Exchangeable Cation Concentrations Research Articles

Acetamiprid retention in agricultural acid soils: Experimental data and prediction.

The overuse of pesticides in agriculture has led to widespread pollution of soils and water resources, becoming a problem of great concern. Nowadays, special attention is given to neonicotinoids, particularly acetamiprid, the only neonicotinoid insecticide allowed for outdoor use in the European Union. Once acetamiprid reaches the soil, adsorption/desorption is the main process determining its bioavailability and environmental fate. Therefore, in this work, the adsorption/desorption behaviour of acetamiprid in 60 agricultural soils was studied. The results indicate that acetamiprid has a low affinity for soil constituents, with values ranging from 0.2 to 4.28 L kg-1 for Kd(ads). At the same time, acetamiprid shows high desorption levels (up to 96.3%), indicating that it is poorly retained in soils, thus presenting high bioavailability and a potential risk for transport to other environmental compartments. Regarding the influence of soil properties on the adsorption/desorption process, soils with a high content of organic matter, clay, and exchangeable basic cations showed higher retention of acetamiprid, with greater adsorption and lower desorption. Finally, robust and universal models were successfully developed to predict the adsorption and desorption behaviour of acetamiprid in soil.

Effects of long-term nitrogen and phosphorus fertilization on soil phosphorus forms and dynamics under continuous wheat production in Saskatchewan, Canada

Many agricultural crops require both nitrogen (N) and phosphorus (P) fertilizers to sustain crop yields. However, long-term application of NH4–N fertilizers can cause soil acidification, which alters soil abiotic and biotic processes, including soil P dynamics. Long-term continuous wheat plots in Saskatchewan, Canada, were used to assess effects of N and P fertilization from 1967 and P fertilizer cessation in subplots from 1995. General soil chemical properties and soil P pools and forms were determined and then correlated with soil pH, total N (TN), and total P (TP) concentrations to show the relative importance on soil P dynamics of (a) crop nutrition (TN and TP); (b) soil acidification (pH); or (c) P fertilization/cessation. Fertilization with NH4–N decreased soil pH and altered exchangeable cation concentrations; however, long-term crop growth was poor in no-N plots and was best with both N and P fertilizers, in turn increasing soil carbon and organic matter. Applying P fertilizers without N increased soluble phosphates and the risk of P losses in runoff. Soil organic P (TPo) concentrations were correlated negatively to pH and positively to TN, but the concentrations of P compounds were not correlated to pH. This suggests that TPo accumulation may be from increased long-term crop residue inputs from crops with N and P fertilizers, rather than increased sorption from reduced pH. However, soil pH will continue to decrease with continued NH4–N fertilization, affecting soil chemistry and future P cycling; monitoring with a suite of wet chemistry and spectroscopic techniques is recommended.

CHARACTERIZATION AND CLASSIFICATION OF SOILS DEVELOPED ON COASTAL PLAIN SOILS FOR CROP PRODUCTION IN ORON LGA, SOUTH- SOUTH, NIGERIA

Soils are characterized and classified based on its unique properties. Detailed characterization of four representative areas of Oron coastal plain soils in South –South, Nigeria was carried out. Soil samples were collected from pedogenic horizons of soils in four sampling sites. Routine analysis of soil properties was carried out in the laboratory with standard laboratory procedures. Soil data was subjected to descriptive statistics using statistical analytical system. The soils have a deep well drafted profile of about deep 200 cm. The soil texture varied in areas ranging from loamy sand to sandy loam, sandy and sandy clay loam while bulk density increased down the natural horizons. The pH varied between moderately acidic to strongly acidic in the soils of the study area. The morphology of soils ranged in various colour matrix of hues (10-7.5) and Chroma values (1-8) in all horizons. The soils were characterized by Dark Brown (10YR3/3), Dark Greyish Brown (10YR4/2) and Yellowish Brown (10YR 5/4) to Grey (7.5YR6/2). The soils had low concentrations of exchangeable cations (Ca, Mg, Na and K). The Coefficient of variation (CV%) values ranged from 0.74 to 91.6 in Ca, Mg, Na and K. All the parameters in the soils of the study area showed low and medium mean values except soils of Esin Ufot1 and 2 which showed high mean values of Na with Esin Ufot 2 having the highest mean value of sodium to be 0.18 Cmol/kg. Suborder soils were classified as Grossarenic Kandiaqualfs (CEC > 16 Cmol/kg) for Esin Ufot1.Esin Ufot2, Esuk Oron1 while Esuk Oron 2 were classified as Typic Kandaquults (CEC < 16 Cmol/kg). A great importance in providing adequate data to enable right decision taking in the choice of site for developmental projects and crop production.

