Characteristics of the microbial communities regulate soil multi-functionality under different cover crop amendments in Ultisol

The use of cover crops is a promising strategy for influencing the soil microbial consortium,which is essential for the delivery of multiple soil functions(i.e.,soil multifunctionality).Nonetheless,relatively little is known about the role of the soil microbial consortium in mediating soil multifunctionality under different cover crop amendments in dryland Ultisols.Here,we assessed the multifunctionality of soils subjected to four cover crop amendments(control,non-amended treatment;RD,radish monoculture;HV,hairy vetch monoculture;and RDHV,radish-hairy vetch mixture),and we investigated the contributions of soil microbial richness,network complexity,and ecological clusters to soil multifunctionality.Our results demonstrated that cover crops whose chemical composition differed from that of the main plant crop promoted higher multifunctionality,and the radish-hairy vetch mixture rendered the highest enhancement.We obtained evidence that changes in soil microbial richness and network complexity triggered by the cover crops were associated with higher soil multifunctionality.Specifically,specialized microbes in a key ecological cluster(ecological cluster 2)of the soil microbial network were particularly important for maintaining soil multifunctionality.Our results highlight the importance of cover crop-induced variations in functionally important taxa for promoting the soil multifunctionality of dryland Ultisols.

Manure substitution improves maize yield by promoting soil fertility and mediating the microbial community in lime concretion black soil

Synthetic nitrogen(N)fertilizer has made a great contribution to the improvement of soil fertility and productivity,but excessive application of synthetic N fertilizer may cause agroecosystem risks,such as soil acidification,groundwater contamination and biodiversity reduction.Meanwhile,organic substitution has received increasing attention for its ecologically and environmentally friendly and productivity benefits.However,the linkages between manure substitution,crop yield and the underlying microbial mechanisms remain uncertain.To bridge this gap,a three-year field experiment was conducted with five fertilization regimes:i)Control,non-fertilization;CF,conventional synthetic fertilizer application;CF_(1/2)M_(1/2),1/2 N input via synthetic fertilizer and 1/2 N input via manure;CF_(1/4)M_(3/4),1/4 N input synthetic fertilizer and 3/4 N input via manure;M,manure application.All fertilization treatments were designed to have equal N input.Our results showed that all manure substituted treatments achieved high soil fertility indexes(SFI)and productivities by increasing the soil organic carbon(SOC),total N(TN)and available phosphorus(AP)concentrations,and by altering the bacterial community diversity and composition compared with CF.SOC,AP,and the soil C:N ratio were mainly responsible for microbial community variations.The co-occurrence network revealed that SOC and AP had strong positive associations with Rhodospirillales and Burkholderiales,while TN and C:N ratio had positive and negative associations with Micromonosporaceae,respectively.These specific taxa are implicated in soil macroelement turnover.Random Forest analysis predicted that both biotic(bacterial composition and Micromonosporaceae)and abiotic(AP,SOC,SFI,and TN)factors had significant effects on crop yield.The present work strengthens our understanding of the effects of manure substitution on crop yield and provides theoretical support for optimizing fertilization strategies.

Afforestation increases microbial diversity in low-carbon soils

Afforestation has an important role in biodiversity conservation and ecosystem function improvement.A meta-analysis was carried out in China,which has the largest plantation area globally,to quantify the effects of plantings on soil microbial diversity.The results showed that the overall effect of afforestation on soil microbial diversity was positive across the country.Random forest algorithm suggested that soil carbon was the most important factor regulating microbial diversity and the positive response was only found with new plantings on low-carbon bare lands but not on high-carbon farmlands and grasslands.In addition,afforestation with broadleaved species increased microbial diversity,whereas planting with conifers had no effect on microbial diversity.This study clarified the effects of plantings on soil microbial diversity,which has an important implication for establishing appropriate policies and practices to improve the multiple functionalities(e.g.,biodiversity conservation and climate change mitigation)during plantation establishment.

