Stages Of Pedogenesis Research Articles

Cyclic and linear trajectories of ecosystem evolution on sand dunes in Siberian taiga: A comprehensive analysis

Extensive unforested sandy areas on the margins of floodplains and riverbeds, formed by dunes, barchans, and accumulation berms, are a ubiquitous feature across northern Eurasia and Alaska. These dynamic landscapes, which bear witness to the complex Holocene and modern climatic fluctuations, provide a unique opportunity to study ecosystem evolution. Within this heterogeneous assemblage, active dunes, characterized by their very sparse plant communities, contrast sharply with the surrounding taiga (boreal) forests common for the stabilized dunes. This juxtaposition makes these regions to natural laboratories to study vegetation succession and soil development. Through a comprehensive analysis of climate, geomorphology, vegetation, soil properties, and microbiome composition, we elucidate the intricacies of cyclic and linear ecosystem evolution within a representative sandy area located along the lower Nadym River in Siberia, approximately 100 km south of the Arctic Circle. The shift in the Holocene wind regime and the slow development of vegetation under harsh climatic conditions promoted cyclical ecosystem dynamics that precluded the attainment of a steady state. This cyclical trajectory is exemplified by Arenosols, characterized by extremely sparse vegetation and undifferentiated horizons. Conversely, accelerated vegetation growth within wind-protected enclaves on marginally stabilized soils facilitated sand stabilization and subsequent pedogenesis towards Podzols. Based on soil acidification due to litter input (mainly needles, lichens, and mosses) and the succession of microbial communities, we investigated constraints on carbon and nutrient availability during the initial stages of pedogenesis. In summary, the comprehensive study of initial ecosystem development on sand dunes within taiga forests has facilitated the elucidation of both common phases and spatiotemporal dynamics of vegetation and soil succession. This analysis has further clarified the existence of both cyclic and linear trajectories within the successional processes of ecosystem evolution.

Conceptual Modelling of the Dynamics of Soil Macroporosity Based on an in Situ and Direct Observation of Major Soil Structuring Agents During Early Stage of Pedogenesis

Many factors affect soil porosity but major of them are soil fauna, plant roots and the climate. Many studies attempted to investigate the effect of these factors on the evolution of soil porosity separately. The objective of this study is, based on an in situ experiment including three major porosity factors, propose a conceptual model of soil macroporosity evolution. In situ observation and quantification of the evolution of macroporosity under the influence of each agent separately and the three agents combined allow to propose a model for each case. Results show that the evolution of macroporosity due to plant roots is linear and reachs its maximum at the end of the plant cycle. Earthworms create and destruct macroporosity during the up and down movement for food searching. At long term, the consequence of earthworm action results to an increase of macroporosity. Wetting and drying cycle has the same effect as earthworm. At the beginning, when soil shrinks, it leads to a creation of macroporosity that could be disturbed by swelling during soil humectation. Some soil particles migrate in the shrink and reduce the surface of macroporosity. When faced to many wetting drying cycles, the surface of macropores increase during time. Mathematical algorithms and computing are necessary to formalize this model and long-term experiment is needed to validate it.

Plant-soil feedback across spatiotemporal scales from immediate effects to legacy

Plants and soil biota are important ecosystem engineers interacting via plant-soil feedback on large gradient of temporal scales from immediate interactions to long term legacy, which also operate on various spatial scales. Here I emphasize three major pathways of plant-soil feedbacks: i) the biota pathway, when plants affect soil biota, such as plant symbionts or antagonists, which affect plants, ii) the soil pathway, when plants affect soil environment, which then feedbacks to plants and finally iii) the biota-soil pathway, when plants affect soil biota, which then affect soil environment, which then effect plants. Living plant roots are major driver for biota pathway, which is more important for immediate effect, while litter largely supports the biota-soil pathway important for legacy effects. Many processes that have immediate effects, produce also small but more persistent changes in soil. Legacy is produced by accumulation of this small changes over time. This is supported by soil ability to preserve and accumulate, these small changes. Legacy also alternate outcome of immediate interactions between plants, soil and soil biota. The soil property changes, caused by legacy, happen either as slow gradual changes, or relatively fast, abrupt shifting between two steady states. In both cases, soil changes can reach tipping points, altering functioning of whole plant soil system. Apart from plants, also soil conditions or soil biota can be manipulated either intentionally (e.g. by land uses change, various agriculture, forestry or ecosystem restoration practices), or non-intentionally (e.g. biological invasion), which trigger changes in plant – soil - soil biota interactions as described above and cause immediate and legacy effects. Examples, presented in this review, suggest that legacy effect is particularly important in soils in early stages of pedogenesis or during response to or recovery after disturbance. Review highlight necessity studying plant soil feedback on all relevant spatiotemporal scales.