AI-guided investigation of biochar’s efficacy in Pb immobilization for remediation of Pb contaminated agricultural land

This study evaluated the lead (Pb) immobilization efficiency of biochar in contaminated agricultural soil. The biochar was produced from a range of major biomass residues and pyrolyzed under well-controlled conditions. Ten different types of standard biochar samples were derived from five different feedstocks (i.e., softwood, miscanthus straw, rice husk, oilseed rape straw, wheat straw) and pyrolyzed at 550 ℃ and 700 ℃. Pb-contaminated soil near an abandoned mine was incubated with 2.5% (w w− 1) of biochar. Incubation was conducted for various durations at room temperature under both short-term (21 days) and long-term (214 days) conditions. This variation explicitly accounted for the simulated microplastic contamination during the long-term incubation period. A novel framework has been developed to predict the long-term immobilization effect of various biochar types using a machine-learning approach, following the successful identification of optimal biochar implementations. This prediction method utilizes a small on-field dataset by employing a data augmentation approach, showcasing an innovative approach to forecasting the effects of different biochar types over time. After the incubation period, soil samples were analyzed for their chemical properties. As a result, oil seed rape biochar was the highest in pH, EC, exchangeable Ca2+, Mg2+, and K+, total nitrogen content, soil organic matter content, and available phosphate. In return, OSR 700 treated soils showed the highest content of exchangeable cations and the lowest content of available Pb after the incubation period. The most efficient biochar for immobilizing lead (Pb) in soil appears to be OSR 700, based on the available evidence.

A 44-year balanced fertilizer application affected rill erosion resistance by changing humus, aggregates, and polyvalent cation

Fertilizer application can affect the physicochemical properties of soil, such as the contents of large aggregates, humus, and exchangeable cations, thereby influencing soil erosion resistance. However, the rill erosion resistance and its key influencing factors of soil following long-term balanced fertilizer application remains unclear. This study aimed to analyze the change in rill erosion resistance following 44 years of balanced fertilizer application (No changes in the type of fertilizer) to non-calcareous soils and establish a Partial Least Squares Regression (PLSR) model of rill erodibility (kd) and soil critical shear stress (τc) to changes in the physical and chemical properties of the soil. Five treatments were designed: (1) CK (no fertilizer applied), (2) N (nitrogen), (3) NP (nitrogen plus phosphorus), (4) NK (nitrogen plus potassium), and (5) NPK (nitrogen, phosphorus, and potassium). Compared to CK, the N, NP, NK, and NPK application significantly increased τc by 49.6, 96.7, 73.6, and 36.2 %, respectively. Whereas, kd increased significantly only in the NPK treatment group. The optimal partial least squares regression model showed that mean weight diameter (MWD) had the greatest positive influence on soil critical shear stress, followed by fulvic acid (FA) content, whereas water-dissolved substances had a negative influence. Long-term balanced fertilizer application can increase MWD and τc by combining micro-aggregates and humus into large aggregates. Ca2+ content had the greatest positive effect on kd. Compared with that of CK, exchangeable Ca2+ content increased significantly with NP and NPK application (7.9 and 34.3 %, respectively). Ca2+ can increase kd by binding to the polar functional groups in FA to promote the shedding of hydration shells in large aggregates. Among all treatments, the NP treatment showed the best performance for reducing kd and increasing τc. This study could contribute to the understanding of the rill erosion process and modeling in non-calcareous soils and offer a reference for agricultural erosion control treatments.

