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Introduction:Nitrogen (N) deposition seriously affects the function of carbon (C) and N cycling in terrestrial ecosystems by altering soil microbial communities, especially in desert steppe ecosystems. However, there is a need for a comprehensive understanding of how microorganisms involved in each C and N cycle process respond to N deposition. Methods: In this study, shotgun metagenome sequencing was used to investigate variations in soil C and N cycling-related genes in the desert steppe in northern China after 6 years of the following N deposition: N0 (control); N30 (N addition 30 kg ha-1 year-1): N50 (N addition 50 kg ha-1 year-1). Results: N deposition significantly increased the relative abundance of Actinobacteria (P < 0.05) while significantly decreased the relative abundances of Proteobacteria and Acidobacteria (P < 0.05). This significantly impacted the microbial community composition in desert steppe soils. The annual addition or deposition of 50 kg ha-1 year-1 for up to 6 years did not affect the C cycle gene abundance but changed the C cycle-related microorganism community structure. The process of the N cycle in the desert steppe was affected by N deposition (50 kg ha-1 year-1), which increased the abundance of the pmoAamoA gene related to nitrification and the nirB gene associated with assimilation nitrite reductase. There may be a niche overlap between microorganisms involved in the same C and N cycling processes. Discussion: This study provides new insights into the effects of N deposition on soil microbial communities and functions in desert steppe and a better understanding of the ecological consequences of anthropogenic N addition. [ABSTRACT FROM AUTHOR]

Increasing amounts of greenhouse gases, such as CO2, released into the atmosphere have a profound impact on global climate change. Understanding how soil organic carbon (SOC) mineralization changes as a result of land‐use change can shed light on the mechanisms by which SOC mineralization occurs, thus illuminating pathways to achieve global C neutrality targets. Accordingly, the Grain for Green Project (GGP) on the Loess Plateau was used as the starting point to observe how microorganisms affect SOC mineralization through field sampling and laboratory incubation experiments. We found a significant increase in SOC mineralization rates resulting from the GGP, though only at the soil surface (0.47–6.40 mg·kg−1 soil·day−1). We also found that soil microorganisms had a significant effect on different types of C sources, and Proteobacteria and Ascomycota/Mortierellomycota were the dominant bacterial and fungal groups at the GGP sites. The factors limiting SOC mineralization varied with farmland conversion to other land‐use types, and the direct and interactive contributions of these factors were quantified. The explanatory power examined in terms of land‐use ability to directly predict SOC mineralization rates was as follows: farmland (0.82), grassland (0.76), shrubland (0.41), and forestland (0.29). Along the increasing vegetative complexity gradient from farmland to forestland, the individual variable explanatory values decreased, while the relative importance of the interactive effects between variables increased. Our research demonstrates that the GGP increased soil biological activity and improved microbial community ability to metabolize C sources, thereby accelerating SOC mineralization. This will provide a scientific basis for decisions to enhance global semidrought recovery. [ABSTRACT FROM AUTHOR]

In recent decades, ecological cyclic cultivation models have attracted increasing attention, primarily because the decomposition of crop residues and litter enhances soil organic matter content, thereby altering the soil microenvironment and regulating the diversity and functions of soil microbial communities. However, the effects of different coffee waste mulching on the diversity of soil microbial communities and their functions are still unclear. Therefore, this study set up four kinds of covering treatments: uncovered coffee waste (C), covered coffee litter (L), covered coffee pericarp (P), and both covered coffee litter and pericarp (PL). The results showed that compared to the control, coffee pericarp mulching significantly increased the soil available potassium (SAK) content by 18.45% and alkali hydrolyzed N (SAN) content by 17.29%. Furthermore, coffee pericarp mulching significantly increased bacterial richness and diversity by 7.75 and 2.79%, respectively, while litter mulching had little effect on bacterial abundance and diversity was smaller. The pericarp mulching significantly increased the abundance of Proteus by 22.35% and the abundance of Chlamydomonas by 80.04%, but significantly decreased the abundance of Cyanobacteria by 68.38%, while the coffee litter mulching significantly increased the abundance of Chlamydomonas by 48.28%, but significantly decreased the abundance of Cyanobacteria by 73.98%. The increase in soil SAK promoted bacterial Anoxygenic_photoautotrophy, Nitrogen_respiration, Nitrate_respiration, Nitrite_respiration, and Denitrification functions. The above results indicate that the increase in available soil potassium and alkali hydrolyzed N content under coffee pericarp cover is the main reason for promoting the diversity and richness of bacterial community and promoting the changes in bacterial community structure and function. The use of coffee pericarps in coffee plantations for ecological recycling helps to improve the diversity of the soil microbial community and maintain the relative stability of the microbial community structure and function, promoting soil health conservation and the sustainable development of related industries. [ABSTRACT FROM AUTHOR]

Decontamination of oil‐affected soil is an urgent worldwide issue. In this study, a microcosm experiment was conducted to explore the effect of combined utilization of urea and biochar on oil‐contamination remediation in an eastern China oil‐field soil and explored their impact on soil physicochemical properties, organic pollutants degrading‐related enzyme and functional genes, microbiome, and metabolome. Then, a pot experiment was conducted to verify the impact of the remediation experiment. Results showed that a combined application of biochar and nitrogen reduced 78.6% of total petroleum hydrocarbons in soil. Combined treatment enhanced soil dehydrogenase and catalase activities, alkB, and CYP gene abundances relative to Control. Moreover, nitrogen input reduced soil microbial α‐diversity, while improving the relative abundances of Alcanivorax and Pseudogym. In addition, the pathways of glyoxylate and dicarboxylate metabolism, naphthalene and anthracene degradation, butanoate metabolism, pyruvate metabolism, and glycolysis or gluconeogenesis were up‐regulated in combined treatment relative to Control. Besides, both biochar and nitrogen addition can increase the number of edges and clustering coefficient of the microbial network, and improve the network robustness. The pot experiment showed that combined treatments enhanced ryegrass shoot length, root length, and biomass by 57.8%, 38.5%, and 42.8%, respectively. Overall, this study proved the feasibility of combined biochar and urea co‐application in remedying oil‐contaminated soil and shed light on the inner mechanism. [ABSTRACT FROM AUTHOR]

