The number of microorganisms and the microbiological activity of human-modified cryogenic pale soils of Yakutia

Specific features of the microbial population—the high number of all the groups of microorganisms (1.6 × 10³–3.5 × 10⁷) similar to their abundance in steppe soils of the Transbaikal region and the distribution of microorganisms along the soil profile (without a decrease in their number with depth)—were revealed in a cryogenic weakly solodized loamy sandy pale soil. Unlike the soils of the Transbaikal region and central Russia, where bacteria, as a rule, are accumulated in the litter and upper soil horizons, in the undisturbed and weakly disturbed soils of Yakutia, the number of microorganisms is rather high within the whole soil profile. In the strongly disturbed agropale soil of croplands, the distribution of microorganisms is the same as in the soils of the Transbaikal region and European Russia. In the cryogenic soils studied, actinomycetes predominated, and their number varied from 47 000 to 35 000 000 CFU/g of soil. The number of microorganisms positively (r = 1) correlated with the soil moisture.     

Microbial cenoses of alas soils on the Lena-Amga interfluve in Central Yakutia

The specific features of the microbial population in the soils of alases (thermokarst depressions) of Central Yakutia were revealed: a high number of microorganisms of all the groups (1.1 × 10³–3.9 × 10⁸ cell/g), which is compatible with the microbial density in the steppe soils of Transbaikalia; a particular distribution of the microorganisms along their profiles without decreasing of their number with the depth; and insignificant fluctuations of their population density in some soil horizons. The enrichment of these soils with microorganisms depends on the hydrothermal conditions. The microbial number gradually increases from the elevated peripheral parts of the alases to their centers and drastically decreases towards the lower lakeside areas of the alases. At the same time, the composition of the microorganisms changes, and nitrogen-fixing bacteria appear.     

Transformation of microbial cenoses in soils of light coniferous forests caused by cuttings and fires in the Lower Angara River basin

The influence of surface fires and cutting on the quantitative and functional parameters of microbial cenoses in the soils of light coniferous forests in the Lower Angara River basin was studied. In the litters of soddy-podzolic soils under pine forests, the microbial biomass was 4080–4700 μg C/g; the basal respiration was 17.00–20.32 μg C-CO₂/g/h; and the qCO₂, 4.17–4.33 μg C-CO₂/mg C_mic/h. In the humus-accumulative horizon, these values were 880–1160 μg C/g, 2.48–4.12 μg C-CO₂/g/h, and 2.83–3.55 C-CO₂/mg C_mic/h, respectively. In the litter of the one-year-old felled area, the content of microbial biomass carbon was by two times lower; in the litter of burned plots, it was by 60–70% lower than in the litter of the control area. The intensity of the microbial respiration did not change proportionally to the microbial biomass content, which resulted in an imbalance between the processes of the organic matter mineralization-immobilization towards a release of CO₂ as evidenced by the increase of the qCO₂ values by 2–4 times. In the five-year-old felled area, at the stage of restoring the herbaceous vegetation, a tendency towards the stabilization of the destructive microbiological processes was revealed. In the felled areas, the high number of heterotrophic microorganisms, the reduced oligotrophy of the soil organic horizons, and the more intense microbiological mineralization of the organic matter were observed. The surface fires in the felled areas and forests significantly affected the structure and the number of ecological-trophic groups of microorganisms in the litters, the humus-accumulative horizons, and in the upper mineral soil layers. The maximal structural and functional disturbance in the soil microbial complex was found in the logged areas affected by fires.     

Soil microbial biomass and activity: the effect of site characteristics in humid temperate forest ecosystems

