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- Unique genes carried by abundant species enhance CH4 emissions during the
growing season at the Tibetan Plateau-
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Abstract: Abstract • CH4 emission rates followed an increased pattern during the growing season at Tibetan Plateau. • Unique genes carried by abundant species were positively correlated with CH4 emission rates. • Climate factors influenced CH4 emission rates by regulating microbial community and their genes. Microorganisms play pivotal roles in soil methane (CH4) emissions and their functional genes are origins of a key mechanism for soil CH4-cycling. However, understanding of the roles of specific genes (e.g., unique or shared genes carried by species) underlying CH4-cycling remains elusive. Here, we measured CH4 emission rates and investigated variations in microbial community and the abundance of genes carried by species during the growing season in alpine meadow on the Tibetan Plateau. We discovered that CH4 emission rates increased from 394.4, 745.9, and 1 092.7 µg CH4 m−2 h−1, in April, June, and August, respectively, and had a positive correlation with unique genes carried by abundant species during the growing season. Moreover, we found that unique genes carried by abundant species involved in methanogenesis processes have a higher abundance than methanotrophic processes. Further analysis indicated that climate factors (i.e., mean monthly temperature (MMT) and mean monthly precipitation (MMP)) influenced microbial community and their functional genes, and therefore affected the CH4 emission rates. Overall, the present study provides a novel insight into the variation of soil CH4 emissions from a functional gene perspective, highlighting the important roles of unique genes carried by abundant species in CH4 emissions in the Tibetan Plateau under seasonal variation. 
PubDate: 2023-12-05
- A single degenerated primer significantly improves COX1 barcoding
performance in soil nematode community profiling-
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Abstract: Abstract • A new COX1 primer for soil nematode metabarcoding was designed, and this primer outperforms other commonly used COX1 primer pairs in species recovery and quantity of PCR products. • The lack of reference database is the main reason that led to the low species recovery in COX1 metabarcoding. • We expanded current NCBI database by adding 51 newly generated COX1 reference sequences. Microscopic nematodes play important roles in soil ecosystems and often serve as bioindicators of soil health. The identification of soil nematodes is often difficult due to their limited diagnostic characters and high phenotypic plasticity. DNA barcoding and metabarcoding techniques are promising but lack universal primers, especially for mitochondrial COX1 gene. In this study a degenerated COX1 forward primer COIFGED was developed. The primer pair (COIFGED/JB5GED) outperforms other four commonly used COX1 primer pairs in species recovery and quantity of polymerase chain reaction (PCR) products. In metabarcoding analysis, the reads obtained from the new primer pair had the highest sequencing saturation threshold and amplicon sequence variant (ASV) diversity in comparison to other COX1 as well as 18S rRNA primers. The annotation of ASVs suggested the new primer pair initially recovered 9 and 6 out of 25 genera from mock communities, respectively, outperformed other COX1 primers, but underperformed the widely used 18S NF1/18Sr2b primers (16 out of 25 genera). By supplementing the COX1 database with our reference sequences, we recovered an additional 6 mock community species bringing the tally closer to that obtained with 18S primers. In summary, our newly designed COX1 primers significantly improved species recovery and thus can be supplementary or alternative to the conventional 18S metabarcoding. 
PubDate: 2023-12-04
- High nitrogen fertilizer input enhanced the microbial network complexity
in the paddy soil-
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Abstract: Abstract • N fertilizer altered bacterial community compositions by changing soil nutrients. • Bacterial ammonia oxidation became predominated with the increasing N rate. • Excessive N input caused the information of a more complex microbial network. • Intensified microbial competition by excessive N was due to negative link increase. Nitrogen (N) fertilization drives the structure and function of soil microbial communities, which are crucial for regulating soil biogeochemical cycling and maintaining ecosystem stability. Despite the N fertilizer effects on soil microbial composition and diversity have been widely investigated, it is generally overlooked that ecosystem processes are carried out via complex associations among microbiome members. Here, we examined the effects of five N fertilization levels (0, 135, 180, 225, and 360 kg N ha−1) on microbial co-occurrence networks and key functional taxa such as ammonia-oxidizers in paddy soils. The results showed that N addition altered microbial community composition, which were positively related to soil total N and available phosphorus (P) contents. The abundance of ammonia-oxidizing archaea (AOA) significantly decreased after N addition, whereas ammonia-oxidizing bacteria (AOB) increased in N360 treatment. Compared with low-N group (N0 and N135), the high-N group (N225 and N360) shaped more complex microbial webs and thus improved the stability of the microbial community. Partial least squares path modeling further revealed that N fertilizer had a higher effect on microbial network complexity in the high-N group (0.83) than the low-N group (0.49). Although there were more positive links across all microbial networks, the proportion of negative links significantly increased in the high-N network, suggesting that excess N addition aggravated the competition among microbial species. Disentangling these interactions between microbial communities and N fertilization advances our understanding of biogeochemical processes in paddy soils and their effects on nutrient supply to rice production. Our findings highlighted that highly N-enriched paddy soils have more stable microbial networks and can better sustain soil ecological functions to cope with the ongoing environmental changes. 
