Soil Substrate Research Articles

Soil Substrate Characteristics for Planting Hole Greening Technology for High, Steep, Rocky Slope Vegetation in Semi-Arid Areas

Soil substrate plays a central role in the vegetation restoration of high and steep slopes, especially in semi-arid regions. This study aims to develop an optimal soil substrate that can provide a favorable environment for the vegetation growth of the high and steep rocky slopes in semi-arid areas. Within the framework of planting hole greening technology, we developed a synthetic substrate comprising base soil, peat, water-retaining and agglomerating agents, biochar, and controlled-release compound fertilizer. We conducted pot experiments to assess the impact of compound additions on soil properties and Parthenocissus himalayana growth. Field tests on exposed, high, and steep rocky slopes in a semi-arid region validated the optimal ratio of substrate components. The results showed that the base soil-to-peat ratio significantly influenced soil density, moisture, pH, organic matter, nitrogen content, and vegetation growth (Ps < 0.05). The controlled-release compound fertilizer significantly affected soil electrical conductivity and alkali-hydrolyzable nitrogen content (Ps < 0.05). Meanwhile, the water-retaining agent, biochar, and agglomerating agent had inconsequential effects on soil characteristics and plant growth. The optimal substrate composition included a 7:3 ratio of base soil to peat, 1.5 g/L of water retainer, 10 mg/L of agglomerating agent, 5 g/L of biochar, and 5 g/L of controlled-release compound fertilizer. The field verification showed that the developed optimal substrate possessed desirable pore structure, moisture, and nutrients, resulting in excellent growth of Parthenocissus himalayana. This optimal soil substrate could be suitable for establishing vegetation on high, steep, rocky slopes in semi-arid areas using planting hole greening technology.

Fate of dimethylsilanediol (DMSD) in outdoor bare surface soil and its relation to soil water loss

Dimethylsilanediol (DMSD) is a primary degradation product of silicone materials in the environment. Due to its low air/water partition coefficient and low soil/water distribution coefficient, this compound is not expected to undergo sorption and volatilization in wet soil. In an accompanying paper, we confirm that under controlled indoor conditions in test tubes, there is little to no volatilization of DMSD from soil and soil constituents if soil is wet. However, a significant amount of DMSD was volatilized when the soil substrates became air dried. Given the importance of water on the partition and fate of DMSD, we now report a continuation of this study focusing on the relation between DMSD removal and water loss in re-constituted soil columns under outdoor conditions. Consistent with predictions based on its partition properties and reconciling this evidence with previously reported field and laboratory studies, DMSD distribution was found to be largely dependent on water partitioning. The results suggested that DMSD moved upward in soil profile as soil water was evaporated from topmost layers with little DMSD retention by the soil matrix. As soil dried, a fraction of DMSD was sorbed by the soil matrix in the topmost layer, while most of the spiked radio-labeled DMSD was removed from soil through volatilization.

Role of Soil Microbiota Enzymes in Soil Health and Activity Changes Depending on Climate Change and the Type of Soil Ecosystem.

The extracellular enzymes secreted by soil microorganisms play a pivotal role in the decomposition of organic matter and the global cycles of carbon (C), phosphorus (P), and nitrogen (N), also serving as indicators of soil health and fertility. Current research is extensively analyzing these microbial populations and enzyme activities in diverse soil ecosystems and climatic regions, such as forests, grasslands, tropics, arctic regions and deserts. Climate change, global warming, and intensive agriculture are altering soil enzyme activities. Yet, few reviews have thoroughly explored the key enzymes required for soil fertility and the effects of abiotic factors on their functionality. A comprehensive review is thus essential to better understand the role of soil microbial enzymes in C, P, and N cycles, and their response to climate changes, soil ecosystems, organic farming, and fertilization. Studies indicate that the soil temperature, moisture, water content, pH, substrate availability, and average annual temperature and precipitation significantly impact enzyme activities. Additionally, climate change has shown ambiguous effects on these activities, causing both reductions and enhancements in enzyme catalytic functions.

