Specific features of the development of soils of hydromorphic ecosystems in the northern taiga of Western Siberia under conditions of cryogenesis

Differently directed and heterochronous cryogenic processes have contributed to the contrasting soil cover patterns and spatial heterogeneity of the properties of soils in hydromorphic ecosystems of the discontinuous permafrost zone of the northern taiga in Western Siberia. Frost heave and permafrost thawing within ecosystems of highmoor bogs have led to the development of specific cryogenic landforms, such as flat-topped and large peat mounds. A set of cryogenic soils is developed in these ecosystems; it includes different variants of cryozems, gleyzems (Cryosols), and peat soils (Histosols). The distribution of these soil types is controlled by the local topography and thawing depth, other factors being insignificant. Alternation of peat horizons of different types and ages, whirl-like patterns of horizon boundaries, considerable variations in the thickness of soil horizons, and inversions of soil horizons under the impact of frost cracking, frost heave, and cryoturbation are typical of the considered soils. Thawing depth is the most significant factor affecting the thickness of organic horizons, the soil pH, and the degree of decomposition of peat. As a result of the upward movement of bog ecosystems under the impact of frost heave, peat soils are subjected to considerable transformation: peat horizons undergo mineralization, and the thickness of organic horizons decreases; in some cases, eluvial–illuvial differentiation of the mineral horizons takes place, and peat podzols are developed. However, the opposite process of the return of the soils to the bog stage of pedogenesis with peat accumulation may take place in any time in the case of activation of thermokarst processes.     

Cryometamorphic gleyzems in the taiga of Western Siberia: Chemical and mineralogical properties,ecology, and genesis

Earlier studies showed considerable differences in the properties of automorphic loamy soils developing under middle-taiga vegetation in Western Siberia and on the Russian Plain. It was found that the soils without clear features of textural differentiation are common in Western Siberia. In particular, they are represented by cryometamorphic gleyzems. In this study, we analyze the properties of a cryometamorphic gleyzem in the Vakh area (the Khanty-Mansi Autonomous Okrug). The distribution pattern of clay minerals in the soil profile is analyzed in relation to the specific features of the soil hydrothermic regime. In the upper mineral horizons, the clay fraction is enriched in minerals of the group of soil chlorites and somewhat depleted of labile phyllosilicates. In the cryometamorphic horizon and in the underlying permafrost, the degree of crystallization of the clay minerals somewhat decreases. An even distribution pattern of aluminum oxide in the soil profile is explained by the increased content of Al in the clay fraction from the upper horizons combined with the loss of Al from the coarse fractions (as judged from data on the bulk elemental composition of clay-free samples). These features can be explained by the specificity of the hydrothermic regime of the cryometamorphic gleyzems with late thawing of the soil profile and frequent phase transitions of soil water in the upper humus and middle-profile cryometamorphic horizons.     

Methane emissions from north and middle taiga mires of Western Siberia: Bc8 standard model

During summer and autumn of 2008–2010 in the north and middle taiga, measurements of methane emissions from different types of wetland landscapes in Khanty-Mansi and Yamalo-Nenets Autonomous Okrugs were made by the static chamber method. Total methane emission from West-Siberian northern and middle taiga mires is estimated at 550 and 530 kt C-CH₄ per year.     

Multiparametric analysis of soil properties in the drained forest bogs of Western Siberia

The application of multiparametric statistical methods has confirmed that peat soils are different in the degree of their drainage and properties because of their modification during a 20–25 year period of artificial drainage operation. The following sequence represents the relative significance of the contribution to the soil changes of the parameters studied: groundwater table > air capacity > pH > ⁰T > Eh > water-soluble: C > Fe³⁺ > NH ₄ ⁺ and the activity of soil oxidoreductases in the following sequence: peroxidase > catalase > dehydrogenase. The necessity to supplement the substantive-genetic principle of the classification of drained peat soils with characterization of their water regime is substantiated.     

Specific features of soil temperature regimes in Georgia

Soil temperature regimes in Georgia are assessed on the basis of records of 60 meteorological stations within the period from 1947 to 1995. Heat exchange in the soil-air system, the effect of soil types and landforms on the temperature, and regularities of the temperature distribution pattern in the topsoil are discussed.     

