European North-East Of Russia Research Articles

Seasonal development rhythm of representatives of the genus <i>Spiraea</i> L. during introduction in the European North-East of Russia (Komi Republic)

Shrubs of the genus Spiraea L. are distinguished by a great variety of ornamental features, but are still underused in ornamental horticulture in the northern territories. The issues of passing the seasonal cycle of plants under new harsh climatic conditions remain fragmentarily studied. The research was aimed at examining the features and identifying patterns of the seasonal rhythm of introduced species of the genus Spiraea L. The research was carried out on the basis of the collection of the Botanical Garden of the Institute of Biology, located in the middle taiga subzone of Komi Republic. Plants to be observed included nine species of three taxonomic sections of the genus Spiraea L. The long-term averages of phenological phases and periods of seasonal rhythm of species, as well as variability of features based on the results of phenological observations for six years in the period 2013-2018 were determined. The vegetation period of plants under new conditions lasts up to 145 days and corresponds to the vegetation period of the introduction station. Shoot growth lasts from 65 to 80 days in different species. The sequence of flowering, differences in the dates of onset and duration of flowering in different Spiraea species of three sections were noted. The duration of the prefloral period ranges from 18 to 41 %, the flowering period – from 8 to 31 % of the total vegetation period of plants. The total duration of flowering of the studied species accounts for almost 100 days. The least variability is specific for the period of vegetation of species (variability index up to 5.9 %), the greatest variability – for the period of flowering of plants (variability – up to 26.7 %). The taxonomic factor (85-91 %) was revealed to influence the passage of the generative phases of the seasonal cycle. The correlation interaction was determined between the main phenophases and the early leaf fall phase. The seasonal type of growth and phenological development of Spiraea plants is characterized by an early beginning and end of vegetation, a relatively short period of growth of shoots, and the consistency of average phenological dates. This phenorhythm of the studied species of the genus Spiraea demonstrates their potential for ornamental gardening in the northern region.

Ecosystem exchange of CO2 and CH4 in boreal peatlands of the North-East European Russia

Ecosystem exchange of CO2 and CH4 in boreal peatlands of the North-East European Russia

Monitoring of a <i>Cypripedium guttatum</i> (Orchidaceae, Liliopsida) population on the northern border of its distribution range (Komi Republic, European Russia)

The results of our 12-year study of a population of the rare orchid Cypripedium guttatum Sw. on the northern border of its range, on the territory of the Komi Republic (north-east of European Russia) are presented. Our research has shown that weather factors (temperature and precipitation) have an impact on the seasonal development of shoots and plant size. The number of shoots is influenced by the weather conditions of the previous growing season, namely: the temperature of the first decade of August influences positively while early autumn frosts and the amount of precipitation of the entire period do negatively. A negative correlation was found between the number of flowering shoots and the temperature of the second decade of July of the previous growing season and a positive relationship between the number of juvenile plants and the precipitation of August of the previous growing season. Fruit set was quite low (17.1%), which is typical for this species. The pollination efficiency of C. guttatum was negatively affected by the high temperature during its flowering (the second decade of June). One box contained an average of 4065 seeds. The real seed productivity per shoot varied from 1989 to 7064 pcs., it is associated with precipitation in the second decade of July of the current growing season. The high number of the population studied (25 thousand shoots), the correspondence of the ontogenetic spectrum to the basic one of the species, the annual presence of juvenile plants of seed origin indicates its stable condition.

Carbon Dioxide Emission from the Soil Surface of the 10-Year Felled Area of the Pine Forest in the European North-East of Russia

Carbon Dioxide Emission from the Soil Surface of the 10-Year Felled Area of the Pine Forest in the European North-East of Russia

Carbon Dioxide Emission from the Soil Surface in a 10-Year-Old Felled Area of Pine Forest in the European Northeast of Russia

Carbon Dioxide Emission from the Soil Surface in a 10-Year-Old Felled Area of Pine Forest in the European Northeast of Russia

Forest Growing Conditions Affect the CO<sub>2</sub> Emission from the Soil Surface in the Middle Taiga Pine Forests of the Komi Republic