Experimental and Numerical Modeling of the Freeze–thaw Response of U-Shaped Channel Lining on Sulfate Saline Soil Foundation

Under the influence of seasonal freeze-thaw cycles, the concrete lining of channels situated on saline soil foundations is highly vulnerable to an array of deleterious phenomena, such as frost heave, salt expansion, and corrosion. To investigate the synergistic interplay among saline soil substrates, U-shaped channel lining structures, and ambient temperatures during freeze-thaw cycles, a novel Hydraulic-Thermal-Salt-Mechanical (HTSM) model is established in this study. The HTSM model elucidates the migration of moisture and salt solute, ice-water phase transitions, and sodium sulfate crystallization within unsaturated saline soils throughout the freeze-thaw cycles. It considers the variations in volume and pore solution volume before and after the phase transition of sodium sulfate. Temperature and salt frost heaving force measurements obtained from outdoor freeze-thaw cycles are compared with numerical simulation results to validate the efficacy of the HTSM model and investigate the distribution patterns of salt frost heaving force (frost swelling force) along the channel. The results showed that the frost swelling force and depth exhibit a great linear relationship and the maximum stress of the U-shaped channel appears at the bottom of the channel, highlighting the good arching force characteristics of the U-shaped structure which prove that bottom of the channel is also the most prone to fracture. Significantly, the initial water content significantly impacts the frost swelling force—it increases by 4% while the frost swelling force increases by 76%. Comparing the numerical simulation results of temperature variations, moisture changes, and salt-frost heaving forces with the outdoor experimental data, it is evident that the proposed HTSM model effectively simulates the salt-frost heaving patterns observed in U-shaped channel linings.

Analyzing the Impact of Simulated Nitrogen Deposition on Stoichiometric Properties and Yield of Ma Bamboo (Dendrocalamus latiflorus Munro) Shoots, Leaves, and Soil Substrate

The growth dynamics of Ma bamboo (Dendrocalamus latiflorus Munro) are intricately linked to nitrogen availability, a pivotal nutrient. Escalating global nitrogen deposition, primarily driven by anthropogenic factors, is reshaping nutrient fluxes and productivity within forest and bamboo ecosystems. Such alterations bear significant implications for the growth equilibrium and yields of rapid-growth species such as Ma bamboo, thereby influencing their sustainable management strategies. This investigation delves into the responses of Ma bamboo under varying nitrogen deposition scenarios (0 g·clump−1, 11.2 g·clump−1, 13.5 g·clump−1, and 22.5 g·clump−1), examining stoichiometric attributes in bamboo shoots, leaves, and soil across distinct growth phases. Our empirical findings reveal that in the early growth stage, nitrogen enrichment markedly augmented N and P concentrations in the foliage and shoots, alongside a corresponding enhancement in soil P content. This was paralleled by a substantial reduction in the C:N ratio in leaves and the C:P ratio in shoots and soil, indicating an amplified uptake of P and N in both plant and soil matrices. During the middle stage, all nitrogen treatments boosted nitrogen levels across various plant tissues, while concurrently, soil C content exhibited a notable decline with increased nitrogen supplementation. In the late stage, leaf and soil N content continued to ascend; however, alterations in C content in both soil and leaves were not pronounced. Contrastingly, N and P levels in shoots showed a gradual decrement. Yield assessments disclosed that during the early stage, the N3 treatment (22.5 g·clump−1) not only delayed shoot emergence by 14 days but also surged the yield by 115.87% in comparison to the control (CK). In the late stage, the N2 treatment (13.5 g·clump−1) extended emergence duration by 10 days, with the yield apex under N3 treatment (22.5 g·clump−1) evidencing a 116.67% yield augmentation over CK. In summation, this study elucidates the stoichiometric balancing and distribution strategies within the plant–soil system of Ma bamboo, investigating its adaptability and responsive feedback to diverse nitrogen deposition gradients. This research contributes to a deeper understanding of plant nutrient adaptation mechanisms in the context of nitrogen deposition, enriches the discourse on plant population stoichiometry, and offers valuable insights and scientific underpinnings for broader-scale community or ecosystem stoichiometry studies.