Straw is widely incorporated into soil worldwide, but most studies have concentrated on the effects of straw mulching or incorporation with topsoil. To determine the effect of depth of straw incorporation on bacterial and fungal communities, we established a field experiment in a region in Northeast China with Haplic Chernozems using four treatments: conventional tillage (CT, tillage to a depth of 15 cm with no straw incorporation), straw incorporation with conventional tillage (SCT, tillage to a depth of 15 cm), inversion tillage (IT, tillage to a depth of 35 cm) and straw incorporation with inversion tillage (SIT, tillage to a depth of 35 cm). The soils were managed by inversion to a depth of 15 or 35 cm after harvest. The results show that soil organic carbon content was significantly higher and pH and bulk density were significantly lower in the 15–35 cm layer in IT and SIT than CT and SCT. Fungal abundance was higher with straw incorporation, but fungal diversity was lower in the 0–15 cm layer in SCT and SIT than in CT and IT. Path length in the bacterial network was shorter and connectivity was higher in CT + SCT than in IT + SIT, leading to a more complex ecosystem, and the fungal network had opposite patterns. The key taxa in the phylum Actinobacteriota and Ascomycota in the microbial networks changed dramatically at the genus level following inversion tillage with straw amendment, which may increase bacterial network resistance to environmental disturbances and unstable fungal networks, resulting in large changes in the fungal community involved in the decomposition of recalcitrant straw-derived C and the more efficient acquisition of limiting resources. [ABSTRACT FROM AUTHOR]

Buddleja sessilifolia is a plant species with extremely small populations (PSESP) in southwest China. The trial of transplantation failed in our Buddleja outdoor garden, and only succeeded in the flowerpots of greenhouse. In this study, we conducted metagenomic analyses on microbial diversity in bulk soil from wild habitat of B. sessilifolia, the Buddleja garden and the B. sessilifolia pots of greenhouse, and meanwhile analyzed soil physicochemical properties. We aimed to uncover the related soil factors which may influence the transplantation of B. sessilifolia. Our results showed the bulk soil from the wild habitat of B. sessilifolia and the B. sessilifolia pots had significantly richer total potassium content than that from the Buddleja garden. Bacterial order Rhizobiales and archaeal class Nitrososphaeria showed a higher diversity in both the wild habitat and the pot than the garden. Furthermore, soil total potassium content was the most correlated to bacterial community structure of the bulk soil, while soil total nitrogen content and total phosphorus content were most important to archaeal and fungal community structures. We accordingly inferred that B. sessilifolia had a high demand on potassium and microbial Rhizobiales and Nitrososphaeria in soil for its survival. Our findings will contribute to the ex-situ conservation of B. sessilifolia. [ABSTRACT FROM AUTHOR]

Grazing is the most extensive land use in grassland worldwide, wherein the soil microbiome is known to support multiple ecosystem functions. Yet, the experimental impact of livestock grazing and dung deposits on the soil microbiome in degraded grassland remains poorly understood. We examined the effects of sheep dung depositions on the bacterial and fungal microbiome of two grasslands: non-degraded and degraded (long-term overgrazing) in northern China. Specifically, sheep dung was experimentally added to the soil and its effects on the soil microbial community were determined 3 months later (corresponding to livestock excreta deposited throughout the entire growing season of grassland, June to September). Our results showed that sheep dung additions showed negative effects on the soil microbiome of already degraded grassland, while with a diminished impact on the non-degraded grassland. In particular, dung deposition decreased soil microbial Shannon index, notably significantly reducing fungal diversity in degraded grassland. Moreover, sheep dung deposition modifies soil bacterial community structure and diminishes bacterial community network complexity. The alteration of soil pH caused by sheep dung deposition partially explains the decline in microbial diversity in degraded grassland. However, sheep dung did not alter the relative abundance and community composition of bacterial and fungal dominant phyla either in the non-degraded or in the degraded grassland. In conclusion, the short-term deposition of sheep dung exerted a detrimental influence on the microbial community in degraded grassland soil. It contributes new experimental evidence regarding the adverse effects of livestock grazing, particularly through dung deposition, on the soil microbiome in degraded grassland. This knowledge is crucial for guiding managers in conserving the soil microbiome in grazed grasslands. • We simulated the rapid response of soil microbiome to sheep dung deposition between non-degraded and degraded grassland. • Sheep dung applications on soil microbiome in non-degraded and degraded were first illustrated. • Sheep dung deposition reduced soil Shannon diversity in degraded grassland. • Bacterial community structure changes and network complexity decreases in degraded grassland. • Soil microbiomes in non-degraded grassland were not insensitive to sheep dung applications. [ABSTRACT FROM AUTHOR]

Replacement of primary old-growth forests by secondary woodlands in threatened subtropical biomes drives important changes at the level of the overstory, understory and forest floor, but the impact on belowground microbial biodiversity is yet poorly documented. In the present study, we surveyed by metabarcoding sequencing, the diversity and composition of soil bacteria and fungi in the old-growth forest, dominated by stone oaks (Lithocarpus spp.) and in the secondary Yunnan pine woodland of an iconic site for biodiversity research, the Ailaoshan National Nature Reserve (Ailao Mountains, Yunnan province, China). We assessed the effect of forest replacement and other environmental factors, including soil horizons, soil physicochemical characteristics and seasonality (monsoon vs. dry seasons). We showed that tree composition and variation in soil properties were major drivers for both bacterial and fungal communities, with a significant influence from seasonality. Ectomycorrhizal Operational Taxonomic Units (OTUs) dominated the functional fungal guilds. Species richness and diversity of the bacterial and fungal communities were higher in the pine woodland compared to the primary Lithocarpus forest, although prominent OTUs were different. The slightly lower complexity of the microbiome in the primary forest stands likely resulted from environmental filtering under relatively stable conditions over centuries, when compared to the secondary pine woodlands. In the old-growth forest, we found a higher number of species, but that communities were homogeneously distributed, whereas in the pine woodlands, there is a slightly lower number of species present but the communities are heterogeneously distributed. The present surveys of the bacterial and fungal diversity will serve as references in future studies aiming to assess the impact of the climate change on soil microbial diversity in both old-growth forests and secondary woodlands in Ailaoshan. [ABSTRACT FROM AUTHOR]