Effects of land-use patterns on soil microbial diversity and composition in the Loess Plateau,China

In the Loess Plateau of China,land-use pattern is a major factor in controlling underlying biological processes.Additionally,the process of land-use pattern was accompanied by abandoned lands,potentially impacting soil microbe.However,limited researches were conducted to study the impacts of land-use patterns on the diversity and community of soil microorganisms in this area.The study aimed to investigate soil microbial community diversity and composition using high-throughput deoxyribonucleic acid(DNA)sequencing under different land-use patterns(apricot tree land,apple tree land,peach tree land,corn land,and abandoned land).The results showed a substantial difference(P<0.050)in bacterial alpha-diversity and beta-diversity between abandoned land and other land-use patterns,with the exception of Shannon index.While fungal beta-diversity was not considerably impacted by land-use patterns,fungal alpha-diversity indices varied significantly.The relative abundance of Actinobacteriota(34.90%),Proteobacteria(20.65%),and Ascomycota(77.42%)varied in soils with different land-use patterns.Soil pH exerted a dominant impact on the soil bacterial communities'composition,whereas soil available phosphorus was the main factor shaping the soil fungal communities'composition.These findings suggest that variations in land-use pattern had resulted in changes to soil properties,subsequently impacting diversity and structure of microbial community in the Loess Plateau.Given the strong interdependence between soil and its microbiota,it is imperative to reclaim abandoned lands to maintain soil fertility and sustain its function,which will have significant ecological service implications,particularly with regards to soil conservation in ecologically vulnerable areas.

PLFA Analysis of Soil Microbial Community Structure in Different Forest Types

Soil soluble organic matter is an important component in the study of carbon and nitrogen cycling in terrestrial ecosystems. Soil microorganisms, as soil decomposers, participate in soil biogeochemical processes and play an important role in maintaining the balance of soil ecosystems. As a typical subtropical regional unit, Queensland, Australia, is a relatively concentrated distribution area of forests in Australia. It is very sensitive to climate change and plays an important role in Australian climate and even global climate change. Its unique natural environment and ecosystem occupy a special position in the world. However, the knowledge of available carbon and nitrogen pool and microbial activity in forest soil is still very limited. Pinus elliottii, Araucaria cunninghamii and Agathis australis are the three most important forest types in southern Queensland, Australia. In our research, the function and structural diversity of soil microbial communities of these three forest types were studied using biochemical and molecular biological methods, and the effective carbon and nitrogen pools of soil of different forest types and related microbial processes were discussed, which has important theoretical guiding significance for further research on the structure and function of soil ecosystem. The number of PLFAs in the soil of P. elliottii was 45, the number of PLFAs in the soil of Araucaria cunninghamii and Agathis australis was 39 and 35, respectively. The number and content of PLFAs monomer in P. elliottii were higher than those in the other two kinds of forest soil.

The competition between Bidens pilosa and Setaria viridis alters soil microbial composition and soil ecological function

