Mineral Horizons Research Articles

Rectorite as a Syngenetic Component of a Soddy-Podzolic Soil

Rectorite (allevardite) is a regularly interstratified mica–smectite, in which each mica (A) layer is “sandwiched” between smectite (B) layers creating ABABAB…. sequence with 50% contribution of each layer. Similar to other ordered minerals, rectorite is rare in nature. The paper provides the results of the study on properties and mineral composition of the soddy weakly podzolic soil (Umbric Albeluvisol) in the Komi Republic, Russian Federation. Rectorite is found in fine fractions of A1 and A2 horizons of this soil. The studied soil has been formed on the light-textured parent material. The soil profile is texturally differentiated by the eluvial type. In the mineral horizons, $${\text{p}}{{{\text{H}}}_{{{{{\text{H}}}_{2}}{\text{O}}}}}$$ varies within 5.1–5.3. The mineral composition of fractions <2, 2.0-0.5 and <0.5 μm was studied by X-ray diffractometry (XRD). In the parent material, smectite predominates and is represented by the high-charged beidellite. In addition, its clay fraction contains mica, vermiculite, kaolinite and chlorite, as well as fine quartz. Vermiculite structure is chloritized. The mineral composition of the clay fraction undergoes transformation within the upper 40 cm of the profile, which is maximally pronounced in the upper 20 cm. The content of smectite is lower there; and that of fine quartz is higher, fine fractions additionally contain rectorite. This mineral is identified on the base of the integer (00h) reflection series 24.54 and 12.27 A for air-dry samples. After saturation with ethylene glycol, the (001) peak shifts to 26.77 A. Calcination during 2 h at 550°C results in shifting of this peak to 10 A. Rectorite is believed to be a syngenetic component of this soils and is formed at the early stage of smectite transformation into illite, being a transitional product of this transformation.

Elemental composition of soils of the Pur-Taz interfluve

In order to evaluate the chemical composition of natural background environments of Pur-Taz interfluve (Western Siberia), the mineral components of soils, peats, lichens, and sphagnum mosses have been analyzed. The samples were tested using X-ray fluorescence technology. The average contents of hazardous metals in the soils of the Pur-Taz interfluve are either lower (for Cu, Pb, Zn, Ni, Sr) or equal to (for Hg, Co) the average values of these elements in the Earth's crust. This finding corresponds to the commonly held view that the contents of elements in the soils located in the north of Western Siberia are lower than the world averages. Additionally, in our samples low concentrations of copper and zinc have been observed. Since these microelements are important for soil physiology, this finding indicates unfavorable biochemical conditions in the research area. On the other hand, high concentrations are observed for inactive elements such as Mo, Sn and Zr. The significant differences have been identified in the composition of mineral and organic soil horizons. For instance, the average concentrations of P, Zn and S in organic horizons are 7.1, 8.1 and 18 times greater than in the illuvial mineral horizons, respectively. The intense accumulation of Zn, Cu, Cd, Hg has been recorded, all of them are chalcophiles in the ombrotrophic peat. This means that the chemical composition of soil is largely determined by biological accumulation of chalcophile elements. The content of lithophilic Al, Si, Ti and Zr, coming with dust precipitation from the atmosphere increases in the peat of dwarf shrub-moss-lichen tundras and larch woodlands. The revealed values of the elemental composition of soils can be recommended as background in the course of the environmental monitoring.

Spatial variability of forest floor and topsoil thicknesses and their relation to topography and forest stand characteristics in managed forests of Norway spruce and European beech