[Display omitted] • We investigated the assembly of soil bacteria, fungi, archaea, protists & animals across different soil depths in five stand ages. • Soil biotic communities exhibited a decreasing trend in alpha diversity with increasing soil depth. • Acidobacteriia, Agaricomycetes, Bathyarchaeia, Chlorophyceae and Clitellata, were most abundant classes. • Total nitrogen, available phosphorus and pH were the most influencing factors for changes in soil biotic communities. • As compared to soil depth, stand age was not dominatingly influencing the structure of other biotic communities. Soil biota plays a crucial role in the terrestrial ecosystem. There is growing momentum to understand the community structure and diversity of total belowground soil biota across large ecological scales. Soil biota follow divergent trends with respect to soil physiochemical properties in different ecosystems; however, little is known about their response to stand development across multiple soil depths in Chinese fir plantations, which is the most important tree species across all over China, popular for its timber production. Here, we investigated the community assembly of soil bacteria, fungi, archaea, protists and animals across three different vertical soil profiles (0–10, 10–20, 20–40 cm) using a chronosequence of Chinese fir representing five different stand ages (5, 8, 21, 27, 40 years) in South China. High throughput illumine Hiseq2500 sequencing. Our results showed that soil biotic communities exhibited a decreasing trend in alpha diversity of bacteria, fungi, protists and animals with increasing soil depth; however, archaea showed an opposite trend. Most abundant soil bacterial, fungal, archaeal, protist and animal classes were Acidobacteriia, Agaricomycetes, Bathyarchaeia, Chlorophyceae and Clitellata, respectively. Correlation of vertical distribution of biotic communities and variations in soil physiochemical properties explained that total nitrogen (TN), available phosphorus (AP) and pH were the most influencing factors for changes in soil biotic communities. Although the stand age was a contributing factor for fungal and animal beta diversity, however, as compared to soil depth, it was not dominatingly influencing the structure of other biotic communities. Collectively, these results reveal a new perspective on the vertical variation and distinct response patterns of soil biotic communities at a fine scale across different stand ages of Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Soil microbial communities play important roles in biogeochemical cycles and ecosystem functioning. However, how tree and grass species affect soil microbial structure and functions in semi-arid regions is poorly understood. In this study, we used sequencing of representative genes and bioinformatic analysis to compare the soil bacterial and fungal communities and their functional groups among legume and non-legume broad-leaved plantations, conifer plantations, artificial grassland, and adjacent farmland in a semi-arid area of Northern China. We found that soil bacterial diversity and abundance were significantly increased by legume plantations, especially Robinia pseudoacacia , compared to farmland. Soil bacterial communities were dominated by K-strategists in plantation soils and by r-strategists in farmland and grassland soils. Soil fungal communities showed contrasting patterns between Ascomycetes and Basidiomycota across treatments, and the highest abundance of nutrient indicator taxa Mortierellomycota was observed in plantation soils. Functional analysis revealed that afforestation altered the capacity of soil bacteria for organic compound mineralization and C and N cycling, and that different plant species enriched different types of ectomycorrhizal and saprophytic fungi. Moreover, we found that plantations and grasslands formed more connected but less complex and stable bacterial co-occurrence networks than farmland, and that conifer plantations increased the closeness of soil fungal networks compared to broad-leaved plantations. Our results suggest that tree and grass species play a key role in shaping the soil microbial community structure and functional groups, and provide valuable information for choosing suitable tree and grass species for ecosystem restoration and management in semi-arid regions. [ABSTRACT FROM AUTHOR]

The microbiome plays a crucial role in soil nitrogen (N) cycling and in regulating its bioavailability. However, the functional and genomic information of microorganisms encoding N cycling in response to copper (Cu) and cadmium (Cd) contamination is largely unknown. Here, metagenomics and genome binning were used to examine microbial N cycling in Cu and Cd co-contaminated red paddy soils collected from a polluted watershed in southern China. The results showed that soil Cu and Cd concentrations induced more drastic changes in microbial N functional and taxonomic traits than soil general properties. Soil Cu and Cd co-contamination stimulated microbial nitrification, denitrification, and dissimilatory nitrate reduction processes mainly by increasing the abundance of Nitrospira (phylum Nitrospirota), while inhibiting N fixation by decreasing the abundance of Desulfobacca. These contrasting changes in microbial N cycling processes suggested a potential risk of N loss in paddy soils. A high-quality genome was identified as belonging to Nitrospirota with the highest abundance in heavily contaminated soils. This novel Nitrospirota strain possessed metabolic capacities for N transformation and metal resistance. These findings elucidate the genetic mechanisms underlying soil N bioavailability under long-term Cu and Cd contamination, which is essential for maintaining agricultural productivity and controlling heavy metal pollution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Understanding the interaction between heavy metals and soil microbiomes is essential for maintaining ecosystem health and functionality in the face of persistent human-induced challenges. This study investigated the complex relationships between heavy metal contamination and the functional characteristics of soil microbial communities in the tidal soils of Hangzhou Bay, a region experiencing substantial environmental pressure due to its proximity to densely populated and industrialized regions. The north-shore sampling site showed moderate contaminations (mg/kg) of total arsenic (16.61 ± 1.13), cadmium (0.3 ± 0.05), copper (31.28 ± 1.23), nickel (37.44 ± 2.74), lead (34.29 ± 5.99), and zinc (120.8 ± 5.96), which are 1.29-2.94 times higher than the geochemical background values in Hangzhou Bay and adjacent areas. In contrast, the south-shore sampling site showed slightly higher levels of total arsenic (13.76 ± 1.35) and cadmium (0.13 ± 0.02) than the background values. Utilizing metagenomic sequencing, we decoded microbial functional genes essential for nitrogen, phosphorus, sulfur, and methane biogeochemical cycles. Although soil available nickel content was relatively low at 1 mg/kg, it exhibited strong associations with diverse microbial genes and biogeochemical pathways. Four key genes-hxlB, glpX, opd, and phny-emerged as pivotal players in the interactions with available nickel, suggesting the adaptability of microbial metabolic responses to heavy metal. Additionally, microbial genera such as Gemmatimonas and Ilumatobacter, which harbored diverse functional genes, demonstrated potential interactions with soil nickel. These findings highlight the importance of understanding heavy metal-soil microbiome dynamics for effective environmental management strategies in the tidal soils of Hangzhou Bay, with the goal of preserving ecosystem health and functionality amidst ongoing anthropogenic challenges., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Cover cropping is a sustainable agricultural practice that profoundly influences soil microbial communities and ecosystem functions. However, the responses of soil ecosystem functions and microbial communities to cover cropping under the projected changes in precipitation, remain largely unexplored. To address this gap, a field experiment with cover cropping (control, hairy vetch, ryegrass, and hairy vetch plus ryegrass) and precipitation reduction (ambient precipitation and 50 % reduction in ambient precipitation) treatments was conducted from 2018 to 2020 in an agroecosystem located in the Guanzhong Plain of China. Soil ecosystem functions related to nutrient storage, nutrient cycling, and organic matter decomposition were measured to assess the soil multifunctionality index and bacterial and fungal communities were determined by Illumina NovaSeq sequencing. The results indicated that cover cropping enhanced soil multifunctionality index, and reduced precipitation strengthened this effect. Microbial community composition, rather than microbial diversity, was significantly altered by cover cropping regardless of precipitation reduction. Cover cropping increased the microbial network complexity and stability, but this effect was dampened by reduced precipitation. The microbial community composition and network complexity significantly and positively correlated with soil multifunctionality index under ambient and reduced precipitation conditions. Linear regression analyses and structural equation models collectively demonstrated that the increase in soil multifunctionality index was attributed to cover cropping-induced changes in microbial community composition and network complexity, irrespective of precipitation reduction. This study highlights the crucial role of microbial communities in driving the response of soil multifunctionality to cover cropping in the context of reduced precipitation, which has important implications for agricultural management and sustainability under future climate change scenarios., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