Digestate from an Agricultural Biogas Plant as a Factor Shaping Soil Properties

In the context of a circular economy, special attention should be paid to the rational management of biodegradable waste. Currently, a potentially valuable waste material, rich in ingredients available to plants, is digestate, obtained as a by-product in agricultural biogas plants. The presented study aimed to determine the impact of digestate (DIG) from an agricultural biogas plant on soil reaction (pH), electrical conductivity (EC), sorption properties (SBC, HAC, CEC, BS), and chemical composition of soil. The research was based on a pot experiment in which increasing doses of liquid (LD) and solid (SD) forms of DIG were used in corn cultivation, balanced in terms of the amount of N introduced into the soil. The composition of DIG varied and depended on the LD or SD form. The LD was characterized by a lower pH value and higher EC compared to the SD form. The LD contained much less TC, fewer macroelements, and fewer trace elements. The application of LD significantly increased in the soil the content of TC, Ntot, available K, P, Fe, and Mn, and exchangeable cations K+. The SD significantly increased the content of available P, Mg, and Mn and exchangeable cations Ca2+ and Mg2+ in the soil. Both forms of digestate increased the total content of heavy metals (Cu, Cr, Pb, and Ni) in the soil. However, they did not pose a threat to the environment concerning their legally permissible levels.

Characterization of Lateralite: An Environment Friendly Chemical Additive for Soil Stabilization

The objective of this paper is to determine the chemical composition of Lateralite stabilizer and to characterize Lateralite, stabilizer as a solution for improving the engineering properties of fined grained lateritic and clayey soil for road construction. Oxides and metallic compositions of Lateralite was determined by Atomic Absorption Spectroscopy, AAS, composition of chemical elements of Lateralite stabilizer was determined by X-ray Photoelectron Spectroscopy (XPS) and a quantitative analysis by Scanning Electron Microscopy (SEM) associated with Energy Dispersive X-ray spectroscopy (EDX). The oxide composition of Lateralite as determined by AAS is: Calcium Oxide (63.89%), Silicon Oxide (18.31%), Aluminium Oxide (5.89%), Ferrous oxide (1.67%), Magnesium oxide (1.56%), Sulphur oxide (1.22%), Potassium oxide (0.78%), Sodium oxide (0.41%) and L.O.I 6.27%. The elemental composition analysis by XPS revealed ten (10) elements with Percentage Atomic Concentration, PAC, as: Oxygen (54.33%), Carbon (18.26%), Silicon (9.38%), Calcium (7.56%), Magnesium (4.08%), Aluminium (2.90%), Sodium (2.47%), Ferrous (0.44%), Sulphur (0.31%) and Nitrogen (0.27%) while SEM revealed eleven (11) elements: Oxygen (57.9%), Calcium (21.13%), Silicon (11.08%), Aluminium (4.23%), Ferrous (1.89%), Sulphur (1.07%), Magnesium (1.02%), Sodium (0.99%), Potassium (0.35%), Tin (0.18%) and Barium (0.17%). The three (3) characterization techniques used, (AAS, XPS and SEM) revealed the exchangeable cations in Lateralite are Calcium (7.56%), Magnesium (4.08%), Aluminium (2.90%) and Sodium (2.47%) which are in the ratio 3: 1.65:1.17:1, (Ca2+: Mg2+: Al3+ :Na+). This shows a high concentration and quantity of exchangeable calcium cations over other cations. This will enable the formation of Calcium compounds with very strong and stable inter-particle bonds and a stable Lateralite-stabilized soil mixture.

Biochar-nanoparticle combinations enhance the biogeochemical recovery of a post-mining soil

Here we addressed the capacity of distinct amendments to reduce arsenic (As), copper (Cu), selenium (Se) and zinc (Zn) associated risks and improve the biogeochemical functions of post-mining soil. To this, we examined nanoparticles (NPs) and/or biochar effects, combined with phytostabilization using Lolium perenne L. Soil samples were taken in a former metal mine surroundings. Ryegrass seeds were sown in pots containing different combinations of NPs (zero-valent iron (nZVI) or hydroxyapatite (nH)) (0 and 2 %), and biochar (0, 3 and 5 %). Plants were grown for 45 days and the plant yield and element accumulation were evaluated, also soil properties (element distribution within the soil fractions, fertility, and enzymatic activities associated with microbiota functionality and nutrient cycling) were determined. Results showed biochar-treated soil had a higher pH, and much higher organic carbon (C) content than control soil and NP-treated soils, and it revealed increased labile C, total N, and available P concentrations. Soil treatment with NP-biochar combinations increased exchangeable non-acid cation concentrations and reduced exchangeable Na%, improved soil fertility, reduced sodicity risk, and increased ryegrass biomass. Enzymatic activities, particularly dehydrogenase and glucosidase, increased upon the addition of biochar, and this effect was fostered by NPs. Most treatments led to a significant reduction of metal(loid)s contents in biomass, mitigating contamination risks. The two different NPs had similar effects in many parameters, nH outperformed nZVI in terms of increased nutrients, C content, and enzymatic activities. On the basis of our results, combined biochar-NP amendments use, specially nH, emerges as a potential post-mining soil restoration strategy.

