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To gain a better understanding of the biological effect on the water-gas-carbonate interaction, 15 sample plots from five ecotypes (grass land, ecological demonstration, artificial forest, tree-shrub, and forest community) in three experimental sites of SW China due to the absence of time-series succession ecotypes at the same karst site were selected to discuss the relationship between soil microbial populations, carbonic anhydrase (CA) and limestone dissolution rate. The results show that the soil microbial populations and soil CA activities within different ecotypes have the significantly positive correlation ( r = 0.968), which vary significantly and tend to decrease along the ecological succession process. In view of moist character and water-holding capacity in the evergreen forest, which can fleetly participate in water-gas-carbonate interaction, the limestone dissolution rate is not matching to the total microbial population and CA activity in forest community. If the ecotype for forest community was removed, the correlative coefficient between CA and the limestone dissolution rate is 0.950, the correlative coefficient between CA and total microbial population is 0.999 and the correlative coefficient between limestone dissolution rate and total microbial population is 0.952. It can be inferred that soil CA secreted by the soil microorganisms has the important role to promote the production of bicarbonate ions which affects limestone dissolution rate. [ABSTRACT FROM AUTHOR]

The green development of agriculture, the rational use of pesticides, and soil health are closely related. However, our understanding of them is still limited. Pyraclostrobin (PYRA) is one of the most popular strobilurin fungicides due to its broad-spectrum control of fungal diseases. However, PYRA has been shown to have negative effects on bacterial communities and soil enzyme activities under laboratory conditions. The effects of PYRA on soil microbes (mainly bacteria) in actual field environments still need to be addressed. In the present study, after applying PYRA in a wheat/maize rotation field for 2 years, we determined the level of residual PYRA and assessed the soil bacterial community structure, soil enzyme activity, and ammonia-oxidizing functional gene expression. The results show that the DT 50 of PYRA in agricultural soil was 2.16–38.93 days. The final residual levels of PYRA in wheat/maize grain were less than 0.01 mg kg−1, which is lower than the maximum residue limit (MRL) recommended (0.2 mg kg−1) by China and the European Union. The culturable fungi and bacteria populations were significantly reduced after applying PYRA. The genera's abundance (Sphingomonas and Lysobacter) and urease activity associated with phosphorus cycle were inhibited. The amoA genes abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) showed that the N-cycle function of soil microbes was inhibited. Overall, applying PYRA for 2 years did not increase the negative response of soil microbes. However, in some indicators, such as culturable microorganism populations, more significant reductions in populations were observed in the double recommended dose group than in the recommended dose group. The results obtained in this study reflect the response of soil microbes subjected to pyraclostrobin in an actual field and provide new insights into how agricultural development influences soil health. [Display omitted] • Pyraclostrobin formulation was applied to a wheat/maize rotation field for 2 years. • Soil functions sustaining microbial life and cycling nutrients were negatively affected. • Negative effects of pyraclostrobin on soil fungi and bacteria were observed. • The genus abundance and urease activity associated with P cycle were inhibited. • Expression of functional genes associated with N cycle was downregulated. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) additions to forest ecosystems are known to influence various above-ground properties, such as plant productivity and composition, and below-ground properties, such as soil nutrient cycling. However, our understanding of how soil microbial communities and their functions respond to nutrient additions in subtropical plantations is still not complete. In this study, we added N and P to Chinese fir plantations in subtropical China to examine how nutrient additions influenced soil microbial community composition and enzyme activities. The results showed that most soil microbial properties were responsive to N and/or P additions, but responses often varied depending on the nutrient added and the quantity added. For instance, there were more than 30% greater increases in the activities of β-glucosidase (βG) and N-acetyl-β-D-glucosaminidase (NAG) in the treatments that received nutrient additions compared to the control plot, whereas acid phosphatase (aP) activity was always higher (57 and 71%, respectively) in the P treatment. N and P additions greatly enhanced the phospholipid fatty acids (PLFAs) abundance especially in the N2P (100 kg ha-1 yr-1 of N C50 kg ha-1 yr-1 of P) treatment; the bacterial PLFAs (bacPLFAs), fungal PLFAs (funPLFAs) and actinomycic PLFAs (actPLFAs) were about 2.5, 3 and 4 times higher, respectively, than in the CK (control). Soil enzyme activities were noticeably higher in November than in July, mainly due to seasonal differences in soil moisture content (SMC). βG or NAG activities were significantly and positively correlated with microbial PLFAs. These findings indicate that βG and NAG would be useful tools for assessing the biogeochemical transformation and metabolic activity of soil microbes. We recommend combined additions of N and P fertilizer to promote soil fertility and microbial activity in this kind of plantation. [ABSTRACT FROM AUTHOR]