Stronger compensatory thermal adaptation of soil microbial respiration with higher substrate availability.

Ongoing global warming is expected to augment soil respiration by increasing the microbial activity, driving self-reinforcing feedback to climate change. However, the compensatory thermal adaptation of soil microorganisms and substrate depletion may weaken the effects of rising temperature on soil respiration. To test this hypothesis, we collected soils along a large-scale forest transect in eastern China spanning a natural temperature gradient, and we incubated the soils at different temperatures with or without substrate addition. We combined the exponential thermal response function and a data-driven model to study the interaction effect of thermal adaptation and substrate availability on microbial respiration and compared our results to those from two additional continental and global independent datasets. Modeled results suggested that the effect of thermal adaptation on microbial respiration was greater in areas with higher mean annual temperatures, which is consistent with the compensatory response to warming. In addition, the effect of thermal adaptation on microbial respiration was greater under substrate addition than under substrate depletion, which was also true for the independent datasets reanalyzed using our approach. Our results indicate that thermal adaptation in warmer regions could exert a more pronounced negative impact on microbial respiration when the substrate availability is abundant. These findings improve the body of knowledge on how substrate availability influences the soil microbial community-temperature interactions, which could improve estimates of projected soil carbon losses to the atmosphere through respiration.

Microbial and thermal indices of organic matter stability in lowland soils with variable texture

Soil organic carbon (SOC) stabilization and turnover are important processes of global carbon cycle. This study evaluates microbial activity and thermal stability of soil organic matter (SOM) in lowland soils of central Europe during relatively dry summer period. We observed that the intensity of soil respiration and substrate availability are positively affected by soil moisture. Soil water availability was correlated with clay content that supported water retention and capillary elevation from the subsurface. Besides moisture, soil respiration was partially controlled also by nutrient availability (Ca, Mg, K, P). Microbial C content was not correlated with any of the properties that were measured. To assess SOM stability, we used thermogravimetry combined with differential scanning calorimetry (TG-DSC). Correlations between TG-DSC data and soil respiration indicate that heterotrophic microorganisms degrade SOM without significant preference for either labile, intermediate, or stable organic fraction. The heat released per mass unit of labile SOM correlated positively with the ratio of microbial vs. total organic C in the sample. This suggests that the energy density of labile OM affects positively the C amount that is converted to microbial biomass. More heat was released per mass of labile OM from the samples that showed higher SOC/SOM ratio and organic C/O value. This indicates that higher portion of C bound in SOM affects positively the energy density of labile fraction. The samples with higher clay content released relatively more heat at higher temperatures in comparison to more coarse-textured soils. Considering the effect of clay on SOC stabilization, the findings of this study pointed on the two contradicting aspects. Although the results suggest that interaction of OM with inorganic clay components results in formation of stable C fraction, fine-textured soils showed higher respiration rate, during the drier period, due to the higher water availability.

Propagation of Campanula bayerniana (Campanulaceae) by seeds as a reproduction model for the conservation of threatened small-seed plant species

The in vitro seed propagation of small seeded Campanula species often incurs complications in the manual handling of the tiny seed material from seed sterilisation to seedling transplantation in soil. The lack of a simple and effective protocol which minimises manual operations makes the propagation of such species both challenging and inefficient. This study aimed to develop a protocol for the seed reproduction of threatened Campanula and other threatened small-seed plant species. The method was successfully tested on Campanula bayerniana subsp. bayerniana. The saplings were cultivated over a 5-month period through seed germination under in vitro conditions followed by their transfer to containers with a soil mix. The protocol employs small filter paper discs on which the seeds germinate and continue their development in soil substrate until the full biodegradation of the discs. The method involves surface treatment of the seeds with potassium permanganate solution, thus avoiding additional washing phases and direct contact with the seeds and seedlings, thereby preventing mechanical damage. This also facilitates the handling of each seed separately, minimising seed loss particularly when working with a small number of seeds. This study is also the first known example of the ex situ propagation of Campanula bayerniana.