6 PPD-Q (6 PPD-Quinone) is an ozone-induced byproduct derived from the degradation of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6 PPD), commonly found in road dust resulting from tire wear. However, the extent of 6 PPD-Q pollution in urban soil remains unclear. This study investigates the spatial and temporal accumulation patterns of 6 PPD-Q in greenbelt soils in Ningbo, and explores the correlation between 6 PPD-Q accumulation and soil microbial community composition and functions. Our findings indicate that 6 PPD-Q is present (ranging from 0.85 to 12.58 μg/kg) in soil samples collected from both sides of urban traffic arteries. Soil fungi exhibit higher sensitivity to 6 PPD-Q accumulation compared to bacteria, and associated fungi (Basidiomycota) may be potential biomarkers for environmental 6 PPD-Q contamination. Co-occurrence network analysis reveals that the bacterial microbial network in summer exhibits greater stability and resilience in response to 6 PPD-Q inputs than in winter. However, 6 PPD-Q accumulation disrupts the network structure of fungal communities to some extent, leading to reduced diversity in fungal microbial communities. Long-term accumulation of 6 PPD-Q weakens the nitrogen and phosphorus cycling potential within urban soil, while the enhancement of carbon cycling may further promote 6 PPD-Q degradation in urban soil. Taken together, this study provides new insights into the ecological risks of 6 PPD-Q in urban soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Atrazine, a triazine herbicide, is widely used around the world. The residue of atrazine due to its application in the fore-rotating crop maize has caused phytotoxicity to the following crop sweet potato in China. Bioaugmentation of atrazine-contaminated soil with atrazine-degrading strains is considered as the most potential method to remove atrazine from soil. Nevertheless, the feasibility of bioaugmentation and its effect on soil microbiome still need investigation. In this study, Paenarthrobacter sp. AT-5, an atrazine-degrading strain, was inoculated into agricultural soils contaminated with atrazine to investigate the bioaugmentation process and the reassembly of the soil microbiome. It was found that 95.9% of 5 mg kg−1 atrazine was removed from the soils when inoculated with strain AT-5 with 7 days, and the phytotoxicity of sweet potato caused by atrazine was significantly alleviated. qRT-PCR analysis revealed that the inoculated strain AT-5 survived well in the soils and maintained a relatively high abundance. The inoculation of strain AT-5 significantly affected the community structure of the soil microbiome, and the abundances of bacteria associated with atrazine degradation were improved. [ABSTRACT FROM AUTHOR]

Understanding the driving factors of soil multifunctionality is of great significance for the protection and restoration of degraded terrestrial ecosystems. However, the effects of above‐ and belowground factors are rarely evaluated simultaneously, and the driving mode of both factors on soil multifunctionality is not clear. Here, we evaluated the restoration of mobile dunes threatened by desertification through aerial seeding, that is, the sowing of seeds through aerial devices, from 1983 to 2015 in Mu Us Desert, China, using soil and plant data. The effect of aerial seeding on the restoration of soil multifunctionality, plant diversity, and soil microbial diversity in mobile dunes was significant, which was tested by loess regression. Further, the plant diversity becomes saturated in the later stages of restoration. The effect also leads to the restoration of soil multifunctionality lags behind plant and soil microorganisms. The factors (plant and soil microorganisms) driving soil multifunctionality is not a separate action or a joint action that test by structural equation models (SEMs), but that plants restore first and then indirectly drive soil multifunctionality through soil microorganisms during the restoration process. We also found that bacteria are the main direct indicators of soil multifunctionality, which was tested using Random forests modelling. This study highlights that plants indirectly drive soil multifunctionality through soil microorganisms, and soil microorganisms are key to elucidating the restoration mechanism and process. [ABSTRACT FROM AUTHOR]

Despite important progress in understanding the impacts of forest clearing and logging on above‐ground communities, how these disturbances affect soil microbial β‐diversity and the ecological processes driving microbial assemblages are poorly understood. Furthermore, whether and how the microbial shifts affect vegetation composition and diversity during recovery of post‐logged forests remain elusive.Using a spatial grid experiment design in a primary tropical forest intermixed with post‐logged patches naturally recovered for half century in Hainan Island, China, we characterized and explained the distance–decay relationships of soil microbial similarities in primary, selectively logged and clear‐cut forests.Selectively logged sites showed a lower spatial turnover rate of bacterial assemblages based on phylogenetic and taxonomic β‐diversity, but a higher spatial turnover rate of fungal assemblages based on phylogenetic β‐diversity, suggesting a higher level of phylogenetic variability in fungal composition. Clear‐cut sites showed lower spatial turnover for both bacterial and fungal assemblages based on the two β‐diversity, indicating community homogenization. Main drivers of microbial assemblages shifted from soil properties in primary forest to tree composition in selectively logged sites, whereas microbial–tree associations declined in clear‐cut sites, leading to stochastically organized microbial assemblages.Synthesis and applications. The increased fungal phylogenetic turnover with tree turnover following selective logging promotes unassisted recovery of plant diversity. In contrast, the decoupling of tree and microbial turnover following clear‐cutting suggests restoration approaches based on tree planting, and tree species that have strong associations with bulk soil microbial community should be considered. Our findings advance the understanding of spatial patterns, processes and drivers of soil microbial assemblages in parallel with tree community recovery during regeneration of post‐logged tropical forests, and highlight the importance of coupling assemblage patterns between tree and soil fungal communities for conserving tropical forest biodiversity. [ABSTRACT FROM AUTHOR]

Miscanthus spp. are increasingly cultivated in cropland worldwide due to their bioenergy potential and multiple ecological services. Effects of long‐term cropland‐to‐Miscanthus conversion without N fertilizer on soil microbiome and N cycling largely remain unknown. We aimed to explore the effects of Miscanthus conversion on soil microbiome and N cycling over a 15‐year period. We analyzed diversity, composition, and abundance of bacterial and archaeal communities using 16S rRNA amplicon sequencing, and abundances of N‐cycling‐related genes using quantitative polymerase chain reaction of 0–10 cm soils collected from bare land, cropland, 10‐year Miscanthus × giganteus, and 15‐year Miscanthussacchriflorus land in Beijing. Conversion decreased soil sand and micro‐aggregate proportion, nitrate N (NiN), available phosphorus levels, conductivity, temperature, and pH, while increasing proportion of soil clay and macro‐aggregate (MAA), soil organic C (SOC), available N (AN), exchangeable Mg2+ (EMg2+), and available potassium (AK) contents as well as microbial C/N. Consequently, diversity, composition, and abundance of soil bacterial community exhibited larger changes than those values of archaeal community after conversion. Soil AP, EMg2+, AK, and SOC were key factors in shifting microbiome from the cropland to Miscanthus pattern. Moreover, abundances of bacterial and archaeal communities and the N fixer gene nifH increased, whereas that of the bacterial ammonia monooxygenase gene decreased. The copies of other N‐cycling‐related genes in the two Miscanthus lands seemed similar to those values of cropland. The nifH copies negatively correlated with soil NiN and positively correlated with AN, EMg2+, ECa2+, SOC, AK, and MAA. We conclude that changes in soil microbiome pattern induced by the variation of soil properties enhance microbial N fixation potential, maintaining stable N levels and robust N cycling with lower N leakage risk after conversion. These results should inspire farmers and governments to large‐scale use Miscanthus on marginal cropland in Northern China. [ABSTRACT FROM AUTHOR]