Soils play a significant role in climate regulation, especially due to soil organic carbon (SOC). The SOC pool is therefore modeled for various environments, and forest floor and topsoil thicknesses are important parameters for most of these models as they store most of the SOC. However, the forest floor and topsoil thicknesses show high spatial variability which is a result of multiple factors which are not agreed upon among scientists. Out of these factors, we choose topography parameters (elevation, slope, and topography wetness index) and forest stand characteristics (stand age, dominant tree species, and forest floor cover), and soil moisture, and we analyzed their relationship to the forest floor and topsoil thicknesses. The study was performed in a managed submontaneous forest in Central Europe dominated by Picea abies (L.) Karsten with small patches of Fagus sylvatica L. or other species. The thicknesses of the O horizons (Oi, Oe, Oa) and topsoil were measured at 221 sampling pits. Geographically weighted regression showed that the spatial variability of the overall forest floor plus topsoil thickness (OA) is responsible for 8% of its variability. The thickness of the OA is the most strongly controlled by forest floor cover explaining approximately 6% of its variability and soil moisture explaining 2–6% of the variability. The Oi + Oe horizon thickness is controlled only by forest floor cover explaining 10.7% of its variability, and the thickness of Oa + A horizon can be explained mainly by soil moisture in mineral horizon explaining 9% of the variability.

Linking Forest Vegetation and Soil Carbon Stock in Northwestern Russia

Research Highlights: It was found that both tree species and ground vegetation affected soil carbon stock in boreal forests. Carbon stocks in the mineral layers were related negatively to the C/N ratio in the organic horizon and pine proportion in the growing stock volume, and positively to the share of herbaceous plants and the proportion of spruce. Background and Objectives: Existing research showed the effects of tree species on soil carbon stocks in organic horizons, but these effects were less clear in mineral horizons. Little is known about the effects of ground vegetation on soil carbon stock. This study aims to identify associations between the forest vegetation composition and soil carbon stocks in northwestern Russia. Materials and Methods: Research data from 109 pine, spruce and birch forests of different Cajander’s and Sukachev’s types with different functional compositions of ground vegetation at autonomous positions are discussed in this paper. The V-test was used to assess the impact of vegetation on soil carbon stocks. Results: Variations in Carbon stocks in the mineral layers were associated with the soil types and vegetation composition. Carbic Albic Podzols accumulated the least amount of carbon in the mineral profile. Carbon stock in the mineral layers in pine forests was considerably lower than in spruce and birch forests. Spruce forests with the highest share of herbaceous plants were characterised by the highest carbon stocks in the mineral layers, while pine forests with dwarf shrubs and green mosses accumulated more carbon in the organic layers, but carbon stocks in the mineral layers here were the lowest. Conclusions: Differences in soil carbon stocks between and within northern and middle taiga in northwestern Russia were associated not only with soil types but also with the proportions of forest types dominated by different tree species and ground vegetation functional groups.

Technogenic contamination or geogenic enrichment in Regosols and Leptosols? Magnetic and geochemical imprints on topsoil horizons

Determination of the origin (geogenic or technogenic) of magnetic and geochemical imprints in soils and the role of weathering processes is crucial for the assessment of relationship between technogenic magnetic particles (TMPs) and potentially toxic elements (PTEs), iron and manganese. Our primary aim is to distinguish the most reliable methods for the appropriate interpretation of measured parameters strictly attributed to particular soil horizons (including bedrock), which is not yet very common in soil magnetometry. We examined six soil profiles developed from/on five different rock types (sedimentary and igneous rocks). The magnetic parameters reflect the concentration, type and grain size of the magnetic particles. Geochemical analysis consists of the determination of PTEs (Co, Cr, Cu, Ni, Pb and Zn), Fe and Mn. Quantification of soil contamination is based on calculating the index of geoaccumulation and enrichment factors. Interpretation is based on plots and magnetic and geochemical data, evaluated by principal component analysis for particular soil horizons. The results show that the volume magnetic susceptibility of the topsoil (mineral horizon Ah) in areas where the soil is developed from strongly magnetic bedrock is primarily influenced by geogenic magnetic particles (GMPs) derived from weathering processes. In cases of magnetic susceptibility determined on organic subhorizons (Oea or Oa), the magnetic parameters indicate the occurrence of TMPs. Moreover, the ratios of saturation isothermal remanent magnetization over magnetic susceptibility, and magnetic susceptibility over iron content help in distinguishing both geogenic and technogenic magnetic contributions. The variations of magnetic susceptibility and iron concentration reflect the presence of the strongly magnetic fraction in total soil iron content. Lead and zinc exhibit unambiguous technogenic influx into topsoil horizons. We conclude that the technogenic contamination dominates over geogenic enrichment in soils developed from/on weakly magnetic bedrock, but also strongly magnetic bedrock (without weathering effects).

