Soil Fertility,Microbial Biomass,and Microbial Functional Diversity Responses to Four Years Fertilization in an Apple Orchard in North China

Soil microbial communities play an essential role in maintaining soil fertility and are considered as ecological indicators to evaluate soil health.In the present study,we examined the influence of almost 4 years of fertilization[no fertilizer(CK),nitrogen alone(N),nitrogen,phosphorus and potassium chemical fertilizer(NPK),organicmanure(M),nitrogen plus organic manure(NM),and NPK plus organic manure(NPKM)]on soil fertility and the functional diversity of soil microbial communities in an apple orchard.Compared to CK,fertilization increased soil organic carbon,total nitrogen,and available nutrients,but reduced soil pH in N and NPK treatments.The highest microbial biomass carbon and nitrogen,most probable number of actinomycetes,bacteria,and fungi occurred in the NPKM treatment.The average well color development(AWCD)values followed the order of NPKM>M>NPK and NM>CK and N.The Shannon index in organic manure treatments were significantly higher than in control and in treatments without organic manure.The principal component analysis showed that manure treatment was significantly separated from other treatments.These results indicated that organic manure applied alone or in combination with chemical fertilizers would increase soil fertility and functional diversity of soil microbial communities.Moreover,applying balanced N,P,K fertilizer in combination with organic manure was found to be superior to the use of a single fertilizer in improving soil microbial community quality.

Changes in Transformation of Soil Organic C and Functional Diversity of Soil Microbial Community Under Different Land Uses

Changes in soil biological and biochemical properties under different land uses in the subtropical region of China were investigated in order to develop rational cultivation and fertilization management. A small watershed of subtropical region of China was selected for this study. Land uses covered paddy fields, vegetable farming, fruit trees, upland crops, bamboo stands, and forestry. Soil biological and biochemical properties included soil organic C and nutrient contents, mineralization of soil organic C, and soil microbial biomass and community functional diversity. Soil organic C and total N contents, microbial biomass C and N, and respiration intensity under different land uses were changed in the following order： paddy fields （and vegetable farming） 〉 bamboo stands 〉 fruit trccs （and upland）. The top surface （0-15 cm） paddy fields （and vegetable farming） were 76.4 and 80.8% higher in soil organic C and total N contents than fruit trees （and upland） soils, respectively. Subsurface paddy soils （15-30 cm） were 59.8 and 67.3% higher in organic C and total N than upland soils, respectively. Soil microbial C, N and respiration intensity in paddy soils （0-15 cm） were 6.36, 3.63 and 3.20 times those in fruit tree （and upland） soils respectively. Soil microbial metabolic quotient was in the order： fruit trees （and upland） 〉 forestry 〉 paddy fields. Metabolic quotient in paddy soils was only 47.7% of that in fruit tree （and upland） soils. Rates of soil organic C mineralization during incubation changed in the order： paddy fields 〉 bamboo stands 〉 fruit trees （and upland） and soil bacteria population： paddy fields 〉 fruit trees （and upland） 〉 forestry. No significant difference was found for fungi and actinomycetes populations. BIOLOG analysis indicated a changing order of paddy fields 〉 fruit trees （and upland） 〉 forestry in values of the average well cell development （AWCD） and functional diversity indexes of microbial community. Results also showed that the conversion from paddy fields to vegetable farming for 5 years resulted in a dramatic increase in soil available phosphorus content while insignificant changes in soil organic C and total N content due to a large inputs of phosphate fertilizers. This conversion caused 53, 41.5, and 41.3% decreases in soil microbial biomass C, N, and respiration intensity, respectively, while 23.6% increase in metabolic quotient and a decrease in soil organic C mineralization rate. Moreover, soil bacteria and actinomycetes populations were increased slightly, while fungi population increased dramatically. Functional diversity indexes of soil microbial community decreased significantly. It was concluded that land uses in the subtropical region of China strongly affected soil biological and biochemical properties. Soil organic C and nutrient contents, mineralization of organic C and functional diversity of microbial community in paddy fields were higher than those in upland and forestry. Overuse of chemical fertilizers in paddy fields with high fertility might degrade soil biological properties and biochemical function, resulting in deterioration of soil biological quality.

