Органопедогенез – незамеченный базовый процесс почвообразования

Effect of bacterial cell addition on Fe(III) reduction and soil organic matter transformation in a farmland soil

Peat organic soils play a major role in the accumulation of soil organic matter (SOM) and the mercury (Hg) cycle. Large mercury resources in peatlands can be a source of methylmercury for many decades and centuries, even if deposition is significantly reduced. The organic matter of peatland soils drained for agricultural use is subject to secondary transformation, which may affect the accumulation and resources of mercury. The aim of our work is to assess the secondary transformation of organic matter in the soils of drained peatlands of the temperate climate zone and to examine whether it affects mercury resources and profile distribution in organic soils. Field research was conducted in peatlands located in eastern Poland. In the present study, evaluation of secondary transformations occurring after drainage was based on observations of soil morphological characteristics, physical and chemical properties as well as fractional composition of organic matter of the identified soil horizons (to depth 70 cm). Standard cold vapor atomic absorption spectrometry (CV-AAS) was used to measure the total mercury content. In our research, we found a significant effect of the secondary transformation of organic matter occurring in drained peatlands of the temperate climate zone on the total mercury content and stock in soils. The highest content and differentiation of mercury occurred in murshic horizons (up to a maximum depth of 43 cm). The average mercury content of the distinguished soil horizons is grouped in the following series (in μg kg−1): M1 (212.0) > M2 (182.8) > M3 (126.3) > Pt (84.9). The mercury stock, up to a depth of 70 cm in the tested soils, ranged from 17.5 to 39.6 mg m−2. As much as 82.2% of soil mercury was found in the upper murshic horizons. We found strong correlations between soil properties characteristically variable in the secondary transformation process and total mercury content. The increased content of humic substances in murshic horizons caused a significant increase in the total mercury content. Our research is of great importance for soil monitoring, as the amount of determined mercury was greatly influenced by the depth of sampling (up to 25 cm). The results of the research should be taken into account when planning the restoration of peatlands of the temperate climate zone. There is a potential risk that elevated mercury concentrations in the upper murshic horizons may be a source of methylmercury for a long period of time. In peat soils with a high concentration of mercury, the risk of contamination with this toxic metal should be determined before re-irrigation.

Dissolved organic carbon (DOC) is a major controlling factor in soil formation (Dawson et al. 1978), mineral weathering (Raulund–Rasmussen et al. 1998), nutrient cycling, microbial activity, and organic matter decomposition and transformation in soils (Magill and Aber 2000; Williams et al. 2000). The sorption of DOC is the dominant factor in DOC concentration in soil solutions, transport and transformation and the microbial availability of DOC. It is not only the major control for organic matter (OM) and OM–assisted transport (Kaiser and Zech 1999); it also contributes to the stabilization and accumulation of organic matter in soils (Guggenberger and Kaiser 2003).KeywordsSorption CapacityDissolve Organic Carbon ConcentrationThaw CycleWetland SoilHigh Organic Matter ContentThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Soil organic matter (SOM) transformation processes are regulated by the activities of plants, microbes, and fauna. Compared with plants and microbes, effects of soil fauna are less understood because of their high taxonomic and functional diversity, and mix of direct and indirect effect mechanisms. Trait‐based approaches offer a generic perspective to quantify mechanistic relationships between soil fauna and SOM transformations, including decomposition, translocation, and stabilisation of organic carbon. Yet, at present, we lack a consensus concerning relevant key effect traits of soil fauna (i.e. those affecting ecosystem functioning). Here, we address this knowledge gap by focusing on relationships between soil fauna effect traits and SOM transformations. Based on existing literature, we identify key processes linked to SOM transformations, and fauna effect traits universally applicable across taxa and soil types, and discuss the process‐trait links. We define eight SOM transformation processes that are directly affected by soil fauna: (i) litter mass loss, (ii) litter fragmentation, (iii) SOM aggregation in faeces, (iv) SOM aggregation in soil mineral particles, (v) decomposition of faeces, (vi) SOM and mineral translocation, (vii) pore space creation and maintenance and (viii) SOM stabilisation. We link these processes to general effect traits classified into four categories: (a) food selection and ingestion, (b), digestion and excretion, (c) mobility, and (d) body mass and metabolic rate. We also propose proxies when effect trait measurements are laborious. The proposed links between effect traits and SOM transformation processes need to be validated in targeted experiments. We urge researchers to obtain quantitative experimental data, together with metabolic approaches, to integratively quantify soil fauna contributions to soil functioning. Read the free Plain Language Summary for this article on the Journal blog.