Microbial biomass, respiratory activity, and in‐situ substrate decomposition were studied in soils from humid temperate forest ecosystems in SW Germany. The sites cover a wide range of abiotic soil and climatic properties. Microbial biomass and respiration were related to both soil dry mass in individual horizons and to the soil volume in the top 25 cm. Soil microbial properties covered the following ranges: soil microbial biomass: 20 µg C g^–1–8.3 mg C g^–1 and 14–249 g C m^–2, respectively; microbial C–to–total organic C ratio: 0.1%–3.6%; soil respiration: 109–963 mg CO₂‐C m^–2 h^–1; metabolic quotient (qCO₂): 1.4–14.7 mg C (g C_mic)^–1 h^–1; daily in‐situ substrate decomposition rate: 0.17%–2.3%. The main abiotic properties affecting concentrations of microbial biomass differed between forest‐floor/organic horizons and mineral horizons. Whereas microbial biomass decreased with increasing soil moisture and altitude in the forest‐floor/organic horizons, it increased with increasing N_tot content and pH value in the mineral horizons. Quantities of microbial biomass in forest soils appear to be mainly controlled by the quality of the soil organic matter (SOM), i.e., by its C : N ratio, the quantity of N_tot, the soil pH, and also showed an optimum relationship with increasing soil moisture conditions. The ratio of C_mic to C_org was a good indicator of SOM quality. The quality of the SOM (C : N ratio) and soil pH appear to be crucial for the incorporation of C into microbial tissue. The data and functional relations between microbial and abiotic variables from this study provide the basis for a valuation scheme for the function of soils to serve as a habitat for microorganisms.     

Soil microbial biomass C:N:P stoichiometry and microbial use of organic phosphorus

Microbial mineralization and immobilization of nutrients strongly influence soil fertility. We studied microbial biomass stoichiometry, microbial community composition, and microbial use of carbon (C) and phosphorus (P) derived from glucose-6-phosphate in the A and B horizons of two temperate Cambisols with contrasting P availability. In a first incubation experiment, C, nitrogen (N) and P were added to the soils in a full factorial design. Microbial biomass C, N and P concentrations were analyzed by the fumigation-extraction method and microbial community composition was analyzed by a community fingerprinting method (automated ribosomal intergenic spacer analysis, ARISA). In a second experiment, we compared microbial use of C and P from glucose-6-phosphate by adding ¹⁴C or ³³P labeled glucose-6-phosphate to soil. In the first incubation experiment, the microbial biomass increased up to 30-fold due to addition of C, indicating that microbial growth was mainly C limited. Microbial biomass C:N:P stoichiometry changed more strongly due to element addition in the P-poor soils, than in the P-rich soils. The microbial community composition analysis showed that element additions led to stronger changes in the microbial community in the P-poor than in the P-rich soils. Therefore, the changed microbial biomass stoichiometry in the P-poor soils was likely caused by a shift in the microbial community composition. The total recovery of ¹⁴C derived from glucose-6-phosphate in the soil microbial biomass and in the respired CO₂ ranged between 28.2 and 37.1% 66 h after addition of the tracer, while the recovery of ³³P in the soil microbial biomass was 1.4–6.1%. This indicates that even in the P-poor soils microorganisms mineralized organic P and took up more C than P from the organic compound. Thus, microbial mineralization of organic P was driven by microbial need for C rather than for P. In conclusion, our experiments showed that (i) the microbial biomass stoichiometry in the P-poor soils was more susceptible to additions of C, N and P than in the P-rich soils and that (ii) even in the P-poor soils, microorganisms were C-limited and the mineralization of organic P was mainly driven by microbial C demand.     

Microbial biomass and activity in salt affected soils under arid conditions

The effects of salinity on the size, activity and community structure of soil microorganisms in salt affected arid soils were investigated in Shuangta region of west central Anxi County, Gansu Province, China. Eleven soils were selected which had an electrical conductivity (EC) gradient of 0.32–23.05 mS cm⁻¹. There was a significant negative exponential relationship between EC and microbial biomass C, the percentage of soil organic C present as microbial biomass C, microbial biomass N, microbial biomass N to total N ratio, basal soil respiration, fluorescein diacetate (FDA) hydrolysis rate, arginine ammonification rate and potentially mineralizable N. The exponential relationships with EC demonstrate the highly detrimental effect that soil salinity had on the microbial community. In contrast, the metabolic quotient (qCO₂) was positively correlated with EC, and a quadratic relationship between qCO₂ and EC was observed. There was an inverse relationship between qCO₂ and microbial biomass C. These results indicate that higher salinity resulted in a smaller, more stressed microbial community which was less metabolically efficient. The biomass C to biomass N ratio tended to be lower in soils with higher salinity, reflecting the bacterial dominance in microbial biomass in saline soils. Consequently, our data suggest that salinity is a stressful environment for soil microorganisms.     