Impact of fluxapyroxad on the microbial community structure and functional diversity in the silty-loam soil

The aim of this work was to assess the effect of applying three different doses of fluxapyroxad on microbial activity, community structure and functional diversity as measured by respiration, microbial biomass C, phospholipid fatty acid （PLFA） and community-level physiological profiles （CLPPs）. Our results demonstrated that substrate-induced respiration （on day 15） and microbial biomass C （on days 7 and 15） were inhibited by fiuxapyroxad, but stimulation was observed thereafter. In contrast, fluxapyroxad addition increased the basal respiration and metabolic quotients （qCO2） and respiratory quotients （QR）. Analysis of the PLFA profiles revealed that the total and bacterial biomass （both Gram-positive bacteria （GP） and Gram-negative bacteria （GN）） were decreased within the initial 15 days, whereas those as well as the GN/GP ratio were increased at days 30 and 60. Fluxapyroxad input decreased the fungi biomass but increased the bacteria/fungi ratio at all incubation time. Moreover, high fluxapyroxad input （75 mg fluxapyroxad kg-1 soil dry weight） increased the microbial stress level. A principal component analysis （PCA） of the PLFAs revealed that fluxapyroxad treatment significantly shifted the microbial community structure, but all of the observed effects were transient. Biolog results showed that average well color development （AWCD） and functional diversity index （H′） were increased only on day 60. In addition, the dissipation of fluxa- pyroxad was slow in soil, and the degradation half-lives varied from 158 to 385 days depending on the concentration tested.

Development and applications of functional gene microarrays in the analysis of the functional diversity,composition,and structure of microbial communities

Functional gene arrays(FGAs)are a special type of microarrays containing probes for key genes involved in microbial functional processes,such as biogeochemical cycling of carbon,nitrogen,sulfur,phosphorus,and metals,biodegradation of environmental contaminants,energy processing,and stress responses.GeoChips are considered as the most comprehensive FGAs.Experimentally established probe design criteria and a computational pipeline integrating sequence retrieval,probe design and verification,array construction,data analysis,and automatic update are used to develop the GeoChip technology.GeoChip has been systematically evaluated and demonstrated to be a powerful tool for rapid,specific,sensitive,and quantitative analysis of microbial communities in a high-throughput manner.Several generations of GeoChip have been developed and applied to investigate the functional diversity,composition,structure,function,and dynamics of a variety of microbial communities from different habitats,such as water,soil,marine,bioreactor,human microbiome,and extreme ecosystems.GeoChip is able to address fundamental questions related to global change,bioenergy,bioremediation,agricultural operation,land use,human health,environmental restoration,and ecological theories and to link the microbial community structure to environmental factors and ecosystem functioning.

Effects of Different Forest Fire Intensities on Microbial Community Functional Diversity in Forest Soil in Daxing’anling

Microbial community functional diversity is a sensitive indicator of soil.Forest fires can change microbial community functional diversity.In this research,the fired soil samples were collected from Huzhong of Daxing’anling in Heilongjiang Province. The functional diversity of soil microbial community was detected by BIOLOG system.The average well color development(AWCD) in BIOLOG plates indicated the ability of carbon substrate utilization of microbial community.The indices of Shannon, Simpson and Mcintosh were calculated to show the richness,dominance and evenness of the functional diversity,and the principal component analysis of substrate reactions reflected the main carbon sources utilized by microbial community.The results showed that all the samples exhibited the reduction of AWCD during the first 144 hours of incubation,but there were obvious differences in the reduction degree among the samples.All kinds of fire intensities could influence microbial community functional diversity. The low fire intensity increased the richness (Shannon),dominance(Simpson) and evenness (Mcintosh) of microbial community.However,the intermediate and high fire intensity reduced these parameters,suggesting that the burned soil emitted gaseous nitrogen,a number of organic carbon and available phosphorus,which caused the reduction of the microorganism in quantity and type,and change in soil ingredients.The organic material reduced in the burned soil,in the same time,the pH values rose,which changed environment in which microorganism lives.The changed environment might not be conducive to activities of the microorganism.The principal component analysis showed that the main carbon sources for soil microbes were carbohydrates and amino acids and the carbon substrate utilization patterns in different samples were significant different.The results indicated that functional diversity of soil microbes were altered by forest fires,and the ability of microbes to utilize carbon source and the type of carbon sources were affected by different forest fire intensities.