Carbon Stock in Sandy Soils of Pine Forests in the West of Russia

A comparative assessment of carbon accumulation in the soils of pine forests in western Russia (the Republic of Karelia, the Karelian Isthmus, and Bryansk region) developed on coarse-textured parent materials has been made. The total carbon stock in the litter and upper soil layer (0–50 cm) varied from 47 t/ha in the soils of pine forests of Bryansk region to 116 t/ha in the soils of pine forests of the Karelian Isthmus. It has been shown that the main factors of carbon accumulation in the soils of pine forests in western Russia were the climate, parent materials, vegetation, agricultural activity, and fires. The influence of climatic conditions has been clearly manifested in the levels of carbon accumulation in the litter and in the upper humus-accumulative soil horizons. In the pine litter within the zone of mixed forests (Bryansk region), the level of carbon accumulation was the lowest, whereas the litter layer of pine forests in the northern taiga (Karelia) has the highest stock of carbon. At the same time, the lowest carbon stocks in the upper mineral soil layers has been noted for the soils of northern taiga forests, which had no humus-accumulative mineral horizon. The variability of carbon stocks in the litter layer was largely controlled by the C/N ratio, as well as by the fraction of deciduous undergrowth and grasses producing high-quality litter. The influence of agricultural activity on soil carbon stock in pine forests was especially pronounced on the Karelian Isthmus with the high agricultural activity in the past, as well as in Bryansk region, where pine forests are formed from pine plantations. The effect of fires on soil carbon stock was most pronounced in heather and lingonberry pine forests of the northern taiga of Karelia.

Importance of Soil, Stand, and Mycorrhizal Fungi in Abies balsamea Establishment in the Boreal Forest

Research highlights: To understand differences in the establishment of balsam fir regeneration observed in the boreal forest, we examined how soil layer and microorganisms explained differences in growth and mycorrhization in three different stand types. Our experiment revealed positive and negative effects on growth of seedlings, and highlights the importance of biotic interactions in balsam fir establishment. Background and Objectives: In a context of climate change, understanding tree migration can be examined through changes in tree regeneration. At the ecotone between mixed and conifer boreal forest, regeneration of balsam fir northward is of particular interest because it thrives better under aspen-dominated stands as compared to adjacent spruce-dominated stands. As the understorey differs between these stands, with more Ericaceae under spruce and different ectomycorrhizal fungal communities in organic and mineral horizons, we hypothesized that biotic factors could explain differences in balsam fir establishment. Materials and Methods: Using a growth chamber experiment, we tested if differences in soil layers and modification of soil fungal communities would affect germination, mycorrhization, and growth of balsam fir seedlings in three different stand vegetation. We compared 12 treatments and followed 120 seedlings over three growth seasons. Results: We found similar survival in soils from aspen- and spruce-dominated stands, and a greater biomass on organic layers. In addition to this, a greater mycorrhization rate was found in aspen soils but improved germination in spruce soils. The presence of Ericaceae in spruce soils was associated with lower mycorrhization but did not affect other traits. Sterilization and therefore microorganisms affected mainly the number of ectomycorrhizae and the investment in root biomass. Finally, mycorrhization and biomass were correlated, but independent from N nutrition measured in needles. Conclusions: Our results highlighted the positive effects of organic soil layers and of mycorrhization on biomass, and showed that mycorrhization was increased under aspen as compared to other stand types. Our experiment also revealed positive effects of spruce soil on fir germination and showed that fir was able to grow and survive in all conditions. Our study suggests that fir establishment is affected by belowground multi-species interactions, and therefore highlights that biotic interactions shall be taken into account to understand and predict future tree migrations in the boreal forest.