Bidens pilosa is recognized as one of the major invasive plants in China.Its invasion has been associated with significant losses in agriculture,forestry,husbandry,and biodiversity.Soil ecosystems play an important role in alien plant invasion.Microorganisms within the soil act as intermediaries between plants and soil ecological functions,playing a role in regulating soil enzyme activities and nutrient dynamics.Understanding the interactions between invasive plants,soil microorganisms,and soil ecological processes is vital for managing and mitigating the impacts of invasive species on the environment.In this study,we conducted a systematic analysis focusing on B.pilosa and Setaria viridis,a common native companion plant in the invaded area.To simulate the invasion process of B.pilosa,we constructed homogeneous plots consisting of B.pilosa and S.viridis grown separately as monocultures,as well as in mixtures.The rhizosphere and bulk soils were collected from the alien plant B.pilosa and the native plant S.viridis.In order to focus on the soil ecological functional mechanisms that contribute to the successful invasion of B.pilosa,we analyzed the effects of B.pilosa on the composition of soil microbial communities and soil ecological functions.The results showed that the biomass of B.pilosa increased by 27.51% and that of S.viridis was significantly reduced by 66.56%.The organic matter contents in the bulk and rhizosphere soils of B.pilosa were approximately 1.30 times those in the native plant soils.The TN and NO_(3)^(-)contents in the rhizosphere soil of B.pilosa were 1.30 to 2.71 times those in the native plant soils.The activities of acid phosphatase,alkaline phosphatase,and urease in the rhizosphere soil of B.pilosa were 1.98-2.25 times higher than in the native plant soils.Using high-throughput sequencing of the16S rRNA gene,we found that B.pilosa altered the composition of the soil microbial community.Specifically,many genera in Actinobacteria and Proteobacteria were enriched in B.pilosa soils.Further correlation analyses verified that these genera had significantly positive relationships with soil nutrients and enzyme activities.Plant biomass,soil p H,and the contents of organic matter,TN,NO_(3)^(-),TP,AP,TK,and AK were the main factors affecting soil microbial communities.This study showed that the invasion of B.pilosa led to significant alterations in the composition of the soil microbial communities.These changes were closely linked to modifications in plant traits as well as soil physical and chemical properties.Some microbial species related to C,N and P cycling were enriched in the soil invaded by B.pilosa.These findings provide additional support for the hypothesis of soil-microbe feedback in the successful invasion of alien plants.They also offer insights into the ecological mechanism by which soil microbes contribute to the successful invasion of B.pilosa.Overall,our research contributes to a better understanding of the complex interactions between invasive plants,soil microbial communities,and ecosystem dynamics.

Characteristics of different aged plantations of Ormosia hosiei with regards to soil microbial biomass and enzymatic activities

Stand age is an important indicator of tree growth and life cycle,and has implications for ecological and biological processes.This study examined changes in soil microbial biomass(SMB)as well as enzyme activities of different aged plantations and revealed their relationship to soil properties.SMB,microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),microbial biomass phos-phorous(MBP)and enzyme activities(β-1,4-glucosidase(β-G),β-1,4-xylosidase(β-X),cellobiohydrolase(CBH),leucine aminopeptidase(LAP),β-1,4-n-acetylglucosamine(NAG)and acid phosphatase(ACP))were measured in Oro-mosia hosiei plantations of different ages.The soil qual-ity index(SQI)model assessed soil quality.SMB contents significantly decreased in young(7-year-old)and mature plantations(45-year-old)compared to middle-aged(20-year-old)plantations.Activity of soilβ-G,β-X,CBH and NAG in the 20-year-old plantations was markedly higher than in the other plantations except forβ-G,CBH and NAG in the 45-year-old plantations.Soil organic carbon(SOC),total potassium(TK),total porosity,dissolved organic carbon,nitrate nitrogen(NO_(3)--N)and non-capillary porosity were key factors affecting SMB,while soil bulk density,pH,SOC,NO_(3)--N,TK and forest litter(FL)were the main factors affecting soil enzyme activities.SQI decreased in the order:middle-aged>mature>young.The efficiency of soil organic matter conversion,the effect of nitrogen min-eralization and fixation by microorganisms,and the better efficiency of phosphorus utilization in mid-age plantations,which improves soil physical properties,better facilitates tree growth,and further improves the buffering of the soil against acidity and alkalinity.FL quality was the only soil biological factor affecting soil enzyme activity.Our findings demonstrate that different aged plantations affect soil micro-bial biomass,enzyme activity,and soil quality.