PubDate: 2023-12-04
- Stochastic community assembly of abundant taxa maintains the relationship
of soil biodiversity-multifunctionality under mercury stress-
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Abstract: Abstract • Soil abundant taxa diversity positively related to multifunctionality under Hg stress. • Microbial network complexity of soil abundant taxa supported the strength of SBF. • Stochastic assembly of soil abundant subcommunity supported the strength of SBF. • Stochastic ratio was the most important predictor for the strength of SBF. It is known that soil microbial communities are intricately linked to multiple ecosystem functions and can maintain the relationship between soil biodiversity and multifunctionality (SBF) under environmental stresses. However, the relative contributions and driving forces of abundant and rare taxa within the communities in maintaining soil biodiversity-multifunctionality relationship under pollution stresses are still unclear. Here, we conducted microcosm experiments to estimate the importance of soil abundant and rare taxa in predicting these relationships under heavy metal mercury (Hg) stress in paired paddy and upland fields. The results revealed that the diversity of abundant taxa, rather than rare taxa, was positively related to multifunctionality, with the abundant subcommunity tending to maintain a larger proportion of soil functions including chitin degradation, protein degradation, and phosphorus mineralization. Soil multitrophic network complexity consisting of abundant species showed positive correlations with biodiversity and multifunctionality, and supported the strength of SBF within a network complexity range. Stochastic assembly processes of the abundant subcommunity were positively correlated with the strength of SBF, although stochastic processes decreased the biodiversity and the multifunctionality, respectively. After simultaneously accounting for multiple factors on the strength of SBF, we found that the stochastic community assembly ratio of abundant taxa was the most important predictor for SBF strength under Hg stress. Our results highlight the importance of abundant taxa in supporting soil multifunctionality, and elucidate the linkages between community assembly, network complexity and SBF relationship under environmental stresses. 
PubDate: 2023-12-04
- Effects of nitrogen and phosphorus additions on soil nematode community of
soybean farmland-
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Abstract: Abstract The nitrogen (N) and phosphorus (P) addition promotes the abundance of soybean soil nematodes. The addition of nitrogen can alleviate the suppression of phosphorus on nematodes. Phosphorus addition affects nematode abundance by ammonium nitrogen. With global warming, the increasing of industrial and agricultural activities and demand for fossil fuels, large amounts of nitrogen and phosphorus compounds are released into the atmosphere, resulting in an annual increase in nitrogen and phosphorus deposition. The nematodes, as one of the main functional groups of soil organisms, occupy multiple trophic levels in soil detritus food networks. However, few studies on the effects of nitrogen and phosphorus on soil nematodes, and the results are uncertain. This experiment was conducted in soybean farmland and four treatments included control, nitrogen addition, phosphorus addition, and N + P addition. The results showed that both phosphorus and N + P addition significantly increased the abundance of soil nematodes, but that had no effects on soil nematodes richness. Redundancy analysis showed that nitrate nitrogen, soil moisture content, and pH were environmental factors driving different dietary changes in soil nematode communities. The effect of phosphorus addition on the abundance of nematode communities mainly affects ammonium nitrogen. Our findings revealed that nitrogen addition when phosphate fertilizer is added to soybean farmland will have a certain positive effect on the soil underground food web, which provides a basis for better explaining the effect of nitrogen and phosphorus addition on soybean farmland. 
