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.

Effect of heavy metals on soil microbial activity and diversity in a reclaimed mining wasteland of red soil area

The microbial biomass, basal respiration and substrate utilization pattern in copper mining wasteland of red soil area, southern China, were investigated. The results indicated that soil microflora were obviously different compared with that of the non-mine soil. Microbial biomass and basal respiration were negatively affected by the elevated heavy metal levels. Two important microbial ecophysiological parameters, namely, the ratio of microbial biomass C（ Cmic ）/organic C（ Corg ） and metabolic quotient（qCO2 ） were closely correlated to heavy metal stress. There was a significant decrease in the Cmic/Corg ratio and an increase in the metabolic quotient with increasing metal concentration. Multivariate analysis of Biolog data for sole carbon source utilization pattern demonstrated that heavy metal pollution had a significant impact on microbial community structure and functional diversity. All the results showed that soil microbiological parameters had great potential to become the early sensitive, effective and liable indicators of the stresses or perturbations in soils of mining ecosystems.

Influence of soil microorganisms and physicochemical properties on plant diversity in an arid desert of Western China

Soil microorganisms and physicochemical properties are considered the two most influencing factors for maintaining plant diversity.However,the operational mechanisms and which factor is the most influential manipulator remain poorly understood.In this study,we examine the collaborative influences of soil physicochemical properties(i.e.,soil water,soil organic matter(SOM),salinity,total phosphorus and nitrogen,pH,soil bulk density and fine root biomass)and soil microorganisms(fungi and bacteria)on plant diversity across two types of tree patches dominated by big and small trees(big trees:height≥7 m and DBH≥60 cm;small trees:height≤4.5 m and DBH≤20 cm)in an arid desert region.Tree patch is consists of a single tree or group of trees and their accompanying shrubs and herbs.It was hypothesized that soil physicochemical properties and microorganisms affect plant diversity but their influence differ.The results show that plant and soil microbial diversity increased with increasing distances from big trees.SOM,salinity,fine root biomass,soil water,total phosphorus and total nitrogen contents decreased with increasing distance from big trees,while pH and soil bulk density did not change.Plant and soil microbial diversity were higher in areas close to big trees compared with small trees,whereas soil physicochemical properties were opposite.The average contribution of soil physicochemical properties(12.2%-13.5%)to plant diversity was higher than microbial diversity(4.8%-6.7%).Salinity had the largest negative affect on plant diversity(24.7%-27.4%).This study suggests that soil fungi constrain plant diversity while bacteria improve it in tree patches.Soil physicochemical properties are the most important factor modulating plant diversity in arid desert tree patches.

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.

Plant functional trait diversity and structural diversity co-underpin ecosystem multifunctionality in subtropical forests

Tree species diversity is assumed to be an important component in managing forest ecosystems because of effects on multiple functions or ecosystem multifunctionality.However,the importance of tree diversity in determining multifunctionality in structurally complex subtropical forests relative to other regulators(e.g.,soil microbial diversity,stand structure,and environmental conditions)remains uncertain.In this study,effects of aboveground(species richness and functional and structural diversity)and belowground(bacterial and fungal diversity)biodiversity,functional composition(community-weighted means of species traits),stand structure(diameter at breast height and stand density),and soil factors(pH and bulk density)on multifunctionality(including biomass production,carbon stock,and nutrient cycling)were examined along a tree diversity gradient in subtropical forests.The community-weighted mean of tree maximum height was the best predictor of ecosystem multifunctionality.Functional diversity explained a higher proportion of the variation in multifunctionality than that of species richness and fungal diversity.Stand structure-played an important role in modulating the effects of tree diversity on multifunctionality.The work highlights that species composition and maximizing forest structural complexity are effective strategies to increase forest multifunctionality while also conserving biodiversity in the management of multifunctional forests under global environmental changes.

