Population and biomass of soil microorganisms in old-growth primary spruce forests in the Northern Taiga

The number and biomass of microorganisms in the soils under lichen, grass-bilberry, and grass spruce forests of old age were studied on the Kola Peninsula. The dry biomass of microorganisms in the organic soil horizons was shown to reach 28 mg/g with a predominance (96 to 99%) of micromycetes. At tree trunk sites, in the organic horizons of all the soils studied, where the contents of organic carbon and mineral nutrients were higher, the number and biomass of all the groups of microorganisms was lower than in those in the soils of the gaps. The factors limiting the functioning of microorganisms in the soils under spruce tree crowns are thought to be the high acidity of the water flowing down the tree trunks and the high phenol content in it. In the mineral horizons of the soils, the patterns of the microorganisms were opposite: in all the spruce forests, the fungal biomass was the highest in the soils of the trunk zones, as well as the bacterial population and biomass in the grass spruce forest. In the latter, the maximal length of the actinomycete mycelium was also recorded in the soil of the trunk zones with the elevated contents of carbon and mineral nutrients.     

Post-fire transformation of the microbial complexes in soils of larch forests in the lower Angara River region

The postfire transformation of the functional activity of the microbial cenoses and the main soil properties under mixed larch forests were studied in the lower reaches of the Angara River. It was shown that the intensity of the postfire changes in the population density, biomass, and activity of the microorganisms in the dark podzolized brown forest soil depended on the degree of burning of the ground cover and the surface litter during the fire. The maximum effects of the fire on the microbial cenoses were observed in the litter and the upper 5-cm-thick layer of the dark-humus horizon in the areas of intense burning. The postfire restoration of the structural-functional activity of the microbial cenoses was determined by the degree of transformation of soil properties and by the postpyrogenic succession in the ground cover. The microbial complexes of the dark podzolized brown forest soils under mixed larch forests in the studied region restored their functional activity after the fires of different intensities quicker than the microbial cenoses of the sandy podzols in the pyrogenic lichen-green-moss pine forests of the same zone.     

Comparative Analysis of the Number and Structure of the Complexes of Microscopic Fungi in Tundra and Taiga Soils in the North of the Kola Peninsula

The number, biomass, length of fungal mycelium, and species diversity of microscopic fungi have been studied in soils of the tundra and taiga zones in the northern part of the Kola Peninsula: Al-Fe-humus podzols (Albic Podzols), podburs (Entic Podzols), dry peaty soils (Folic Histosols), low-moor peat soils (Sapric Histosols), and soils of frost bare spots (Cryosols). The number of cultivated microscopic fungi in tundra soils varied from 8 to 328 thousand CFU/g, their biomass averaged 1.81 ± 0.19 mg/g, and the length of fungal mycelium averaged 245 ± 25 m/g. The number of micromycetes in taiga soils varied from 80 to 350 thousand CFU/g, the number of fungal propagules in some years reached 600 thousand CFU/g; the fungal biomass varied from 0.23 to 6.2 mg/g, and the length of fungal mycelium varied from 32 to 3900 m/g. Overall, 36 species of fungi belonging to 16 genera, 13 families, and 8 orders were isolated from tundra soils. The species diversity of microscopic fungi in taiga soils was significantly higher: 87 species belonging to 31 genera, 21 families, and 11 orders. Fungi from the Penicillium genus predominated in both natural zones and constituted 38–50% of the total number of isolated species. The soils of tundra and taiga zones were characterized by their own complexes of micromycetes; the similarity of their species composition was about 40%. In soils of the tundra zone, Mortierella longicollis, Penicillium melinii, P. raistrickii, and P. simplicissimum predominated; dominant fungal species in soils of the taiga zone were represented by M. longicollis, P. decumbens, P. implicatum, and Umbelopsis isabellina.     

Structure of the microbial biomass and trophic groups of nematodes in soddy-podzolic soils of a postagrogenic succession in the southern taiga (Tver oblast)

The structure of the microbial biomass and trophic nematode groups were studied in soddy-podzolic soils under phytocenoses of a secondary succession initiated by the growth of forests on agricultural lands in the southern taiga. The microbial biomass became greater with the increasing amount of fungal mycelium, and the bacterial pool little changed in these soils. Bacteriovorous nematodes predominated (64% of the total number of nematodes) in the soils of a potato field, where the bacterial biomass was maximal; it was greater or close to the fungal biomass. In the soil under a mown meadow, where the fungal biomass was greater, the populations of fungivorous and bacteriovorous nematodes were close in number and share in the nematode complex (by 40%). In the soil under a spruce forest (climax stage), the main biomass pool was composed of fungi (97%), whose biomass is maximal, while fungivorous nematodes and nematodes with a mixed type of feeding occupy the dominant positions (69% in the nematode complex). In the course of the succession, the number of fungivorous and bacteriovorous nematodes decreased, but their ratio increased from 0.4 in the soil of the potato field to 0.8–1.0 under the meadows and mixed forest and to 2.0 in the soil under the sorrel spruce forest. These changes corresponded to the increasing microbial pool and the share of the fungal biomass in it.     