Pattern of microbial indicators in forest soils along an European transect

Microbial biomass C and activity were determined in six forest soils along a gradient in physical and chemical climate in Europe. Both parameters were measured microcalorimetrically. The upper 22 cm of the soils were sampled in undisturbed columns (24 cm deep). Measurements were made in homogenized samples of the different surface organic horizons (Ol, Of, Oh) and the mineral horizons (Ah, Aeh, Bv) down to 22 cm.On a mass basis values for both the biomass and the activity showed an exponential decrease with depth in all soils. Expressed on a volume basis these relationships varied with soil pH. in the strongly acidified soils most of the microbial biomass and activity was located in the forest floor. In less acidified soils both parameters were highest in the mineral soil.Further relationships between biomass and activity and between soil chemical properties showed significant positive correlations with exchangeable Ca²⁺, Mg²⁺, Ca/Al and negative correlations with Al³⁺. There were no significant correlations with exchangeable cations in less acidified soils. It was calculated that the microbial biomass is more affected by soil chemistry than activity. The caloric quotient (qW) is a good parameter for determining the ecophysiological state of microorganisms in acidified soils.     

Mineralization of soil organic matter initiated by the application of an available substrate to the profiles of surface and buried podzolic soils

The priming effect (PE) initiated by the application of ¹⁴C-glucose was studied for copiotrophic microbial communities of organic horizons and for oligotrophic microbial communities of mineral soil horizons, as well as for mineral horizons of buried soils depleted in the input of fresh organic matter. The intensity of the PE depended on the reserves of C_org, the initial amount of the microbial biomass, and the enzymatic activity, which decreased from the organic to the mineral soil horizons. The ratio of the PE to the applied carbon was two times higher in the mineral horizons as compared with the organic horizons. This is explained by the predominance of K-strategists capable of decomposing difficultly available organic compounds in the mineral horizons, so that the turnover of the microbial biomass in the mineral horizons was more active than that in the organic horizons. The predominance of K-strategists was confirmed by the close correlation between the PE and the activity of the cellobiohydrolase enzyme decomposing cellulose (R = 0.96). In general, the absolute value of the PE was controlled by the soil organic matter content, whereas the specific PE was controlled by the functional features of the microorganisms. It was shown that the functional features of the soil microorganisms remained unchanged under the conditions of their preservation in the buried soil.     

Microbial communities of alluvial soils in the Volga River delta

The number and biomass of the microbial community in the upper humus horizon (0–20 cm) were determined in the main types of alluvial soils (mucky gley, desertified soddy calcareous, hydrometamorphic dark-humus soils) in the Volga River delta. Fungal mycelium and alga cells predominate in the biomass of the microorganisms (35–50% and 30–47%, respectively). The proportion of prokaryotes in the microbial biomass of the alluvial soils amounts to 2–6%. No significant seasonal dynamics in the number and biomass of microorganisms were revealed in the alluvial soils. The share of carbon of the microbial biomass in the total carbon content of the soil organic matter is 1.4–2.3% in the spring. High coefficients of microbial mineralization and oligotrophy characterize the processes of organic matter decomposition in the alluvial soils of the mucky gley, desertified soddy calcareous, and hydrometamorphic dark humus soil types.     

Distribution of <Superscript>137</Superscript>Cs in the particle-size fractions and in the profiles of alluvial soils on floodplains of the Iput and its tributary Buldynka Rivers (Bryansk oblast)

Pits of sandy alluvial soils were studied in different parts of the floodplains of the Iput River and its tributary the Buldynka River near the settlement of Starye Bobovichi (Bryansk oblast). The ¹³⁷Cs content in the soil horizons varied from 0.01 to 31.2 Bq/g reaching the maximum in the initially polluted layers buried at depths of 6 to 40 cm. Radiocesium was found in all the particle-size fractions with its predominate concentration in the finest fractions. The specific ¹³⁷Cs activity in the fractions of <1, 1–5, 5–10, and >10 μm comprised 44.1 ± 11.5; 33.3 ± 7.6, 20.9 ± 4.9, and 2.4 ± 0.6 Bq/g of soil. However, the contribution of the coarse (>10 μm) fractions to the total radiocesium pool in the soils (19–60%, or 34 ± 2% on the average) was comparable with that of the clay fraction (16–71%, or 38 ± 3% on the average), because of the predominance of the sand-size fractions in the soils. The highest coefficient of variation with respect to the relative contribution of particular fractions to the total soil pool of ¹³⁷Cs was characteristic of the fraction of 5–10 μm; in the other fractions, it varied from 31 to 41%. The portion of ¹³⁷Cs bound with the finest fractions increased in the deeper layers. The total ¹³⁷Cs activity in the polluted horizons of the soils was mainly determined by its concentration in the clay fraction (Spearman’s coefficient of rank correlation (r) for the moderately polluted horizons comprised 0.926 at n = 14). It was experimentally proved that clay particles, upon the destruction of organic films on their surface, could readsorb the released radiocesium for a second time.     