Nitrogen Addition Promotes the Accumulation of Soil Particulate Organic Carbon in a Subtropical Forest

Nitrogen (N) deposition rates of terrestrial ecosystems have gradually declined but are still high in some areas. Previous studies have reported that N addition elicits diverse impacts on soil organic carbon (SOC) pools. SOC can be divided into different functional fractions, namely, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). The responses of these fractions to N addition should be elucidated to better understand the changes in SOC pools. Here, we conducted a N addition experiment (0, 40, and 80 kg N ha−1 yr−1) in a subtropical Castanopsis fabri forest to simulate N deposition. The surface (0−10 cm) SOC fractions, aboveground litter product, fine root (diameter < 2 mm) biomass, soil exchangeable cation content, and soil enzyme activity under different N addition treatments were measured. The results showed the following: (1) N addition showed a positive effect on POC and SOC contents but did not significantly affect MAOC content; (2) POC content was negatively correlated with pH and soil enzyme activity and positively correlated with aboveground litter product, suggesting that POC accumulation was influenced by aboveground litter input and microbial decomposition; (3) a close negative relationship was observed between exchangeable Al3+ and Ca2+ or K+ contents, indicating that there is likely to be a trade-off between the mineral sorption and desorption, thus resulting in an insignificant reaction of MAOC to N addition. Overall, the accumulation of SOC under short-term N addition was found to be primarily driven by POC, and the response of different SOC functional fractions to N addition was inconsistent. By incorporating these nuances into ecosystem models, it is possible to predict SOC dynamics more accurately in response to global change.

Brine formation in cold desert, shallow groundwater systems: Antarctic Ca-Cl brine chemistry controlled by cation exchange, microclimate, and organic matter

Groundwater in the McMurdo Dry Valleys of Antarctica is commonly enriched in calcium and chloride, in contrast to surface and groundwater in temperate regions, where calcium chemistry is largely controlled by the dissolution of carbonates and sulfates. These Antarctic Ca-Cl brines have extremely low freezing points, which leads to moist soil conditions that persist unfrozen and resist evaporation, even in cold, arid conditions. Several hypotheses exist to explain these unusual excess-calcium solutions, including salt deliquescence and differential salt mobility and cation exchange. Although the cation exchange mechanism was shown to explain the chemistry of pore waters in permafrost cores from several meters depth, it has not been evaluated for near-surface groundwater and wetland features (water tracks) in which excess-calcium pore-water solutions are common. Here, we use soluble salt and exchangeable cation concentrations to determine whether excess calcium is present in water-track brines and if cation exchange could be responsible for calcium enrichment in these cold desert groundwaters. We show that calcium enrichment by cation exchange is not occurring universally across the McMurdo Dry Valleys. Instead, evidence of the present-day formation of Ca-Cl−rich brines by cation exchange is focused in a geographically specific location in Taylor Valley, with hydrological position, microclimate, soil depth, and organic matter influencing the spatial extent of cation exchange reactions. Up-valley sites may be too cold and dry for widespread exchange, and warm and wet coastal sites are interpreted to host sediments whose exchange reactions have already gone to completion. We argue that exchangeable cation ratios can be used as a signature of past freeze-concentration of brines and exchange reactions, and thus could be considered a geochemical proxy for past groundwater presence in planetary permafrost settings. Correlations between water-track organic matter, fine sediment concentration, and cation exchange capacity suggest that water tracks may be sites of enhanced biogeochemical cycling in cold desert soils and serve as a model for predicting how active layers in the Antarctic will participate in biogeochemical cycling during periods of future thaw.