PubDate: 2023-12-04
- Contrasting response of rice rhizosphere microbiomes to in situ
cadmium-contaminated soil remediation-
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Abstract: Abstract • Changes in soil properties and microbial communities regulated rhizosphere protistan assemblages. • Bacterial community was more sensitive to soil amendments than protists and fungi. • Soil amendments trigger the role of specific protistan taxa Cercozoa on microbial interactions. Understanding the responses of different rhizosphere microbial lineages to soil amendments during in situ remediation of Cd-contaminated soil is of great importance in the assessment of the restoration and crop health. Here, we evaluated the effects of lime (LM), biochar (BC), pig manure (PM), and a commercial Mg-Ca-Si conditioner (CMC) on the rice rhizosphere soil physicochemical properties and community assembly of bacteria, fungi, and protists in a six-year consecutive application of soil amendments field trial. Our results indicated that among the four amendments, the BC and CMC had the best efficiency in increasing soil pH, which were 5.2% and 16.2%, respectively. Despite the differences in soil Cd concentrations is not noticeable, all the soil amendment treatments significantly decreased the proportion of available Cd in total Cd compared to the control. Soil amendments significantly altered the diversity of bacterial community, while they had no effect on fungal and protistan communities. Linear discriminant analysis effect size (LEfSe) showed that the bacteria was more sensitive to soil amendment-induced changes. For protists, treatments with LM and BC changed the groups of protistan consumers, while treatments with PM and CMC significantly increased the relative abundances of protistan phototrophs. Co-occurrence network analysis revealed that soil amendments increased microbial network complexity and triggered the role of protists, especially for the predatory protists Cercozoa, on microbial trophic interactions. Further variation partitioning analysis revealed that edaphic properties, bacterial and fungal communities compositions together explained the 77% of the total variation in protistan community, and the stronger correlations between diversity of bacterial and protistan communities suggested that the bacteria community was a more important biotic driver of the protistan community. Overall, our findings demonstrate the distinct responses of rice rhizosphere microbial communities to soil amendment applications, highlighting the interactive associations between microbiomes, which is vital for enhancing our ability to develop effective strategies for sustainable soil management. This study enhances our understanding of the ecological roles of protists under soil amendment applications and highlights their potential contributions in bioremediation and environmental applications for Cd-contaminated soil. 
PubDate: 2023-12-04
- Different responses of soil fauna gut and plant rhizosphere microbiomes to
manure applications-
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Abstract: Abstract • Microbial attributes were compared between soil fauna gut and plant rhizosphere. • Manure applications decreased or increased gut or rhizosphere bacterial diversity. • Stochastic or deterministic processes drove gut or rhizosphere bacterial assembly. • Manure applications increased bacterial network complexity of gut and rhizosphere. Diverse microbes inhabit animals and plants, helping their hosts perform multiple functions in agricultural ecosystems. However, the responses of soil fauna gut and plant rhizosphere microbiomes to livestock manure applications are still not well understood. Here we fed Protaetia brevitarsis larvae (PBL) with chicken manure and collected their frass. The frass and manure were applied as fertilizers to lettuce pots. We then compared the changes of microbial diversity, community assembly, and potential functions between the gut group (i.e., all PBL gut and frass samples) and the rhizosphere group (i.e., all rhizosphere soil samples). We revealed that manure applications (i.e., feeding or fertilization) decreased bacterial diversity in the gut group but increased that in the rhizosphere group. Particularly, the proportions of Bacilli in the gut group and Gammaproteobacteria in the rhizosphere group were increased (up to a maximum of 33.8% and 20.4%, respectively) after manure applications. Stochastic and deterministic processes dominated community assembly in the gut and rhizosphere microbiomes, respectively. Manure applications increased the microbial co-occurrence network complexity of both the gut and rhizosphere groups. Moreover, the proportions of functional taxa associated with human/animal pathogens in the gut group and carbon/nitrogen cycling in the rhizosphere group were enhanced (up to 2.6-fold and 24.6-fold, respectively). Our findings illustrate the different responses of microbial diversity, community assembly, and potential functions in soil fauna gut and plant rhizosphere to manure applications. The results could enhance our knowledge on the reasonable utilization of animal and plant microbiomes in agricultural management. 