Conditions of the formation of ice barriers in eroded chernozems of Western Siberia

It is shown that the water content in the upper part of chernozems in Western Siberia in the late fall period exceeds the field capacity. An ice-rich barrier is formed in the humus horizon of these soils at temperatures below zero in the cold period. This barrier has both negative and positive effects. Being impermeable for snowmelt water, it favors the development of erosion processes. At the same time, it prevents infiltration of snowmelt water beyond the soil profile with the formation of a percolative water regime (favoring soil leaching) in the chernozems.     

Changes in soil respiration in the course of the postagrogenic succession on sandy soils in the southern taiga zone

The dynamics of the CO₂ emission from sandy soils in the course of the postagrogenic succession in the southern taiga zone were studied. We measured total emission from the soil surface and, separately, respiration from the litter and mineral soil horizons during the warm (snowless) seasons of 2010 and 2011 on differently aged fallow plots: 0 years (cropland) and 7, 23, 55, 100, and 170 years. It was demonstrated that changes in the CO₂ emission in the course of the succession have a nonlinear pattern: the emission sharply increases in the first decade, then somewhat decreases, and then gradually increases again up to the maximum values. This is explained by the dependence of the rate of the emission on the soil carbon pools (humus + litter + underground phytomass) that are also subjected to nonlinear changes. Initially, the emission is mainly due to mineralization of labile organic substances added to the plowed soils in the form of organic fertilizers. Then, in parallel with a gradual increase in the pools of litter and underground phytomass, the total pool of soil organic carbon increases, and its role in the emission becomes more pronounced. The seasonal dynamics of the soil respiration are mainly controlled by the soil temperature; the soil moistening plays an important role only during the initial meadow stage of the succession.     

Biological activity of ant nests in the middle taiga zone

Ants are the most widespread social insects. Many species of ants influence a range of soil properties when building their nests in soil. The paper discusses the effects of ants on soil biological activity (nitrogen fixation, denitrification), as well as on biomass and the diversity of microorganisms. In many cases, these processes were more active in anthills. Changes in soil pH caused by nest-building activity of ants were also. There were no patterns in the distribution of pH values. Specific differences between microbial complexes of anthills and corresponding reference soils were revealed.     

Specific features of the morphology and chemical properties of coarse-textured postagrogenic soils of the southern taiga,Kostroma oblast

The properties of loamy sandy postagrogenic soils in the course of their natural overgrowing were studied in the southeastern part of Kostroma oblast. Micromorphological indications of tillage were preserved in these soils at least 35–40 years after the cessation of their agricultural use. In the course of the soil overgrowing with forest vegetation, the bulk density of the upper part of the former plow horizon decreased, the pH and the ash content of the litter horizon somewhat lowered with a simultaneous increase in the acidity of the upper mineral horizon, especially at the beginning of the formation of the tree stand. In 5–7 years after the cessation of tillage, the former plow horizon was differentiated with respect to the organic carbon content. The total pool of organic carbon in the upper 30 cm increased. In the course of the further development, in the postagrogenic soil under the 90to 100-year-old forest, the organic carbon pool in this layer became lower. The soil of the young fallow (5–7 years) was characterized by the higher values of the microbial biomass in the upper mineral horizon in comparison with that in the plowed soil. In general, the microbial biomass in the studied postagrogenic ecosystems (the soils of the fields abandoned in 2005 and 2000 and the soil under the secondary 40-year-old forest) was lower than that in the soil of the subclimax 90to 100-year-old forest. The enzymatic activity of the soils tends to increase during the succession. The restoration of the invertase and, partly, catalase activities to the values typical of the soils under mature forests takes place in about 40 years.     

Soils and the soil cover of the taiga zone in the northern Urals (upper reaches of the Pechora River)

The territory in the upper reaches of the Pechora River is characterized by the predominance of Al-Fe-humus and metamorphic soils with gley features developing under the middle taiga fir-spruce forests rather than gley-podzolic soils as had been considered before. Some of the described soil profiles represent intergrades between brown taiga soils (burozems) and gleysols; these soils are absent in the new Russian soil classification system. General regularities of the soil cover are controlled by the geomorphic position of the soils on slopes and by the conditions of ground moistening and lateral soil water flows. The development of modern soil cover patterns is determined by the impact of herbaceous and woody vegetation, bioturbation of the soils by windfalls, the presence of dead tree trunks on the soil surface, and other factors.     