Responses of soil microbial communities to freeze–thaw cycles in a Chinese temperate forest

Background:Freeze–thaw events are common in boreal and temperate forest ecosystems and are increasingly infuenced by climate warming.Soil microorganisms play an important role in maintaining ecosystem stability,but their responses to freeze–thaw cycles(FTCs)are poorly understood.We conducted a feld freeze–thaw experiment in a natural Korean pine and broadleaf mixed forest in the Changbai Mountain Nature Reserve,China,to determine the dynamic responses of soil microbial communities to FTCs.Results:Bacteria were more sensitive than fungi to FTCs.Fungal biomass,diversity and community composition were not signifcantly afected by freeze–thaw regardless of the stage.Moderate initial freeze–thaw resulted in increased bacterial biomass,diversity,and copiotrophic taxa abundance.Subsequent FTCs reduced the bacterial biomass and diversity.Compared with the initial FTC,subsequent FTCs exerted an opposite efect on the direction of change in the composition and function of the bacterial community.Soil water content,dissolved organic carbon,ammonium nitrogen,and total dissolved phosphorus were important factors determining bacterial community diversity and composition during FTCs.Moreover,the functional potentials of the microbial community involved in C and N cycling were also afected by FTCs.Conclusions:Diferent stages of FTCs have diferent ecological efects on the soil environment and microbial activities.Soil FTCs changed the soil nutrients and water availability and then mainly infuenced bacterial community composition,diversity,and functional potentials,which may disturb C and N states in this temperate forest soil.This study also improves our understanding of microbial communities regulating their ecological functions in response to climate change.

The “neighbor avoidance effect” of microplastics on bacterial and fungal diversity and communities in different soil horizons

Microplastics are a new type of environmental pollutant,and pose a serious threat to soil ecosystems.It is important to study microplastics effects on soil microorganisms to better understand their effects on terrestrial ecosystems.Therefore,we collected soil and microplastic samples from corn,pepper,peanut and cucumber fields in Shunyi District,Beijing,China,and used Illumina MiSeq high-throughput sequencing technology to analyze bacterial and fungal community composition and diversity.We focused on microplastic surface and its surrounding“rhizosphere-like”soil in the 0e10 cm(humus)and 10e20 cm(eluvial)deep horizons.Microbial richness and diversity on microplastic surface were significantly lower than those in surrounding“rhizosphere-like”soil,and microbial richness and diversity were reduced to a greater extent in the humus horizon than in the eluvial horizon.Microplastics likely enriched the microbes involved in their biodegradation.The relative abundance levels of Cyanobacteria and Basidiomycota on microplastic surfaces were significantly higher than those in surrounding“rhizosphere-like”soil,while the relative abundance levels of Acidobacteria,Chloreflexi,and Mortierellomycota were higher in“rhizosphere-like”soil.Furthermore,the relative abundance levels of pathways related to human diseases,animal pathogen,and fungal parasites were significantly higher on microplastic surfaces than in“rhizosphere-like”soil.These results show that the microbial diversity,richness,community structure and function between microplastic surfaces and surrounding“rhizosphere-like”soil are significantly different,leading to a“rhizosphere-like neighbor avoidance effect”between microplastic surfaces and the surrounding soil.

传统食醋酿造过程中微生物群落的多样性及功能研究进展

采用传统酿造工艺的传统食醋,不仅具有独特的风味,而且是一种健康的功能食品。传统食醋的酿造过程靠经验控制,酿造微生物经过自发地在生产原料中富集,形成了复杂的群落结构。传统酿造工艺经过上千年的改良和传承,酿造微生物不断地发生着驯化,逐渐形成了相对稳定的菌群结构,不同的微生物群落结构可能是造成不同食醋风味迥异的原因。近年来,各国科研人员对食醋的传统酿造工艺机制展示出了浓厚的兴趣,本文综述了国内外在传统食醋酿造过程中的微生物群落的多样性和功能方面的研究进展。