Termitaria enhance soil and forest diversity in Deciduous Dipterocarp Forest, Northern Thailand

Abstract We characterised the soils and vegetation in 15 sets of four quadrats on and around mounds of Macrotermes annandalei (Isoptera, Macrotermitinae) on a plain of deep dystric clay over limestone in Deciduous Dipterocarp Forest in Northern Thailand. Termites have excavated the mounds from the deep calcareous substrate. The mound soils have darker subsoils, larger contents of clays and exchangeable cations, and higher pH values than the surrounding dystric clay loams. The thickets on the mounds are visually different from the surrounding Deciduous Dipterocarp Forest. They have few dipterocarps and are floristically similar to the regionally important Mixed Deciduous Forest. The clear visual differences are confirmed by floristic similarity, cluster, and canonical correspondence analyses for each of the tree, sapling and seedling size classes. The differences between the mound clays and surrounding red clay loams and the associations between soil and forest types are confirmed by ‘t tests’ and the significant correlations of the soil base status with the main floristic axis of the canonical correspondence analyses. Soil variability due to termites and other agents of pedoturbation can significantly contribute to short-range floristic and structural diversity in some dry tropical forests.

Почвы степей Нижнеоронгойской котловины (Западное Забайкалье)

The morphological structure, granulometric composition and basic physical and chemical properties of steppe soils in the model site of the Nizhneorongoy Depression (Republic of Buryatia) were investigated on the basis of data from a series of full-profile transects and excavations on petrophytic and meadow steppes. The diversity of steppe areas of the Nizhneorongoy Basin is represented by three types of soils: lithozem, light-humus saline and non-saline, light-humus accumulativecarbonate solonetzic. Lithozems and light-humus soils are widespread in the foothill part of the Khamar-Daban ridge. They are characterized by good aeration, light granulometric composition (sandy, sandy loam), low content of humus and exchangeable cations, dominance of exchangeable calcium in the composition of cations (60-82 % of the sum) typical for steppe type of soil formation, absence of salinization. Differences between lithozem and light-humus soils are expressed in profile thickness, stoniness. Complex neotectonic structure of the territory determined heterogeneity of geomorphologic structure of the inner field of the depression. In its accumulative part there are numerous rises, on which grass steppes grow. Soils of these positions are represented by light-humus saline and light-humus accumulative-carbonate solonetzic soils. These soils have neutral and slightly alkaline pH reaction, higher indices of humus quantity and absorption capacity in comparison with lithozems. The features of these soils are heavier granulometric composition (loam, clay), high share of exchangeable magnesium in the composition of exchangeable cations, carbonation and weak salinization of the lower part of the profile. Salinization chemistry is chloride-sodium and soda-chloride in terms of anions, sodium and magnesium-sodium in terms of cations. In all studied soils there are no median metamorphic horizons. The main soil-forming processes are light-humus accumulation of organic matter, hydrogenic accumulation of carbonates and salinization processes. The diagnostic value of exchangeable calcium and magnesium ratios has been established, which shows steppe (calcium dominance) or meadow (magnesium dominance) trends of soil formation.

Evaluating soil acidification risk and its effects on biodiversity–ecosystem multifunctionality relationships in the drylands of China

BackgroundSoil acidification caused by anthropogenic activities may affect soil biochemical cycling, biodiversity, productivity, and multiple ecosystem-related functions in drylands. However, to date, such information is lacking to support this hypothesis. MethodsBased on a transect survey of 78 naturally assembled shrub communities, we calculated acid deposition flux in Northwest China and evaluated its likely ecological effects by testing three alternative hypotheses, namely: niche complementarity, mass ratio, and vegetation quantity hypotheses. Rao's quadratic entropy and community-weighted mean traits were employed to represent the complementary aspect of niche complementarity and mass ratio effects, respectively. ResultsWe observed that in the past four decades, the concentrations of exchangeable base cations in soil in Northwest China have decreased significantly to the extent of having faced the risk of depletion, whereas changes in the calcium carbonate content and pH of soil were not significant. Acid deposition primarily increased the aboveground biomass and shrub density in shrublands but had no significant effect on shrub richness and ecosystem multifunctionality (EMF), indicating that acid deposition had positive but weak ecological effects on dryland ecosystems. Community weighted mean of functional traits (representing the mass ratio hypothesis) correlated negatively with EMF, whereas both Rao's quadratic entropy (representing the niche complementarity hypothesis) and aboveground biomass (representing the vegetation quantity hypothesis) correlated positively but insignificantly with EMF. These biodiversity–EMF relationships highlight the fragility and instability of drylands relative to forest ecosystems. ConclusionsThe findings from this study serve as important reference points to understand the risk of soil acidification in arid regions and its impacts on biodiversity–EMF relationships.