Assessment of soil aggregate pore structure after 8 years of cultivation from the parent material of a Mollisol

Soil erosion exposes the underlying parent material (PM) to the surface and an appropriate soil restoration approach is required to maintain soil quality. However, the current knowledge on soil restoration (e.g., improvement of soil aggregate structure) is mainly obtained from studies on well-developed soils. It remains unclear how aggregate pore structure of soils can be improved following different agricultural practices during the early stage of pedogenesis. The present study quantified the effects of 8 years of different agricultural practices (land use types, mineral fertilizers, and different amounts of organic inputs) on the aggregate stability, aggregate pore morphology, and surface properties of a topsoil (0–20 cm) and compared the findings with those of a prior PM and a long-cultivated Mollisol (MO). The results showed that clay content and the specific surface area of soil aggregates decreased, while soil organic carbon, aggregate stability, and surface fragment structure increased for all treatments as compared to those for the PM. Mineral fertilization alone did not increase aggregate stability; however, the combination of mineral and organic fertilization increased aggregate stability by 117%. Compared to the PM, the treated soils showed an increase in porosity as determined by synchrotron radiation X-ray micro-computed tomography (SR-µCT). Compared to naturally restored grasslands, the soil under crop rotation with tillage showed a decrease in pore roundness by 15%; however, supplementation with a large amount of organic input during cultivation increased pore roundness. The principal component analysis using all the indicators showed that the soil structure after 8-year cultivation was not comparable to that of the well-developed MO. Our results revealed the development of PM structure under various agricultural practices and highlighted the co-interaction effects of mineral fertilizers and organic inputs on the properties of soil aggregates during the early stage of pedogenesis.

Differentiation of fine-textured podzolic soils controlled by climate and landscape in Taiwan

Podzolization is considered to be facilitated by factors such as cool and humid climate, sufficient supply of certain types of organic acids, and coarse-textured parent materials. However, podzolic soils in subalpine areas in Taiwan are characterized by clay content higher than 30%, which differed from that in typical podzolic soils in temperate and boreal regions. This study examined the importance of factors controlling the differentiation of fine-textured podzolic soils in Taiwan. Samples from 31 pedons were examined in this study, and the pedons were grouped into four types, namely Spodosols, Ultisols, Inceptisols, and Inceptisols with placic horizons. Soil colors with 7.5YR 5/6 (the accumulation of spodic materials) and micromorphological observation of oriented clay coatings in the Spodosols confirmed the occurrence of podzolization and clay illuviation, and the selective extraction of Fe and Al confirmed that the Spodosols (Type I) had a higher accumulation of organometallic complexes than the other podzolic soils. A two-step mechanism, namely (1) clay illuviation at an early stage of pedogenesis and (2) podzolization after the canopy vegetation formed, was proposed for the formation of fine-textured Spodosols. Photomicrographs of the Ultisols (Type II) displayed clay hypocoatings masked by spodic materials, and argillic horizons were characterized by a high amount of nanocrystalline iron and high optical density of the oxalate extract. However, the accumulated nanocrystalline iron oxides in the Ultisols were due to the degradation of organic matter under high summer temperatures. Moreover, the leaching of iron in the albic horizons of the Ultisols was attributed to episaturation caused by high clay contents. The Inceptisols (Type III) were transitional soils before forming the Spodosols or the Ultisols, and high clay contents further induced episaturation and formed placic horizons in the Inceptisols (Type IV). Principal component analysis revealed that soil texture and precipitation were the main factors controlling the differentiation of podzolic soils in Taiwan. These factors determined the penetrability and leaching potential of soils, and only the coarse-textured soils with higher leaching potential had the chance of developing Spodosols. However, the developments of Ultisols and Inceptisols with placic horizons were controlled by air temperature and landscape, namely elevation and slope. The bleached E horizons in podzolic Ultisols were attributed to their flat landscape, which favored episaturation and caused the reduction of iron. Low elevation and high temperature in these regions also facilitated the degradation of organic matter and the accumulation of nanominerals.