Obtaining the experimental data on soil respiration is relevant due to significant range of CO2 emission estimates in different ecosystems. The aim of work was to characterize CO2 emission from soil surface of pine forests growing in different conditions on North-East of European part of Russia. The studies have been carried out in immature and mature pine forests Sphagnosa, Myrtillus and Lichen types located in the Institute of biology of the Komi Science Center, RAS forest stations. Carbon dioxide emission was measured using LI COR 8100 during the May-October periods in 2008–2017. A brief weather conditions characteristic was given. Higher values of the CO2 flux from the soil surface was observed in July (1.9–2.9 g С m–2 day–1 in Sphagnosa type) and August (2.5–6.6 g С m–2 day–1 in Myrtillus and Lichen types). The year-to-year variability and influence of weather conditions on soil respiration were shown. The soil temperature had a close and positive relationship (R2 = 0.49–0.77) with CO2 emission whereas correlation with soil moisture was weak. During summertime the efflux of C-CO2 in a pine forest of Myrtillus type was 188–442 g C m–2, during the vegetation period (01.05–30.09) – 279–563 g C m–2 and the snowless period (01.05–31.10) – 308–583 g C m–2, which is 1.5–1.8 times higher than in the pine forests of Sphagnosa and Lichen types during the snowless period (р = 0.014) and growing season (р = 0.020). In summertime the losses of carbon were similar (р = 0.106). The pine forests of Sphagnosa and Lichen types were comparable in С-СО2 efflux both during the vegetation and the snowless periods (p 0.05). These data are important in assessing the expenditure part of the carbon balance in forest ecosystems in the European North-East of Russia.

Living at the Edge: A Comparative Study of the Central and Marginal Populations of Dactylorhiza traunsteineri (Orchidaceae) in the European Northeast of Russia

Living at the Edge: A Comparative Study of the Central and Marginal Populations of Dactylorhiza traunsteineri (Orchidaceae) in the European Northeast of Russia

Hematological parameters of free-ranging moose Alces alces (Linnaeus 1758) (Ruminantia, Cervidae)

Comparative studies that feature the physiology of wild and domestic animals replenish the fundamental knowledge in the field of biology and adaptive potential, thus increasing the efficiency of domestication. Semi-free conditions and artificial environment create prerequisites for epidemics and stress. However, early detection can prevent critical situations. This research provides new data on moose biology and physiology by establishing age and sex hematological parameters.
 The study featured moose blood samples (n = 55) obtained in the Kirov Region in the northeast of European Russia. Hematological tests relied on a veterinary version of a MicroCC-20 Plus automatic analyzer (High Technology).
 This research was the first of its kind to introduce a comparative hematological analysis of local European moose according to age and sex. Adults and calves demonstrated significant differences (p < 0.05) in red blood cells, hemoglobin, hematocrit, mean corpuscular volume, mean concentration hemoglobin, mean corpuscular hemoglobin concentration, platelet distribution width, red blood cell distribution width, platelet crit, platelets, leukocytes, and eosinophils. Females and males also had significant differences (p < 0.05) in red blood cells, hemoglobin, mean corpuscular volume, red blood cell distribution width, platelet distribution width, platelets, and eosinophil content. The single- and multivariate analysis made it possible to establish the effect of physiological factors on the blood parameters in moose.
 The hematological values were in line with the most indicators reported in other publications on wild artiodactyls. The existing differences in blood parameters depended on the species, habitat, food supply, age, and sex.