Exploring the mechanisms of diverging mechanical and water stability in macro‐ and microaggregates

AbstractBackgroundSoil stability is often evaluated using either mechanical or hydraulic stress. The few studies that use both approaches suggest that these two types of stability behave differently.AimsOur aim was to explore the mechanisms of aggregate stability regarding mechanical and water stability at the macro‐ and microscale, among other things, the effect of differing pore structure and soil organic matter content.MethodsSamples were taken from two adjacent plots that were expected to differ in stability due to land use, that is, cropped versus bare fallow (BF). The stability of dry‐separated macroaggregates (8–16 mm) and microaggregates (53–250 µm) was determined via wet sieving and unconfined uniaxial compression tests. To explore the mechanisms of stability, 3D pore characteristics were analyzed with microtomography scans. Furthermore, the contents of carbon and exchangeable polyvalent cations as well as contact angles were determined.ResultsWater stability of macroaggregates was much higher in the cropped plot (geometric mean diameter 0.65–2.37 mm [cropped] vs. 0.31–0.56 mm [BF]), while mechanical stability was very similar (median work 17.3 [cropped] and 17.5 N mm [BF]). The two size fractions behaved similarly regarding both types of stability, with more pronounced differences in macroaggregates. Several soil characteristics, like carbon, exchangeable calcium, and higher connectivity of pores to the aggregate exterior, contributed to water stability. Regarding mechanical stability, the destabilizing effect of lower carbon content and exchangeable calcium in the BF plot was counterbalanced by a lower porosity.ConclusionsMechanical and water stability behaved differently in the two plots due to the different deformation mechanisms.

Experimental study of water-extractable sulphate in Opalinus Clay and implications for deriving porewater concentrations

In northern Switzerland, the Opalinus Clay, a Jurassic claystone formation, is foreseen as host rock for a deep geological repository for radioactive waste. Characterizing its porewater is of particular importance for assessing the mobility of radionuclides and the stability of the engineered barriers. Although the porewater composition of the Opalinus Clay is fairly well known, there is still controversy on the sources of sulphate obtained by different porewater characterization methods. A striking observation is that sulphate concentrations from aqueous extraction and recalculated to in-situ conditions are consistently much higher than sulphate concentrations measured in borehole waters, squeezed waters and advectively displaced waters (“excess sulphate”). Accordingly, the main objective of this study is to better investigate the processes affecting dissolved sulphate concentrations during aqueous extraction and, thus, to reduce uncertainties in predicting the concentrations of this compound in the Opalinus Clay porewater. To this end, a series of extraction experiments were conducted using variable solid/liquid ratios, extraction times and extract solutions. In order to suppress sulphide-mineral oxidation, all the experiments were performed in a glovebox under oxygen-free conditions (atmosphere and solutions). Measurements of the sulphur and oxygen isotope composition of the dissolved sulphate in aqueous extracts are aimed to further constrain the source of the “excess sulphate”. Finally, the plausibility of the SO4 data from extraction experiments in terms of their representativeness for in-situ conditions was evaluated by simple geochemical modelling. The modelling shows that SO4 concentrations from aqueous extracts recalculated to in-situ conditions imply dissolved and exchangeable cation concentrations which are not consistent with measured data, thus, attesting non-conservative behaviour for sulphate during aqueous extraction. However, the various extraction experiments showed that pyrite oxidation was successfully suppressed during the experiments and neither contributions from e.g. organic material, congruent calcite dissolution and/or sulphate mineral dissolution provide enough SO4 to explain the “excess sulphate”. Ultimately, the various extraction experiments failed to definitely identify the source of the “excess sulphate” in aqueous extracts. However, the good agreement found between the δ18O and δ34S values of dissolved SO4 in aqueous extracts and those of borehole waters suggest that the “excess sulphate” might be weakly bound to mineral surfaces.