The importance of mycological studies for soil quality control

Published and original data obtained in the course of long-term studies of mycobiota of several soil types in regions with different pollution levels and composition of the pollutants (Tver, Moscow, and Samara oblasts; West Siberia; and the Komi Republic) are analyzed. The expediency of using mycological characteristics for soil quality control and estimation of the toxic impact on the environment is discussed. The most pollutant-sensitive mycological characteristics were determined for the following soils: oligotrophic peat gley, eutrophic peat, whitish podzolic, Al-Fe-humus podzol, soddy pale podzolic, soddy-podzolic, and brown forest soils. These are (a) the structure of the fungal biomass, (b) the taxonomic diversity of the fungi, and (c) the percentage of melanized forms of micromycetes. At the same time, the total number of fungi (in colony-forming units) and the indices of the richness of individual species and genera proved to be poorly informative for assessing the ecological status of the soils. Criteria for the choice of mycobiotic parameters suitable for scaling the soil ecological quality are suggested.     

Postpyrogenic transformation of soils under Pinus sibirica forests in the southern Lake Baikal basin

The results of experimental investigations of the postpyrogenic dynamics of the widespread rawhumus podzols under Pinus sibirica forests in the southern Lake Baikal basin are discussed. Ground fires transform the diagnostic surface organic soil horizons into organic pyrogenic horizons (Opir, OL/Opir, and AOpir). The adverse effect of ground fires of different intensities on the changes in the reserves, the fractional composition of the litters, and the chemical composition of the organic horizons is shown. The soils of dark coniferous forests are inclined to long-lasting restoration. The Pinus sibirica regrowth under the canopy of deciduous species serves as the basis for the restoration of native stands and the formation of the soils characteristic of the southern part of the Lake Baikal basin.     

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.     

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.     

Development of microorganisms in the chernozem under aerobic and anaerobic conditions

A microbial succession was studied under aerobic and anaerobic conditions by means of experiments with microcosms in different horizons of a chernozem. It was revealed that, under aerobic conditions, all the microorganisms grow irrespective of the soil horizon; fungi and bacteria grow at the first succession stages, and actinomycetes grow at the last stages. It was shown that, in the case of a simulated anaerobiosis commonly used to study anaerobic populations of bacteria, the mycelium of micromycetes grows in the upper part of the chernozem’s A horizon. Under anaerobic conditions, the peak of the mycelium development is shifted from the 3rd to 7th days (typical for aerobic conditions) to the 7th to 15th days of incubation. The level of mycelium length’s stabilization under aerobic and anaerobic conditions also differs: it is higher or lower than the initial one, respectively. Under anaerobic conditions, the growth of fungal mycelium, bacteria, and actinomycetes in the lower part of the A horizon and in the B horizon is extremely weak. There was not any observed growth of actinomycetes in all the chernozem’s horizons under anaerobic conditions.     

Dynamics of gas condensate removal from an Al-Fe-humus podzol and its effect on the complexes of soil fungi

The time period for the removal of gas condensate from the cultivated and forest Al-Fe-humus podzols in the northwestern region of Russia was determined in an experiment. The content of the light fractions of oil decreased more slowly in the forest soil than in the cultivated soil due to the lower rates of evaporation and photochemical reactions under the forest canopy. During the first five days after applying the gas condensate, its content decreased by nearly 70% in the cultivated soils and by only 8% in the forest soil. In three months of the growing period, the gas condensate was completely removed from the cultivated soils and by 91% from the forest soil. The species composition and structure of the fungal communities significantly changed in the polluted soils with an increase in the portion of conventionally pathogenic fungi from 45% in the control soil to 60–70% in the polluted soil.     

Hydromorphism and Al-Fe-humus pedogenesis on sandy parent materials in the Kola Peninsula

Al-Fe-humus podzols developed from sandy materials of continental and marine origins can be arranged into the following sequence with respect to the degree of soil hydromorphism: iron-illuvial podzols—humus-illuvial podzols—dark (high-humus) humus-illuvial podzols—peat podzols. These soils do not differ much in their particle-size distribution and bulk elemental composition. The most informative indices reflecting the effect of soil hydromorphism are the contents of oxalate-extractable iron and aluminum compounds and the contents and composition of the soil organic matter.     

Communities of microscopic fungi in contaminated and reference Al-Fe-humus podzols and their influence on copper mobility

The transformation of microscopic fungi communities under the impact of contamination, the influence of environmental conditions (soil temperature and moisture) on the development of fungal communities in the course of model successions and on the copper mobility in soil, and the most favorable conditions for copper mobilization were studied in Al-Fe-humus podzols of the Kola peninsula contaminated with heavy metals (Cu and Ni). The long-term aerotechnogenic contamination affects the structure of the microbial communities; the species diversity of the communities can somewhat increase at the expense of the increasing diversity of rare, atypical, and “weed” species and decreasing numbers of dominants. The dynamics of fungal communities are less expressed in the contaminated soils as compared with the reference soils. The conditions of rather low temperature (5°C) and an increased moisture content (120% of the field water capacity) are the most favorable for mycelium growth and copper mobilization. Such conditions are typical of the soils in the studied region. Hence, there is a possibility for the soil self-purification due to gradual mobilization of the copper and its subsequent leaching.     