PubDate: 2023-12-04
- Lignocellulosic fraction-induced niche differentiation within
dissimilatory iron reducing bacterial groups in a paddy soil-
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Abstract: Abstract Responses of soil DIRB to lignocellulosic fractions during a 6-week microcosm incubation were investigated. Anaeromyxobacter, Bacillus, and Clostridium maintained their dominance throughout the incubation. Distinct DIRB groups proliferated under specific lignocellulosic fraction amendments. Limits of insufficient ferric iron on the proliferation varied by DIRB group. Dissimilatory iron reducing bacteria (DIRB) are phylogenetically and physiologically diverse in paddy soils, where iron reduction closely couples with the oxidation of rice straw-derived carbon in the straw returning scenarios. However, few studies have addressed the niche differentiation within DIRB groups during the degradation of lignocellulosic fractions of rice straw. This study conducted a 6-week microcosm incubation experiment to reveal the distinct responses of DIRB groups under specific lignocellulosic fraction amendments with and without ferrihydrite (Fh) addition in a flooded paddy Ultisol. Results showed that the total absolute abundance of the 19 detected DIRB groups did not vary significantly during the incubation. Anaeromyxobacter, Bacillus, and Clostridium were the dominant DIRB groups for all lignocellulosic treatments whereas Thermincola was dominant but only under xylan amendment with Fh addition. DIRB-nodes in the co-occurrence networks of bacterial community mainly belonged to Anaeromyxobacter and Bacillus. Clostridium and Thermincola, Alkaliphilus and Anaeromyxobacter, and Alicyclobacillus, Desulfobulbus, and Desulfosporosinus were specifically proliferated under xylan, cellulose, and lignin amendments, respectively. Whether the proliferation was limited by insufficient ferric iron varied by bacterial group. These findings suggested the lignocellulosic fraction-induced niche differentiation within DIRB groups, which advanced our understanding of the ecology of DIRB in paddy soils under straw returning. 
PubDate: 2023-12-02
- Collembolans maintain a core microbiome responding to diverse soil
ecosystems-
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Abstract: Abstract The unique gut habitat led to a core intestinal microbiome in diverse soil ecosystems. The collembolan guts may help eliminate soil pathogens. Host-selection carried more weight on community assembly of gut microbiome. Soil invertebrates are widely distributed in the ecosystem and are essential for soil ecological processes. Invertebrate gut microbiome plays an important role in host health and has been considered as a hidden microbial repository. However, little is known about how gut microbiome in soil invertebrates respond to diverse soil ecosystems. Based on a laboratory microcosm experiment, we characterized the assembling of microbiome of soil collembolans (Folsomia candida) from six representative regions of the soil ecosystem which they inhabit. Results showed that collembolan gut microbial communities differed significantly from their surrounding soil microbial communities. A dominant core gut microbiome was identified in gut habitat. Community analyses indicated that deterministic process dominated in the community assembly of collembolan gut microbiome. The results further demonstrate a dominant contribution of host selection in shaping gut microbiome. It is also worthy to mention that pathogens, such as common agricultural phytopathogenic fungi Fusarium, were involved in core microbiome, indicating that collembolans could act as vectors of pathogens. Our results unravelled the existence of gut core microbiome of collembolans in soil ecosystems and provided new insights for understanding the crucial role of gut microbiome of soil fauna in maintaining microbial biodiversity and stability of soil ecosystems. 
PubDate: 2023-12-02
- Impact of metal polluted sewage water on soil nematode assemblages in
agricultural settings of Aligarh, India-
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Abstract: Abstract Sewage water in agriculture threatens human health and soil ecosystems through metal pollution. Nematodes show promise as bioindicators of soil health due to their abundance and position in soil food webs. Metal-polluted water decreased abundance of certain nematode groups and Sigma Maturity Index. Metal pollution positively affected nematode groups with r-selected life cycles. Sewage water has been inappropriately used in agriculture, posing possible threats to human health and the soil ecosystems by its constituent pollutants, especially heavy metals. Correct evaluation of its influences on soil biomes needs to consider the response of soil fauna. Among soil organisms, nematodes are seen as the best promising candidates for bioindicators of soil health. Here in, we collected soil samples from fresh water irrigated field from three sites (S1, S2 and S3) and sewage water irrigated distance gradient (5 m–40 m), to assess the influence of metal (Cu, Zn, Cd, Mn, Pb) polluted water on various characteristics of nematode communities. The results indicated that the heavy metals decreased the abundance of C-p3 nematodes, herbivores, and predatory nematodes as well as sigma maturity index, whereas, C-p1, C-p2, bacterivore and fungivore nematodes abundance and diversity positively responded to the metal pollution. Generally, nematode genera with r-selected life cycle were positively affected and those with K-selected life cycle were negatively affected by metal pollution. Overall nematode community has potential to be used as indicator of pollution stress in agricultural soils to check soil health and sustainability. 