Dimeric and monomeric laccases of soil-stabilizing lichen Solorina crocea: Purification, properties and reactions with humic acids

Given that microbial mediated input of crop residues and their humification products may be more conducive to the transformation and sequestration of soil organic matter. The study aims to use 13C15N double labeling tracing technology in incubation experiments to quantify the differences in the fate and distribution contribution of the C and N of crop residues and their decomposition products under the mediation of different exogenous microorganisms with different life strategies in soil organic matter (SOM) and dissolved organic matter (DOM). The study utilized exogenous microorganisms, such as Trichoderma reesei, Trichoderma harzianum, and Phanerochaete chrysosporium (K-strategists), as well as Bacillus subtilis (r-strategist). Additionally, a combination microbial treatment comprised of Trichoderma harzianum, Phanerochaete chrysosporium, and Bacillus subtilis was also employed. The study also aims to reveal the variation patterns of soil active organic carbon and humic carbon components in response to different exogenous microorganisms. The main conclusions of the study are as follows:The addition of exogenous k-strategy microorganisms was more favorable than r-strategy microorganisms in mediating the increase in soil SOM contribution of crop residues derived C and N.Trichoderma treatments were more adept at mediating crop residues derived dissolvd organic carbon, and k-strategy microorganisms were more likely to stimulate soil production of dissolved nitrogen. Although the combination microbial treatment was the most effective at translational immobilization of crop residues in SOM, the Trichoderma reesei treatment had the best ability to increase soil organic carbon content by mediating crop residues translational immobilization with the lowest depletion of SOM. In addition, the addition of K-strategy microorganisms was more effective than r-strategy microorganisms in increasing the content of labile organic carbon and humic carbon fractions in the soil. Fungimediated humification products was significantly better than bacterial and no microbe mediated for translational immobilization in soil, and the fungal treatments contributed more to DOM and stimulated soil deriving dissolved nitrogen. The Trichoderma reesei treatment was the most effective in immobilizing the carbon and nitrogen dereived from humification products. Fungi mediated humification products was superior to bacteria in boosting labile organic carbon and humic acid fractions. The Trichoderma reesei treatment was the most effective in boosting contents of easily oxidizable organic carbon, microbial biomass carbon and humic acid carbon, whereas the combination microbial treatments significantly increased fvlic acid carbon and substantially reduced PQ values in the early part of the experiment, and the three fungal treatments were effective in increasing fvlic acid carbon in the later part of the experiment. In summary, these conclusions provide a theoretical basis for seeking suitable microbial regulation of farmland management measures to improve SOM transformation and humification effects and provide practical reference for scientifically guiding agricultural production and soil carbon sequestration and fertilization.

Fungi play an important role in the accumulation and transformation of soil organic matter (SOM) and nutrient cycling. To investigate the relationship between the fungal community and soil organic carbon functional groups under gradient SOM contents in arable mollisols, arable mollisols with 2%-9% SOM content were collected in Northeast China. Solid-state 13C-NMR technology was used to explore the differences in the functional group structure of SOM, and ITS high-throughput sequencing was used to investigate the fungal community structure. The potential interactions between different taxonomic groups of soil fungal community and their associations with organic carbon molecular structures were compared by constructing molecular ecological networks under low SOM (2%-5%) and high SOM (7%-9%) conditions. The 13C-NMR results indicated an increase in the relative abundance of Alkyl C (25.8% to 35.9%). The decrease in Alkyl C/O-Alkyl C indicated a smaller degree of decomposition in high SOM soils. Sordariomycetes and Mortierellomycotina dominated the fungal community and their relative abundance increased with the SOM gradient (P<0.05) from 14.33% to 28.17% and from 7.32% to 23.14%, respectively. The network analysis showed simpler ecological topological properties of the fungal community in low SOM soils, with lower numbers of nodes, edges, and average clustering coefficients than those in high SOM soils. A closer relationship between fungi and organic carbon functional groups, especially LOC, was observed in low SOM soils. The random forest model showed that LOC had the largest amount for fungal interactions in low SOM soils (10%), followed by recalcitrant organic carbon (ROC). In comparison, LOC contributed less to the variations in fungal interactions in high SOM soils (7.4%). With globally increasing soil carbon loss, the limition of the carbon resources, especially the reduction of LOC, may reduce the stability and ecological functions of soil fungal communities.