Verticillium wilt is a disastrous disease in cotton‐growing regions in China. As a common management method, cotton rotation with cereal crops is used to minimize the loss caused by Verticillium dahliae. However, the correlation between soil microbiome and the control of Verticillium wilt under a crop rotation system is unclear. Therefore, three cropping systems (fallow, cotton continuous cropping, and cotton–maize rotation) were designed and applied for three generations under greenhouse conditions to investigate the different responses of the soil microbial community. The soil used in this study was taken from a long‐term cotton continuous cropping field and inoculated with V. dahliae before use. Our results showed that the diversity of the soil bacterial community was increased under cotton–maize rotation, while the diversity of the fungal community was obviously decreased. Meanwhile, the structure and composition of the bacterial communities were similar even under the different cropping systems, but they differed in the soil fungal communities. Through microbial network interaction analysis, we found that Verticillium interacted with 17 bacterial genera, among which Terrabacter had the highest correlation with Verticillium. Furthermore, eight fungal and eight bacterial species were significantly correlated with V. dahliae. Collectively, this work aimed to study the interactions among V. dahliae, the soil microbiome, and plant hosts, and elucidate the relationship between crop rotation and soil microbiome, providing a new theoretical basis to screen the biological agents that may contribute to Verticillium wilt control. [ABSTRACT FROM AUTHOR]

The underground community of soil organisms, known as soil biota, plays a critical role in terrestrial ecosystems. Different ecosystems exhibit varied responses of soil organisms to soil physical and chemical properties (SPCPs). However, our understanding of how soil biota react to different soil depths in naturally established population of salinity tolerant Tamarix ramosissima in desert ecosystems, remains limited. To address this, we employed High-Throughput Illumina HiSeq Sequencing to examine the population dynamics of soil bacteria, fungi, archaea, protists, and metazoa at six different soil depths (0–100 cm) in the naturally occurring T. ramosissima dominant zone within the Taklimakan desert of China. Our observations reveal that the alpha diversity of bacteria, fungi, metazoa, and protists displayed a linear decrease with the increase of soil depth, whereas archaea exhibited an inverse pattern. The beta diversity of soil biota, particularly metazoa, bacteria, and protists, demonstrated noteworthy associations with soil depths through Non-Metric Dimensional Scaling analysis. Among the most abundant classes of soil organisms, we observed Actinobacteria, Sordariomycetes, Halobacteria, Spirotrichea, and Nematoda for bacteria, fungi, archaea, protists, and metazoa, respectively. Additionally, we identified associations between the vertical distribution of dominant biotic communities and SPCPs. Bacterial changes were mainly influenced by total potassium, available phosphorus (AP), and soil water content (SWC), while fungi were impacted by nitrate (NO 3 -) and available potassium (AK). Archaea showed correlations with total carbon (TC) and AK thus suggesting their role in methanogenesis and methane oxidation, protists with AP and SWC, and metazoa with AP and pH. These correlations underscore potential connections to nutrient cycling and the production and consumption of greenhouse gases (GhGs). This insight establishes a solid foundation for devising strategies to mitigate nutrient cycling and GHG emissions in desert soils, thereby playing a pivotal role in the advancement of comprehensive approaches to sustainable desert ecosystem management. • Soil nutrients and diversity of soil biota across different soil depths in Tamarix ramosissima was investigated. • Declining pattern in the alpha diversity of soil biota was recorded with an increase in soil depth except archaea. • The most prevalent classes were Actinobacteria, Sordariomycetes, Halobacteria, Spirotrichea, and Nematoda. • AP and SWC influenced bacteria and protists, while AK affected fungi and archaea and metazoa by AP and pH. • Our findings provide a new perspective on the vertical distribution of soil biota in T. ramosissima in desert ecosystem. [ABSTRACT FROM AUTHOR]

Land desertification poses a significant challenge in the Brazilian semiarid region, encompassing a substantial portion of the country. Within this region, the detrimental effects of human activities, particularly unsuitable anthropic actions, have resulted in diminished vegetation cover and an accelerated rate of soil erosion. Notably, practices such as overgrazing and the conversion of native forests into pasturelands have played a pivotal role in exacerbating the process of land desertification. Ultimately, land desertification results in significant losses of soil organic matter and microbial diversity. To address this pressing issue and contribute to the existing literature, various land restoration practices, such as grazing exclusion, cover crops, and terracing, have been implemented in the Brazilian semiarid. These practices have shown promising results in terms of enhancing soil fertility and restoring microbial properties. Nonetheless, their effectiveness in improving soil microbial properties in the Brazilian semiarid region remains a subject of ongoing study. Recent advances in molecular techniques have improved our understanding of microbial communities in lands undergoing desertification and restoration. In this review, we focus on assessing the effectiveness of these restoration practices in revitalizing soil microbial properties, with a particular emphasis on the soil microbiome and its functions. Through a critical assessment of the impact of these practices on soil microbial properties, our research aims to provide valuable insights that can help mitigate the adverse effects of desertification and promote sustainable development in this ecologically sensitive region., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Soil microbes and enzymes play important roles in plant growth and metabolism. However, for Glechoma longituba (Nakai) Kupr., an important crop with edible and medicinal uses in China, their effects are not well elucidated. To explore their impacts on plant morphology and bioactive compounds, the plant samples and rhizosphere soil of five different G. longituba populations were collected and investigated in this study. After high-throughput sequencing combined with data analyses, high microbial diversity and richness in the rhizosphere soil of each G. longituba population were observed, and the variations on bacterial and fungal community compositions among these soil samples were also proved. The activities of urease, neutral phosphatase, sucrase, protease, and polyphenol oxidase were significantly different among the rhizosphere soils from different G. longituba populations. Among the major microbial communities and soil enzymes we studied, the genera of Tomentella, Sebacina, Fusarium, Nitrospira, and the activity of soil sucrase were remarkably correlative with both the morphological indices and the contents of bioactive compounds of G. longituba by redundancy analysis. These findings would help guide the scientific plantation of G. longituba to promote its medicinal quality. [ABSTRACT FROM AUTHOR]