Carbon Sequestration by Soils of Ash Dump Forest Areas in the Middle Urals (Russia)

The purpose of this article was to assess the participation of young soils of ash dump forest communities in carbon sequestration by soils of southern taiga forests, considering the physico-chemical properties of the ash substrate and forest litter (pH, TOC, TN, content of P and K mobile compounds, and exchangeable Ca and Mg ions). It was revealed that on three Middle Ural ash dumps (composed of fly ash from various brown coals) over 50–60 years, forest communities spontaneously formed according to the zonal type (with the dominance of Betula pendula Roth and Populus tremula L.) with poorly differentiated young soils—technosols. For the first time, as a result of using an integrated approach to assess the direction of forest ecosystem formation on fly ash dumps, a tendency to increase carbon stocks in technogenic soils that have not reached the level of zonal soils was revealed, as well as the dependence of C accumulation on some physico-chemical characteristics of ash was established. Carbon stocks in Technosols are on average equal to 44 t/ha but vary significantly. It was shown that there is a medium negative relationship between the content and stocks of organic carbon in soils formed on a technogenic substrate and the content of mobile phosphorus compounds in them (the correlation coefficient is −0.58 and −0.53, respectively). The average carbon stocks in the litter of technosols, which is the main source of organic carbon in forest soils, are 3.2 t/ha. It was revealed that the carbon stocks in the litter are most influenced by the content of exchangeable calcium cations and magnesium in it (the correlation coefficients are −0.68 and −0.69, respectively). Any correlation between the studied litter parameters and carbon accumulation in the soils of ash dumps was found. The study revealed that the carbon stocks in the technosols of ash dump forest communities are two times less than the carbon stocks in the zonal forest soils of the Middle Ural southern taiga. The stocks of this element in the litter of young soils are equal to 1/3 of the litter of zonal soils. The composition of the humus substance system formed in the soils of forest areas of ash dumps and zonal soils is similar. The results of this study can serve to fill gaps in the knowledge about carbon sequestration by soils and aim to draw attention to forest communities of technogenic ecosystems to consider the contribution of their components to carbon sequestration.

The nutritional status and root development of silver fir (Abies alba Mill.) seedlings growing on decaying deadwood in temperate forest ecosystem

The study aimed to compare two substrates, soil and deadwood, for the regeneration of silver fir (Abies alba Mill.) seedlings. Three-year-old fir seedlings growing both on deadwood and in the soil were collected. The examination involved determining the physical, chemical, and biochemical properties of soil and deadwood, as well as assessing the morphology of the roots and the nutrition of seedlings growing on the soil and deadwood. The examined substrates differed in physical, chemical and biochemical properties. It was shown that strongly decomposed fir logs are a good substrate for the growth of fir seedlings, mainly due to the high content of exchangeable cations (especially calcium, magnesium and potassium) and high phosphorus and nitrogen content. The type of substrate had a significant impact on the root morphology of fir seedlings. In our study, the most responsive root traits to differences in growing substrates were specific root area (SRA) and specific root length (SRL). Our analyses did not confirm significant differences in the stoichiometry of C, N and P in the roots and needles of seedlings grown on different substrates. The stoichiometry of roots and needles suggests no limitations in the uptake of nutrients by seedlings growing on deadwood. This study validated that heavily decomposed wood can provide favourable microhabitats for the growth of the young generation of fir.

Natural gamma-ray spectrometry as a rapid sensing method for detecting variations in soil shrinking and cracking behaviour: An application case study

Soils which develop desiccation cracks after drying are unsuitable for the making of earthenware. The present work was carried out to demonstrate the use of Natural Gamma-ray Spectrometry (NGS) as a rapid sensing method to detect the variation of cracking behaviour and types of clay dominant in soil using samples collected from the study region. Natural gamma-ray intensities due to potassium (K) and equivalent thorium (eTh) radioisotopes present in soil were recorded using an NGS device. Circular soil cakes of set diameter were sun-dried to find shrinking and cracking variations. Other tests included measurement of particle size distribution, Atterberg indices, basic soil physico-chemical properties, exchangeable cation contents using ICP-OES and XRD identification of clays. 6 soil varieties were identified from the distribution of data points in the binary plots of gamma-ray potassium (GR-K) and thorium (GR-eTh) counts per sec (C/s). Variation of GR-K was observed to be wider (2.14 C/s to 2.54 C/s) than GR-eTh (0.44 C/s to 0.63 C/s). The measured GR-K counts reflect changes in illite content. The soils displayed 3 categories of shrinking and cracking behaviour. The soil variety which displayed maximum mild shrinkage without fine desiccation cracks on the set surface area has the highest GR-K counts. The soil shrinking and cracking variations were not clearly defined by the classification based on the texture and plasticity chart, though the latter indicated dominant smectites. A strong linear relationship between GR-K and exchangeable K (R2 = 0.84) indicates K+ contribution mainly from illite and dominance of other clay types in outliers. Higher levels of polyvalent cations known for binding clay aggregates were observed in the non-cracking soils. Concomitant higher GR-K levels indicate that shrinking soils lacking fine desiccation cracks are associated with fluvial sediments of the recent past with parental mica. This research concludes that NGS-based portable devices can be used for rapid sensing of soils to detect variation in shrinking and cracking behaviour and dominant clay type and thus can be used for identification of soil suitable for earthenware making.