Microbial Biomass and Tolerance of Microbial Community on an Aged Heavy Metal Polluted Floodplain in Japan

The objective of the present study was to increase understanding of the effects of heavy metal pollution and soil properties on microorganisms in relation to the biomass and microbial functional community. Soil samples were collected from aged polluted and reference sites on a floodplain. The soil Cu, Zn and Pb total concentrations were much higher at the polluted sites (average 231.6–309.9 mg kg^?1, 195.7–233.0 mg kg^?1, and 72.4–86.0 mg kg^?1, respectively) than at the reference site (average 33.3–44.0 mg kg^?1, 76.7–98.0 mg kg^?1, and 30.8–41.6 mg kg^?1, respectively), while the available heavy metal concentrations in CaCl₂ extraction were similar in all sites. Small seasonal variations in the size of microbial biomass were observed. Ambient soil properties (e.g. total C, N, pH, moisture content, and CEC) affected the soil microbial biomass more than the heavy metal pollution. However, the aged pollution tended to impact on the composition of the microbial community. PICT (pollution-induced community tolerance) test using BIOLOG Ecoplates showed enhanced tolerance of the microbial community to Cu stress in the polluted site. In non polluted but low nutrient, low pH and low moisture soil, the microbial biomass was lower and the microbial community was more vulnerable to Cu stress. In spite of the low heavy metal availability due to ageing, the BIOLOG technique provided sensitive detection of microbial community level changes in PICT analysis.     

Microbial reaction of secondary tropical forest soils to the addition of leaf litter

Two soils from a secondary tropical forest at La Union, Philippines, predominantly vegetated with Swietenia marcrophylla and Gmelina arborea were amended with different leaf litter types (Eucalyptus camaldulensis, S. macrophylla, G. arborea, and Calliandra calothyrsus) and incubated in the laboratory for 49 days at 25 °C. The experiment was carried out to elucidate the reasons for a low ATP-to-microbial biomass C ratio and a high microbial biomass C-to-N ratio. This has been measured repeatedly in tropical forest soils. In the non-amended soils, the microbial biomass C-to-N ratio of 12.1 exceeded the soil organic C-to-total N ratio of 11, while the ergosterol-to-microbial biomass C ratio of 0.14% and the ATP-to-microbial biomass C ratio of 4.1 μmol g⁻¹ were both low. At the end of the incubation, the addition of the different leaf litter types led generally to a decrease in the microbial biomass C-to-N ratio and to an increase in the ATP-to-microbial biomass C ratio, adenylate energy charge (AEC) and especially to an increase in the ergosterol-to-microbial biomass C ratio. The increase in the ATP-to-microbial biomass C ratio and the decrease in the microbial biomass C-to-N ratio were positively related to the N concentration in the leaf litter, the increase in the ergosterol-to-microbial biomass ratio negatively. The reasons for a low ATP-to-microbial biomass C ratio and a high microbial biomass C-to-N ratio are P deficiency and probably a reduced access of soil microorganisms to N containing organic components at low soil organic C levels.     

Changes in the structure of soil microbial biomass under fallow

The number and biomass of various groups of microorganisms in fallow soils is greater as compared to plowed soils. The microbial biomass in all fallow and plowed soils is dominated by fungal mycelium (from 90% in the top horizons to 97% in the lower ones). The part of spores in the fungal biomass is higher in plowed soils (from 9% in the top horizons to 4% in the lower ones) as compared to fallow soils (3.5?C6%). The fallow soils are characterized by the greater part of prokaryotic microorganisms in the biomass, and the reserves and structure of the microbial biomass are more similar to those in the undisturbed soils. These characteristics changed during a ten-year-long period in a soddy-calcareous soil and during a 25-year-long period in a leached chernozem.     