Soil Phosphorus Dynamics Across a Holocene Chronosequence of Aeolian Sand Dunes in a Hypermaritime Environment on Calvert Island, BC, Canada

Phosphorus (P) is an essential nutrient for plant growth, but soil P concentrations decline with increasing soil age. Phosphorus often limits tree growth within the hypermaritime Coastal Western Hemlock zone in British Columbia, Canada, particularly where parent material with low P concentrations have experienced rapid weathering. To sustainably manage forests in this region, more information is needed about changes in soil P concentrations and dynamics that occur with time. This study characterized the forms and abundance of soil and foliar P compounds using a soil chronosequence developed on aeolian sand dunes on Calvert Island and compared results to chronosequences in other locations. Eight time points were examined, from a modern foredune to a relict, stabilized dune (~10,760 years old). Soil horizons were analyzed for bulk density, pH, and concentrations of total carbon (C), nitrogen (N) and total P (TP), iron (Fe) and aluminum (Al), total organic P (Po), and Mehlich-extractable P and cations. For each site, P forms in L, H and organically-enriched mineral (M) horizons were characterized with solution 31P nuclear magnetic resonance spectroscopy (P-NMR), as were foliar samples from tree species spanning all age classes except the youngest dune. This chronosequence followed the Walker and Syers (1976) model, with an exponential decline in TP mass and a humped-shape curve in Po mass with increasing age. The L horizon had lower TP concentrations than foliage samples, but similar P forms. The H horizons had a greater proportion of DNA, phosphonates and nucleotides than the L horizon and increased proportions of myo- and scyllo-inositol hexakisphosphate (IHP) with increasing age. The mineral horizons had much lower TP concentrations than other horizons and increased proportions of IHP and DNA with increasing age, which were correlated to increased exchangeable and amorphous Al concentrations. In all sample types, the proportion of orthophosphate declined with increasing age. These results enhance knowledge of P cycling within hypermaritime soils, particularly the P decline that will occur with age. This will aid in the sustainable management of the low-productivity forests typical of these ecosystems.

The Conversion of Abandoned Chestnut Forests to Managed Ones Does Not Affect the Soil Chemical Properties and Improves the Soil Microbial Biomass Activity

Recently, several hectares of abandoned chestnut forests (ACF) were recovered into chestnut stands for nut or timber production; however, the effects of such practice on soil mineral horizon properties are unknown. This work aimed to (1) identify the better chestnut forest management to maintain or to improve the soil properties during the ACF recovery, and (2) give an insight into the effect of unmanaged to managed forest conversion on soil properties, taking in consideration sweet chestnut (Castanea sativa Mill.) forest ecosystems. The investigation was conducted in an experimental chestnut (Castanea sativa Mill.) forest located in the northern part of the Apennine chain (Italy). We identified an ACF, a chestnut forest for wood production (WCF), and chestnut forests for nut production with a tree density of 98 and 120 plants ha−1 (NCFL and NCFH, respectively). WCF, NCFL and NCFH stands are the result of the ACF recovery carried out in 2004. After 15 years since the ACF recovery, generally, the effects on the main soil chemical properties were negligible. Some differences occurred for the water-soluble organic carbon (WSOC) and microbial biomass and its activity. NCFL showed the highest WSOC content in the uppermost soil horizon likely due to higher amount of roots which are source of labile organic compounds. The higher WSOC amount might explain the greatest amount of microbial biomass in the A horizon of NCFL. Furthermore, the microbial biomass harboring in the A horizon of NCFL has also shown both a better C use efficiency and a larger soil organic carbon immobilization in the microbial biomass itself. Our data would indicate that the ACF recovery into pure chestnut forests did not have negative impacts on soil chemical and biochemical properties, though chestnut stands for nut production with a low plant density are the most suitable ones.

Ectomycorrhizal community composition of organic and mineral soil horizons in silver fir (Abies alba Mill.) stands.