Microorganisms drive stabilization and accumulation of organic phosphorus: An incubation experiment

At the earliest stage of pedogenesis, microorganisms are the main biological drivers of nutrient transformation and mobilization from rock minerals. However, this driving process is not yet well understood despite its importance for the formation and fertility of soil. The aim of this study was to determine the microbial accumulation of organic phosphorus (Po) and microbial release of bioavailable phosphorus (bio-P) from rock minerals and to analyse which factors control these processes. We hypothesized that microorganisms contribute to stabilization and accumulation of Po. For this purpose, we carried out a series of incubation experiments with model soils (with soil Po removed) and soil extracts of natural soil from the earliest stage of pedogenesis in the newest retreat area of the Hailuogou glacier. A modified Hedley fractionation method was used to characterize the P forms in soils. Microbial synthesis of Po was clearly observed in this study. In view of the fact that carbon (C) and nitrogen (N) are the main energy and material sources of microorganisms and that their stoichiometry plays an important role in microbial metabolism, we hypothesized that the C and N (ratio and level) play a regulatory role in microbial transformation of P. Therefore, the different C/N gradients were constructed in our incubation experiments. Results showed addition of C and N resulted in an accumulation of stable Po and decrease in pH in soils. These results suggest that not all microbial biomass P is easily degraded. Along two C/N ratio gradients (same ratio but keeping C vs N constant), opposite patterns of total Po (TPo) changes was observed. Opposite patterns were also observed for bio-P along the two C/N ratio gradients. Regardless of the C/N ratio, high CN additions always led to lower TPo accumulations, higher bio-P releases and higher phosphatase activity compared to low CN additions. We conclude that microbial synthesis of Po contributed to the P fractions in soil stable residual pools and that microbial release of bioavailable P was driven by two modes (i.e., N-driven mode and C-driven mode). Our study highlights that microorganisms drive the accumulation of soil Po during the earliest stage of pedogenesis in our study area.

Pedogenesis shapes predator-prey relationships within soil microbiomes

Pedogenesis determines soil physicochemical properties and many biodiversity facets, including belowground microbial bacteria and fungi. At the local scale, top-down predation by microbial protists regulates the soil microbiome, while the microbiome also affects protistan communities. However, it remains unknown how pedogenesis affects protistan communities and the potential protist-microbiome predator-prey relationships. With 435 soil samples representing different stages of pedogenesis ranging in soil age from centuries to millennia, we examined the influence of pedogenesis on the main protistan groups, and the interrelationships between protistan predators and microbial prey biomass. We revealed an enrichment in the diversity of total protists across pedogenesis and increasing richness of phototrophic protists in the medium compared with the early stages of pedogenesis. The richness of predatory protists accumulated throughout pedogenesis, which was more strongly determined by microbial biomass than environmental factors. Predator-prey associations were stronger in the young and the medium soils than in the older soils, likely because prey biomass accumulated in the latter and might be no longer limit predators. Together, our work provides evidence that pedogenesis shapes predatory protists differently than their prey, leading to shifts in predator-prey relationships. This knowledge is critical to better understand how soil food webs develop across soil development which might lead to changes in ecosystem functions.

Soil phosphorus status and P nutrition strategies of European beech forests on carbonate compared to silicate parent material

Sustainable forest management requires understanding of ecosystem phosphorus (P) cycling. Lang et al. (2017) [Biogeochemistry,https://doi.org/10.1007/s10533-017-0375-0] introduced the concept of P-acquiring vs. P-recycling nutrition strategies for European beech (Fagus sylvatica L.) forests on silicate parent material, and demonstrated a change from P-acquiring to P-recycling nutrition from P-rich to P-poor sites. The present study extends this silicate rock-based assessment to forest sites with soils formed from carbonate bedrock. For all sites, it presents a large set of general soil and bedrock chemistry data. It thoroughly describes the soil P status and generates a comprehensive concept on forest ecosystem P nutrition covering the majority of Central European forest soils. For this purpose, an Ecosystem P Nutrition Index (ENIP) was developed, which enabled the comparison of forest P nutrition strategies at the carbonate sites in our study among each other and also with those of the silicate sites investigated by Lang et al. (2017). The P status of forest soils on carbonate substrates was characterized by low soil P stocks and a large fraction of organic Ca-bound P (probably largely Ca phytate) during early stages of pedogenesis. Soil P stocks, particularly those in the mineral soil and of inorganic P forms, including Al- and Fe-bound P, became more abundant with progressing pedogenesis and accumulation of carbonate rock dissolution residue. Phosphorus-rich impure, silicate-enriched carbonate bedrock promoted the accumulation of dissolution residue and supported larger soil P stocks, mainly bound to Fe and Al minerals. In carbonate-derived soils, only low P amounts were bioavailable during early stages of pedogenesis, and, similar to P-poor silicate sites, P nutrition of beech forests depended on tight (re)cycling of P bound in forest floor soil organic matter (SOM). In contrast to P-poor silicate sites, where the ecosystem P nutrition strategy is direct biotic recycling of SOM-bound organic P, recycling during early stages of pedogenesis on carbonate substrates also involves the dissolution of stable Ca-Porg precipitates formed from phosphate released during SOM decomposition. In contrast to silicate sites, progressing pedogenesis and accumulation of P-enriched carbonate bedrock dissolution residue at the carbonate sites promote again P-acquiring mechanisms for ecosystem P nutrition.