The transition of soils into fallow state has a significant impact on the accumulation and transformation of soil organic matter (SOM). However, the issue of SOM transformation as a result of soil transition to fallow state in cryolithozone conditions is insufficiently studied. The aim of this study is to investigate the molecular weight (MW) distribution of humic acids (HAs) isolated from soils of central Yakutia. Native, fallow and agricultural soils in the vicinity of Yakutsk city were studied. MW distributions of HA preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersam Biosciences, Uppsala, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10-600 kDa). The data on the molecular-mass distribution of HAs of fallow and agricultural soils of Central Yakutia were obtained for the first time. According to the obtained data, it was found that the highest carbon content in the structure of HAs was observed in agricultural soils (52.56%), and is associated with soil cultivation and fertilizer application. Among the HAs of fallow soils, we note that those soils that are in the process of self-vegetation have a relatively high carbon content in the HAs (45.84%), but the highest content was observed in fallow soils used as hayfields (49.98%), indicating that the reinvolvement of agriculture in fallow soils leads to an increase in the carbon content of HAs. According to the data of the MW distribution of HAs, it was found that the highest content of a high MW fraction of HAs was recorded in native soil (18.8%); this is due to the early stages of humification and the low maturity of organic matter. The highest content of a low MW fraction of HAs was recorded in agricultural soil (73.3%); this is due to the formation of molecular complexes of a "secondary" nature, which are more stable in the environment than the primary transformation products of humification precursors. The molecular composition of the HAs of fallow soils in the process of self-overgrowing is characterized by values closer to the HAs of native soils, which indicates their transformation towards HAs of native soils. The obtained results indicate that the reinvolvement of fallow soils leads to the transformation of the molecular composition of HAs towards HAs of agricultural soils, and to an increase in the resistance of SOM to biodegradation.

In this review we have summarized the results of long-term investigations on the transformations of soil organic matter (SOM) in soils under shelterbelts of different ages located in the Agroecological Landscape Park in Turew (40 km south of Poznan, West Polish Lowland). The first shelterbelts were planted in Turew ~ 200 years ago. The youngest shelterbelt was created in 1993. Here we present the data on the effect of the age of these shelterbelts on some biologically active substances in soil, such as phytohormone indole-3-acidic acid (IAA), free-extractable lipids, and especially humic acids (HA), their chemical structure, and hydrophobic–hydrophilic properties. The conversion from arable cropping to shelterbelts not only influenced the accumulation of SOM and biologically active substances in soils but also changed the composition, structure, and stability of free-extractable lipids and HA with the age of shelterbelts being the principal factor. The SOM under the old shelterbelt during ~ 200 years has undergone the most significant biochemical and chemical transformations (oxidation, hydrolysis, polymerization) and advanced stages of humification with the accumulation of resistant compounds in humic substances (HS) and lipids and destruction of some anthropogenic contaminants.

Processes underlying soil organic matter (SOM) transformations are meeting growing interest as SOM contains more carbon (C) than global vegetation and the atmosphere combined. Therefore, SOM is a crucial element of the C cycle, especially in ecosystems rich in organic matter, such as boreal forests. However, climate change may shift the fate of this SOM from C sink into C source, accelerating global warming. These processes require a better understanding of the involved mechanisms driving both the C cycle and the interlinked nitrogen (N) cycle. SOM transformations are balanced by a network of interactions between biological, chemical and physical factors. In this review, we discuss the findings of the most recent studies to the current state of knowledge about the main drivers in SOM transformations. We focus on plant-derived secondary metabolites, as their biochemical traits, especially interactions with soil microbial communities, organic N compounds and enzymes make them potential regulators of SOM decomposition. However, these regulatory abilities of plant-derived compounds are not fully explored.