Salt stress has been increasingly constraining crop productivity in arid and semiarid lands of the world. In a previous study, salt stress was alleviated and maize productivity improved remarkably with soil amendment with biochar poultry-manure compost (BPC) in conjunction with pyroligneous solution (PS) in a saline soil from Central China Plain. In 2010, before maize sowing, BPC was incorporated into topsoil at 12 t ha −1 following surface spray of diluted PS solution at 0.15 t ha −1 one week in advance (BPC-PS2). Such an experiment was repeated in adjacent fields in 2011 (BPC-PS1). Both bulk and rhizosphere samples of these experiment plots were collected at the vegetative growth stage of maize in 2012. Microbial biomass carbon (C mic ) and nitrogen (N mic ), and soil enzyme activity were measured. Based on 16S rRNA and 18S rRNA gene, bacterial and fungal community structure and abundance were respectively characterized using denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR (qPCR). With the amendment, C mic and N mic , and bacterial gene abundance were significantly and greatly increased in both bulk and rhizosphere samples, being greater under BPC-PS2 than under BPC-PS1. On contrast, smaller increase in fungal gene abundance was observed, along with a significant reduction in fungal diversity under BPC-PS2. In addition, two single bands belonging respectively to Alphaproteobacteria and Deltaproteobacteria emerged in the amended soil. Meanwhile, activities of urease, invertase and phosphatase in both bulk soils and rhizosphere soils were increased by 19–44% with the amendment except of urease in rhizosphere soils. Therefore, with the great enhancement of microbial growth and enzyme activities, combined use of biochar and poultry manure with pyroligneous solution could be a practical option to alleviate salt stresses on plant and soil microbial community in order to improve crop production in saline soils. [ABSTRACT FROM AUTHOR]

Highlights: [•] Soil microorganisms redistribute within the sloping land during and after erosion. [•] Physical mechanism drives changes of soil microbial abundance during erosion. [•] Soil properties shaped by erosion control microbial dynamics after erosion. [•] Bacterial and fungal abundance was positively correlated with soil organic carbon. [•] Bacteria and fungi exhibit different responses to erosion in microbial communities. [ABSTRACT FROM AUTHOR]

In many areas of China, tidal wetlands have been converted into agricultural land for rice cultivation. However, the consequences of land use changes for soil microbial communities are poorly understood. Therefore, we investigated bacterial and archaeal communities involved in inorganic nitrogen turnover (nitrogen fixation, nitrification, and denitrification) based on abundances and relative species richness of the corresponding functional genes along a soil chronosequence ranging between 50 and 2,000 years of paddy soil management compared to findings for a tidal wetland. Changes in abundance and diversity of the functional groups could be observed, reflecting the different chemical and physical properties of the soils, which changed in terms of soil development. The tidal wetland was characterized by a low microbial biomass and relatively high abundances of ammonia-oxidizing microbes. Conversion of the tidal wetlands into paddy soils was followed by a significant increase in microbial biomass. Fifty years of paddy management resulted in a higher abundance of nitrogen-fixing microbes than was found in the tidal wetland, whereas dominant genes of nitrification and denitrification in the paddy soils showed no differences. With ongoing rice cultivation, copy numbers of archaeal ammonia oxidizers did not change, while that of their bacterial counterparts declined. The nirK gene, coding for nitrite reductase, increased with rice cultivation time and dominated its functionally redundant counterpart, nirS, at all sites under investigation. Relative species richness showed significant differences between all soils with the exception of the archaeal ammonia oxidizers in the paddy soils cultivated for 100 and 300 years. In general, changes in diversity patterns were more pronounced than those in functional gene abundances. [ABSTRACT FROM AUTHOR]