Zonal Patterns of Changes in the Taxonomic Composition of Culturable Microfungi Isolated from Permafrost Peatlands of the European Northeast

This paper provides the results of a study on fungal species diversity in the active and permafrost layers of peatlands within frozen peatbogs in the flatland areas of the cryolitozone, European Northeast of Russia (forest-tundra zone, southern and northern tundra subzones). Fungal taxonomic list includes eighty-three species from seventeen genera and two forms of Mycelia sterilia. The phylum Mucoromycota is represented by fifteen species (18% of total isolate number), and these species exhibit the following distribution by genus: Mucor (four), Mortierella (seven), Umbelopsis (three), Podila (one). Ascomycota is represented by sixty-eight species from thirteen genera. The genus Penicillium dominates the species saturation (thirty-seven species, 44%). Soil microfungal complex is represented by rare species (51%), random species (32%), frequent species (15%), and dominant species (2%). In peat soils, dominant species are Penicillium canescens (72%) and non-pigmented (albino) Mycelia sterilia (61%); abundant species are Talaromyces funiculosus (41%), Pseudogymnoascus pannorum (36%), albino Mycelia sterilia (29%), Umbelopsis vinacea (25%), Mortierella alpina (17%), Penicillium decumbens (21%), P. spinulosum (20%), and P. canescens (17%). In active layers of peat soils, abundant species are Penicillium thomii (14%), Mycelia sterilia (13%), Penicillium spinulosum (13%), Penicillium simplicissimum (13%) in forest-tundra; Talaromyces funiculosus (21%), albino Mycelia sterilia (15%), Umbelopsis vinacea (14%) in southern tundra; Penicillium decumbens (23%), P. canescens (17%), P. thomii (13%) in northern tundra. In permafrost peat layers, abundant species are Penicillium spinulosum (17%), Talaromyces funiculosus (34%), and Umbelopsis vinacea (15%) in forest-tundra; Pseudogymnoascus pannorum (30%) and Mortierella alpina (28%) in southern tundra; Pseudogymnoascus pannorum (80%) in northern tundra.

Lichen-Associated Oribatid Mites in the Taiga Zone of Northeast European Russia: Taxonomical Composition and Geographical Distribution of Species

We examined 35 species of ground and epiphytic lichens, including fruticose, foliose, and crustose lichen, as habitats of oribatid mites. Observations were carried out in the taiga forests of northeast European Russia, and 87 oribatid species from 38 families were found. The Crotoniidae, Carabodidae, Oppiidae, and Suctobelbidae are the most numerous families in ground lichens and the Oribatulidae are in the epiphytes. The families Micreremidae and Licneremaeidae were only noted in epiphytes. A complex of species characteristic of epiphytic lichens as habitats of oribatid mites have been identified, these are Carabodes labyrinthicus, Oribatula (Z.) propinqua, Phauloppia nemoralis, Micreremus brevipes, Licneremaeus licnophorus, Furcoppia (Mexicoppia) dentata, Cymbaeremaeus cymba. Only in epiphytes, rarely, the species were also Jacotella frondeus, Ameronothrus oblongus, Mycobates (Calyptozetes) tridactylus, and Liebstadia humerata. Characteristic for ground lichens are species Trhypochthonius cladonicolus, Carabodes marginatus, Carabodes subarcticus. Often found in both ground and epiphytic lichens are species Eueremaeus oblongus s. str., E. oblongus silvestris, Ceratoppia quadridentata, Adoristes ovatus poppei, Graptoppia (Apograptoppia) foveolata, Suctobelbella acidens duplex, Tectocepheus velatus, Trichoribates berlesei, Chamobates pusillus, Diapterobates oblongus, Oribatula tibialis, Oribatula (Z.) exilis, Scheloribates laevigatus, Neoribates aurantiacus, Pergalumna nervosa. In epiphytic lichens, we observed species that are rare in the North (Oribatula (Z.) frisiae, O. (Z.) propinqua, P. nemoralis, L. licnophorus, F. (M.) dentata, et al.), with some noted in the taiga zone for the first time (J. frondeus).