Soil conditioners improve Cd-contaminated farmland soil microbial communities to inhibit Cd accumulation in rice

The addition of silicon(Si)and organic fertilizers to soil conditioners can inhibit the transfer of heavy metal ions from soil to crops.However,it is not clear how Si and organic fertilizers affect soil properties and the micro-ecological environment and thereby reduce cadmium(Cd)accumulation in rice.In this study,the effects of L-type soil conditioners containing Si and organic fertilizers on bacterial and fungal community diversity,soil pH,organic matter,and available Si were analyzed with field experiments at two sites in Liuzhou City and Hezhou City,respectively,in Guangxi,China.With the increase of Si and organic fertilizer content in soil conditioner,rice yield respectively increased by 16.8–25.8 and 6.8–13.1%,and rice Cd content decreased significantly by 8.2–21.1 and 10.8–40.6%,respectively,at the two experimental sites.Soil microbiome analysis showed that the increase in abundance of Firmicutes and Actinobacteriota bacteria associated with Cd adsorption and sequestration,and Basidiomycota fungal populations associated with degradation of macromolecules favored the inhibition of soil Cd activity(soil exchangeable Cd decreased by 14.4–14.8 and 18.1–20.6%).This was associated with an increase in organic matter and Si content caused by applying soil conditioners.In conclusion,L-type soil conditioners,rich in Si and organic fertilizer,can reduce soil Cd bioavailability by regulating the dominant Cd passivating flora in the soil and ultimately reduce Cd accumulation in rice.

Afforestation with an age-sequence of Mongolian pine plantation promotes soil microbial residue accumulation in the Horqin Sandy Land, China

Land use change affects the balance of organic carbon(C)reserves and the global C cycle.Microbial residues are essential constituents of stable soil organic C(SOC).However,it remains unclear how microbial residue changes over time following afforestation.In this study,16-,23-,52-,and 62-year-old Mongolian pine stands and 16-year-old cropland were studied in the Horqin Sandy Land,China.We analyzed changes in SOC,amino sugar content,and microbial parameters to assess how microbial communities influence soil C transformation and preservation.The results showed that SOC storage increased with stand age in the early stage of afforestation but remained unchanged at about 1.27-1.29 kg/m2 after 52 a.Moreover,there were consistent increases in amino sugars and microbial residues with increasing stand age.As stand age increased from 16 to 62 a,soil pH decreased from 6.84 to 5.71,and the concentration of total amino sugars increased from 178.53 to 509.99 mg/kg.A significant negative correlation between soil pH and the concentration of specific and total amino sugars was observed,indicating that the effects of soil acidification promote amino sugar stabilization during afforestation.In contrast to the Mongolian pine plantation of the same age,the cropland accumulated more SOC and microbial residues because of fertilizer application.Across Mongolian pine plantation with different ages,there was no significant change in calculated contribution of bacterial or fungal residues to SOC,suggesting that fungi were consistently the dominant contributors to SOC with increasing time.Our results indicate that afforestation in the Horqin Sandy Land promotes efficient microbial growth and residue accumulation in SOC stocks and has a consistent positive impact on SOC persistence.

Analysis of Microbial Community Structure and Diversity in Crop Rhizosphere Soil Based on Illumina NovaSeq Sequencing Platform

[Objectives]To make full use of crop rhizosphere microbial resources.[Methods]Illumina NovaSeq sequencing platform was used to analyze the richness and diversity of microbial community structure in rhizosphere soil of rice and maize crops in Baitu Town,Gaoyao District,Zhaoqing City.[Results]A total of 14936 OTUs of bacteria and 1905 OTUs of fungi were obtained from three samples of rice rhizosphere soil,and 13437 OTUs of bacteria and 1413 OTUs of fungi were obtained from three samples of maize rhizosphere soil.The diversity and richness of bacterial communities were higher than those of fungi.There are differences in soil bacterial and fungal communities among different crop samples.The analysis of species with bacteria difference at genus level among crop rhizosphere soil samples showed that 18 genera with significant differences were obtained from 6 samples;species analysis of fungi at the genus level showed that 3 genera with significant differences were obtained from 6 samples.[Conclusions]The research results of this paper have positive significance for the development and utilization of soil resources in Zhaoqing City and the full exploitation of rice and maize rhizosphere microbial resources.