Grazing causes changes in microbiome metabolic pathways affecting plant growth and soil physicochemical properties. However, how grazing intensity affects microbial processes is poorly understood. In semiarid steppe grassland in northern China, shotgun metagenome sequencing was used to investigate variations in soil carbon (C) and nitrogen (N) cycling-related genes after six years of the following grazing intensities: G0, control, no grazing; G1, 170 sheep days ha−1 year−1; G2, 340 sheep days ha−1 year−1; and G3, 510 sheep days ha−1 year−1. Taxa and functions of the soil microbiome associated with the C cycle decreased with increasing grazing intensity. Abundances of genes involved in C fixation and organic matter decomposition were altered in grazed sites, which could effects on vegetation decomposition and soil dissolved organic carbon (DOC) content. Compared with the control, the abundances of nitrification genes were higher in G1, but the abundances of N reduction and denitrification genes were lower, suggesting that light grazing promoted nitrification, inhibited denitrification, and increased soil NO 3 − content. Q-PCR further revealed that the copies of genes responsible for carbon fixation (cbbL) and denitrification (norB) decreased with increasing grazing intensity. The highest copy numbers of the nitrification genes AOA and AOB were in G1, whereas copy numbers of the denitrification gene nirK were the lowest. A multivariate regression tree indicated that changes in C fixation genes were linked to changes in soil DOC content, whereas soil NO 3 − content was linked with nitrification and denitrification under grazing. Thus, genes associated with C fixation and the N cycle affected how C fixation and N storage influenced soil physicochemical properties under grazing. The findings indicate that grazing intensity affected C and N metabolism. Proper grassland management regimes (e.g., G1) are beneficial to the balances between ecological protection of grasslands and plant production in the semiarid steppe. • Grazing intensity affected soil microbial carbon (C) and nitrogen (N) metabolism. • Grazing affected C cycling by increasing C fixation and decreasing C decomposition. • Dissolved organic C was the predominant driver of changes in soil C fixation. • Changes in soil nitrate content under grazing impacted the N cycle. [ABSTRACT FROM AUTHOR]

Revealing the effects of reforestation on soil antibiotic resistome is essential for assessing ecosystem health, yet related studies remain scarce. Here, to determine the responses of the soil antibiotic resistome to reforestation, 30 pairs of cropland and forest soil samples were collected from southwestern China, a region with high environmental heterogeneity. All the forests had been derived from croplands more than one decade ago. The diversity and abundance of soil antibiotic resistance genes (ARGs), metal resistance genes (MRGs), mobile genetic elements (MGEs), and pathogens were determined by metagenomic sequencing and real-time PCR. The results showed that reforestation significantly increased soil microbial abundance and the contents of Cu, total carbon, total nitrogen, total organic carbon, and ammonium nitrogen. Nevertheless, it decreased the contents of soil Zn, Ba, nitrate nitrogen, and available phosphorus. The main soil ARGs identified in this region were vancomycin, multidrug, and bacitracin resistance genes. Reforestation significantly increased the soil ARG abundance by 62.58%, while it decreased the ARG richness by 16.50%. Reforestation exerted no significant effects on the abundance of heavy metal resistance genes and pathogens, but it doubled the abundance of MGEs. Additionally, reforestation substantially decreased the co-occurrence frequencies of ARGs with MRGs and pathogens. In contrast, the correlation between ARGs and MGEs was greatly enhanced by reforestation. Similarly, the correlations between soil ARG abundance and environmental factors were also strengthened by reforestation. These findings suggest that reforestation can substantially affect the soil antibiotic resistome and exerts overall positive effects on soil health by decreasing ARG richness, providing critical information for assessing the effects of "grain for green" project on soil health. [Display omitted] • Reforestation decreases the diversity of soil antibiotic resistance genes (ARGs). • Reforestation increases the abundance of soil ARGs. • Reforestation reduces ARG-metal resistance gene co-occurrence frequency. • Reforestation enhances the horizontal transfer potential of soil ARGs. • Reforestation decreases soil antibiotic-resistant pathogen occurrence probability. [ABSTRACT FROM AUTHOR]

Soil biota are critical for services and the functionality of terrestrial ecosystems. Studying the composition of total belowground soil biota across different ecological scales has become popular in recent years. Soil biota follow divergent responses to soil physiochemical properties (SPP) in different forest ecosystems; however, little is known about their comparative responses to various stand ages across different soil depths in Chinese fir (CF) and secondary natural forests (NF). The community assemblages of soil bacteria, fungi, archaea, protists, and animals were compared across three soil depths (0–10, 10–20, 20–40 cm) using five age (5, 8, 21, 27, and 40 years) chronosequences of CF and NF in Southern China. Our results revealed that with increased soil depth and stand age, a comparatively high abundance and increased diversity of soil biota were observed in the NF as compared to CF. Across different stand ages, NF had significantly higher total nitrogen, total carbon, available potassium, and a significantly high abundance of top soil biota classes i.e., Acidobacteriia, Planctomycetacia, Gammaproteobacteria (Bacteria), Agaricomycetes (Fungi), Group 1.1c (Archaea), Colpodea (Protists), and Enoplea (Animals). Similarly, a significantly high alpha diversity was recorded in NF for bacterial, protists, and animal communities. We observed that the composition of soil bacteria and fungi were more influenced by changes in soil depth and stand ages, while negligible or least changes were observed for soil animals in both CF and NF chronosequences. Correlations between soil biota and environmental factors indicated that total nitrogen and available potassium had the greatest influence on NF. Our results highlight the importance of NF for the enrichment of soil fertility and improvement in the assemblage of soil biota. These findings are important for an insightful understanding regarding the dynamics of total belowground soil biota in CF and NF that can be helpful for more sustainable forest management in subtropical ecosystems. [ABSTRACT FROM AUTHOR]