Climate and salinity drive soil bacterial richness and diversity in sandy grasslands in China

Bacteria constitute a large proportion of the biodiversity in soils and control many important processes in terrestrial ecosystems.However,our understanding of the interactions between soil bacteria and environmental factors remains limited,especially in sensitive and fragile ecosystems.In this study,geographic patterns of bacterial diversity across four sandy grasslands along a 1,600 km north-south transect in northern China were characterized by high-throughput 16S rRNA gene sequencing.Then,we analyzed the driving factors behind the patterns in bacterial diversity.The results show that of the 21 phyla detected,the most abundant were Proteobacteria,Actinobacteria,Acidobacteria and Fir‐micutes(average relative abundance>5%).Soil bacterial operational taxonomic unit(OTU)numbers(richness)and Faith's phylogenetic diversity(diversity)were highest in the Otindag Sandy Land and lowest in the Mu Us Sandy Land.Soil electrical conductivity(EC)was the most influential factor driving bacterial richness and diversity.The bacterial communities differed significantly among the four sandy grasslands,and the bacterial community structure was signifi‐cantly affected by environmental factors and geographic distance.Of the environmental variables examined,climatic factors(mean annual temperature and precipitation)and edaphic properties(pH and EC)explained the highest propor‐tion of the variation in bacterial community structure.Biotic factors such as plant species richness and aboveground bio‐mass exhibited weak but significant associations with bacterial richness and diversity.Our findings revealed the impor‐tant role of climate and salinity factors in controlling bacterial richness and diversity;understanding these roles is critical for predicting the impacts of climate change and promoting sustainable management strategies for ecosystem services in these sandy lands.

Novel Inorganic Pyrophosphatase from Soil Metagenomic and Family and Subfamily Prediction

Inorganic pyrophosphatase (PPase) is widely studied, to be extremely important for survival of plants and microorganisms. PPases catalyze an essential reaction the hydrolysis of inorganic pyrophosphate (PPi) to inorganic phosphate (Pi). Studies involving the mechanism of PPase were performed in microorganisms culture. We didn’t found reports of PPase derived from soil meta-genomic libraries. Soil environment has immense diversity of microorganisms, yet most remains unexplored and the metagenome are the technologies used and investigate uncultured microorganisms potential. The aim is to identify novel genes using the metagenomic approaches from a bioinformatics perspective and hopefully will serve as a useful resource. With this purpose, we used the metagenomic library of Eucalyptus spp. arboretum (EAA). We did a screening to select a positive clone and submitted them to the process of shotgun. The data obtained was submitted to bioinformatics analyses. These analyses identified were the novel MetaPPase gene and were classified according to the predict family and subfamily.

Monitoring impact of mefenacet treatment on soil microbial communities by PCR-DGGE fingerprinting and conventional testing procedures

The effect of acetanilide herbicide mefenacet on soil microbial communities was studied using paddy soil samples with different short-term treatments. The culturable bacteria （plate counts）, dehydrogenase activity and changes in community structure （denaturing gradient gel electrophoresis （DGGE） analysis） were used for biological community assessments. Mefenacet was a significant stimulus to cultural aerobic bacteria and dehydrogenase activity while Sphingobacterium multivorum Y1, a bacterium efficiently degrading the mefenacet, only induced the increasing colony-forming unit （CFU） of bacteria but little effect on dehydrogenase activity during the whole experiment. The degree of similarity between the 16S rDNA profiles of the communities was quantified by numerically analyzing the DGGE band patterns. Similarity dendrograms showed that the microbial community structures of the mefenacet-treated and non-treated soils were not significantly different. But supplement of S. multivorum Y1 could increase the diversity of the microbial community in the mefenacet-polluted paddy soil. This work is a new attempt to apply the S. multivorum Y1 for remediation of the mefenacet-polluted environments.

Changes of soil microbial communities during decomposition of straw residues under different land uses

Monitoring soil microbial communities can lead to better understanding of the transformation processes of organic carbon in soil. The present study investigated the changes of soil microbial communities during straw decomposition in three fields, i.e., cropland, peach orchard and vineyard. Straw decomposition was monitored for 360 d using a mesh-bag method. Soil microbial metabolic activity and functional diversity were measured using the Biolog-Eco system. In all three fields, dried straws with a smaller size decomposed faster than their fresh counterparts that had a larger size. Dried corn straw decomposed slower than dried soybean straw in the early and middle stages, while the reverse trend was found in the late stage. The cropland showed the highest increase in microbial metabolic activity during the straw decomposition, whereas the peach orchard showed the lowest. There was no significant change in the species dominance or evenness of soil microbial communities during the straw decomposition. However, the species richness fluctuated significantly, with the peach orchard showing the highest richness and the cropland the lowest. With different carbon sources, the peach orchard utilised carbon the most, followed by the cropland and the vineyard. In all three fields, carbon was utilized in following decreasing order： saccharides〉amino acids〉polymers〉polyamines〉carboxylic acids〉aromatic compounds. In terms of carbon-source utilization, soil microbial communities in the peach orchard were less stable than those in the cropland. The metabolic activity and species dominance of soil microbial communities were negatively correlated with the straw residual percentage. Refractory components were primarily accumulated in the late stages, thus slowing down the straw decomposition. The results showed that dried and crushed corn straw was better for application in long-term fields. The diversity of soil microbial communities was more stable in cropland than in orchards during the straw decomposition.

