the soil state parameters have been ranked. It has been found that the largest contributions to the variation of the resulting parameter (⁶⁵Zn accumulation coefficient, K_a) are made by mobile Fe (25%), free carbonates (21%), and acid-soluble Zn (18%). The largest contributions to the Zn_acK_a are made by free carbonates (13%) and mobile Fe (8%). The contributions of physical clay and organic carbon in soils and qualitative composition of humic substances are almost similar (4% for each). No differences in the inactivating capacity of different soils (soddy-podzolic soils, gray forest soils, and chernozems) for ⁶⁵Zn are observed. This is related to the fact that the transfer of ⁶⁵Zn to plants is statistically significantly controlled by the contents of free carbonates, mobile iron, and potentially plantavailable forms of stable natural Zn (carrier of ⁶⁵Zn) rather than the quantitative and qualitative composition of organic matter and the degree of dispersion of mineral particles. The analysis of the Zn_acK_a/⁶⁵Zn K_a ratios has shown that the share of plant-available Zn in the acid-soluble form of the metal (1 M HCl) is 0.61 on the average for the studied soils, and its share in the total Zn content in the soils is only 0.14.     

Soil yeasts and their role in seed germination

A collection of yeasts isolated from soils of different types (soddy-podzolic, gray forest, and chernozems) in European Russia was analyzed. Soil yeasts were found to accelerate the development of seeds of common crops (wheat, barley, and rye). Cultures of yeasts from different taxa (representatives of the Rhodotorula, Cystofilobasidium, Sporobolomyces, Metschnikowia, Saccharomyces, Aureobasidium, Debaryomyces, Cryptococcus genera) are shown to stimulate the seed germination. The impact of soil yeasts (and preparations made on their basis) on seed germination is determined by their penetration to seed endosperm (endophytic microflora) followed by the isolation of amylolytic enzymes and physiologically active substances stimulating seed germination. The method of seed treatment is shown to affect greatly the direction of the preparations’ action. When soaking seeds in solutions with the preparation, microorganisms multiply on the seed surface, and when treating seeds using a semi-dry method, seeds themselves and endophytic microorganisms inside them begin to develop. This study can be considered one of the new directions of soil microbiology related to studying the participation of soil microorganisms in the formation of endophytic communities and their role in the germination of vascular plant seeds.     

Relationships between parameters of the humus status of forest and meadow soils and their altitudinal position on the main Crimean range

The influence of bioclimatic conditions related to the elevation above sea level on the quantitative and qualitative parameters of humus in mountain soils has been studied. It is shown that changes in the water and temperature conditions with the altitude do not exert significant effect on the humus content in mountain- forest soils, because the total amount of soil organic matter mainly depends on the composition and state of the vegetation cover. The humus content is the highest in meadow soils formed on mountain plateau with excessive moistening, which determines the formation of dense grass cover and the temperature regime favorable for humification. The percentage of Cha in the composition of Corg and the optical density of humic acids (HAs) are the qualitative parameters of the soil humus status changing with the altitude. The intensity of humus coloring of the soil depends on the content and optical density of HAs. A comparison of color intensity in the mountainous meadow chernozemlike soils and plain chernozems has shown its significant dependence on the hydrothermic conditions.     

New processes of microbial transformation of nitrogen in soils as a source of greenhouse gases

DNA isolation from soil samples and amplification of fragment of a key gene of nitrification, archaeal and bacterial amoA, revealed presence of the product in all investigated soil samples. Characteristics of ammonia-oxidizing microbial communities in agrocenoses and undisturbed soil were determined. Bacteria were predominant in agrocenoses (at circum-neurtal pH), whereas the share of representatives of domain Archaea (phylum Thaumarchaeota) increased in prokaryotic ammonia-oxidizing complexes of undisturbed forest ecosystems (at low pH). It was demonstrated that the contribution of taumarhaea in nitrous oxide emission from gray forest soil may reach 20–25%.     

Algological and Mycological Characterization of Soils under Pine and Birch Forests in the Pasvik Reserve

The structure of algological and mycological complexes in Al–Fe-humus podzols (Albic Podzols) under pine and birch forests of the Pasvik Reserve is characterized. The number of micromycetes is higher in more acid soils of the pine forest, while the species diversity is greater under the birch forest. The genus Penicillium includes the largest number of species. The greatest abundance and occurrence frequency are typical for Penicillium spinulosum, P. glabrum, and Trichoderma viride in pine forest and for Umbelopsis isabellina, Mucor sp., Mortierella alpinа, P. glabrum, Aspergillus ustus, Trichoderma viride, and T. koningii in birch forest. Cyanobacteria–algal cenoses of the investigated soils are predominated by green algae. Soils under birch forest are distinguished by a greater diversity of algal groups due to the presence of diatoms and xanthophytes. Species of frequent occurrence are represented by Pseudococcomyxa simplex and Parietochloris alveolaris in soils of the pine forest and by Tetracystis cf. aplanospora, Halochlorella rubescens, Pseudococcomyxa simplex, Fottea stichococcoides, Klebsormidium flaccidum, Hantzschia amphioxys, Microcoleus vaginatus, and Aphanocapsa sp. in soils under birch forest     