Crop management practices can strongly affect soil microbial communities and their ecosystem services, but it remains unclear how these effects extend to different agroecosystem contexts, such as in tea plantations. A comparison of paired tea plantations (organic vs. conventional managements) in Eastern China was conducted to investigate the ways in which agricultural management can affect soil physicochemical parameters, composition, diversity and assembly of soil bacterial communities. Compared with conventional management, organically managed tea plantations on average increased soil microbial C by 164.4% and soil microbial N by 482.9%, respectively in Wuyi and Xiangshang sites. The results of 16S rRNA pyrosequencing analyses revealed that the diversity and richness of bacterial communities was similar under both managements, but the structure of soil bacterial communities was significantly reshaped by the management type (R2 = 0.410, p < 0.01) used in the tea plantation as well as geographical origin (R2 = 0.268, p < 0.01). Co-occurrence network analysis uncovered that organic management weakened the connectivity among soil bacteria taxa in tea plantations, indicating more stable microbial associations under conventional management practices. These results emphasized the importance of management and geological origins in reshaping soil bacterial structures in tea plantations. [Display omitted] • Organic management of tea plantations significantly increased soil MBC and MBN. • H′ of soil bacterial communities was negatively correlated with TOC and TON. • Organic management weakened interactions of soil bacteria taxa in tea plantations. • Management type shaped soil bacterial communities structures in tea plantations. [ABSTRACT FROM AUTHOR]

For urban planning and infrastructural projects, considerable attention has been paid to the relationship between soil biota, especially protists, and edaphic conditions in various land-use types having different plant species in the Xiong'an New Area of China. To elucidate this relationship, we assessed edaphic variables and soil biota compositions and compared them among 5 habitat types: human-made forests, crop cultivations, arid rivers, Baiyangdian (BYD) Lake, and around oil wells. In all, 12 experimental plots from terrestrial and aquatic ecosystems were assessed using high-throughput sequencing of environmental DNA, targeting the V3-V4 region of the 16S rRNA gene, internal transcribed spacer 1, and V4 region of the 18S rRNA gene for bacteria, fungi, and protists, respectively. The abundance of bacterial and protist communities was higher than fungi, possibly because fungi prefer acidic soil conditions and likely have greater susceptibility to anthropogenic activities. Across all experimental plots, land-use types contributed the most to the β-diversity of soil biota, followed by soil moisture. Diversity and richness were significantly higher at aquatic habitats than at terrestrial habitats. Predictive metagenomic analysis of trophic groups predicted relatively high frequency of functional genes from bacterial metabolism pathways (carbohydrate and amino acid); contrary to expectation, phototrophic protists, but not fungal symbionts and protistan consumers, were the dominant group at the BYD Lake. Geographical coordinates showed significant (P < 0.05) relationships with all microbiome taxa (nodes at network) from all land-use types. Moreover, soil-microbiome relationships were more complex and more intense at crop habitats. Links between protist and fungal taxa were the highest at the petroleum-contaminated sampling sites, indicating the importance of these two soil microbiomes in polluted soil. Thus, our findings suggest that human manipulation and land-use types are crucial factors for soil biota structure and composition across our sampling sites., Competing Interests: Declaration of competing interest All authors confirmed the manuscript submission, and we have no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Azoxystrobin is a widely used systemic fungicide in the Northeast of China, but it is unclear how azoxystrobin impacts the soil microbiome. Thus, we studied the impact of azoxystrobin on the microbial community structure and function in Chinese Spodosols. Field soil that had never been exposed to azoxystrobin was amended in laboratory batch experiments with 0 mg kg-1, 2 mg kg-1, 25 mg kg-1 and 50 mg kg-1 of azoxystrobin. Four soil enzymes (urease, invertase, phosphatase and catalase) were monitored to assess the impact of azoxystrobin on carbon, nitrogen and phosphorus cycling as well as the microbial activity. The results show that the urease, invertase, and phosphatase (hydrolytic enzymes) activities was inhibited by as little as 2 mg kg−1 of azoxystrobin after 35 days, whereas the catalase (oxidoreductase enzyme) activity was promoted by the same concentration in most cases. Biolog Ecoplate analysis indicated that the utilization of different carbon sources was inhibited by azoxystrobin. 16S rRNA sequencing showed the bacterial operational taxonomic unit richness and the Shannon index decreased with increasing azoxystrobin concentration. Relative abundances of Sphingomonas decreased while Amycolatopsis and Sphingomonas increased by addition of increasing levels of azoxystrobin. In conclusion, azoxystrobin application to Spodosols leads to reduced urease, invertase, and phosphatase activities, which can impact nutrient cycling and carbon utilization. Furthermore, azoxystrobin application changed the microbiome community structure. • Hydrolytic enzymes are inhibited by increasing concentrations of azoxystrobin. • Azoxystrobin changes the relative abundances of soil microbial communities. • Decreased urease activity from azoxystrobin may impact nutrient cycling. [ABSTRACT FROM AUTHOR]

Mine tailings contain dangerously high levels of toxic metals which pose a constant threat to local ecosystems. Few naturally grown native plants can colonize tailings site and the existence of their root-associated microbial populations is poorly understood. The objective of this study was to give further insights into the interactions between native plants and their microbiota during natural attenuation of abandoned V-Ti magnetite mine tailings. In the present work, we first examined the native plants' potential for phytoremediation using plant/soil analytical methods and then investigated the root microbial communities and their inferred functions using 16 S rRNA-based metagenomics. It was found that in V-Ti magnetite mine tailings the two dominant plants Bothriochloa ischaemum and Typha angustifolia were able to increase available nitrogen in the rhizosphere soil by 23.3% and 53.7% respectively. The translocation factors (TF) for both plants indicated that B. ischaemum was able to accumulate Pb (TF = 1.212), while T. angustifolia was an accumulator of Mn (TF = 2.502). The microbial community structure was more complex in the soil associated with T. angustifolia than with B. ischaemum. The presence of both plants significantly reduced the population of Acinetobacter. Specifically, B. ischaemum enriched Massilia, Opitutus and Hydrogenophaga species while T. angustifolia significantly increased rhizobia species. Multivariate analyses revealed that among all tested soil variables Fe and total organic carbon (TOC) could be the key factors in shaping the microbial structure. The putative functional analysis indicated that soil sample of B. ischaemum was abundant with nitrate/nitrite reduction-related functions while that of T. angustifolia was rich in nitrogen fixing functions. The results indicate that these native plants host a diverse range of soil microbes, whose community structure can be shaped by plant types and soil variables. It is also possible that these plants can be used to improve soil nitrogen content and serve as bioaccumulators for Pb or Mn for phytoremediation purposes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Earthen sites are immobile cultural relics and an important part of cultural heritage with historical, artistic and scientific values. The deterioration of features in earthen sites result in permanent loss of cultural information, causing immeasurable damage to the study of history and culture. Most research on the deterioration of earthen sites has concentrated on physicochemical factors, and information on microbial communities in earthen sites and their relationship with the earthen site deterioration is scarce. We used high-throughput sequencing to analyze bacterial and fungal communities in soils from earthen walls with different degree of deterioration at Jinsha earthen site to characterize the microbial communities and their correlation with environmental factors, and to compare microbial community structures and the relative abundances of individual taxa associated with different degree of deterioration for identifying possible marker taxa., Results: The relative abundances of Proteobacteria and Firmicutes were higher and that of Actinobacteria lower with higher degree of deterioration. At the genus level, the relative abundances of Rubrobacter were highest in all sample groups except in the most deteriorated samples where that of Bacteroides was highest. The relative abundance of the yeast genus Candida was highest in the severely deteriorated sample group. The bacterial phylum Bacteroidetes and genus Bacteroides, and fungal class Saccharomycetes that includes Candida sp. were specific for the most deteriorated samples. For both bacteria and fungi, the differences in community composition were associated with differences in EC, moisture, pH, and the concentrations of NH 4 + , K + , Mg 2+ , Ca 2+ and SO 4 2- ., Conclusion: The microbial communities in soil with different degree of deterioration were distinctly different, and deterioration was accompanied with bigger changes in the bacterial than in the fungal community. In addition, the deteriorated soil contained higher concentrations of soluble salts. Potentially, the accumulation of Bacteroides and Candida plays an important role in the deterioration of earthen features. Further work is needed to conclude whether controlling the growth of the bacteria and fungi with high relative abundances in the deteriorated samples can be applied to alleviate deterioration.