Estimation of Methane Fluxes in the Ecosystem of the Palsa Mire in the Far North Taiga Subzone in the European Northeast of Russia (According to the Results of Two Measurement Methods)

Estimation of Methane Fluxes in the Ecosystem of the Palsa Mire in the Far North Taiga Subzone in the European Northeast of Russia (According to the Results of Two Measurement Methods)

Calypso bulbosa (Orchidaceae) on the northern border of its distribution range (Komi Republic, Russia): population structure, fruit and seed set

Orchids form one of the most threatened plant families in the world. For a successful conservation of these species, comprehensive studies of their biology and ecology are necessary, and long-term demographic studies are especially valuable in this regard. This article aimed to present results of long-term observations of two populations of Calypso bulbosa , a rare orchid included in the Red Data Book of the Russian Federation, on the northern border of its range, in the Komi Republic (northeast of European Russia). Seasonal development, ontogenesis, number of individuals and structure of populations, and reproductive success of C. bulbosa were studied. The influence of weather factors on the peculiarities of the small and large life cycles of this species has been revealed. Populations of C. bulbosa located in various habitats differ in a number of characteristics (e.g. number of individuals, spatial placement of plants, their size, the number of generative individuals). The fruit set of C. bulbosa on the northern border of the range is quite low (28.4%). This is compensated by the formation of a large number of tiny (0.68 × 0.11 mm) seeds. The pollination efficiency of the species is affected by the temperature of the beginning of the growing season and precipitation of the second decade of June, as well as by the flowering time. With deterioration of habitat conditions (more northern or shaded habitats), the seed index increases. The seeds become more volatile, which increases chances of reaching favourable sites for seed germination. One capsule of C. bulbosa contains an average of 19 900 seeds. The real seed production is 6500 seeds per plant. The seed production of C. bulbosa varies greatly year by year; it depends on the weather conditions of the first decade of June. In both studied populations, the presence of juvenile individuals (from 3.3% to 41.4%) during all years of the study indicates a successful seed regeneration, which, along with vegetative growth, ensures the stable existence of C. bulbosa populations on the northern border of the range.

Manifestation of the Late Aeronian event in the Silurian section on the western slope of the Subpolar Urals

Research subject. The article presents the results of studying traces of the global Late Aeronian biotic and isotopic (δ13Ccarb) events preserved in a new reference section of the Lower Silurian in the Subpolar Urals.Materials and methods. The samples of sedimentary rocks and microfauna, the results of isotope analysis, as well as the collections with remains of benthic fauna collected by the authors in different years during fieldwork were investigated. The studies were confirmed by sedimentological, biostratigraphic and chemostratigraphic data obtained by the authors.Results. The The event-stratigraphic interval, established in the upper part of the Lolashor stage (Aeronian) of the Silurian, is characterized by increasing regressive tendencies, decreasing biodiversity, disappearance of Pranognathus tenuis conodonts and brachiopods of the genus Pentamerus, as well as by δ13Ccarb anomalies in the upper strata of the Lolashor stage.Conclusions. The obtained data indicate a eustatic drop in the sea level, a major ecosystem restructuring, and a sedimentation gap at the end of the Lolashor time. The boundary between the Lolashor and Philippel stages (Aeronian and Telychian) records a sharp negative isotopic shift of δ13Ccarb, which was first observed in the Lower Silurian section in the European Northeast of Russia.

Karst Ecosystems of Middle Timan, Russia: Soils, Plant Communities, and Soil Oribatid Mites

Oribatid mites are distinguished by high taxonomic diversity and abundance in almost all natural zones; they are used as an indicator group of microarthropods in the study of natural landscapes and anthropogenically disturbed ecosystems. In the karst landscapes of the North, the oribatid mites are very poorly studied. The aim of this study was to investigate the diversity of soil types, plant communities, and oribatid mites in karst relief forms in the conditions of the northern taiga forests. The material was collected in July 2020 in the karst landscapes of Timan Ridge, found in the European northeast of Russia. The research sites were located in the profile of the karst crater and in the profile of the slope in the Ukhta River Valley. A sedge wetland community, and pine–bilberry–green-moss forest, located in the depression between glacial hills and uplands were also examined. A total of seven sites were examined. Geobotanical descriptions were made by standard methods, descriptions of the soil profile, and samples of the soil microfauna; 12 in each site were collected. A total of 51 oribatid mite species from 39 genera and 31 families were found. The highest taxonomic diversity of oribatids was noted in forest phytocenoses located in the upper part of the karst crater slope, the lower part of the karst crater slope, and on rock outcrops in the lower part of the slope in Ukhta river valley. Ordination of the oribatid mite community by NMDS method showed the association of sites S3, S4, and S5 located on the slope of the karst crater in one group, and sites S6 and S7 located on a slope in the Ukhta River Valley, as well as S2 (pine–bilberry–green-moss forest located in the depression between glacial hills and uplands), in another group. The swamp community was located separately from other communities. Species of oribatid mites, which created the specifics of each community, were noted. The specifics of the population of oribatid mites of karst landscapes were that along with the features of fauna, characteristic for zonal north-taiga forests (the predominance of polyzonal widespread species) were found the “conditionally southern” species, the main area of distribution of which is located in lower latitudes. The study provides the basis for future studies of poorly known oribatid mites of karst landscapes of Northern Europe.