Effects of two substrates at different phosphorus levels on morphology and physiology of Dianthus barbatus Linn.

Dianthus barbatus linn. is widely used in gardens, mainly as flower beds and flower borders. The effects of different gradients of P on the growth and root morphology of Dianthus barbatus were studied to explore its morphological and physiological responses and adaptive strategies. Hence, this study provides a theoretical basis and practical guidance for D. barbatus production. Two soil substrates, namely loess and vegetable soil, and five phosphorus concentration gradients were set; no phosphorus application was used as the control. The morphology and physiology of D. barbatus were also investigated. Low-to-medium- and low-phosphorus treatments promoted the growth of D. barbatus in the above and underground parts of the plants grown on both substrates. Chlorophyll content, flower quantity, and acid phosphatase activity in the rhizosphere soil were significantly increased in the H1 and H2 treatments of loess and in the C4 treatment of vegetable soil. Thus, D. barbatus seems to reduce the damage caused by phosphorus stress by increasing chlorophyll content and root acid phosphatase activity. The latter was significantly higher in vegetable soil than in loess. Vegetable soil was more conducive to D. barbatus growth than loess.

Elemental assay of the fumarolic microecology of the Los Azufres (México) volcanic complex using nuclear analytical techniques

The elemental composition of the mantle is a key factor for the understanding of the science of the earth’s interior. However, the direct sampling of the mantle is a difficult and involved task. Fumarolic vapours carry a certain imprint of the mantle composition but are also relatively difficult to sample directly given their high temperature and acidity. Many terrestrial fu- marolic vents are colonized by extremophilic mosses that absorb the vapours and become repositories of the mantle elements brought up by the vapours. The elemental composition of the niche ecology of the fumarole therefore may serve as a near “proxy” for the deep-earth elemental profile of the region. Our study concerns the elemental composition of fumarolic plants, their rhizospheric soil, hydrothermal sediment and volcanic substrate collected from three geothermal microecological sites of the Los Azufres volcanic complex of Mexico. This work presents the results for the heavy elements (HE) Cd, Hg, Pb, Th and U that have been determined using the nuclear analytical techniques of Polarized Energy Dispersive Xray Fluorescence (PEDXRF) spectrometry, Instrumental Neutron Activation Analysis (INAA) as well as Inductively Coupled Plasma Mass spectrometry (ICPMS). The distributions of these HE in the aforesaid biogeochemical matrices are examined and rationalized with respect to possible mechanisms of their deposition. Comparisons with literature reports of the HE composition of fumarolic sulphur deposits and fumarolic vapours of the volcanoes of the Kuril Islands and geothermal aquifers of Iceland, are made. The HE composition is found to vary considerably by the geographic location of the fumarole. However, the trend of the concentrations of these 5 HE is found to be approximately the same for the fumarolic plants of Los Azufres as with the fumarolic vapours of the Kuril volcanoes the displacement being only in the magnitudes. Consequently, the concentrations of these 5 HE in the fumarolic plants are direct qualitative analogues of the vapours of those particular fumaroles of Los Azufres and thereby of the deep-earth geochemistry of that particular geothermal zone.