Vertical ectomycorrhizal (ECM) community composition was assessed on silver fir (Abies alba Mill.) in beech-silver fir forests in Bosnia and Herzegovina. Organic and upper mineral horizons were described by pedological analyses. Silver fir root tips were divided into vital ECM, old and non-mycorrhizal for each horizon separately. Morpho-anatomical classification of vital ECM root tips with an assessment of abundance was followed by ITS-based molecular characterization and classification into exploration types. The percentage of vital ECM root tips was not affected by the soil horizon. Altogether, 40 ECM taxa were recorded. Several taxa have not previously been reported for silver fir: Hebeloma laterinum, Inocybe fuscidula, I. glabripes, Lactarius acris, L. albocarneus, L. blennius, L. fluens, Ramaria bataillei, Russula badia, R. lutea, R. mairei, Sistotrema sp., Tarzetta catinus, Tomentella atroarenicolor, T. badia, T. cinerascens, T. bryophylla, and T. ramosissima, indicating high potential for diversity of ECM fungi in silver fir stands. No significant differences in community composition and species richness and diversity were detected between mineral and organic horizons. Community composition was affected by CaCO3, organic carbon concentration, organic carbon stock, total nitrogen stock, C/N ratio and soil bulk density. No significant effects of soil parameters were detected for exploration types. The contact exploration type was dominant in both soil horizons. Significantly different relative abundances of dominant taxa Tomentella stuposa, Cenococcum geophilum and Piloderma sp. 1 were detected in the two horizons. Twelve taxa were limited to the organic horizon and eight to the mineral horizon.

Spatial variability of nutrients in soils and plants of forest ecosystems located near the highway.

The variability of selected biogenic elements in soils and leaves of three dominant plant species was studied in segments of Querci-Fageta typica and Fagi-Querceta typica forest ecosystems located near R1 Pribina highway in SW Slovakia. The amounts of nutrients (Mg, K, Na and Zn) in soils distant 30m from the highway were mostly low and increased significantly with a depth of soil. On the other hand, the highest Ca concentrations were found in the surface humus horizons and decreased significantly with soil depth. The Mg, K and Zn contents found in soil mineral horizons 8000m from the highway were more balanced than those found at 30m from the highway. The nutrient content of plant leaves was mostly significantly higher at a distance of 30m from the highway than 8000m from the highway, for Ca (Prunus spinosa, Melica uniflora), Mg (P. spinosa), Na (Quercus cerris, P. spinosa) and Zn (Q. cerris, M. uniflora). The tightness of the relationships between nutrient contents in leaves and the distance from the highway was the highest for Ca (P. spinosa, M. uniflora), Mg, Na, Zn (Q. cerris, P. spinosa) and K (M. uniflora). The K/(Mg + Ca) ratios in Q. cerris and P. spinosa leaves distant 8000m from the highway were more balanced than those found at 30m from the highway. This markedly points to favourable biological activity and better stability of the more distant control ecosystem with lower level of pollutants.

Nitrogen Compounds in the Soil of the Continental Margins of the European Russian Arctic

The specific features in the distribution of organic and mineral nitrogen compounds in marsh and tundra soils of the European Russian Arctic (coastal areas of the Barents and White Seas) were analyzed. Total nitrogen was determined by gas chromatography (CHNS-O elemental analyzer), and inorganic nitrogen, by photometry. The composition of hydrolyzable amino acids was analyzed by liquid chromatography on ion exchange resins. Mineral compounds accounted for an insignificant part of the total soil nitrogen; its major part (to 97% of the total content) was represented by organic substances (Nоrg). The Nоrg varied within a wide range in both marsh (0.3–15.8 g/kg) and tundra soils (5–20 g/kg in the peat horizons and 0.3–2 g/kg in the mineral horizons). The content of N- $${\text{NH}}_{4}^{ + }$$ varied from 5 to 20 mg/kg in marsh soils and from 30 to 200 mg/kg in tundra soils. In marsh soils, the content of nitrate nitrogen was 0.2–4.6 mg/kg in the upper horizons. Marsh soils were characterized by the accumulation of Nоrg either on the surface or in the middle part of the profile in the presence of humus-accumulative horizons buried under recent marine sediments. The accumulation of Nоrg and N- $${\text{NH}}_{4}^{ + }$$ was observed above the permafrost in the peat-gley soil and in the permafrost in the oligotrophic peat soil. The content of hydrolyzable amino acids in the soils of different geneses was 0.6–8 g/kg, which corresponded to 30–60% of the soil organic nitrogen and 2–12% of the soil organic carbon. Distribution patterns of the amino acid nitrogen and organic nitrogen in the soil profiles were similar. The qualitative composition of amino compounds was relatively uniform, and the ratios of most of them were close. The shares of arginine, histidine, phenylalanine, tyrosine, and isoleucine were less than 4% each; of lysine, valine, proline, serine, and threonine, 5 to 7%; and of alanine and leucine, 10–12%. The share of glycine increased downward the profile from 12 to 20%, and the shares of aspartic and glutamic acids decreased from 11 to 6%. In marsh soils, Nоrg, N- $${\text{NH}}_{4}^{ + }$$ , and nitrogen of most amino acids correlated (r = 0.6–0.9) with the clay content and nonsilicate iron forms. The tightest correlations were observed between the dithionite-soluble iron and the nitrogen of threonine and histidine.