Organic Inputs Positively Alter the Bacteriome of Post-Agricultural Soils

Agriculture can degrade soils and reduce microbial diversity. The reduction in microbial diversity of degraded soils is due to their long-term agricultural use. In most cases, such areas are afforested but rarely succeed in converting them into first-generation pine forests without adequately revitalizing the soils and restoring the natural relationships characteristic of forest habitats. This is possible thanks to the positive changes in soil biodiversity. To facilitate and enhance this phenomenon in the present experiment, various forms of organic matter were added to the soil: pine bark compost scattered on the soil surface (BCS) or placed under the roots of the seedlings at planting (BCR), woody debris (WW) and sawdust (S), while the control plot was not treated. The studies started in 2001 on two experimental plots, a poorer one in Bielsk and a more fertile one in Czarne Człuchowskie (eastern and northern Poland, respectively). The following year, 2-year-old pine seedlings (Pinus sylvestris L.) were planted on the plots. After 20 years, the physicochemical properties of the soil and its microbial composition were determined and compared with the control. The results encourage the use of organic matter for established pine forest crops on post-agricultural land for revitalization: C, N, and P content increased both in the organic layer and in the topsoil (up to 40 cm), where most fine roots are located. The total content of exchangeable base cations (Ca, Mg, K) and the sorption capacity of the soils (a measure of the ion binding capacity of the soil) also improved. The genetic analyses carried out using the molecular method (NGS) showed positive changes in the composition of the soil microbiome. Compared to poorer soil conditions in richer habitats, the number of taxa increases when organic matter is added, leading to significant qualitative changes in the bacteriome. The addition of organic material from the forest had a positive effect on the bacterial communities, which in turn accelerated the changes in the diversity of bacteriomes characteristic of agricultural soils and brought them closer to the forest ecosystem. The organic horizon was restored, and at the same time, the biodiversity of the soil microbiome increased, which is important for the health and sustainability of pine stands on formerly agricultural land.

From site to state – Quantifying multi-scale legacy effects of historic landforms from charcoal production on soils in Connecticut, USA

Relict charcoal hearth (RCH) landforms are relatively small (average diameters of 11 m) and circular microrelief features found in many forests of the North-Eastern USA and Central Europe. Soils on RCHs are special in that they are significantly enriched in organic- (OC) and pyrogenic carbon (PyC), caused by the admixture of charcoal. Many studies have shown that this results in changed soil chemical and physical properties, making RCHs unique soil microhabitats. However, questions about their larger impact on a soil landscape’s carbon storage have hardly been studied so far; an aspect that could become more relevant with growing RCH site location databases. Here we show that RCHs can substantially add to a landscape soil organic- and pyrogenic carbon storage. This effect is scale dependent, i.e. a larger scale of observation (1:20,000) will result in significant additions for areas with high site densities (+22.6 % OC, +128.6 % PyC), contrary to smaller scales of observation (>1:650,000) where the effect is diminished (+0.2 % OC, +1.2 % PyC). A comparison with a nationwide soil database (gSSURGO) shows that in areas with high site densities, individual soil unit OC contents are increased by up to 91.6 %. An exemplary comparison to historic terrace/lynchet systems shows that RCHs store vastly more carbon when pedons of the same size are compared. However, if the actual landform surface areas are taken into account, RCHs store a lot less. This is showcasing the spot-like distribution of RCHs on a landscape scale. Furthermore, we broaden the knowledge about RCH site specific properties in Connecticut by a first analysis of pedogenic (hydr-)oxide and exchangeable cation concentrations, with the result indicating increased weathering rates and enrichment of exchangeable Ca2+, Mg2+ and Mn2+ in RCH soils.