Can soil microbial diversity influence plant metabolites and life history traits of a rhizophagous insect？ A demonstration in oilseed rape

Interactions between plants and phytophagous insects play an important part in shaping the biochemical composition of plants. Reciprocally plant metabolites can influ- ence major life history traits in these insects and largely contribute to their fitness. Plant rhizospheric microorganisms are an important biotic factor modulating plant metabolites and adaptation to stress. While plant-insects or plant-microorganisms interactions and their consequences on the plant metabolite signature are well-documented, the impact of soil microbial communities on plant defenses against phytophagous insects remains poorly known. In this study, we used oilseed rape （Brassica napus） and the cabbage root fly （Delia radicum） as biological models to tackle this question. Even though D. radicum is a belowground herbivore as a larva, its adult life history traits depend on aboveground signals. We therefore tested whether soil microbial diversity influenced emergence rate and fitness but also fly oviposition behavior, and tried to link possible effects to modifications in leaf and root metabolites. Through a removal-recolonization experiment, 3 soil microbial modalities （＂high,＂ ＂medium,＂ ＂low＂） were established and assessed through amplicon sequencing of 16S and 18S ribosomal RNA genes. The ＂medium＂ modality in the rhizosphere significantly improved insect development traits. Plant-microorganism interactions were marginally associated to modulations of root metabolites profiles, which could partly explain these results. We highlighted the potential role of plant-microbial interaction in plant defenses against Delia radicum. Rhizospheric microbial communities must be taken into account when analyzing plant defenses against herbivores, being either below or aboveground.

Plant diversity is coupled with soil fungal diversity in a natural temperate steppe of northeastern China

Soil fungi and aboveground plant play vital functions in terrestrial ecosystems,while the relationship between aboveground plant diversity and the unseen soil fungal diversity remains unclear.We established 6 sites from the west to the east of the temperate steppe that vary in plant diversity(plant species richness:7-32)to explore the relationship between soil fungal diversity and aboveground plant diversity.Soil fungal community was characterized by applying 18S rRNA gene sequencing using MiSeq PE300 and aligned with Silva 132 database.As a result,soil fungal community was predominately composed of species within the Ascomycota(84.36%),Basidiomycota(7.22%)and Mucoromycota(6.44%).Plant species richness occupied the largest explanatory power in structuring soil fungal community(19.05%–19.78%).The alpha(α)diversity of the whole soil fungi and Ascomycota showed a hump-backed pattern with increasing plant species richness,and the beta(β)diversity of the whole soil fungi and Ascomycota increased with increasing plantβdiversity.Those results indicated that soil fungi and external resources were well balanced at the 20-species level of plant and the sites were more distinct in the composition of their plant communities also harbored more distinct soil fungal communities.Thus,plant diversity could predict both soil fungalαandβdiversity in the temperate steppe of northeastern China.

Deep soil microbial carbon metabolic function is important but often neglected:a study on the Songnen Plain reed wetland,Northeast China

Soil microbial carbon metabolism is critical in wetland soil carbon cycling,and is also a research hotspot at present.However,most studies focus on the surface soil layer in the wetlands and the microorganisms associated with this layer.In this study,0-75 cm soil profiles were collected from five widely separated reed wetlands in the Songnen Plain,which has a large number of middle-high latitude inland saline-sodic wetlands.The Biolog-ECO method was used to determine the carbon metabolic activity and functional diversity of soil microorganisms.The results showed that soil carbon metabolic activity decreased with increasing soil depth.The carbon metabolic activity of soil microorganisms in the 60-75 cm layer was approximately 57.41%-74.60%of that in the 0-15 cm layer.The soil microbial Shannon index and utilization rate of amines decreased with an increase in soil depth,while the Evenness index and utilization rate of polymers tended to increase with soil depth.Dissolved organic carbon(DOC)is the most important factor affecting microbial carbon source utilization preference,because microorganisms mainly obtain the carbon source from DOC.The result of the correlation analysis showed that the soil microbial carbon metabolic activity,Shannon index,and Evenness index significantly correlated with soil total carbon(TC),microbial biomass carbon(MBC),DOC,total nitrogen(TN),ammonium nitrogen(NH_(4)^(+)-N),nitrate nitrogen(NO_(3)_(−)-N)contents,and electrical conductivity(EC).This study emphasized the important role of microbial carbon metabolic function in deep soil.