Effects of desert plant communities on soil enzyme activities and soil organic carbon in the proluvial fan in the eastern foothills of the Helan Mountain in Ningxia,China

It is of great significance to study the effects of desert plants on soil enzyme activities and soil organic carbon(SOC)for maintaining the stability of the desert ecosystem.In this study,we studied the responses of soil enzyme activities and SOC fractions(particulate organic carbon(POC)and mineral-associated organic carbon(MAOC))to five typical desert plant communities(Convolvulus tragacanthoides,Ephedra rhytidosperma,Stipa breviflora,Stipa tianschanica var.gobica,and Salsola laricifolia communities)in the proluvial fan in the eastern foothills of the Helan Mountain in Ningxia Hui Autonomous Region,China.We recorded the plant community information mainly including the plant coverage and herb and shrub species,and obtained the aboveground biomass and plant species diversity through sample surveys in late July 2023.Soil samples were also collected at depths of 0–10 cm(topsoil)and 10–20 cm(subsoil)to determine the soil physicochemical properties and enzyme activities.The results showed that the plant coverage and aboveground biomass of S.laricifolia community were significantly higher than those of C.tragacanthoides,S.breviflora,and S.tianschanica var.gobica communities(P<0.05).Soil enzyme activities varied among different plant communities.In the topsoil,the enzyme activities of alkaline phosphatase(ALP)andβ-1,4-glucosidas(βG)were significantly higher in E.rhytidosperma and S.tianschanica var.gobica communities than in other plant communities(P<0.05).The topsoil had higher POC and MAOC contents than the subsoil.Specifically,the content of POC in the topsoil was 18.17%–42.73%higher than that in the subsoil.The structural equation model(SEM)indicated that plant species diversity,soil pH,and soil water content(SWC)were the main factors influencing POC and MAOC.The soil pH inhibited the formation of POC and promoted the formation of MAOC.Conversely,SWC stimulated POC production and hindered MAOC formation.Our study aimed to gain insight into the effects of desert plant communities on soil enzyme activities and SOC fractions,as well as the drivers of SOC fractions in the proluvial fan in the eastern foothills of the Helan Mountain and other desert ecosystems.

Advances in Research on Synthetic Microbial Communities

The synthetic microbial community is a synthetic microbial system co-cultured with multiple species, which has the characteristics of clear composition and strong controllability. Compared with a single colony, it can achieve more complex functions and adapt to the changing environment more easily, so as to meet a wide range of needs. In this paper, the contents and concepts of microbial community and synthetic microbial community are briefly introduced, the principles that should be followed in the construction of microbial community are expounded, the methods and mathematical models used in the construction of synthetic microbial community are introduced, and the applications of synthetic microbial community in various fields are summarized. Finally, the challenges in the research of synthetic microbial communities are briefly described.

Changes in soil microbial communities induced by warming and N deposition accelerate the CO 2 emissions of coarse woody debris

Warming and nitrogen(N)deposition are two important drivers of global climate changes.Coarse woody debris(CWD)contains a large proportion of the carbon(C)in the total global C pool.The composition of soil microbial communities and environmental changes(i.e.,N deposition and warming)are the key drivers of CWD decomposition,but the interactive impact between N deposition and warming on the composition of soil microbial communities and CWD decomposition is still unclear.In a laboratory experiment,we study and simulate respiration during decomposition of the CWD(C 98)of Cryptomeria japonica(CR)and Platycarya strobilacea(PL)in response to warming and N deposition over 98 days.Resuts show that either warming or N addition signifi cantly accelerated the C 98 of the two tree species by altering the soil microbial community(bacterial:fungi and G+:G–).The combined treatment(warming+N)resulted in a decomposition eff ect equal to the sum of the individual eff ects.In addition,the species composition of bacteria and fungi was obviously aff ected by warming.However,N deposition had a remarkable infl uence on G+:G–.Our results indicated that N deposition and warming will observably alter the composition and growth of the microbial community and thus work synergistically to accelerate CWD decomposition in forest ecosystems.We also present evidence that N deposition and warming infl uenced the composition and balance of soil microbial communities and biogeochemical cycling of forest ecosystems.