Ecological speciation in sympatric palms: 5. Evidence for pleiotropic speciation genes using gene knockout and high-throughput phenotyping

Abstract Theoretical models predict that sympatric, ecological speciation may be facilitated more readily when so-called ‘magic traits’ are present, linking traits under divergent selection with assortative mating. Such traits might be encoded by pleiotropic genes, that is, genes that affect multiple, apparently unrelated, phenotypes. However, few convincing examples of sympatric speciation exist, and empirical evidence for the role of magic traits in driving such speciation is rare. One of the strongest cases of sympatric speciation is the Howea palms of Lord Howe Island, Australia, comprising the sister species Howea belmoreana and Howea forsteriana, which have diverged due to soil substrate preferences and flowering time displacement. Here we investigate the role that pleiotropy may have played in the speciation process by carrying out high-throughput phenotyping experiments using 1830 Arabidopsis thaliana plants with knockouts of candidate Howea ‘speciation genes’. We identify several genes that show signatures of adaptive divergence between the Howea species and demonstrate pleiotropic roles in soil stress tolerance and flowering time, consistent with the Howea speciation scenario—notably, Howea orthologues of the A. thaliana loci At2-MMP, DCL1, RCD1, SAL1, and SIZ1. Empirical evidence is provided, therefore, for a range of pleiotropic genes with the potential to have driven sympatric speciation by generating magic traits which link divergent selection to non-random mating.

Complex dispersion analysis of true and pseudo surface waves propagating in two-dimensional viscoelastic seismic metamaterials

In this paper, the wave characteristics of true surface waves (TSWs) and pseudo surface waves (PSWs) in two-dimensional (2D) seismic metamaterials are explored. The 2D seismic metamaterial is formed by placing periodic concrete pillars on the surface of the soil substrate. The complex dispersion curves of the seismic metamaterial are numerically calculated by the ω–kapproach. The Kelvin–Voigt model is adopted to describe the material viscoelasticity. The results show that not only the TSW modes but also the PSW modes should be taken into account to evaluate the mitigation capacity of the seismic metamaterials. Due to the introduction of material viscoelasticity, the TSWs and PSWs convert from the propagative mode to the evanescent mode. When the PSW modes propagate along the substrate surface, their energy gradually leaks into the bulk of the substrate, leading to their transmission coefficient smaller than that of the TSW modes. Compared to the concrete pillars on the substrate surface, the viscoelasticity of the soil substrate plays a more important role in surface wave reduction. Moreover, the wave propagating length in the seismic metamaterials can be predicted by using complex dispersion relations.

Assessment of factors determining the rate and direction of plant communities development on coal mining spoils (the case study of the Gorlovskoye anthracite deposit)

The aim of the study. Identification and assessment of specific succession processes on self-revegetating coal mining spoils of the Gorlovskoye anthracite deposit, as related to the abiotic factors. Location and time of the study. The coal mining spoils of the Gorlovskoye anthracite deposit (54.568880 NL, 83.588956 EL), Novosibirsk region, Iskitimsky district, June 2023. Methods. The properties of soil substrates in technogenic landscapes were determined by officially attested and widely used methods of soil analyses. In field conditions, soil hardness was measured with a penetrometer, then soil density was calculated from its values using the dependence function. Total carbon and nitrogen contents were determined using a Perkin Elmer 2400 Series II CHNS/O analyzer. Statistical processing of the data was carried out using cluster, principal components and Spearman's correlation analyses. Results. In the anthracite coal mining spoils in the forest-steppe conditions of West Siberia, the high content of physical clay and clay-producing rocks in the developing soils promotes predominantly herbaceous plant groups, whereas slope areas with a high content of stones benefits the growth of woody vegetation.

Prospects of artificial soil substrate use for flower crops cultivation in protected ground

Harsh continental climate of Orenburg region is characterized by extremely low rates of precipitation at vegetation period, so the cultivation of flowers with protected root system has wide usage and is highly developed. The search for the optimal combined artificial soil in terms of physico-chemical composition is of great scientific and practical importance. In the short-term model experiment, variants of artificial soils are under exploration, with differing ratios of basic fillers that cover the physiological needs of flower crops when grown with a closed root system in greenhouse complexes. The results of laboratory study of artificially constructed soils based on essential materials (peat, coconut filler, river sand) and agricultural waste (horse manure, sunflower seed husk, raw fawl dung) are also presented. Combined soils are developed for the purpose of growing gerbera on “Bounty” soil and garden chrysanthemum on “Elysium” soil. These soils take into account the bioecological and agrotechnological features of greenhouse cultivation of these types of flower plants. The studied flower crops respond quite well to the physico-chemical composition of soils, showing stable growth of vegetative and generative organs.