In a laboratory model experiment, the dynamics of the number of bacteria and micromycetes in the soil mass of podzolized chernozem after a one-time treatment of its surface with fungicides of various origins investigated. Chemical fungicides based on the active substances carbendazim, tebuconazole and azoxystrobin, and biological fungicides based on the antagonistic fungi Trichoderma viride (lignorum) and Chaetomium cohliodes were used. The soil mass for the experiment was taken from the arable layer of the soil on the site without fertilizers in the field experiment of the Department of Agrochemistry NSC "Institute for Soil Science and Agrochemistry Research named after O. N. Sokolovsky" (NSC "ISSAR") on the territory of SE "EF Hrakivske" (Noviy Korotych village, Kharkiv district, Kharkiv region). During 110 days of composting at a constant temperature, changes in the state of microbial communities, in particular soil micromycetes, and the speed and completeness of their recovery compared to soil not treated with fungicides evaluated. The state of the microflora was monitored four times during the study period according to the parameters of the number of microorganisms belonging to various ecological-trophic and taxonomic groups, the total biological index (TBI) and indicators reflecting the functional state of microbial coenoses (oligotrophy and mineralization indices, the coefficient of microbial transformation of soil organic matter (MTSOM). On the fifth day after treatment with fungicides, the number of bacteria and micromycetes in the samples of the treated soil mass was slightly higher higher than in the control samples, and on the twentieth day, on the contrary, it was significantly lower. The number of bacteria was lower by 20-46 %, micromycetes by 16-34 % compared to the control. On the fortieth day, a partial restoration of the number of bacteria to the level of the untreated control soil observed, and the number of micromycetes remained lower by 9-36 % compared to the control in the case of chemical fungicides. When using biological fungicides, the number of micromycetes approached the values in control soil and accounted for 84-94 % of them. On the one hundred and tenth day, the number of microflora in the soil treated with chemical fungicides according to TBI was 79-89 % of the control values, and in the soil treated with biofungicides it was 102-104 %. The number of micromycetes decreased to a lesser extent and recovered most completely and quickly in the case of the application of the biological fungicide Hetomic. Given the important role of soil micromycetes in the functioning of soils, a decrease in their number due to the accumulation of residual amounts of chemical fungicides in the soil can have a negative impact on many soil-biological processes, in particular the decomposition of plant residues and further transformation of organic matter, as well as on the phytosanitary state of the soil. Therefore, in order to avoid the possible consequences of their excessive or repeated application and the associated threat of soil contamination, it is necessary to carry out microbiological monitoring of soils in areas with a high fungicide load.

Размер и содержание органических частиц в копролитах Aporrectodea caliginosa и Lumbricus rubellus

This study investigates the composition and transformation of soil organic matter (SOM) across seven sites in Maritime Antarctica, focusing on the impact of bird activity and vegetation cover on SOM dynamics. There is limited knowledge of the stability of Antarctic SOM and the effects of seabird colonies on it. This study aims to address the knowledge gap regarding drivers of soil organic matter transformations in polar ecosystems. Hot water-extractable carbon (HWC) and carbon extracted with phosphoric acid (PHP-C) were chosen as parameters for the labile carbon pool. A stable carbon pool was here characterized as one with alkali-soluble organic compounds opposing microbial decomposition. This carbon pool has long (decades) turnover rates, and therefore is regarded stable. The mentioned carbon pools were used to calculate humification indices. The HWC in studied soils ranged from 1.5 to 4.3% of total carbon, while the PHP-C varied largely and was not correlated with HWC. Soils influenced by current or historical bird colonies (particularly penguins and skuas) exhibited elevated labile carbon fractions, indicating active microbial processing. In contrast, sites without bird influence showed lower biological activity. The stable carbon peaked at 18.9% of total carbon, indicating distinct soil transformation stages. The humification degree (HD) and labile-to-stable carbon (L/S) ratio were used to assess SOM stability, revealing that former bird rookeries had the most stabilized SOM, while recently deglaciated sites were in early stages of organic matter accumulation. Vegetation cover, though secondary to bird impact, was positively correlated with SOM humification, supporting the role of vascular plant-derived organic input in carbon stabilization. The study showed a clear link between bird activity and SOM dynamics, supporting the concept of biological legacies in soil formation in Antarctica. It highlighted the role of vegetation in SOM stabilization, which is crucial for understanding how terrestrial ecosystems may evolve as ice retreats and plant colonization expands.

Oxidoreductases and cellulases in lichens: Possible roles in lichen biology and soil organic matter turnover

At the current stage of soil microbiology development the study of the entire complex of microorganisms inhabiting the soil became possible, which helps finding the optimal combination of factors resulting in the formation of soil fertility as well as the development of stable and stress resistant phytocenosis. Soil metagenome is the largest genetic depository for all purposes, from the soil formation processes - transformation of barren rock into a substrate for plant growth and development, to the temporary adaptations in the short-term interests of the plant. The investigation of genetic potential of soil metagenome and its mobilization are the main goals of this project. Such studies should be comprehensive and solve actual issues: 1) the study of the mechanisms of soil-forming processes and the analysis of the evolution of metagenomes due to the special features of pedogenesis; 2) investigation of microbiome participation in organic residues decomposition and efficient transformation of soil organic matter; 3) screening of the associative plant-protective and growth promoting microorganisms. The object for the analysis of microbiome evolutionary potential in the process of soil formation may be the technogenic dumps resulting from mining operations, which are chronosequences of soils of different ages. Samples of paleosols are also of particular interest in the evolutionary aspect of the analysis of the soil metagenome. The project is expected to reveal a group of soil microorganisms, which take the most active part in the formation of soil fertility and effectively implement growth-stimulating and protective functions for the plant. The data may be of value for both fundamental science and serve as a base for the design of environmentally friendly high-productive phytocenoses based on the use of the adaptive potential of soil microbiota.