Residue Return Effects Outweigh Tillage Effects on Soil Microbial Communities and Functional Genes in Black Soil Region of Northeast China

Conservation tillage as an effective alternative to mitigate soil degradation has attracted worldwide attention,but the influences of conservation tillage on soil microbial community and especially function remain unclear.Shotgun metagenomics sequencing was performed to examine the taxonomic and functional community variations of black soils under three tillage regimes,namely no-tillage with residue(maize straw)return(NTS),moldboard plow with residue return(MPS),and moldboard plow without residue return(MPN)in Northeast China.The results revealed:1)Soil bacterial and archaeal communities differed significantly under different tillage regimes in contrast to soil fungal community.2)The overlay of less tillage and residues return under NTS led to unique soil microbial community composition and functional composition.Specifically,in contrast to other treatments,NTS increased the relative abundances of some taxa such as Bradyrhizobium,Candidatus Solibacter,and Reyranella,along with the relative abundances of some taxa such as Sphingomonas,Unclassified Chloroflexi and Nitrososphaera decreased;NTS had a unique advantage of increasing the relative abundances of genes involved in‘ATP-binding cassette(ABC)transporters’and‘quorum sensing(QS)’pathways,while MPN favored the genes involved in‘flagellar assembly’pathway and some metabolic pathways such as‘carbon’and‘glyoxylate and dicarboxylate’and‘selenocompound’metabolisms.3)Significantly different soil bacterial phyla(Acidobacteria,Gemmatimonadetes,and Chloroflexi)and metabolic pathways existed between MPN and another two treatments(NTS and MPS),while did not exist between NTS and MPS.4)Dissolved organic carbon(DOC)and soil bulk density were significantly affected(P<0.05)by tillage and accounted for the variance both in microbial(bacterial)community structure and functional composition.These results indicated that a change in tillage regime from conventional to conservation tillage results in a shift of microbial community and functional genes,and we inferred that residue return played a more prominent role than less tillage in functional shifts in the microbial community of black soils.

Effects of Tillage Depth on Nutrients and Microbial Communities in Tobacco-Planting Soil

The implementation of appropriate tillage practices is of great significance for agricultural production. However, the effects of different tillage depths on soil nutrients content and microbial communities in tobacco-planting soils are still lacking systematic research. In this study, three different tillage depths of 15 cm (T1), 20 cm (T2), and 30 cm (T3) were set up for field experiments in Liupanshui, Guizhou Province, to explore the effects of tillage depth on tobacco-planting soil nutrients and bacterial and fungal communities based on 16S rRNA and ITS sequencing and figure out the key factors affecting soil microbial communities. The results showed that T2 and T3 increased the contents of organic matter, total nitrogen, total phosphorus, available phosphorus, and available potassium in tobacco-planting soil, and increased the diversity of bacterial communities compared with T1. There was no significant difference in the structure of bacterial and fungal communities in different tillage depth treatments, but some dominant genera were significantly enriched in T2 and T3. Desulfobacter, Setophoma, Humicola, and Acremonium were significantly enriched in T2. Chthonomonas and Fusarium were significantly enriched in T3. These genera favor the decomposition of organic matter and the cycling of nutrients, and control soil pests and diseases. Redundancy analysis indicated that TP and AK were the key factors influencing the dominant genera of bacteria and fungi. This study provides a scientific basis for the selection of soil tillage depth for tobacco production in this region.