Unravelling substrate availability and redox interactions on methane production in peat soils of China

AbstractThe availability of electron acceptors (EAs) in peatlands determines the potential of methane (CH4) formation under waterlogged conditions. Previous studies suggested that EAs can suppress CH4 production based on Gibbs free energy under the Redox Ladder Theory. However, growing evidence challenges this theory, raising the question of how the coupling of soil substrates with EAs influences CH4 emissions. To answer this key question, peat soils were collected across different climatic zones with different degrees of soil degradation. Anoxic incubation experiments were set up, and continuous addition of SO42−, Fe3+ and humic acid (HA) at different concentrations was followed by characterization of dissolved organic matter using fluorescence spectroscopy. Results suggest that low concentrations of SO42− (1000 μmol L−1), Fe3+ (100 μmol L−1) and HA (30 mgC L−1) promoted CH4 production in most of the peat soils. With the addition of SO42− and HA, increased CH4 emissions were attributed to the facilitation of dissolved organic carbon and increased quinone‐like component C1, which increased the substrate availability for methanogenesis. Furthermore, strengthened microbial activity as indicated by fluorescence component C2 led to higher CH4 production under Fe3+ treatments. On the other hand, at high concentrations of SO42− (5000 μmol L−1), Fe3+ (500 μmol L−1) and HA (50 mgC L−1), CH4 emissions rapidly decreased by 70.65 ± 1.57% to 96.25 ± 0.45% compared to control group without EAs addition, accompanied by increased δ13C‐CH4 signatures indicating the outweighed CH4 production under anaerobic oxidation of methane (AOM) when coupling with reduced EAs. The effect of EAs on CH4 emissions in peat soils could also be related to lability and characteristics of natural organic matter. Our results suggest that the CH4 production in waterlogged peatlands could be facilitated by regulating organic substrates at low EAs concentrations, but excessive EAs will reduce net CH4 emissions through AOM. The valuable discovery of CH4 production and oxidation processes provides insights for mitigating methane emissions from peatlands and regulating global climate change.

Assessment of Phytotoxicity of Used Zeolite as a Sorbent of the Dyeing and Finishing Production Wastewater by the Phytoindication Method

Introduction. The optimization of the technological processes for dyeing textile materials using wastewater adsorption purification via natural zeolite is relevant. The purified water can be used as recycled water for reuse in fabric dyeing technology.Problem Statement. The used zeolite sorbent belongs to the by-products of the dyeing and finishing industry’s wastewater treatment process. However, there is possibility to reuse it as a secondary material resource after determining the level of toxicity.Purpose. The purpose of this research is to assess the phytotoxicity of spent zeolite as a natural adsorbent for the purification of wastewater from dyeing and finishing production of textile dyes and auxiliary substances by the methods of phytoindication to determine possible directions of its use without additional costs for its disposal.Material and Methods. Wastewater from dyeing and finishing production and spent zeolite are research materials and winter barley seeds are the phytotest object. The method of scientific information generalization has been used; chemical analysis of wastewater has been carried out by the method of optical emission spectrometry with inductively coupled plasma; the intensity of winter barley stalks growth has been studied by the method of laboratory phytotesting; phytotoxicity has been evaluated with the use of analytical expression.Results. The phytotoxicity of used zeolite on water, soil, and concentrated substrates does not exceed 20%, which indicates the absence or low level of its toxicity and the possibility of reuse. The phytotoxicity of the aqueous substrate (water extract) of the spent zeolite has a negative value (–6.67%), which indicates that the studied aqueous substrate is not toxic.Conclusions. The experimental assessment of the toxicity of the used sorbent has allowed reusing it in the field of road construction and in the production of building materials.