Fungal communities in the soils of early medieval settlements in the taiga zone

The difference between the mycobiota in anthropogenically transformed soils of the settlements of the 9th–14th centuries and in the background zonal Podzols and umbric Albeluvisols of the middle and southern taiga subzones in the European part of Russia is demonstrated. The mycological specificity of anthropogenically transformed soils with a cultural layer (CL) in comparison with the background soils is similar for all the studied objects. Its characteristic features are as follows: (1) the redistribution of the fungal biomass in the profile of anthropogenically transformed soils in comparison with zonal soils, (2) the lower amount of fungal mycelium in the CL with the accumulation of fungal spores in this layer, (3) the increased species diversity of fungal communities in the CL manifested by the greater morphological diversity of the spore pool and by the greater diversity of the fungi grown on nutrient media, (4) the change in the composition and species structure of fungal communities in the CL, (5) the replacement of dominant species typical of the zonal soils by eurytopic species, and (6) the significant difference between the fungal communities in the CL and in the above-and lower-lying horizons and buried soils of the same age. Most of the mycological properties of the soils of ancient settlements are also typical of modern urban soils. Thus, the mycological properties of soils can be considered informative carriers of soil memory about ancient anthropogenic impacts.     

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...     

Microbial biomass carbon in the profiles of forest soils of the southern taiga zone

In the mineral horizons of the soils under different southern taiga forests (oak, archangel spruce, and aspen in the Kaluzhskie Zaseki Reserve of Kaluga region and the green moss spruce and spruce-broadleaved forests of the Zvenigorod Biological Station of Moscow State University in Moscow region), the carbon content in the microbial biomass (C_mic), the rate of the basal respiration (BR), and the specific microbial respiration (qCO₂= BR/C_mic) were determined. The C_mic content was measured using the method of substrate-induced respiration (SIR). In the upper humus horizons of the soils, the C_mic content amounted to 762–2545 μg/g and the BR ranged from 1.59 to 7.55 μg CO₂-C/g per h. The values of these parameters essentially decreased down the soil profiles. The portion of C_mic in the organic carbon of the humus horizons of the forest soils was 4.4 to 13.2%. The qCO₂values increased with the depth in the soils of the Biological Station and did not change in the soils of the Reserve. The pool of C_mic and C_org and the microbial production of CO₂ (BR) within the forest soil profiles are presented.     

Actinomycetal complexes in drained peat soils of the taiga zone upon pyrogenic succession

The number and diversity of actinomycetes in peat soils vary in dependence on the stage of pyrogenic succession. In the cultivated peat soil, the number of actinomycetes after fires decreases by three-four times, mainly at the expense of acidophilic and neutrophilic groups. An increase in the number of mycelial prokaryotes (at the expense of alkaliphilic forms) is seen on the fifth year of functioning of the pyrogenic peat soil. The species diversity of streptomycetes in peat soils also decreases after fires. An increase in the range of streptomycetal species at the expense of neutrophilic and alkaliphilic forms takes place on the fifth year of the pyrogenic succession. Parameters of the actinomycetal complex—the population density, species composition, and ecological features—are the criteria whose changes allow us to judge the state of peat soils in the course of their pyrogenic succession.     

The effect of salinization on the biomass of microorganisms in the soils of different ages in the forest-steppe zone of Western Siberia

The study of soils of different ages developing on the drying bottom of the shallow-water Yudinsk reach of Lake Chany (Western Siberia) has shown that soil salinization is a powerful factor affecting the biomass and metabolic activity of microorganisms. Strong salinity of parent materials retards the development of microbial population in the young soils. With an increase the soil age of lake depressions, desalinization takes place, and the rate of the formation of microbial biomass increases. Its metabolic activity becomes more pronounced, though the specific rate of metabolic activity slows down. The carbon of the microbial biomass and basal respiration in the soils developing on drying lake bottoms in the forest-steppe zone reach the values typical of the zonal chernozemic soils in about 80 years.     