Five-year warming does not change soil organic carbon stock but alters its chemical composition in an alpine peatland

Climate warming may promote soil organic carbon(SOC)decomposition and alter SOC stocks in terrestrial ecosystems,which would in turn affect climate warming.We manipulated a warming experiment using open-top chambers to investigate the effect of warming on SOC stock and chemical composition in an alpine peatland in Zoigêon the eastern Tibetan Plateau,China.Results showed that 5 years of warming soil temperatures enhanced ecosystem respiration during the growing season,promoted above-and belowground plant biomass,but did not alter the SOC stock.However,labile O-alkyl C and relatively recalcitrant aromatic C contents decreased,and alkyl C content increased.Warming also increased the amount of SOC stored in the silt-clay fraction(<0.053 mm),but this was offset by warming-induced decreases in the SOC stored within micro-and macroaggregates(0.053–0.25 and>0.25 mm,respectively).These changes in labile and recalcitrant C were largely associated with warming-induced increases in soil microbial biomass C,fungal diversity,enzyme activity,and functional gene abundance related to the decomposition of labile and recalcitrant C compounds.The warming-induced accumulation of SOC stored in the silt-clay fraction could increase SOC persistence in alpine peatland ecosystems.Our findings suggest that mechanisms mediated by soil microbes account for the changes in SOC chemical composition and SOC in different aggregate size fractions,which is of great significance when evaluating SOC stability under climate warming conditions.

Effects of rural domestic sewage reclaimed irrigation and regulation on heavy metals,PPCPs,water and nitrogen utilization,and microbial diversity in paddy field

Rural domestic reclaimed water(RDRW)is rural domestic sewage that being safely treated,the irrigation and reuse of RDRW are an effective way to alleviate the contradiction between supply and demand of water resources in South China.In this study,four kinds of irrigation water sources(primary and secondary treated water R1 and R2,purified water R3 and river water CK)and three kinds of water level regulations(low,medium,and high field water level control of W1,W2 and W3)were set to study the impact of RDRW on soil and crop safety,water and nitrogen utilization and biodiversity for establishing the regulation mechanism of RDRW irrigation with field experiment,and monitoring was carried out in RDRW irrigation demonstration area to assess the effectiveness of RDRW.The results showed that,under RDRW irrigation,the contents of Cd and Pb increased slightly,while the contents of Cr,Cu and Zn decreased in paddy soil.The heavy metals content decreased along the direction of stem,leaf and grain in rice plants,but did not increase significantly in rice grains.With the increase of field water level,pharmaceutical and personal care products(PPCPs)content in 60-80 cm soil layer was accumulated,and the PPCPs content in rice husks was higher than that in grains,but it was at a very low level.Compared to CK,RDRW irrigation can effectively increase rice yield,rainwater use efficiency(RUE)and nitrogen use efficiency(NUE)by 5.4%-7.6%,6.7%-9.4%and 21.7%-24.2%,respectively,and the species diversity,community diversity and richness in rice fields were improved.Additionally,water level regulation of W3 with R2 water resource irrigation was conducive to the exertion of comprehensive benefits.The monitoring of demonstration area showed that the consumption of fresh water was reduced by 530 mm,yield was increased by 9.6%,and the soil and crop were both safety.Short-term irrigation of RDRW did not cause soil and crops pollution,however,it is still necessary to track and monitor the effect of the system on soil,crop,and underground water with long-term reclaimed water irrigation.

No-till systems on the Chequen Farm in Chile:A success story in bringing practice and science together

No-till cropping systems provide an opportunity to protect the soil from erosion,while contemporaneously maintaining high yields and contributing to global food security.The historical aspects and the remarkable development of no-till systems on the Chequen Farm in Chile are reviewed.The adoption of no-till over the last 40 years has been a major turning point in reducing the devastating effects of soil erosion and a model for the evolution of sustainable crop production in highly erodible terrain in other parts of the world.The process of adoption of no-till systems in severely eroded foothills of Chile is described,as well as the environmental benefits and the sustainability of the system.The practical aspects of these developments are supported by scientific literature where appropriate,illustrating the value and coincident knowledge gained when combining analogue observations and information with scientific principles.