PubDate: 2023-12-02
- Divergent responses of growth rate and antioxidative system of ten
Bacillus strains to acid stresses-
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Abstract: Abstract Response of growth rate and antioxidative system of ten Bacillus strains to acid stresses was assayed. Strong acid treatment significantly decreased the growth rate of the strains. Acid stresses increased the GPX activity and GSSG content of the tested strains. Divergent changes occurred in ROS and antioxidative system (SOD, CAT, GR, MDA and GSH). Environmental changes including soil acidification exert obvious stresses on soil ecosystems and influence soil microorganisms. In this study, ten microbial strains were incubated under different acid treatments to investigate responses of microbial growth and antioxidative system to acid stress. All the strains belong to Bacillus genus, but exhibit distinct ecological functions. We observed that these microbial strains had obviously different pH tolerance threshold, in spite of the close phylogenetic classification among strains. Acid stresses exerted significant effects on microbial antioxidative system, including superoxide dismutase (SOD), catalase (CAT) and glutathione transferring enzymes (GPX and GR) and reactants (GSH and GSSH), but the effects were strain specific. Furthermore, we found acid stress effects on total variances of the investigated microbial antioxidative system along the first two principal components (PCs). Activities of CAT and SOD contributed substantially to PC1 that reflected obvious acid effects on NC7 and ZC4, and closely related to intracellular malondialdehyde content. The GSSG activities and GSH/GSSG contributed greatly to PC2 that unveiled acid stress effects on most of the microbial strains. Our results highlight substantially heterogeneous responses of microbial strains to acid stress and support that phylogenetic closeness does not imply functional similarity of soil microorganisms under environmental changes. 
PubDate: 2023-11-28
- Soy, soil and beyond
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Abstract: Summary Soy and its quest for future food production.
PubDate: 2023-07-31
DOI: 10.1007/s42832-023-0190-6
- Constraints on enzyme production at low O2 and limitations of
stoichiometric vector analyses: A commentary on Chen et al. (2022)-
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PubDate: 2023-07-01
DOI: 10.1007/s42832-023-0183-5
- Fine root litter quality regulates soil carbon storage efficiency in
subtropical forest soils-
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Abstract: Abstract High-quality and low-quality root litter had contrasting patterns of mass loss. Greater litter-derived C was incorporated into soils under high-quality root litter. Root litter decay rate or litter-derived C were related to soil microbial diversity. Root litter quality had little effect on soil physicochemical properties. High root litter quality was the main driver of enhanced soil C storage efficiency. Decomposing root litter is a major contributor to soil carbon (C) storage in forest soils. During decomposition, the quality of root litter could play a critical role in soil C storage. However, it is unclear whether root litter quality influences soil C storage efficiency. We conducted a two-year greenhouse decomposition experiment using 13C-labeled fine root litter of two tree species to investigate how root litter quality, represented by C to nitrogen (C/N) ratios, regulates decomposition and C storage efficiency in subtropical forest soils in China. ‘High-quality’ root litter (C/N ratio = 26) decayed faster during the first year (0–410 days), whereas ‘low-quality’ root litter (C/N ratio = 46) decomposed faster toward the end of the two-year period (598–767 days). However, over the two years of the study, mass loss from high-quality root litter (29.14 ± 1.42%) was lower than ‘low-quality’ root litter (33.01 ± 0.54%). Nonetheless, root litter C storage efficiency (i.e., the ratio of new root litter-derived soil C to total mineralized root litter C) was significantly greater for high-quality root litter, with twice as much litter-derived C stored in soils compared to low-quality root litter at the end of the experiment. Root litter quality likely influenced soil C storage via changes in microbial diversity, as the decomposition of high-quality litter declined with increasing bacterial diversity, whereas the amount of litter-derived soil C from low-quality litter increased with fungal diversity. Our results thus reveal that root litter quality mediates decomposition and C storage in subtropical forest soils in China and future work should consider the links between root litter quality and soil microbial diversity. 