Phosphorus dynamics during early soil development in a cold desert: insights from oxygen isotopes in phosphate

Abstract. At the early stages of pedogenesis, the dynamics of phosphorus (P) in soils are controlled by microbial communities, the physicochemical properties of the soil and the environmental conditions. While various microorganisms involved in carrying out biogeochemical processes have been identified, little is known about the actual contribution of microbial processes, such as organic P hydrolysis and microbial P turnover, to P cycling. We thus focused on processes driven by microbes and how they affect the size and cycling of organic and inorganic soil P pools along a soil chronosequence in the Chamser Kangri glacier forefield (Western Himalayas). The rapid retreat of the glacier allowed us to study the early stages of soil formation under a cold arid climate. Biological P transformations were studied with the help of the isotopic composition of oxygen (O) in phosphate (δ18OP) coupled to sequential P fractionation performed on soil samples (0–5 cm depth) from four sites of different age spanning 0 to 100–150 years. The P bound to Ca, i.e., 1 M HCl-extractable P, still represented 95 % of the total P stock after approximately 100 years of soil development. Its isotopic composition was similar to the parent material at the most developed site. Primary phosphate minerals, possibly apatite, mostly comprised this pool. The δ18OP of the available P and the NaOH-extractable inorganic P instead differed from that of the parent material, suggesting that these pools underwent biological turnover. The δ18OP of the available P was mostly controlled by the microbial P, suggesting fast exchanges occurred between these two pools possibly fostered by repeated freezing–thawing and drying–rewetting cycles. The release of P from organic P becomes increasingly important with soil age, constituting one-third of the P flux to available P at the oldest site. Accordingly, the lighter isotopic composition of the P bound to Fe and Al oxides at the oldest site indicated that this pool contained phosphate released by organic P mineralization. Compared to previous studies on early pedogenesis under alpine or cold climate, our findings suggest a much slower decrease of the P-bearing primary minerals during the first 100 years of soil development under extreme conditions. However, they provide evidence that, by driving short-term P dynamics, microbes play an important role in controlling the redistribution of primary P into inorganic and organic soil P pools.

PHASING FEATURES OF THE SOIL-FORMING PROCESS IN AGROCHERNOZEMS OF WATERSHED PLATEU IN THE CENTRAL PART OF PODILLIA

The development of the paleosoils during the warm stages (thermochrons) of the Pliocene and Pleistocene, being reflected in the structure of soil-loess and red-brown formations of Ukraine, is characterized by a clear regularity. This is manifested in the formation of complex soil layered constructions (pedocomplexes) reflecting the chronological stages of pedogenesis. Agrochernozems of watershed plateu in the central part of Podillia, formed on the loess rocks of the Late Pleistocene age, also show this general regularity of Pliocene-Pleistocene soil formation. Contrasting changes in the physic-geographical conditions of pedolitogenesis in the ancient Holocene (late glacial) and evolutionary trend of soil formation during the following Holocene periods lasting for 10–8 thousand years led to the formation of a two-stage Holocene soil layering on the plakor lands of the region, represented by chernozem-type soils. Morphological signs of staged soil formation are concentrated in one genetic profile, which, along with the sign of anthropization of landscapes and soil formation significantly complicates the detailed identification of soils and their historical and genetic analysis. The early stage of the local soil formation history is recorded in these soils in the form of solid-phase products of soil-forming processes (puppets, soil wormholes, coprolites, moles drains). These relict pedogenic formations are located in the lower part of the soil profile of agrochernozems. In general, in the soil profile of agrochernozems on the watershed plateu in the central part of Podillia the morphologically hidden stages of soil formation are noticeable, which is typical of the first half of the Holocene thermochron. The soil of the initial stage of pedogenesis correlates with the horizon of the mole loess P(h)k and the lower part of the transitional brown-colour horizon Phk or PhI. The humus profile of the plakor agrochernozems has soil characteristics of the early optimal stage, which lasted for 7–8 thousand years from the preboreal to the late subatlantic. There are no pedogenic signs of other stages of development of the pedocomplex. So, modern day soils of this region (agrochernozems) are polygenetic two-stage formations that have not reached the status of full-fledged pedocomplex. Key words: evolution; pedogenesis; agrochernozem; Holocene; stages of soil formation; pedocomplex; Podillіa.