Contents and Distribution of 137Cs in Podzols in the Area of the Kola Nuclear Power Plant

The content and profile distribution of 137Cs in iron-illuvial dwarf and shallow-podzolic podzols (Albic Podzols) under bilberry-lichen and green-lichen-bilberry pine forests in the located near the Kola Nuclear Power Plant have been analyzed. The pollution density (reserve) of 137Cs in the root-inhabited layer (0–30 cm) in the studied soils was significantly lower than the established control level of 37 000 Bq/m2 and amounts to 530–2459 Bq/m2. A significant part of 137Cs (60 to 90%) was concentrated in mineral horizons. It has been shown that the pollution density of 137Cs in the observation zone of a nuclear power plant was mainly due to global fallout. The greatest influence on 137Cs accumulation in the studied soils was exerted by the organic matter reserve.

A revised pan-Arctic permafrost soil Hg pool based on Western Siberian peat Hg and carbon observations

Abstract. Natural and anthropogenic mercury (Hg) emissions are sequestered in terrestrial soils over short, annual to long, millennial timescales before Hg mobilization and run-off impact wetland and coastal ocean ecosystems. Recent studies have used Hg-to-carbon (C) ratios (RHgC's) measured in Alaskan permafrost mineral and peat soils together with a northern circumpolar permafrost soil carbon inventory to estimate that these soils contain large amounts of Hg (between 184 and 755 Gg) in the upper 1 m. However, measurements of RHgC on Siberian permafrost peatlands are largely missing, leaving the size of the estimated northern soil Hg budget and its fate under Arctic warming scenarios uncertain. Here we present Hg and carbon data for six peat cores down to mineral horizons at 1.5–4 m depth, across a 1700 km latitudinal (56 to 67∘ N) permafrost gradient in the Western Siberian Lowland (WSL). Mercury concentrations increase from south to north in all soil horizons, reflecting a higher stability of sequestered Hg with respect to re-emission. The RHgC in the WSL peat horizons decreases with depth, from 0.38 Gg Pg−1 in the active layer to 0.23 Gg Pg−1 in continuously frozen peat of the WSL. We estimate the Hg pool (0–1 m) in the permafrost-affected part of the WSL peatlands to be 9.3±2.7 Gg. We review and estimate pan-Arctic organic and mineral soil RHgC to be 0.19 and 0.63 Gg Pg−1, respectively, and use a soil carbon budget to revise the pan-Arctic permafrost soil Hg pool to be 72 Gg (39–91 Gg; interquartile range, IQR) in the upper 30 cm, 240 Gg (110–336 Gg) in the upper 1 m, and 597 Gg (384–750 Gg) in the upper 3 m. Using the same RHgC approach, we revise the upper 30 cm of the global soil Hg pool to contain 1086 Gg of Hg (852–1265 Gg, IQR), of which 7 % (72 Gg) resides in northern permafrost soils. Additional soil and river studies in eastern and northern Siberia are needed to lower the uncertainty on these estimates and assess the timing of Hg release to the atmosphere and rivers.