The Influence of Heating Mains on Yeast Communities in Urban Soils

The number and species diversity of yeasts in urban soils (urbanozems) affected by heating mains and in epiphytic yeast complexes of grasses growing above them were studied. The number of yeasts in the soil reached 10³–10⁴ CFU/g; on the plants, 10⁷ CFU/g. Significant (by an order of magnitude) increase in the total number of soil yeasts in the zone of heating mains in comparison with the surrounding soil was found in winter period. Overall, 25 species of yeasts were isolated in our study. Yeast community of studied urbanozems was dominated by the Candida sake, an eurybiont of the temperate zone and other natural ecotopes with relatively low temperatures, but its share was minimal in the zone of heating mains. In general, the structure of soil and epiphytic yeast complexes in the zones of heating mains differed from that in the surrounding area by higher species diversity and a lower share of pigmented species among the epiphytic yeasts. The study demonstrated that the number and species structure of soil yeast communities in urban soils change significantly under the influence of the temperature factor and acquire a mosaic distribution pattern.     

Physicochemical and Microbiological Characteristics of Tundra Soils on the Rybachii Peninsula

The Rybachii Peninsula is composed of Proterozoic sedimentary rocks and differs sharply from the rest of the Kola Peninsula in its geological structure, topographic forms, and parent rocks. It is dominated by Al–Fe-humus soils formed on moraines with an admixture of local rock fragments, including slates. Organic horizons of tundra soils in the peninsula are less acid than those on granitoids of adjacent mainland of the Kola Peninsula. The content of exchangeable calcium in the organic horizons varies from 17.4 to 68.0 cmolc/kg, and the content of water-soluble carbon reaches 400 mg/100 g amounting to 1–2% of the total soil organic matter content. The total number of bacteria in the organic horizons of tundra soils varies from 3.5 × 10⁹ to 4.8 × 10⁹ cells/g; and bacterial biomass varies from 0.14 to 0.19 mg/g. The length of fungal mycelium and its biomass in the organic horizons are significant (>1000 m/g soil). The biomass of fungal mycelium in the organic horizons exceeds the bacterial biomass by seven times in podzols (Albic Podzols) and by ten times in podbur (Entic Podzol), dry-peat soil (Folic Histosol), and low-moor peat soil (Sapric Histosol).     

Interrelationships between microbial and soil properties in young volcanic ash soils of Nicaragua

The activity and biomass of soil microorganisms were measured in soils from 25 different arable sites in the Pacific region of Nicaragua with the objective of elucidating their interrelationship with soil textural and soil chemical properties. All soils developed from recent volcanic deposits but differ in their particle size distribution. Short-term phosphorus fixation capacity varied widely and was, on average, 11% of added P. In contrast, long-term P fixation capacity varied within a small range of around 55%. Mean basal respiration was 8.6 μg CO₂–C d⁻¹ g⁻¹ soil, average contents of biomass C, biomass P, and ergosterol as an indicator of fungal biomass were 116, 1.95, and 0.34 μg g⁻¹ soil, respectively. They were all, except biomass P, significantly lower in the sandy than in the loamy soils. The mean biomass C-to-soil C ratio was 0.69%, the mean metabolic quotient 95 mg CO₂–C d⁻¹ g⁻¹ biomass C, the mean ergosterol-to-biomass C ratio 0.31% and the mean biomass C-to-P ratio 107. The very low ergosterol-to-biomass C ratio indicates that fungi contribute only a relatively small percentage to the microbial biomass. The biomass C-to-P ratio exceeded considerably the soil C-to-total P ratio. Metabolic quotient qCO₂ and ergosterol-to-biomass C were both negatively correlated with biomass C-to-soil C ratio and clay content, indicating positive correlations between qCO₂ and ergosterol-to-biomass C ratio and between biomass C-to-soil C ratio and clay content. Key problems of soil fertility and soil quality in Nicaragua are low availability of soil organic matter and phosphorus to soil microorganisms, which are magnified by a low percentage of fungi, probably reducing the ability of soil to provide nutrients for plant growth.     