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.     

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).     

The structure of fungal biomass and diversity of cultivated micromycetes in Antarctic soils (progress and Russkaya Stations)

The distribution of the fungal biomass and diversity of cultivated microscopic fungi in the profiles of some soils from East (Progress Station, valleys of the Larsemann Hills oasis) and West (Russkaya Station, the Marie Byrd Land) Antarctica regions were studied. The structure of the biomass (spore/mycelium and live cells/dead cells) was analyzed by fluorescence microscopy with staining using a set of coloring agents: calcofluor white, ethidium bromide, and fluorescein diacetate. The species composition of the cultivated microscopic fungi was determined on Czapek’s medium. The fungal biomass in the soils studied is not high (on the average, 0.3 mg/g of soil); the greatest biomass (0.6 mg/g) was found in the soil samples with plant residues. The fungal biomass is mainly (to 70%) represented by small (to 2.5 μm) spores. About half of the fungal biomass is composed of living cells. There are differences in the distribution of the fungal biomass within the profiles of different primitive soils. In the soil samples taken under mosses and lichens, the maximal biomass was registered in the top soil horizons. In the soils with the peat horizon under stone pavements, the greatest fungal biomass was registered in the subsurface horizons. Thirty-eight species of cultivated microscopic fungi were isolated from the soils studied. Species of the genus Penicillium and Phoma herbarum predominated.     

Ein Vergleich von Eisenpodsolen im östlichen Niedersachsen mit Podsolen unter borealem Nadelwald in Finnland

Iron podzols in eastern Lower Saxony compared with podzols under finnish boreal Pine forests Well developed iron podzols with orange-brown Bs-horizons poor in humus are found in isolated small areas of eastern Lower Saxony. Because of their similarity they were compared with finnish podzols under boreal pine forest. Similar soil morphology, low humus illuviation and unconsolidized Bs-horizons are common to both groups of podzols. Different are the smaller thickness of soil horizons and the higher amounts of Fe-oxides in B-horizons of finnish podzols. Despite high grade of activity (Fe_ox/d) this may be due more to iron oxide formation by silicate weathering (micas) than to podzolization. An interpretation of the german podzols as relics from boreal coniferous forests may be supposed but there is no significant evidence by the considered datas.     

Post-pyrogenic changes in the hydrothermal parameters of soils in middle-taiga pine forests

Results of long-term studies in middle-taiga pine forests on sandy podzols after controlled surface fires are presented. The changes in the soil hydrothermal conditions caused by the pyrogenic transformation of the soil and the pyrogenic and postpyrogenic changes in other components of the forest biogeocenoses were revealed. Along with the general character of the changes in the soils’ hydrothermal conditions, some differences in the degree of their manifestation between different regions due to the different fire intensities were revealed. It was concluded that the pyrogenic impact disturbed the existing material and energy exchange between the atmosphere and the soil, which is the main process of soil formation and development. Consequently, forest fires are a powerful and active factor of recent pedogenesis.     

Transformation of old-plowed gray forest soils under the influence of differently aged pine forests in the middle Angara River region

The long-term (55–85 years) influence of pine forests on old-plowed gray forest soils (in the middle Angara River basin) has been reflected in the character of the biological cycle and intensity of the biological processes. The population of actinomycetes decreased, and that of fungi increased, within the whole profiles of these soils. The soil profiles became more differentiated according to eluvial-illuvial types. The thickness of the humus (former plowed) horizons decreased. The thicker differently decomposed litter with the abundant fungal mycelium was formed. The most conservative were relic morphological characteristics: plow sole, humus tongues, and the illuvial-metamorphic horizon.     

Assessment of Soil Water Composition in the Northern Taiga Coniferous Forests of Background Territories in the Industrially Developed Region

The composition of soil water under coniferous forests of Murmansk oblast—an industrially developed region of northern Russia—was investigated. The studied objects were dwarf-shrub–green-moss spruce forests and dwarf-shrub–lichen pine forests on Al-Fe-humus podzols (Albic Rustic Podzols) that are widespread in the boreal zone. The concentrations and removal of organic carbon performing the most important biogeochemical and pedogenic functions were estimated. The results proved significant intra- and inter-biogeocenotic variability in the composition of atmospheric depositions and soil water. Carbon removal with soil water from organic and mineral horizons within elementary biogeoareas (EBGA) under tree crowns was 2–5 and 2–3 times (in some cases, up to 10 times) greater than that in the intercrown areas, respectively. The lowest critical level of mineral nitrogen (0.2 mg/L) was, as a rule, exceeded in tree EBGAs contrary to intercrown areas. Concentrations of sulfates and heavy metals in water of tree EBGA were 3–5 times greater than those in inter-crown areas. Significant inter-biogeocenotic variations related to differences in the height of trees and tree stand density were found. It is argued that adequate characterization of biochemical cycles and assessment of critical levels of components in soil water of forest ecosystems should be performed with due account for the intra- and inter-biogeocenotic variability.     

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.