Development of Jatropha curcas grown under limited amounts of daily water supply

Jatropha curcas plant is known for its soil tolerance and ability to thrive in low humidity conditions; however, there is a lack of systematic reports documenting the impact of limited water availability on its growth and development. This work aimed to analyze the development of J. curcas cultivated with daily supplementation of limited amounts of water. Five daily irrigation treatments were established to simulate varying annual rainfall levels: 250, 750, 1250, 1750 mm and 2250 mm. In each treatment, we used 16 seedlings of J. curcas MAP-08. The seedlings were sown in pots containing loam soil substrate mixed with vermicompost (19: 1 weight to weight). After 60 weeks of cultivation, plants receiving irrigation of 2250 mm per year exhibited growth rates 1.28, 1.51, 1.95 and 1.95 times higher, with respective increases in stem diameter of 15.6, 22.2, 41.9% and 47.7%, as well as 1.2, 1.4, 1.8, and 1.8 more leaves compared to those receiving 1750, 1250, 750, and 250 mm. There was no statistical difference in the number of branches (3.86 branches per plant) between the plants of the treatment with irrigation of 2250, 1750 mm and 1250 mm per year or between the plants belonging to the 750 and 250 mm per year (2.90 branches per plant) treatments. The plants of treatments 1750 and 2250 were the only ones that produced flowers. Although J. curcas typically functions as a succulent deciduous bush, with its stem serving to regulate leaf water potential and acting as a shock absorber against soil water potentials, its morphological and reproductive characteristics were recorded to be negatively affected when subjected to reductions of 22, 44, 67% and 89% in water availability compared to the maximum annual level recorded in the work area (2250 mm).

Contrasting potential impact patterns of unique and shared microbial species on nitrous oxide emissions in grassland soil on the Tibetan Plateau

Microbial nitrogen transformation processes in grasslands are important nitrous oxide (N2O) sources on the Tibetan Plateau. Different microorganisms carrying various functional nitrogen (N) cycling genes colonize different soil types and have varying impacts on N2O emissions. However, the role of specific microbial components such as unique and shared microbial species, in N2O flux in alpine grassland soils remains understudied. Thus, we combined gas chromatography-based static opaque chamber methods with metagenomic sequencing to investigate the role of unique and shared microbial species carrying N-cycling genes in N2O emissions from two alpine grassland types on the Tibetan Plateau. Our results showed that the N2O flux in the alpine meadows (9.48 × 10−9 g m−2 h−1) was higher than that in the alpine steppes (4.21 × 10−9 g m−2 h−1). Furthermore, our study revealed a significant negative correlation between the abundance of unique microbial species and the N2O flux in alpine steppes. In contrast, the abundance of shared microbial species was significantly and positively correlated with N2O flux. The unique microbial species in the phyla Chloroflexi and Actinobacteria carried the ureC, nasA and nirB genes, which could consume nitrogen substrates in forms other than producing N2O, which could explain the N2O reduction seen in the alpine steppes. In addition, the higher abundance of shared microbial species in the phyla Proteobacteria, Actinobacteria, Thaumarchaeota and Acidobacteria carried genes encoding denitrification pathways (nirK, narG, and norB) could interpret the higher N2O emissions in the alpine meadows. In addition, our study revealed that the soil substrate contents (e.g., soil organic carbon and total nitrogen) and soil environment factors (e.g., soil pH and soil moisture) were potentially important drivers of N2O emissions in soil via their regulation of the composition of unique and shared microbial communities carrying N-cycling genes. Collectively, our results suggested that identifying the unique and shared microbial species carrying different N-cycling genes could provide potential biological strategies for mitigating N2O emissions in alpine grasslands, such as blocking the growth of shared microbial species. Future management practices for mitigating N2O emissions in alpine grassland should also focus on adopting appropriate nutrient management strategies, such as balanced fertilization, to prevent excessive nutrient. Our findings provide insights for further elucidating the different potential regulatory effects of unique and shared microbial species on emissions under the control of the soil environment in different types of grasslands on the Tibetan Plateau.