PubDate: 2023-06-22
DOI: 10.1007/s42832-023-0182-6
- Characterization of dissolved organic matter distribution in forestland
and farmland of mollisol based on untargeted metabolomics-
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Abstract: Abstract Characterization of mollisol soil DOM by untargeted metabolomics is possible. The polarity of the extractants determines the polarity of the extracted DOM. Land use patterns affect the biological functions and co-network interaction of DOM. Mollisol soil is a major contributor to food production. Clarification of the molecular characteristics of dissolved organic matter (DOM) will contribute to the overall understanding and management of mollisol soil. However, the complexity of DOM poses a challenge to understanding its molecular characteristics. In this study, we investigated the molecular characteristics of DOM (< 1 000 Da) in mollisol soils with different soil use patterns (forestland and dryland) based on untargeted metabolomics. Here, we confirmed the feasibility of untargeted metabolomics for the molecular characterization of DOM in mollisol soils. DOM in forestland is mainly derived from plant metabolites, and DOM can perform more biological functions. However, DOM in dryland has complex composition and has powerful co-occurrence network interactions due to human activities. Water has better extraction efficiency for polar DOM, while organic reagents can efficiently extract lipid-like DOM, but the polarity of the extractant has less influence on the DOM than the soil physicochemical properties. Meanwhile, 14-dihydroxyzeatin screened based on metabolomics can be used as a potential indicator for corn land. Therefore, untargeted metabolomics can be an effective method to characterize the DOM molecules of mollisol soil, which provides new insights for management of mollisol soil and sustainable agricultural development. 
PubDate: 2023-06-22
DOI: 10.1007/s42832-023-0179-1
- Bacterial biogeography in China and its association to land use and soil
organic carbon-
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Abstract: Abstract • 6102 high-quality sequencing results of soil bacterial samples were re-analyzed. • The type of land use was the principal driver of bacterial richness and diversity. • SOC content is positively correlated with key bacteria and total nitrogen content. Soil organic carbon (SOC) is the largest pool of carbon in terrestrial ecosystems and plays a crucial role in regulating atmospheric CO2 concentrations. Identifying the essential relationship between soil bacterial communities and SOC concentration is complicated because of many factors, one of which is geography. We systematically reanalyzed 6 102 high-quality bacterial samples in China to delineate the bacterial biogeographic distribution of bacterial communities and identify key species associated with SOC concentration at the continental scale. The type of land use was the principal driver of bacterial richness and diversity, and we used machine learning to calculate its influence on microbial composition and their co-occurrence relationship with SOC concentration. Cultivated land was much more complex than forest, grassland, wetland and wasteland, with high SOC concentrations tending to enrich bacteria such as Rubrobacter, Terrimonas and Sphingomona. SOC concentration was positively correlated with the amounts of soil total nitrogen and key bacteria Xanthobacteraceae, Streptomyces and Acidobacteria but was negatively correlated with soil pH, total phosphorus and Micrococcaceae. Our study combined the SOC pool with bacteria and indicated that specific bacteria may be key factors affecting SOC concentration, forcing us to think about microbial communities associated with climate change in a new way. 
PubDate: 2023-06-10
DOI: 10.1007/s42832-023-0172-8
- Diverse organic carbon activates soil microbiome functioning via niche
modulation-
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PubDate: 2023-06-10
DOI: 10.1007/s42832-023-0180-8
- Soil microbial communities as potential regulators of N2O sources in
highly acidic soils-
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Abstract: Abstract • Soil pH was a key driver of N2O emission and sources in acidic soils. • N2O emission was significantly positively associated with the ratio of ITS to 16S. • N2O was significantly correlated with bacterial and fungal community composition. • Fungi contributed to N2O in highly acidic tea plantations and vegetable fields. Acidic soil is a main source of global nitrous oxide (N2O) emissions. However, the mechanism behind the high N2O emissions from acidic soils remains a knowledge gap. The objective of this microcosm incubation study was to pin-point the microbial mechanisms involved in N2O production processes in acidic soils. For that purpose, the isotopic signatures and microbial community structure and composition of four soil samples were examined. The results showed that highly acid soils (pH = 3.51) emitted 89 times more N2O than alkaline soils (pH = 7.95) under the same nitrogen (N) inputs. Fungal denitrification caused high N2O emissions in acidic soils. ITS to 16S abundance ratio was positively correlated with cumulative N2O emissions from the tested soils. The highly acid soils (pH < 4.5) showed greater fungal nirK gene abundance and lower abundance of AOA-amoA, AOB-amoA, nirK, nosZ I and nosZ II genes. The unclassified Aspergillaceae fungi (63.65%) dominated the highly acidic soils and was the most strongly correlated genus with N2O emissions. These findings highlight that soil microbial community structures, denitrifying fungi in particular, shaped by low pH (pH < 4.5) lead to high N2O emissions from acidic soils. 