Effects of nitrogen and phosphorus additions on soil microbial community structure and ecological processes in the farmland of Chinese Loess Plateau

Microorganisms regulate the responses of terrestrial ecosystems to anthropogenic nutrient inputs.The escalation of anthropogenic activities has resulted in a rise in the primary terrestrial constraining elements,namely nitrogen(N)and phosphorus(P).Nevertheless,the specific mechanisms governing the influence of soil microbial community structure and ecological processes in ecologically vulnerable and delicate semi-arid loess agroecosystems remain inadequately understood.Therefore,we explored the effects of different N and P additions on soil microbial community structure and its associated ecological processes in the farmland of Chinese Loess Plateau based on a 36-a long-term experiment.Nine fertilization treatments with complete interactions of high,medium,and low N and P gradients were set up.Soil physical and chemical properties,along with the microbial community structure were measured in this study.Additionally,relevant ecological processes such as microbial biomass,respiration,N mineralization,and enzyme activity were quantified.To elucidate the relationships between these variables,we examined correlation-mediated processes using statistical techniques,including redundancy analysis(RDA)and structural equation modeling(SEM).The results showed that the addition of N alone had a detrimental effect on soil microbial biomass,mineralized N accumulation,andβ-1,4-glucosidase activity.Conversely,the addition of P exhibited an opposing effect,leading to positive influences on these soil parameters.The interactive addition of N and P significantly changed the microbial community structure,increasing microbial activity(microbial biomass and soil respiration),but decreasing the accumulation of mineralized N.Among them,N24P12 treatment showed the greatest increase in the soil nutrient content and respiration.N12P12 treatment increased the overall enzyme activity and total phospholipid fatty acid(PLFA)content by 70.93%.N and P nutrient contents of the soil dominate the microbial community structure and the corresponding changes in hydrolytic enzymes.Soil microbial biomass,respiration,and overall enzyme activity are driven by mineralized N.Our study provides a theoretical basis for exploring energy conversion processes of soil microbial community and environmental sustainability under long-term N and P additions in semi-arid loess areas.

Inversion tillage with straw incorporation affects the patterns of soil microbial co-occurrence and multi-nutrient cycling in a Hapli-Udic Cambisol

Inversion tillage with straw amendment is widely applied in northeastern China, and it can substantially increase the storage of carbon and improve multiple subsoil functions. Soil microorganisms are believed to be the key to this process,but research into their role in subsoil amelioration is limited. Therefore, a field experiment was conducted in 2018 in a region in northeastern China with Hapli-Udic Cambisol 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 every year after harvest. The results indicated that SIT improved soil multi-nutrient cycling variables and increased the availability of key nutrients such as soil organic carbon, total nitrogen, available nitrogen, available phosphorus and available potassium in both the topsoil and subsoil.In contrast to CT and SCT, SIT created a looser microbial network structure but with highly centralized clusters by reducing the topological properties of average connectivity and node number, and by increasing the average path length and the modularity. A Random Forest analysis found that the average path length and the clustering coefficient were the main determinants of soil multi-nutrient cycling. These findings suggested that SIT can be an effective option for improving soil multi-nutrient cycling and the structure of microbial networks, and they provide crucial information about the microbial strategies that drive the decomposition of straw in Hapli-Udic Cambisol.

Functional diversity of soil microbial communities in response to supplementing 50% of the mineral N fertilizer with organic fertilizer in an oat field