Temperate Forests Dominated by Arbuscular or Ectomycorrhizal Fungi Are Characterized by Strong Shifts from Saprotrophic to Mycorrhizal Fungi with Increasing Soil Depth.

In temperate and boreal forests, competition for soil resources between free-living saprotrophs and ectomycorrhizal (EcM) fungi has been suggested to restrict saprotrophic fungal dominance to the most superficial organic soil horizons in forests dominated by EcM trees. By contrast, lower niche overlap with arbuscular mycorrhizal (AM) fungi could allow fungal saprotrophs to maintain this dominance into deeper soil horizons in AM-dominated forests. Here we used a natural gradient of adjacent forest patches that were dominated by either AM or EcM trees, or a mixture of both to determine how fungal communities characterized with high-throughput amplicon sequencing change across organic and mineral soil horizons. We found a general shift from saprotrophic to mycorrhizal fungal dominance with increasing soil depth in all forest mycorrhizal types, especially in organic horizons. Vertical changes in soil chemistry, including pH, organic matter, exchangeable cations, and extractable phosphorus, coincided with shifts in fungal community composition. Although fungal communities and soil chemistry differed among adjacent forest mycorrhizal types, variations were stronger within a given soil profile, pointing to the importance of considering horizons when characterizing soil fungal communities. Our results also suggest that in temperate forests, vertical shifts from saprotrophic to mycorrhizal fungi within organic and mineral horizons occur similarly in both ectomycorrhizal and arbuscular mycorrhizal forests.

Profile Distribution and Migration of Heavy Metals in the Soils of the Kursk Agglomeration (Model Experiments)

Aim. Laboratory evaluation of the characteristics of spatial distribution and migration of heavy metals (HM) in model soil profiles of varied genesis through measurement of the electrokinetic potential of soil solutions. Material and Methods. Undisturbed soils of forest parks landscapes and continental floodplain meadows of the Kursk agglomeration were studied. Experiments were carried out in laboratory conditions. The short‐term temporal dynamics were studied of vertical distribution and migration of the introduced HMs in model soil columns which imitated soil profiles. Results. Analysis of the kinetics of soil solutions and of lysimeter waters of control and polluted samples showed that the model profile of typical dark‐gray soil has the least capacity to capture lead ions from polluted soil solutions. Minimum sorption capacity with respect to zinc was found to be characteristic of sod‐podzol illuvialferruginous soil profiles. Maximum ability to deposit the HMs under analysis (Zn and Pb) was shown in leached chernozem medium loamy soils. Conclusion. The dynamics and kinetics of lead and zinc in soils of the Kursk agglomeration differ significantly and depend on a number of soil factors. In the soils studied, the spatial distribution and the intensity of migration of lead and zinc were determined by the capacity and contrast indices of the internal soil geochemical barriers. Inhibition of the processes of vertical migration of Pb and Zn in the model soil profiles was observed in those rich in humusified humus‐accumulative genetic horizons as well as in mineral horizons with highly contrasting acid‐base and redox conditions. Adsorption zones of lead and zinc are formed with a significant increase in granulometric texture and a decrease in pHKCl.

Distinct fungal successional trajectories following wildfire between soil horizons in a cold-temperate forest.

Soil fungi represent a major component of below-ground biodiversity that determines the succession and recovery of forests after disturbance. However, their successional trajectories and driving mechanisms following wildfire remain unclear. We examined fungal biomass, richness, composition and enzymes across three soil horizons (Oe, A1 and A2) along a near-complete fire chronosequence (1, 2, 8, 14, 30, 49 andc.260yr) in cold-temperate forests of the Great Khingan Mountains, China. The importance of soil properties, spatial distance and tree composition were also tested. Ectomycorrhizal fungal richness and β-glucosidase activity were strongly reduced by burning and significantly increased with 'time since fire' in the Oe horizon but not in the mineral horizons. Time since fire and soil C:N ratio were the primary drivers of fungal composition in the Oe and A1/A2 horizons, respectively. Ectomycorrhizal fungal composition was remarkably sensitive to fire history in the Oe horizon, while saprotroph community was strongly affected by time since fire in the deeper soil horizon and this effect emerged 18 years after fire in the A2 horizon. Our study demonstrates pronounced horizon-dependent successional trajectories following wildfire and indicates interactive effects of time since fire, soil stoichiometry and spatial distance in the reassembly of below-ground fungal communities in a cold and fire-prone region.