PubDate: 2023-06-02
DOI: 10.1007/s42832-023-0178-2
- Erosion effects on soil microbial carbon use efficiency in the mollisol
cropland in northeast China-
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Abstract: Abstract • Soil erosion decreased soil microbial CUE and increased microbial uptake of carbon. • Soil erosion decreased microbial CUE by decreasing substrate C, N and MBC and increasing soil pH. • Soil microbes had to increase their uptake rate to cope with the loss of substrates with increasing erosion rate. • Soil microbial respiration increased with increasing degree of erosion. • Soil microbial growth rate remained relative stable under different degrees of soil erosion. • Microbial CUE in soil surface was less responsive to erosion than that in deeper soil. Soil microbial carbon use efficiency (CUE) is an important synthetic parameter of microbial community metabolism and is commonly used to quantify the partitioning of carbon (C) between microbial growth and respiration. However, it remains unclear how microbial CUE responds to different degrees of soil erosion in mollisol cropland. Therefore, we investigated the responses of soil erosion on microbial CUE, growth and respiration to different soil erosion rates in a mollisol cropland in northeast China based on a substrate independent method (18O−H2O labeling). Soils were sampled at four positions along a down-slope transect: summit, shoulder, back and foot. We found microbial CUE decreased significantly with increasing soil erosion rate in 5–20 cm soil, but did not change in 0–5 cm. The decrease of microbial CUE in subsoil was because microbes increased C uptake and allocated higher uptake C to microbial basal respiration with increasing soil erosion rate. Microbial respiration increased significantly with soil erosion rate, probably due to the more disturbance and unbalanced stoichiometry. Furthermore, soil microbes in surface soil were able to maintain their growth rates with increasing degree of erosion. Altogether, our results indicated that soil erosion could decrease microbial CUE by affecting soil physical and chemical properties, resulting in more decomposition of soil organic matter and more soil respiration, which had negative feedbacks to soil C sequestration and climate changes in cropland soil. 
PubDate: 2023-04-15
DOI: 10.1007/s42832-023-0176-4
- Soil salinization increases the stability of fungal not bacterial
communities in the Taklamakan desert-
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Abstract: Abstract • Bacterial richness declined but fungal richness increased under salinization. • Bacteria did not become interactively compact or facilitative under salinization. • Fungi exhibited more compartmentalized and competitive patterns under salinization. • Fungal stability showed steeper increases under salinization than bacterial stability. Soil salinization is a typical environmental challenge in arid regions worldwide. Salinity stress increases plant convergent adaptations and facilitative interactions and thus destabilizes communities. Soil bacteria and fungi have smaller body mass than plants and are often efficient against soil salinization, but how the stability of bacterial and fungal communities change with a wide range of soil salinity gradient remains unclear. Here, we assessed the interactions within both bacterial and fungal communities along a soil salinity gradient in the Taklamakan desert to examine (i) whether the stability of bacterial and fungal communities decreased with soil salinity, and (ii) the stability of which community decreased more with soil salinity, bacteria or fungi. Our results showed that the species richness of soil fungi increased but that of soil bacteria decreased with increasing salinity in topsoils. Fungal communities became more stable under soil salinization, with increasing compartmentalization (i.e., modularity) and proportion of competitions (i.e., negative:positive cohesion) as salinity increased. Bacterial communities exhibited no changes in modularity with increasing salinity and smaller increases in negative:positive cohesion under soil salinization compared to fungal communities. Our results suggest that, by altering interspecific interactions, soil salinization increases the stability of fungal not bacterial communities in extreme environments. 
PubDate: 2023-04-03
DOI: 10.1007/s42832-023-0175-5
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