Structural organization and composition peculiarities of soil neoformations in some types of automorphic soils in the southeast of the Bolshezemelskaya tundra

Automorphic tundra soils of different gleying degree and various permafrost table depth were studied. The chemical composition and distribution of different structural components, including skeletans (sandy-silty cutans), clay cutans, and Fe-Mn concretions in Dystric Cambisol and Turbic Cryosol profiles (permafrost table occurs 2–5 m and 0.9 m depth) were investigated. It is shown that the upper part of the profile of Dystric Cambisol forms under the current active processes of pedogenesis (gleying, Al-Fe-humus illuviation, specific cryogenic organization), signs of previous stages of soil genesis are preserved (the presence of humus pedorelicts, fragments of clay deposits) in the lower part. The chemical composition of the intraped mass reflects the eluvial-illuvial differentiation of Dystric Cambisol profile. The maximum amount of Fe-Mn concretions is observed in the middle profile part. This is due to redox processes in this type of soil. Turbic Cryosols is characterized by insignificant profile differentiation of structural components by chemical composition, weak intensity of pedogenic processes, cryoturbations, inherited signs of earlier stages of pedogenesis (fragments of clay cutans, humus pedorelicts) in the lower horizons. Gleying is one of the leading soil-forming processes. Cryogenic transformation of the soil layer affects the distribution of small amount of skeletans and concretions.

Pedocomplex buried under the Cabin of Peter the Great in St. Petersburg (1703): Genesis, properties and paleoenvironmental inferences

A study was conducted on the buried soils identified at the base of the foundation of the Cabin of Peter the Great in Saint Petersburg, Russia, to help trace the Late Holocene landscape evolution in the lower reaches of the Neva River. The Cabin is a small wooden house, which was the first residence of Peter the Great in a newly emerged Saint-Petersburg. The house was built of pine logs on the Neva River's right bank. The time of its construction is now regarded as the city's founding date (1703). The pedocomplex with two buried soils has not been truncated and retains a record of the depositional environment, pedogenesis, vegetation history, and human activity before the construction of the city of Saint Petersburg. This pedocomplex was studied using various field and laboratory methods including soil morphology at macro-, meso-, and microlevels, and a full set of microbiomorphic analyses (diatoms, pollen, spores, phytoliths, plant detritus, and amorphous organic matter) supported by radiocarbon dating. The sediment sequence was formed in a contrasting depositional environment. The microbiomorphic studies indicated that the initial substrate was formed in aquatic environments. The analysis of diatoms suggested that these sediments were accumulated as a result of the River Neva breakthrough from Lake Ladoga to the Gulf of Finland ca 3500 yrs BP, which provided additional evidence for the River Neva formation. Soil analyses revealed two inundation events, with the earlier flood related to the termination of the Lake Ladoga transgression (LT) and the breakthrough of the Neva River, whereas the latter flood was likely to be connected with an increase of the fluvial activity. Those two inundation events were followed by two stages of pedogenesis. Both soils indicated the hiatus in sedimentation and were represented by Subquatic Umbric Gleysols that were the most widespread indigenous soils in the XVII century. The pollen data suggest that human impact started at ca 800 yrs BP and eventually resulted in the deforestation and the initial agricultural exploration of the study area. Saint Petersburg is the only large city in Russia that could be at risk from flooding if the sea level rises due to continuing global warming. Our research shows that the city's historical center was twice subjected to flooding in the Late Holocene, even without rises in the sea level. Therefore, the detailed analysis of the environmental dynamics within the Lower Neva area and the assessment of its possible consequences for the city are of great importance.

Geochemical and mineralogical composition of the 2018 volcanic deposits of Mt. Anak Krakatau

Mount Anak Krakatau erupted on 22nd December 2018, resulting in a large deposit of fresh volcanoclastic materials on the island's surface. As the age of these new soil materials is known precisely, and the island is isolated from human activities, studying the ash and pyroclastic materials of Anak Krakatau will provide insights on the first stages of pedogenesis in tropical volcanic regions. This paper reports for the first time the chemical and geochemical characteristics of the fresh volcanic materials of Mt. Anak Krakatau. Samples were collected at 63 days and 82 days after the eruption. Remobilization of newly deposit volcanic materials occurred immediately after the eruption. Rill and gully erosion were observed on the surface of the island. Two types of samples were collected and analysed: volcanic ash (< 2 mm) and lapilli (2–64 mm). The pHH2O of the samples had a mean value of 5.9 (std. dev. 0.6). The CEC of the materials was very low but variable (3.11 ± 2.3 cmolc kg−1) and the cations were easily leached (Mg > Ca > K > Na). Microscopic analysis and XRD patterns showed that the materials were dominated by plagioclases, with labradorite being the dominant species. XRF analysis indicated that there were two types of volcanic materials: the first group had lower SiO2 concentration (mean 39%) and lower Al2O3 (mean 10%) but a higher concentration of Fe2O3 (mean 18.9%), CaO (15.6%), K2O (1.7%), SO4 (2.9%), P2O5 (2.8%), and heavier elements (Mn, Zn, Cu, Ti, Sr, Zr, Cr) and Ag2O (0.76%). The second group was more common with basaltic-andesitic composition with a mean concentration of 54.9% SiO2, 17.2% Al2O3, and 8.5% Fe2O3. Anak Krakatau eruptions and volcanic deposits are rare events; basic information provided in this report offers valuable information on the initial stage of pedogenesis and can be used as a baseline for future pedogenesis study.