Phytochemical characteristic and activity of medicinal raw material from the leaves of pharmacopoeial plant

In 2016-2020 there was carried out a comprehensive study of the problem on involvement into the industrial turnover of ecdysterone-containing substance from the leaf parts of Rhaponticum carthamoides, which is included in the list of plants of the State Pharmacopoeia, in relation to the activity and safety of harvested raw materials. Studied were phytochemical and qualitative characteristics of medicinal raw materials obtained by alternative technology (vegetative shoots instead of roots with rhizomes). Cultivated by organic cultivation in the European North-East of Russia (Archangelsk region) with a cool and humid climate, in an agropopulation with a density of 24-28 thousand plants per 1 ha. Harvesting was carried out at the beginning of the budding phase, the concentration of the active ecdysterone substance was determined by the pharmacopoeial method of high performance liquid chromatography (HPLC) analysis. It has been established that the objects of collection are the fractions of young and adult rosette leaves, where the accumulation of large amounts of ecdysterone is associated with the presence of increased amounts of protein substances (r2 = 0.99-0.98) and there is an inverse negative dependence on fiber (r2 = -0.99…-0.94). An indicator of increased synthesis of ecdysterone is the level of crude protein of 33-27 %, at which the concentration of ecdysterone reaches 4850-3550 mg/kg (0.49-0.36 %) at a standard of 1000 mg/kg (0.1 % based on dry substance). A high degree of availability of ecdysterone from the substance in aqueous extracts, in the temperature range from -10 to +100 ºC, with subsequent preservation of the active substances during the day by 93-98 % was revealed. Total yield of extractive substances is 50.2 % (with the standard value of 12.0 %). Complex biological activity of the extract in biotests was characterized by a stimulating effect at high dilution (10-9-10-11 M per ecdysterone) and inhibitory at low dilution (1:100). Medicinal raw materials meet the established sanitary and toxicological safety standards for the content of pollutants: it does not accumulate heavy metals (Hg, Cd, As, Zn; Ni, Cu, Cr) above the background level; there are no prohibited chlorine and organophosphorus compounds; radionuclide, nitrate and nitrite content is below norms of maximum allowable concentration.

Fire Impact on Carbon Pools and Basic Properties of Retisols in Native Spruce Forests of the European North and Central Siberia of Russia

Fires play an important role in the modern dynamics of boreal ecosystems. The article presents the results of studying the effect of old fires on soils and soil organic matter (SOM) of native spruce forests that were last affected by fires in the previous 100 to 200 years. The studies were carried out in the European north-east of Russia (Komi Republic) and Central Siberia (Krasnoyarsk region). The objects of the study were typical Glossic Stagnic Retisol (Siltic, Cutanic). The time after the fire was determined by dendrochronological methods. Data on the content of water-soluble organic matter and densimetric fractions of soils were obtained; carbon and nitrogen stocks were calculated. The content of polycyclic aromatic hydrocarbons (PAHs) was established to characterize the effect of fires. Pyrogenic carbonaceous inclusions were morphologically diagnosed 200 years after the fire. In this regard, it is proposed to distinguish a “pyrogenic” subtype for soils with pronounced signs of pyrogenesis. Carbon stocks in soils of the Komi Republic varied from 5.7 to 15.7 kg C m−2, and soils of the Krasnoyarsk region had an accumulation of 6.9–12.5 kg C m−2. The contribution of the pyrogenic horizon Epyr to the total carbon and nitrogen stocks was 9–45%. It is suggested that pyrogenic carbon (PyC) can accumulate in light densimetric fractions (fPOM<1.6 and oPOM<1.6). The analysis of PAH content showed their high concentrations in the organic and upper mineral horizons of the studied soils (24 to 605 ng g−1). The coefficient FLA (fluoranthene)/(FLA+PYR(pyrene)) was the most useful to diagnose the pyrogenic origin of PAHs in the studied Retisols.