Understanding the interplay between the farming system and soil microbiomes could aid the design of a sustainable and efficient farming system. A comparative greenhouse experiment consisting of organic (ORG), integrated (INT) and conventional (CON) farming systems was established in northern China in 2002. The effects of 12 years of organic farming on soil microbiomes were explored by metagenomic and 16S rRNA gene amplicon sequencing analyses. Long-term ORG shifted the community composition of dominant phyla, especially Acidobacteria, increased the relative abundance of Ignavibacteria and Acidobacteria Gp6 and decreased the relative abundance of Nitrosomonas, Bacillus and Paenibacillus. Metagenomic analysis further revealed that relative abundance of ammonia oxidizing microorganisms (Bacteria and Archaea) and anaerobic ammonium oxidation bacteria decreased during ORG. Conversely, the relative abundance of bacteria-carrying periplasmic nitrate reductases (napA) was slightly higher for ORG. Long-term organic farming also caused significant alterations to the community composition of functional groups associated with ammonia oxidation, denitrification and phosphorus recycling. In summary, this study provides key insights into the composition of soil microbiomes and long-term organic farming under greenhouse conditions. [ABSTRACT FROM AUTHOR]

Urbanization, the migration of populations from rural to urban areas, has been causing great stress on natural environments, leading to air pollution and nitrogen (N) deposition, negatively affecting forest health. Although there is evidence that urbanization has changed forest N cycling, little is known about whether urbanization also changes the availability of phosphorus (P), which is important for plant growth and forest productivity. To address this question, we carried out a survey in the Pearl River Delta region, the world's largest urban area in southern China, using two types of representative forests, the evergreen broadleaf forests (BFs) and pine plantations (PPs). The leaf N:P ratios in the two forest types were high (20-50) with a significant increasing pattern along the rural-to-urban gradient. The ratios of leaf P:K and P:Na declined along the rural-to-urban gradient, whereas leaf P content did not change in BF but decreased in PP along the rural-to-urban gradient, suggesting that leaf P became limiting along urbanization. The abundance of actinomycetes and gram-negative bacteria decreased along the rural-to-urban gradient, indicating the negative effects of urbanization on soil microorganisms. Principal component analysis indicated that divergent key factors respond to the urbanization and affect plant P limitation in the two forest types. In BF, broadleaf trees showed a greater response to N deposition from urbanization indicating direct leaf N uptake from N deposition is a key factor for plant P limitation. Alternatively, in PP, our findings suggest soil acidification is an important factor accelerating plant P limitation. Our study revealed that urbanization intensifies plant P limitation in subtropical forests, and the effects vary depending on forest types. Our findings provide empirical information to support the management of forest ecosystems and evaluation of urbanization effects on forest health., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Continuous monocropping often influences negatively the soil microbial community and leads to the occurrence of soil-borne diseases. In this study, a pre-cultivation soil management strategy, reductive soil disinfestation (RSD), involving amendment by the use of reed straw, bagasse, and rice straw, and creating anaerobic soil conditions, was used to regulate the microbial community in a soil infested by Fusarium wilt of lisianthus and make it suitable for plant cultivation. The results showed that RSD significantly decreased F. oxysporum population by 97.1%-99.1% and the incidence of lisianthus wilt disease to 3.0%-14.3% compared with that of the untreated soil. The lowest disease incidence was found in the soil treated with RSD where bagasse was incorporated. The replantation of the host plant differently stimulated the pathogen proliferations across the different soils. MiSeq sequencing and culture-dependent investigation showed that the RSD treatments established distinct microbial communities compared to that of the untreated soil. Furthermore, the relative abundances of representatives of the families Cytophagaceae, Chitinophagaceae, Chaetomiaceae, and an unclassified family within Sordariomycetes, as well as soil microbial activity and the proportions of antagonists were significantly and negatively correlated with the pathogen population increase. Overall, the RSD treatment contributed to the reassembly of the soil microbiome which contained more beneficial agents that successfully controlled the pathogen inoculum level and lisianthus Fusarium wilt disease., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Landfills commonly occupy large areas of land that may be ecologically important. Ecological restoration of landfill cover is a necessary approach to rebuild sustainable habitats. However, unfavourable soil conditions and invasion by exotic plants in certain regions hinder the restoration. In this study, the effects of biochar as a soil amendment on the restoration of a landfill cover were investigated under field condition. Topsoils of a landfill cover in the subtropical region (Shenzhen, China) were mixed with 0, 5 and 10% (v/v) of biochar. Soil pH, electronic conductivity, organic matter, total organic carbon, water content, total N and total P were enhanced by biochar amendment. After nine months of self-succession, plant productivity, species richness and diversity were enhanced by biochar. The structures of soil bacterial and arbuscular mycorrhizal (AM) fungal communities were changed, and species richness and diversity were moderately promoted. Enhanced plant growth and diversity were probably attributed to a number of enhanced bacterial functions related to nutrient cycling including aerobic ammonia oxidation, aerobic nitrite oxidation, nitrification, sulphur respiration, nitrate respiration, nitrogen respiration, ureolysis, chemoheterotrophy and fermentation. The higher abundances of bacteria Streptomyces sp. and Pseudomonas sp. in biochar treatments potentially enhanced the AM fungal diversity. The bacterial diversity was more related to the soil properties, especially pH, than AM fungi. Continuous monitoring is necessary to track the changes of species composition and ecological functions over time. This is the first comprehensive study on the effects of biochar on the ecological performance of a man-made ecosystem. In addition to agricultural application, biochar can be used for restoring degraded lands., (Copyright © 2018 Elsevier B.V. All rights reserved.)