Spatial and temporal features of soil erosion in the forest-steppe zone of the East-European Plain

Data on the rate of the erosion-accumulation processes within the sloped junctions of soils studied on key plots in Tula, Kursk, and Belgorod oblasts were analyzed. Using the method of different-age tracers characterizing the erosion-aggradation of the soils during the last 140–150 years (the magnetic tracer) and during the last 20–25 years (the radiocesium tracer), the spatial and temporal features of the redistribution of the drifts on typical slopes in different parts of the forest-steppe zone of the East-European Plain were established. A clear trend of an increase in the soil erosion rate in this zone during the last 20–25 years was revealed compared to the average rate for the last 140- to 150-year-long plowing period, which was related to the climate warming, an abrupt reduction of the surface runoff during the spring snowmelt period, and the increasing soil-protecting role of the agricultural plants in the crop rotations because of the decrease in the proportion of row crops. The obtained results confirmed the continuous nature of the soil erosion and accumulation during the transport of the sediments, which was manifested in the alternation of the erosion zones and deposition zones on the slopes.     

The intensity of organic matter decomposition in gray soils of forest ecosystems in the southern taiga of Central Siberia

The estimates of the carbon pool in the organic matter of gray soils of the southern taiga, the intensity of destruction of its components, and participation of the latter in the formation of the mineralized carbon flux to the atmosphere are presented for different stages of succession of deciduous (birch) and coniferous (fir) forests. The carbon pool varies from 139.7 to 292.7 t/ha. It is distributed between phytodetritus, mobile and stabile humus (32, 19, and 49%, respectively). The intensity of the mineralization carbon flux to the atmosphere amounts to 3.93–4.13 t C per year. Phytodetritus plays the main role in the formation of this flux. In the soils under the forests studied, 4–6% of the carbon flux are formed owing to mineralization of the newly formed soil humus. In birch forests, 2–6% (0.1–0.2% of the humus pool in the 0–20-cm layer) is the contribution to the flux due to mineralization of soil humus. In fir forests, the mineralized humus is compensated by humus substances synthesized in the process of humification during phytodetritus decomposition.     

Influence of forest disturbance on CO2, CH4 and N2O fluxes from larch forest soil in the permafrost taiga region of eastern Siberia

Abstract

To evaluate the effect of increasing forest disturbances on greenhouse gas budgets in a taiga forest in eastern Siberia, CO₂, CH₄ and N₂O fluxes from the soils were measured during the growing season in intact, burnt and clear-felled larch forests (4–5 years after the disturbance). Soil temperature and moisture were higher at the two disturbed sites than at the forest site. A 64–72% decrease in the Q ₁₀ value of soil CO₂ flux from the disturbed sites compared with the forest site (5.92) suggested a reduction in root respiration and a dominance of organic matter decomposition at the disturbed sites. However, the cumulative CO₂ emissions (May–August) were not significantly different among the sites (2.81–2.90 Mg C ha^?1 per 3 months). This might be because decreased larch root respiration was compensated for by increased organic matter decomposition resulting from an increase in the temperature and root respiration of invading vegetation at the disturbed sites. The CH₄ uptake (kg C ha^?1 per 4 months [May–September]) at the burnt site was significantly higher (–0.15) than the uptake at the forest (–0.045) and clear-felled sites (0.0027). Although there were no significant differences among the sites, N₂O emission (kg N ha^?1 per 4 months) was slightly lower at the burnt site (0.013) and higher at the clear-felled site (0.068) than at the forest site (0.038). This different influence of burning and tree felling on CH₄ and N₂O fluxes might result from changes in the physical and chemical properties of the soil with respect to forest fire.     

Agrochemical assessment of bog phosphates in Western Siberia

Bog phosphates of Western Siberia were characterized; the agrochemical properties of vivianite in peat deposits were studied, and its positive effect on the phosphate pool of zonal soils was revealed. A high and prolonged effect of peat vivianite on the main agricultural crops was experimentally proved. It was shown that the wide use of bog phosphates as fertilizers offers much promise for the regional agriculture.