Assessment of the microbial biomass using the content of phospholipids in soils of the dry steppe

Microbiological and biochemical investigations of chestnut soils and solonetzes were conducted in the dry steppe of the southern Privolzhskaya and northern Ergeni uplands. The living biomass of the microbial communities in the soils was estimated based on the content of phospholipids in the soils. Significant correlations were revealed between the contents of phospholipids and the main soil properties (the contents of humus, r = 0.66, P = 0.999; clay, r = −0.41, P = 0.95; physical clay, r = −0.57, P = 0.99; and pH, r = −0.59, P = 0.99). The content of phospholipids varied from 69 to 192 nmol/g of soil in the A1 horizons; with depth it decreased down to 36–135 in the B1 horizon and to 26–79 nmol/g of soil in the B2 horizon. The microbial biomass in the solonetzes was lower by 5 to 38% than that in the chestnut soils. A trend of the decreasing of the microbial biomass in the soils from the north to the south was revealed. Based on the content of phospholipids, the number of living microbial cells was assessed; the weighed averages of their number varied from 0.7–3.2 × 10¹⁰ to 7.5–13.6 × 10¹⁰.     

Microbial biomass and biological activity of soils and soil-like bodies in coastal oases of Antarctica

The method of luminescent microscopy has been applied to study the structure of the microbial biomass of soils and soil-like bodies in East (the Thala Hills and Larsemann Hills oases) and West (Cape Burks, Hobbs coast) Antarctica. According to Soil Taxonomy, the studied soils mainly belong to the subgroups of Aquic Haploturbels, Typic Haploturbels, Typic Haplorthels, and Lithic Haplorthels. The major contribution to their microbial biomass belongs to fungi. The highest fungal biomass (up to 790 μg C/g soil) has been found in the soils with surface organic horizons in the form of thin moss/lichen litters, in which the development of fungal mycelium is most active. A larger part of fungal biomass (70–98%) is represented by spores. For the soils without vegetation cover, the accumulation of bacterial and fungal biomass takes place in the horizons under surface desert pavements. In the upper parts of the soils without vegetation cover and in the organic soil horizons, the major part (>60%) of fungal mycelium contains protective melanin pigments. Among bacteria, the high portion (up to 50%) of small filtering forms is observed. A considerable increase (up to 290.2 ± 27 μg C/g soil) in the fungal biomass owing to the development of yeasts has been shown for gley soils (gleyzems) developing from sapropel sediments under subaquatic conditions and for the algal–bacterial mat on the bottom of the lake (920.7 ± 46 μg C/g soil). The production of carbon dioxide by the soils varies from 0.47 to 2.34 μg C–CO₂/(g day). The intensity of nitrogen fixation in the studied samples is generally low: from 0.08 to 55.85 ng С₂Н₄/(g day). The intensity of denitrification varies from 0.09 to 19.28 μg N–N₂O/(g day).     

Distribution and mobility of radiocesium in relation to the clay fraction mineralogy and soil properties in the Iput River floodplain

The role of the mineralogy of the clay fraction and the physicochemical properties of alluvial soils in the floodplain of the Iput River and its tributary the Buldynka River (in the region of the settlement of Starye Bobovichi in Bryansk oblast) in the distribution and immobilization of radioactive isotope ¹³⁷Cs from the atmospheric fallout after the Chernobyl accident was studied. The soils had a sandy texture; a significant variation in the content of amorphous iron oxides (0.1–0.77%) and labile manganese (11.2–193 mg/kg), the cation exchange capacity (6.1–54.2 meq/100 g soil), and the base saturation (29–100%) was common; an appreciable content of X-ray amorphous mineral substances in the clay fraction (<1 μm) enriched with organic carbon (7.7–13.1%); the predominance of trioctahedral hydromicas (Me=50%) in the clay fraction; and the presence of fine-disperse quartz and lepidocrocite. The specific activity of the ¹³⁷Cs in the clay fraction of the moderately and strongly contaminated layers increased with the increasing portion of smectite formations and (or) hydromicas. On the whole, the presence of the clay fraction favored a decrease in the ¹³⁷Cs mobility (the correlation between its content and that of exchangeable cesium was r=?0.608, n=17). However, the portion of exchangeable radiocesium (extracted with 1 M CH₃COONH₄, 1:10) had a tendency toward an increase with increasing content of hydromicas in the clay fraction. Thus, the minerals of this group were a potential source of exchangeable ¹³⁷Cs in the soils. The significant role of amorphous and mobile iron forms in the immobilization and migration of radiocesium in the secondary contaminated horizons of the alluvial soils was revealed.     

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.