Tillage system affects fertilizer-induced nitrous oxide emissions

Since the development of effective N₂O mitigation options is a key challenge for future agricultural practice, we studied the interactive effect of tillage systems on fertilizer-derived N₂O emissions and the abundance of microbial communities involved in N₂O production and reduction. Soil samples from 0–10 cm and 10–20 cm depth of reduced tillage and ploughed plots were incubated with dairy slurry (SL) and manure compost (MC) in comparison with calcium ammonium nitrate (CAN) and an unfertilized control (ZERO) for 42 days. N₂O and CO₂ fluxes, ammonium, nitrate, dissolved organic C, and functional gene abundances (16S rRNA gene, nirK, nirS, nosZ, bacterial and archaeal amoA) were regularly monitored. Averaged across all soil samples, N₂O emissions decreased in the order CAN and SL (CAN?=?748.8?±?206.3, SL?=?489.4?±?107.2 μg kg^?1) followed by MC (284.2?±?67.3 μg kg^?1) and ZERO (29.1?±?5.9 μg kg^?1). Highest cumulative N₂O emissions were found in 10–20 cm of the reduced tilled soil in CAN and SL. N₂O fluxes were assigned to ammonium as source in CAN and SL and correlated positively to bacterial amoA abundances. Additionally, nosZ abundances correlated negatively to N₂O fluxes in the organic fertilizer treatments. Soils showed a gradient in soil organic C, 16S rRNA, nirK, and nosZ with greater amounts in the 0–10 than 10–20 cm layer. Abundances of bacterial and archaeal amoA were higher in reduced tilled soil compared to ploughed soils. The study highlights that tillage system induced biophysicochemical stratification impacts net N₂O emissions within the soil profile according to N and C species added during fertilization.     

Cyanobacterial–algal cenoses in ordinary chernozems under the impact of different phytoameliorants

General ecological and taxonomic characteristics of cyanobacterial–algal cenoses in ordinary chernozems under different ameliorative plants (phytoameliorants) were studied in the Trans-Ural region of the Republic of Bashkortostan. A comparative analysis of the taxa of studied cenoses in the soils under leguminous herbs and grasses was performed. The phytoameliorative effect of different herbs and their relationships with cyanobacterial–algal cenoses were examined. Overall, 134 cyanoprokaryotic and algal species belonging to 70 genera, 36 families, 15 orders, and 9 classes were identified. Cyanobacterial–algal cenoses included the divisions of Chlorophyta, Cyanoprokaryota, Xanthophyta, Bacillariophyta, and Euglenophyta. Representatives of Ch-, X-, CF-, and P-forms were the leading ecobiomorphs in the studied cenoses.     

Soil actinomycetes in the National Forest Park in northeastern China

The taxonomic and functional structure of actinomycete complexes in the litters and upper horizons of the soils under an artificial coniferous–broad-leaved forest located around the town of Chanchun (Tszilin province, PRС). The complex of actinomycetes included representatives of the Streptomyces, Micromonospora, Streptosporangium, and Streptoverticillium genera and oligosporous forms. In the actinomycete complexes, streptomycetes prevailed in the abundance (61–95%) and frequency of occurrence (100%). In the parcels of Korean pine (Pinus koraiensis) and Mongolian oak (Quercus mongolica), streptomycetes of 19 species from 8 series and 4 sections were isolated. The most representative, as in European forest biomes, was the Cinereus Achromogenes series. A distinguishing feature of the streptomycete complex in the biomes studied was the high participation of species from the Imperfectus series. The verification of the functional activity of natural isolates made it possible to reveal strains with high antagonistic and cellulolytic abilities. A high similarity of actinomycete complexes was found in Eurasian forest ecosystems remote from each other, probably due to the similarity of plant polymers decomposable by actinomycetes.     

Soil organic carbon as a key predictor of N in forest soils of Brazil

Purpose

Despite the ancillary knowledge that soil N is chiefly retained as soil organic matter, little is known about how it is affected by other soil and environmental factors, especially in the tropics. In this study, we performed a comprehensive survey of soils under native vegetation in Minas Gerais, Brazil, aiming to (a) measure soil Kjeldahl-N concentrations to a 1-m depth, (b) identify the main affecting factors of soil N retention, and (c) predict N through soil profile based on organic C (SOC) and its main conditioning factors.

Materials and methods

Soils under 36 fragments of native forest and savanna were sampled at five depths (0–10, 10–20, 20–40, 40–60, and 60–100 cm) and characterized by physical and chemical analyses, including total N determined by the micro-Kjeldahl method. Single and multivariate regressions were used to predict N concentrations based on soil properties and climatic factors.

Results and discussion

The average N concentrations ranged between 0.12 and 7.54 g kg^?1, decreasing with depth, and can be predicted using SOC concentrations (R ² = 0.86). Multivariate regressions using more input data, namely texture, cation exchange capacity (CEC), and altitude increased slightly R ² values (0.68–0.90) for separate soil depths, but not for the whole dataset (R ² = 0.85).