Lichens Bite the Dust - A Bioweathering Scenario in the Atacama Desert.

SummaryBioweathering mediated by microorganisms plays a significant role in biogeochemical cycles on global scales over geological timescales. Single processes induced by specific taxa have been described but could rarely be demonstrated for complex communities that dominate whole landscapes. The recently discovered grit crust of the coastal Atacama Desert, which is a transitional community between a cryptogamic ground cover and a rock-bound lithic assemblage, offers the unique chance to elucidate various bioweathering processes that occur simultaneously. Here, we present a bioweathering scenario of this biocenosis including processes such as penetration of the lithomatrix, microbial responses to wet-dry cycles, alkalinolysis, enzyme activity, and mineral re-localization. Frequently occurring fog, for example, led to a volume increase of microorganisms and the lithomatrix. This, together with pH shifts and dust accumulation, consequently results in biophysical breakdown and the formation of a terrestrial protopedon, an initial stage of pedogenesis fueled by the grit crust.

Time since deglaciation and geomorphological disturbances determine the patterns of geochemical, mineralogical and microbial successions in an Icelandic foreland

Glacier forelands are an ideal natural laboratory to study the initial stages of pedogenesis. Here, we document a build-up in organic carbon (C), nitrogen (N) and phosphorous (P), an increase in bacterial communities as well as a progression of physical and chemical weathering along a ~2 km long and 122 yr old chronosequence in the glacier foreland of Fláajökull in south-eastern Iceland. We complemented this chronosequence dataset with an assessment of the variability in soils that were affected by geomorphological disturbances along a 175-m long toposequence transect. While soils at the crest of the toposequence moraines were anomalously under-developed due to frequent erosion, the soils at the footslopes were characterized by a more advanced successional stage in that they benefited from an ample supply of nutrients, fine and more weathered materials as well as higher moisture. The large variability in soil properties across the toposequence demonstrates that, even across short distances, disturbances driven by hillslope and glacio-fluvial processes can lead to substantial heterogeneities in soil development in glacier forelands. We emphasize that the geochemical and biological features of soil development and patterns of succession in glacier forelands should be interpreted as the result of both changes in time since deglaciation and geomorphological disturbances.

Changes in the Soil-Plant Cover of the High Arctic of Eastern Siberia

Investigations of changes in the soil and plant covers is necessary when designing technical objects—gas and oil pipelines, highways, and power lines—in order to avoid the adverse effects of these activities and to preserve vulnerable northern ecosystems. Recent changes in the soil–plant cover of the High Arctic of Eastern Siberia are directed towards its higher complexity. Chaotic bare stone debris evolve into stony polygons with “soil embryos” and patchy vegetation. Recently deglaciated areas are locally overgrown with plants on weakly developed soils of the initial stage of pedogenesis and then evolve towards the stage of mosaic plant cover with tonguing (glossic) soils. At the next stage, soil–plant complexes are formed with a continuous plant cover on soddy arctic soils. Melt water of glaciers and snow fields saturate the sediments and may induce their textural differentiation. Soil and plant cover changes in the areas with ice wedges have their own specificity. Ice wedges are typical of floodplains, where they form tetragonal complexes of moss or moss–grass tundra with gleyzems and peat soils on tops of the wedges. After the cessation of floods, ice wedges tend to degrade, and small lakes are formed in their places. Bogged tetragons are replaced by the mesophilic forb–grass tundra with gleyic soils. Under conditions of good drainage, this stage is followed by the stage of baydzharakh terrain. When the baydzharakhs are destroyed, a hummocky grass–forb tundra with soddy tundra soils appears.