Распространение и морфометрические особенности обыкновенной жабы Bufo bufo L. (Bufonidae, Amphibia) на Северо-Востоке европейской части России

The distribution and morphometric features of the common toad (Bufo bufo) in the North-East of European Russia are discussed. The northern boundary of the species' range in the region has a complex configuration. In the west and central part of the region, the toad is found up to latitude 65º42'N and 63º01'N, respectively, the eastern border of its habitat moves northwards up to 64º13' and then drops to the south along the Ural Mountain Ridge. The formation of the modern range of the species in the region was influenced by an extensive network of watercourses and global climate changes. For the last 70 years, toads have distributed along the Pechora River at a distance of more than 600 km. The morphometric variability of the common toad was estimated by 13 linear criteria and 7 indices on the example of four localities in the Komi Republic (Pechora, Beloye Lake, Lokchim Lake, and Sysola Lake). Significant sexual differences were found by most criteria: their values in females are higher than in males. Toads of both sexes inhabiting the eastern and northern localities (Pechora, Lake Beloye) are smaller in size than animals from the southwestern parts of the region (Lokchim Lake, Sysola Lake). Discriminant analysis showed that maximal differences between samples were registered on the body length L., femur length F., tibia length T., head length L.c., and head latitude Lt.c.

Holocene and recent fires influence on soil organic matter, microbiological and physico-chemical properties of peats in the European North-East of Russia

The influence of fires on the development and chemical composition of two Rheic Hemic Histosols in the native territory of the middle taiga of the Komi Republic was estimated. The development of peat on site I (SI) located in the south boarder of the middle taiga began in the Boreal period (about nine ths. years ago14C yr BP). The growth of peat on site II (SII) located at the foothills of the Northern Urals started in the middle of the Atlantic Holocene period (about 6.7 ths. years ago14C yr BP). This work shows that during the time of development, peatlands experienced various pyrogenic events. The organic horizons were burned out and often led to a change in the dominant ground cover plants. Also, the charcoal particles formed during the fire at the forest surrounding the bogs were transported by air and accumulated in the peat. The pyrogenic history of the studied peats is different, the SI was subjected to intense fires at least twice: at the beginning of formation and in the modern period (140 years ago). The Histosol on SII experienced only low-intensity and indirect fire effect. The highest burning activity of nearest forests in both sites estimated based on charcoal content occurred at the end of the Atlantic, middle of the Subboreal periods. It was shown that an increase in the aromatic compounds occurs in horizons with pyrogenic features; in some cases, an increase in the concentration of polycyclic aromatic hydrocarbons (PAHs) was revealed. The aromatic compounds content in the SOM is determined by the content of macroscopic charcoal particles with significant correlation (CAr-H(C), R = 0.49, p < 0.05, CAr-O,N, R = 0.68, p < 0.05). It is shown that a high frequency of fires leads to an increase in carbon stocks at Histosols.