The effects of supplementing 50%of the mineral N fertilizer with organic fertilizer on the metabolism and diversity of soil microbial communities in an oat field were investigated using Biolog-Eco plates.The experiment consisted of five treatments:no fertilizer(CK),mineral N fertilizer applied at 90 and 45 kg ha^(-1) N in the form of urea(U1 and U2,respectively),and U2 supplemented with organic fertilizer in the form of sheep manure at 90 and 45 kg ha^(-1) N(U2OM1 and U2OM2,respectively).Each treatment had three replications.The experiment was conducted in 2018 and 2019 in Pinglu District,Shanxi Province,China.The carbon source utilization by soil microbial communities,such as amino acids,amines,carbohydrates,carboxylic acids,and polymers,increased when 50%of the mineral N fertilizer was replaced with organic fertilizer in both years.This result was accompanied by increased richness,dominance,and evenness of the microbial communities.The utilization of amino acid,amine,and carboxylic acid carbon sources and community evenness were further improved when the organic fertilizer amount was doubled in both years.Biplot analysis indicated that amines and amino acids were the most representative of the total carbon source utilization by the soil microbial communities in both years.The highest oat yield was achieved at a total N application rate of 135 kg ha^(-1) in the treatment involving 45 kg ha^(-1) N in the form of urea and 90 kg ha^(-1) N in the form of sheep manure in both years.It was concluded that the application of 50%of the conventional rate of mineral N fertilizer supplemented with an appropriate rate of organic fertilizer enhanced both the functional diversity of soil microbial communities and oat yield.Amine and amino acid carbon sources may be used as a substitute for total carbon sources for assessing total carbon source utilization by soil microbial communities in oat fields in future studies.

Changes in enzymes activity, substrate utilization pattern and diversity of soil microbial communities under cadmium pollution

Heavy metal pollution has received increasing attention in recent years mainly because of the public awareness of environmental issues. In this study we have evaluated the effect of cadmium （Cd） on enzymes activity, substrate utilization pattern and diversity of microbial communities in soil spiked with 0, 20, 40, 60, 80, and 100 mg/kg Cd, during 60 d of incubation at 25℃. Enzyme activities determined at 0, 15, 30, 45, and 60 d after heavy metal application（DAA） showed marked declines for various Cd treatments, and up to 60 DAA, 100 mg/kg Cd resulted in 50.1%, 47.4%, and 39.8% decreases in soil urease, acid phosphatase and dehydrogenase activities, respectively to control. At 60 DAA, substrate utilization pattern of soil microbial communities determined by inoculating Biolog ECO plates indicated that Cd addition had markedly inhibited the functional activity of soil microbial communities and multivariate analysis of sole carbon source utilization showed significantly different utilization patterns for 80 and 100 mg/kg Cd treatments. The structural diversity of soil microbial communities assessed by PCR-DGGE method at 60 DAA, illustrated that DGGE patterns in soil simplified with increasing Cd concentration, and clustering of DGGE profiles for various Cd treatments revealed that they had more than 50% difference with that of control.

Effects of Different Chinese Hickory Husk Returning Modes on Soil Nutrition and Microbial Community in Acid Forest Soil

Chinese hickory(Carya cathayensis Sarg.)is an important economic forest in Southeastern China.A large amount of hickory husk waste is generated every year but with a low proportion of returning.Meanwhile,intensive management has resulted in soil degradation of Chinese hickory plantations.This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment,including soil acidity,soil nutrition,and microbial community.The field experiment carried out four treatments:control(CK),hickory husk mulching(HM),hickory husk biochar(BC),and hickory husk organic fertilizer(OF).The phospholipid fatty acid(PLFA)biomarker method was employed to determine the soil microbial community.After one year of treatment,the results showed that:(i)HM and BC significantly increased soil pH by 0.33 and 1.71 units,respectively;(ii)HM,BC and OF treatments significantly increased the soil organic carbon,alkaline nitrogen,available phosphorous,and available potassium.The OF treatment demonstrated the most significant improvement in the soil nutrient;(iii)The soil microbial biomass significantly increased in the HM,BC and OF treatments,and all microbial groups showed an increasing trend.HM treatment increased the fungal/bacterial ratio(F/B).The OF treatment significantly decreased the Shannon-Wiener diversity(H’)and evenness index(J)of the microbial community(P<0.05).Considering the treatments effects,costs,and ease of operation,our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.