Changes of Technosol properties and vegetation structure along a chronosequence of dredged sediment deposition in areas with alluvial gold mining in Colombia

PurposeAlluvial gold mining leaves a vast amount of dredged sediment that covers the natural soil, destroys riparian ecosystems, and impacts riverbeds and valleys. In Colombia, more than 80,000 ha are covered by dredged sediment. Technosols developed from such deposits undergo strong transformations during the early stages of formation due to the diverse nature of the constituents. The aims of this study are (i) to investigate changes in soil morphological and physicochemical properties at early stages of pedogenesis, (ii) to estimate the variability of size structure distribution of the new plant cover as affected by the time period since establishment and deposit type, and (iii) to determine which soil parameters correlate best with the size structure distribution of vegetation.Materials and methodsSoil characterization through morphological and physicochemical analysis was conducted on Technosols developed from gravel and sandy deposits of different ages (0–12 years). A vegetation survey was conducted to measure tree dimensions and identify the most common species. Data were analyzed using non-parametric tests to avoid the loss of information due to data smoothing.Results and discussionThe studied Technosols are subject to processes similar to those occurring in natural parent materials such as mineral transformations, changes in redox conditions, organic matter accumulation in the topsoil, and a rapid differentiation of horizons. However, the Technosols in our study sites show an unusually fast development not often observed in natural soils, with drastic changes observed at very early stages of formation. Gravel deposits offer more favorable conditions for plant growth, and marked changes in pedogenic processes can be observed compared with sandy deposits, which are reflected in changes of chemical properties.ConclusionsFactors such as the technology used for mining and the continuous deposition of dredged sediments in a cumulative way during the exploitation period, as well as the disturbances after deposition, result in a high diversity of constituents and high heterogeneity of dredged sediment deposits. Gravel and sand deposits, originated from the same sections of the river and after similar separation processes for ore extraction, undergo divergent pedogenic processes at different rates, which could be explained by a remarkable effect of particle size distribution. For vegetation establishment, the selection of tree species should be based on their capacity for nutrient pumping through deep rooting to sequester carbon and to adapt morphologically to heterogeneity in nutrient availability by growing roots in nutrient-rich zones.

Taxonomic diversity of bacterial assemblage in technosol of the revegetating fly ash dump

Background. The aim of the study was to assess the composition and structure of bacterial assemblages by estimating 16S rRNA gene sequences diversity in a young Technosol, developing on a revegetating fly ash dump. Location and place of the study. Two soils were chosen for the study in the environs of the thermoelectric power station No.5 in Novosibirsk region: 1) nine years old Technosol (54°59' NL, 83°03' EL), developing on the spontaneously revegetating fly ash dump, and 2) Phaeozem under undisturbed white birch forest (55°00' NL, 83°04' EL). Soils were sampled from the 0-5 cm layer as three individual replicates each. Materials and methods. The total DNA extracted from soil samples was used as a matrix for PCR amplification using V-3-V4 primers for 16S rRNA genes. The obtained amplicons were sequenced on Illumina MiSeq platform in the Genomics Core Facility of the Institute of Chemical Biology and Fundamental Medicine SB RAS (Novosibirsk, Russia). Descriptive statistics and principal components analysis were used to analyze and present the data. Results. Overall 4887 different operational taxonomic units (OTUs) were found at the 97% similarity level; the OTUs were ascribed to 306 genera, 212 families, 123 orders, 84 classes and 32 phyla of bacteria domain. At the phylum level bacterial assemblages in both soils were dominated by Proteobacteria, Acidobacteria and Actinobacteria, showing rather similar outline of the phyla relative abundance, confirming the direction of pedogenesis towards Phaeozem. Higher abundance of Chloroflexi a physiologically diverse phyla with aerobic and anaerobic thermophiles, anoxigenic phototrophs and anaerobes, able to respire organic halides, in the young Technosol complies with harsh edaphic conditions there. Although the relative abundance of Rhizobiales, Actinomycetales and unclassified Acidobacteria_Gp6 and Acidobacteria_Gp3 was found to be 1.5–2.4 times higher in the undisturbed Phaeozem, they also were predominating in the Technosol samples. The α-biodiversity indices, pertaining mostly to species/OTUs richness, i.e. Chao-1, OTUs number, Margalef, Fisher’s alpha, were higher in Phaeozem, whereas evenness and equitability were higher in Technosol. Both soils demonstrated similar Shanno indices, which were rather high (6.3). Conclusions. Nine years of spontaneous revegetation on the terminated fly ash dump of the thermoelectric power station resulted in the development of the Technosol, containing quite rich and diverse bacterial assemblage, which was rather close in structure at the phylum taxonomic level to the adjacent undisturbed Phaeozem. Overall the early stages of pedogenesis were dominated by specific bacterial assemblage (Chloroflexi, Xanthomonadales, Geobacter, Aciditerrimonas, Iamiaceae and some others), performing weathering of the pedogenic substrate, i.e. fly ash. The present of nitrificators (Nitrospira), denitrificators денитрификаторов (Reyranella) together with diazotrophs (Bradyrhizobium, Rhizobiales) dominance evidences the establishment of the entire network of nitrogen transformation process already at the early stages of revegetation of the fly ash dump. Large percentage (17%) of Bacteria, the information about which ribosomal gene sequences is most likely absent in the respective data bases necessitates more detailed research into the soil microbiome on fly ash dumps.