Spatial relationships of trees in middle taiga post-pyrogenic pine forest stands in the European North-East of Russia

Information on the structural organization of forest stands obtained on sample plots is the basis for long-term monitoring of post-fire pine forest structure and dynamics in the European North-East. These data can be used as a marker of native pine stands of the European taiga. Here, we studied vertical and horizontal structure in the post-pyrogenic pine forests of Vacciniosum, Vaccinioso-cladinosum and Myrtillosum site types in the boreal forest of the Komi Republic. The type of horizontal structure of uneven-aged forest stands changed with age from grouped to random one. Large trees were randomly distributed on the plot. We observed the weak aggregation of undergrowth trees (natural tree regeneration) in stands at distances of 2–6 m. Undergrowth individuals were characterized by group distribution at smaller distances than 1–2 m. Spatial relationships between large, small and codominant trees demonstrated random distribution in most cases. Undergrowth individuals did not show any competitive relations. However, we revealed a “taking off” effect between mature trees of pine and pine undergrowth. The direction of the displacement of tree crown centre projections relative to the bases of their trunks was ambiguous. The shift of the crown space towards the maximum solar radiation was detected in a thinned stand with old age and big size of trees. In other site types, no one-sided orientation of the tree crown development emerged.

Molecular-mass distribution of humus acids of taiga soils

Purpose of the study: to reveal the influence of hydromorphism and agricultural use on the molecular-mass distribution (MMD) of humic (HAs) and fulvic acids (FAs) isolated from the soils of the European northeast of Russia. To assess the influence of the acidity of the medium on the MWD of FAs. Place and time of the event. The studies were carried out on the territory of the middle taiga (Maksimovsky station of the Institute of Biology of the Federal Research Center of the KSC UB RAS, located 8 km west of the city of Syktyvkar and the field of the Syktyvkar state farm, 5 km south-west of Syktyvkar, on the watershed of the Sysola and Vazhel-yu rivers) and northern taiga (3 km west of the Troitsko-Pechorsk station). The objects of the study were humic substances isolated from typical podzolic (Eutric Albic Retisol (Loamic)), gleypodzolic (Eutric Albic Stagnic Retisol (Loamic)), peaty-podzolic surface-gleyed (Eutric Albic Stagnic Histic) Retisol (Loamic Eutric Albic Retisol (Loamic)) soils. The soil sampling period is from 1 to 30 August 2014. Methodology. Quantitative analysis of the MMD of HA and FA preparations was performed using liquid size exclusion chromatography (gel chromatography) on Sephadex G-25 and G-100 gels with continuous automatic registration of the optical density of the eluate (λ = 280 nm) in a quartz flow cell, K 9 × 60 cm column (Pharmacia, Sweden). Distilled water, 0.05 M NaOH solution, and Tris-HCl buffer with pH = 8.2 were used as the eluent. Main results. Studies of the MMD of humic substances have been carried out. It was found that HAs contain three fractions with different molecular weights: ≥ 150 kDa, 73–80 kDa, and 13–23 kDa; FAs – two fractions: ≥ 5 kDa, 1–2 kDa. The low molecular weight of FAs, together with a large amount of oxygen-containing functional groups, contributes to their better solubility and migration ability in soils. The HAs of automorphic soils are characterized by a high content of low molecular weight fractions, and the proportion of the high molecular weight fraction in the HAs of the litter is 1.5–2.0 times higher than in the HAs of the podzolic horizon, which may be due to the migration of the low molecular weight fraction down the profile. The high proportion of the acidic low molecular weight fraction in the podzolic horizon promotes the decomposition of soil minerals and their leaching into the illuvial horizon. The influence of agricultural use of soils on the fractional composition of humic compounds is estimated. A sharp increase in the share of the high molecular weight fraction in the preparations of HAs of arable podzolic soil by 2–4 times compared with the HAs of virgin podzolic soils was noted, which is due to the cultivation of the arable horizon, the nature of the incoming plant residues and the increased microbiological activity of the developed soils. The effect of acidity of the medium on the character of chromatograms of FA preparations isolated from the main types of soils of the Komi Republic was studied. It has been shown that in the region of high pH values of the eluent 9–13, the absence of fractionation is associated with the association of FAs, a change in their conformation, and the effect of “over-exclusion”. Elution with distilled water (pH = 6.5) allows the separation of FAs into two fractions with molecular weights ≥ 5 kDa and 1–2 kDa.