Conclusions

We demonstrated that N can be adequately predicted based on SOC concentrations, for any depth and forest type. The implications of the stable SOC/N relation and their coupled cycles and the environmental factors affecting N retention in Brazilian weathered soils are further discussed.

     

Microbial activity in the profiles of gray forest soil and chernozems

Soil samples were taken from the profiles of a gray forest soil (under a forest) and southern chernozems of different textures under meadow vegetation. The microbial biomass (MB) was determined by the method of substrate-induced respiration; the basal respiration (BR) and the population density of microorganisms on nutrient media of different composition were also determined in the samples. The microbial metabolic quotient (qCO₂ = BR/MB) and the portion of microbial carbon (C mic) in C org were calculated. The MB and BR values were shown to decrease down the soil profiles. About 57% of the total MB in the entire soil profile was concentrated in the layer of 0–24 cm of the gray forest soil. The MB in the C horizon of chernozems was approximately two times lower than the MB in the A horizon of these soils. The correlation was found between the MB and the C org (r = 0.99) and between the MB and the clay content (r = 0.89) in the profile of the gray forest soil. The C mic/C org ratio in the gray forest soil and in the chernozems comprised 2.3–6.6 and 1.2–9.6%, respectively. The qCO₂ value increased with the depth. The microbial community in the lower layers of the gray forest soil was dominated (88–96%) by oligotrophic microorganisms (grown on soil agar); in the upper 5 cm, these microorganisms comprised only 50% of the total amount of microorganisms grown on three media.     

Contribution of Soil Components on the Sorption of Chlorpyrifos

It is generally assumed that the sorption of a nonionic pesticide on soil depends mainly on the content of soil organic matter (SOM); however, there are other factors that can contribute to this process. The possible causes of variation in the carbon-normalized partition coefficient (K _OC) for chlorpyrifos (CPF) for a diverse set of ten soils have been investigated. On the one hand, the analysis of the chemical composition of the SOM was analyzed, and on the other hand, the likely interactions between the organic matter and the mineral phase were assessed. Sorption experiments of CPF were performed on whole soil, on soils treated with 2% hydrofluoric acid (HF), and onto calcined soil at 550 °C. Organic matter chemistry of soil was determined by ¹³C CP/MAS NMR spectroscopy; K _OC values were positively correlated with aryl C relative proportion and negatively correlated with alkyl C and O-aryl C proportions and prediction equation of K _OC was found (R ²?=?0.82, p?<?0.001). To evaluate possible organo-mineral interactions, a mathematical model was proposed which calculates the concentration of CPF at equilibrium (C _cal) considering adsorption coefficients for the organic (K _DHF) and inorganic (K _D550 °C) soil constituents, separately. The comparison between C _cal and the equilibrium concentration obtained from experimental data (C _exp) onto whole soil allowed us to confirm that interactions between the OM and clay affect the adsorption of CPF in whole soil. Such findings should be taken into account in the development of predictive models for the evaluation of the fate and transport of this pesticide in soil.     

Soils of Mountainous Forests and Their Transformation under the Impact of Fires in Baikal Region

Data on postpyrogenic dynamics of soils under mountainous taiga cedar (Pinus sibirica) and pine (Pinus sylvestris) forests and subtaiga–forest-steppe pine (Pinus sylvestris) forests in the Baikal region are analyzed. Ground litter–humus fires predominating in this region transform the upper diagnostic organic soil horizons and lead to the formation of new pyrogenic organic horizons (Opir). Adverse effects of ground fires on the stock, fractional composition, and water-physical properties of forest litters are shown. Some quantitative parameters of the liquid and solid surface runoff in burnt areas related to the slope gradient, fire intensity, and the time passed after the fire are presented. Pyrogenic destruction of forest ecosystems inevitably induces the degradation of mountainous soils, whose restoration after fires takes tens of years. The products of soil erosion from the burnt out areas complicate the current situation with the pollution of coastal waters of Lake Baikal.     

Location of Bare Soil Surface and Soil Line on the RED–NIR Spectral Plane

Soil as a separate natural body occupies certain area with its own set of spectral characteristics within the RED–NIR spectral space. This is an ellipse-shaped area, and its semi-major axis is the soil line for a satellite image. The spectral area for a bare soil surface is neighboring to the areas of black carbon, straw, vegetating plants, and missing RED–NIR values. A reliable separation of the bare soil surface within the spectral space is possible with the technology of spectral neighborhood of soil line. The accuracy of this method is 90%. The determination of the bare soil surface using vegetation indices, both relative (NDVI), and perpendicular (PVI), is incorrect; the accuracy of these methods does not exceed 65%, and for most of the survey seasons it may be lower than 50%. The flat part of the “tasseled cap” described as the soil line, is not a synonym for the area of the bare soil surface. The bare soil surface on the RED–NIR plots occupies significantly smaller areas than the area of soil line according to Kauth and Thomas.