Adaptation of Betula pendula Roth., Pinus sylvestris L., and Larix decidua Mill. to environmental stress caused by tailings waste highly contaminated by trace elements

The seedlings of some tree species can successfully develop in areas polluted by heavy metals. Research on such species is important in order to explore the possibility of introducing tree species for the permanent biological stabilization and reclamation of post-flotation tailings, especially after the final recycling of trace metals, but where concentrations remain much higher than in natural soils. To better understand the adaptation and reaction of Betula pendula Roth., Pinus sylvestris L., and Larix decidua Mill. seedlings to heavy metals pollution caused by tailings waste highly contaminated by trace elements: 1) the relationships between the concentration of heavy metals in the soil substrate, the efficiency of heavy metal ions accumulation in plant organs, and the biometric parameters of the seedlings; and 2) the threshold content of heavy metals in the roots above which the plant physiological response is triggered was determined. We assume that there are certain limit concentrations of heavy metals in the soil and fine roots, which depend on the tree species and beyond which the plant responds strongly to stressThe obtained results showed that Betula is a suitable species for the phytostabilization of post-flotation tailings due to its rapid growth rate and production of root biomass. The accumulation of metals in Betula roots was found to be much greater than in Pinus and Larix. Despite the high concentrations of heavy metals in the prepared substrates, there was only a slight transfer of these elements to the aboveground parts of the plant. At high soil concentrations, the heavy metals adversely affected the cellular and physiological processes of plants. In plants growing in such conditions, the activity of the antioxidant system depended both on the species and organ of the plant, as well as on the type and metal concentration.

Transmission of antimicrobial resistance in the gut microbiome of gregarious cockroaches: the importance of interaction between antibiotic exposed and non-exposed populations.

Antimicrobial resistance (AMR) is a major global health concern, further complicated by its spread via the microbiome bacterial members. While mathematical models discuss AMR transmission through the symbiotic microbiome, experimental studies are scarce. Herein, we used a gregarious cockroach, Pycnoscelus surinamensis, as an in vivo animal model for AMR transmission investigations. We explored whether the effect of antimicrobial treatment is detectable with metagenomic sequencing, and whether AMR genes can be spread and established in unchallenged (not treated with antibiotics) individuals following contact with treated donors, and under various frequencies of interaction. Gut and soil substrate microbiomes were investigated by metagenomic sequencing for bacterial community composition and resistome profiling. We found that tetracycline treatment altered the treated gut microbiome by decreasing bacterial diversity and increasing the abundance of tetracycline resistance genes. Untreated cockroaches that interacted with treated donors also had elevated tetracycline resistance. The levels of resistance differed depending on the magnitude and frequency of donor transfer. Additionally, treated donors showed signs of microbiome recovery due to their interaction with the untreated ones. Similar patterns were also recorded in the soil substrate microbiomes. Our results shed light on how interacting microbiomes facilitate AMR gene transmission to previously unchallenged hosts, a dynamic influenced by the interaction frequencies, using an in vivo model to validate theoretical AMR transmission models.IMPORTANCEAntimicrobial resistance is a rising threat to human and animal health. The spread of resistance through the transmission of the symbiotic gut microbiome is of concern and has been explored in theoretical modeling studies. In this study, we employ gregarious insect populations to examine the emergence and transmission of antimicrobial resistance in vivo and validate modeling hypotheses. We find that antimicrobial treatment increases the levels of resistance in treated populations. Most importantly, we show that resistance increased in untreated populations after interacting with the treated ones. The level of resistance transmission was affected by the magnitude and frequency of population mixing. Our results highlight the importance of microbial transmission in the spread of antimicrobial resistance.