Carbonate Profile of Soils in the Baikal Region: Structure, Age, and Formation Conditions

The results of the study of the carbonate profiles of soils in the western (Cis-Baikal) and eastern (the Selenga middle mountains) Baikal region are presented. There is a similarity in their structure: numerous CaCO3 maxima in the soil profiles are typical, which is associated with the repeated redistribution of carbonates during different stages of pedogenesis. The carbonate profile of soils in the Baikal region is relatively ancient (the youngest accumulations date back to the Middle Holocene) and a rather conservative formation that does not undergo any noticeable rearrangements under modern climatic conditions. The accumulations of secondary carbonates are localized in the carbonate-accumulative horizons of the modern surface soils and buried Kargin (MIS-3) soils and Holocene soils. The exception is hypocoatings that are often found beyond the indicated horizons, which is associated with a more active redistribution of carbonates within the root system of vegetation. The solid-phase effect of carbonatization (carbonate neoformations) is observed in the study area mainly in the soils formed on calcareous rocks and products of their redeposition and does not depend on the type of soil and the nature of the growing vegetation. Based on the analysis of the composition of stable carbon and oxygen isotopes in secondary carbonate accumulations, it was found that carbonate precipitation in soils of the Cis-Baikal region occurs during the degassing of soil solutions in the course of freezing–thawing cycles, dynamic increase and decrease in the soil biological activity, and alternation of the soil moistening with snowmelt and rainwater with its subsequent freezing that can take place in spring and autumn seasons. Under these conditions, atmospheric CO2 has the main influence on the isotopic composition of carbon in pedogenic carbonates; the isotopic composition of oxygen is controlled by the fractionation of isotopes upon freezing of the soil solutions. Secondary carbonate accumulations in the Selenga middle mountains are formed during the soil drying as a result of active water consumption for plant transpiration, which is most pronounced in the first half of summer.

P.865 Structural alterations in the major brain networks in korean adolescents with sleep problems from the general population

The ‘catena concept’, along with previously proposed meanings of this term, has recently acquired a soil evolutionary content. The prospects of wider special and chronological study of dated pedotopocatenas include the possibility of a more detailed analysis of the mutual dependence of soil-geomorphological relationships through distinguishing relatively homogeneous climatic stages of pedogenesis and denudation. With this purpose, the present study comprised earthen defensive constructions, which, within the ‘rampart/ditch’ system, combine erosive, trans-accumulative catenas and accumulators of pedolithosediments. The goal was to develop a system of the most information-rich pedogenetic indicators to reconstruct the dynamics of erosion-accumulative processes on the basis of dated earthen defensive constructions of a historical period (using the example of a frontier rampart within a ditch from the mid-17th century). Soil samples were collected within the limits of the erosion and trans-accumulative catenas, as well as in the closing alignment of the ditch (over the vertical profile in eight strata of pedosediments of up to 1 m high). The granulometric composition, concentration of macroelements and trace elements (25 metals and oxides) in soils and in particles with sizes <1 mm, and the fractional composition of the humus were analysed in soil samples taken from different points in the catena and along the profile of the pedosediments. For the reconstruction of the humidity conditions over 3.5 centuries based on dendrochronological data, the cross-relation approach was applied. This allowed us to represent the chronostratigraphy of pedosediments as stages differing in the rate of accumulation processes. The system of soil indicators in pedosediments including the percentage of particles 0.001–0.005 mm and >0.01 mm in size, the content of organic carbon and its qualitative composition, the sum of the elements accumulated in the soil (P, Ca, K, Mg, Mn, Cu), as well as the geochemical ratios which reflect the processes of leaching, can serve as palaeogeographic tracers of the climatic variability at the level of intra-secular changes under forest-steppe conditions. The history of the formation of pedosediments over 3.5 centuries in the forest-steppe zone of Eastern Europe comprises two wet periods (1890–1935, 1976–2013) when the average annual rates of pedosedimentogenesis were similar (2.80–2.85 mm yr−1) and two periods of geomorphological ‘lull’ and a xeromorphic climatic condition span (1821–1890 and 1666–1741). These periods correspond to diminution of the average rate of accumulation of sediments down to 2.47 mm yr−1. The results of the present study suggest the need for purposeful research and wide inclusion of dated sites of the anthropogenic relief formation with flow-geochemical series over the topographic gradient into studies of soil–geomorphologic interrelations and calibration of mathematic models of natural processes using on-site data.