Surface horizons of forest soils for the diagnosis of soil environment contamination and toxicity caused by polycyclic aromatic hydrocarbons (PAHs).

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that are released into soils primarily from the air, with wet and dry deposition. To assess the contamination of the forest soil environment, soil samples were collected from organic and mineral horizons from three study areas representing a gradient of pollution across Poland (the ‘pollution transect’). The soils examined varied in PAH contents, generally from 124.3 μg·kg-1 dw in the areas deemed to be the background zone to 9165.5 μk·kg-1 dw in industrial areas in the O horizon and from 12.6 μk·kg-1 dw to 4454.6 μk·kg-1 dw in the A horizon. The PAH toxicities oscillated from 20.0–2670.8 μg TEQ·kg-1 dw in the O horizon and from 1.73–694.7 μg TEQ·kg-1 dw in the A horizon. The enrichment factor values point to a more intensive accumulation of PAHs with relatively high molecular weights along the pollution transect. The PAH diagnostic ratio values indicated that the main PAH emission sources were from coal and wood combustion.

Long-term effects of stump removal and tree species composition on the diversity and structure of soil fungal communities.

Stump removal is a common forest management practice used to reduce the mortality of trees affected by the fungal pathogen-mediated root disease, Armillaria root rot, but the impact of stumping on soil fungal community structure is not well understood. This study analyzed the long-term impact of stumping and tree species composition on the abundance, diversity and taxonomic composition of soil fungal communities using internal transcribed spacer (ITS) marker-based DNA metabarcoding in a 48-year-old trial at Skimikin, British Columbia. A total of 108 samples were collected from FH (fermented and humus layers), and soil mineral horizons (A and B) from stumped and unstumped plots of six tree species treatments (pure stands and admixtures of Douglas-fir, western red-cedar and paper birch). Fungal α-diversity in the A horizon significantly increased with stumping regardless of tree species composition, while β-diversity was significantly affected by stumping in all the horizons. We also observed that the relative abundance of the saprotrophic fungal community declined while that of the ectomycorrhizal fungal community increased with stumping. In conclusion, increase in ectomycorrhizal fungal associations, which are positively associated with tree productivity, suggests that stumping can be considered a good management practice for mitigating root disease and promoting tree regeneration.

Signs of Vertically Extending Mineralization in the Nizhnetaezhny Polymetallic Ore District (Northern Primorye)

In this work, to study the vertical extent of mineralization, determine the level of erosion, and identify signs of longitudinal placement of silver mineralization of the Nizhnetaezhny ore district (NOD) For this, the main indicator indicators Ag, Au, Cu, Zn, Pb were identified based on the maximum correlation coefficient, Sn, Sb, As, Mo. Then, the ratios of the linear productivities of the indicator elements for the main ore zones of the Scientific and Technological Logging were made: Kumirnoe - Sb * Ag * As / Cu * Sn, Kabaniy - Sb * As * Ag / Cu * Sn, SredniySukhoy - Sn * Pb * Zn / Au * As, Levoberezhnoe -Sn * Pb * Zn / W * Mo. The obtained geochemical data of changes in the multiplicative coefficients allowed us to identify areas according to their erosion: weakly eroded (Kumirny, SredniySukhoy) and significantly eroded (Kabany, Levoberezhnoe), and then divide them into upper ore, ore and under ore. At all sites (except for the SredniySukhoy), at the level of the conditionally subsided horizon, a tendency of gradual increase in productivity was revealed, which indicates the long-range placement of productive ore zones and makes it possible to suggest the presence of powerful and productive silver zones hidden at depth. The data obtained provide the prerequisites for the revaluation of the prospects of the deep horizons of the NOD silver mineralization.