The aims of this study were to investigate soil microbial community characteristics and their interrelationships with soil geochemistry under different farmlands in Shouguang, China. The traditional dilution plate counts, BIOLOG system, and fatty acid methyl ester (FAME) analyses were used to assess microbial populations, substrate utilization, and fatty acid profiles. The number of aerobic heterotrophic bacteria varied significantly among untilled land, maize, and mungbean fields. The amounts of actinomycetes, fungal fatty acids, and Gram-positive/Gram-negative bacteria ratios varied greatly among celery, tomato, and aubergine fields. In the tomato field, the soil microbial community characteristics were significantly different from other fields. Principal component analysis of BIOLOG and FAME data revealed differences in the catabolic capability and fatty acid profiles of soil microbial communities among different farmlands. Spearman correlation analyses showed that in these sand clay soils of Shouguang, microbial communities in different farmlands were closely correlated with soil geochemical elements, moisture, and organic matter. [ABSTRACT FROM AUTHOR]

Abstract: Eucalyptus is one of the fastest growing woody plants in the world, but few studies have reported the soil microbial community composition in Eucalyptus ecosystems. This study investigated the soil microbial communities in plantations of 3-, 7-, 10- and 13-year-old Eucalyptus in subtropical China based on phospholipid fatty acids (PLFA) analysis. The variation in soil microbial biomass and community compositions were influenced by sampling site and season and the interaction of both, which were consistent with the variation in soil total nitrogen (TN), soil organic carbon (SOC) and soil moisture. The number and abundances of PLFAs, and the amount of soil TN and SOC were higher in plantation of 13-year-old Eucalyptus than those in other younger plantations, suggesting that the soil properties and the soil microbial community composition is not negatively affected by the planting of Eucalyptus. The ratio of monounsaturated-to-branched fatty acids, the proportional abundance (mol%) of bacterial PLFA and fungal PLFA varied significantly with Eucalyptus plantations of different age, suggesting that the individual PLFA signatures might be sensitive indicators of soil properties associated with forest plantations. [Copyright &y& Elsevier]

Understanding the interactions of soil microbial species and how they responded to disturbances are essential to ecological restoration and resilience in the semihumid and semiarid damaged mining areas. Information on this, however, remains unobvious and deficiently comprehended. In this study, based on the high throughput sequence and molecular ecology network analysis, we have investigated the bacterial distribution in disturbed mining areas across three provinces in China, and constructed molecular ecological networks to reveal the interactions of soil bacterial communities in diverse locations. Bacterial community diversity and composition were classified measurably between semihumid and semiarid damaged mining sites. Additionally, we distinguished key microbial populations across these mining areas, which belonged to Proteobacteria, Acidobacteria, Actinobacteria, and Chloroflexi. Moreover, the network modules were significantly associated with some environmental factors (e.g., annual average temperature, electrical conductivity value, and available phosphorus value). The study showed that network interactions were completely different across the different mining areas. The keystone species in different mining areas suggested that selected microbial communities, through natural successional processes, were able to resist the corresponding environment. Moreover, the results of trait-based module significances showed that several environmental factors were significantly correlated with some keystone species, such as OTU_8126 (Acidobacteria), OTU_8175 (Burkholderiales), and OTU_129 (Chloroflexi). Our study also implied that the complex network of microbial interaction might drive the stand resilience of soil bacteria in the semihumid and semiarid disturbed mining areas. [ABSTRACT FROM AUTHOR]