生物炭对设施退化土壤氮相关功能微生物群落丰度的影响

设施栽培土壤在人工调控下进行生产,长期处在高温高湿、无降水淋洗、高复种指数、持续大量施肥等特殊环境条件下,它的物理结构和生化性状产生很大变化.菜农因传统施肥经验而形成的盲目大量施肥行为造成氮肥的过量摄入,从而愈发加重了土壤表层养分富集、酸化板结、养分失调等,继而导致蔬菜品质严重下降,在部分种植年限较长的大棚已不能进行蔬菜生产,严重制约了各地区设施农业的可持续发展[1].而长期过量的施用氮肥还会使设施土壤中硝态氮含量升高,减少土壤中的硝化微生物菌群的丰度,提高反硝化微生物的活性,促进N2O的排放通量[2].因此,为了保证设施栽培产业能够健康、可持续地发展,使蔬菜生产向高产、高效、优质的方向发展,对设施栽培土壤氮循环的研究已迫在眉睫.     

长期耕作对农田黑土几丁质降解菌群及酶活性的影响

为揭示长期耕作对农田黑土几丁质降解菌群及酶活性的影响及其驱动因子,以黑土区耕法长期定位试验为平台,采用荧光定量和高通量测序技术研究不同耕作措施（灭茬起垄、免耕、间隔深松和翻耕）下0～40 cm土层chiA几丁质降解菌基因丰度、微生物群落结构和酶活性。结果表明：0～20 cm土层,免耕显著提高chiA基因丰度;20～40 cm土层,免耕降低chiA基因丰度、alpha多样性和变形菌门（Proteobacteria）相对丰度,但是增加放线菌门（Actinobacteria）相对丰度。土壤pH、平均重量直径和养分含量显著影响chiA基因丰度和群落结构。与灭茬起垄相比,免耕显著提高0～20cm土层几丁质酶活性,而间隔深松和深翻显著提高0～40 cm土层几丁质酶活性。结构方程模型模拟发现耕作方式、土壤深度、平均重量直径、土壤有机碳、全氮、全磷、chiA基因丰度和放线菌门相对丰度对几丁质酶活性具有显著直接效应。研究结果为明确黑土区不同耕作措施对土壤几丁质降解的影响提供理论基础。     

A quantitative evaluation and phylogenetic characterization of oligotrophic denitrifying bacteria harbored in subsurface upland soil using improved culturability

This is the first investigation to show that oligotrophic denitrifying bacteria are dominant denitrifiers in subsurface upland soil. We examined the vertical distribution of denitrifying bacterial populations in upland soil using two kinds of enumeration media. The number of denitrifying bacteria, enumerated in subsurface soil layers by a 100-fold diluted nutrient broth (DNB) medium with NO₃ ⁻, was two to three orders of magnitude greater than those enumerated by a conventional nutrient broth medium with NO₃ ⁻, suggesting the dominance of oligotrophic denitrifying bacteria. Seventy-four percent of the total denitrifying bacterial isolates were DNB organisms of the oligotrophic type, which did not show appreciable growth on a conventional nutrient broth medium. The isolates were heterogeneous and were categorized as alpha (35 strains) and beta (19 strains) subdivisions of proteobacteria and high G+C gram-positive bacteria (7 strains) by 16S rRNA gene sequence analysis. The 35-alpha subdivision of proteobacterial isolates was of oligotrophic type and widely distributed from the surface to subsurface soil layers. Phylogenetic analysis indicated that some isolates belonged to groups with few or no cultivated representatives, and that one isolate may be a member of a new genus. This isolation procedure, using diluted media, is valuable in detecting diverse and novel denitrifying bacteria in the subsurface soil.     

Effect of LDPE microplastics on chemical properties and microbial communities in soil

The accumulation of plastics in the soil ecosystem poses an increasing environmental concern worldwide. However, little is known about the effect of plastic concentrations on soil properties and soil biota. In this study, we investigated the effect of low-density polyethylene (LDPE) microplastics (MPs) on the chemical and microbial properties of agricultural soil using a set of microcosm experiments. The soil was incubated for 100 days with LDPE at concentrations of 0%, 0.1%, 1%, 3%, 5%, and 7% at 25°C with 70% water-holding capacity. Along with soil chemical analysis, we conducted an analysis of soil microbial properties on the first day and again after 100 days of incubation. LDPE concentrations of ≥1% significantly (p < .05) decreased the pH but increased the electrical conductivity of the soil in comparison with the control (0% LDPE at 100 days). Increasing the LDPE concentration did not affect the soil exchangeable cation content or the available Pb concentration. Firmicutes were the most abundant phyla in the soil on the first day, whereas Proteobacteria, Firmicutes and Actinobacteria became dominant in all treatments after 100 days. An increasing LDPE concentration increased the abundance of Actinobacteria and decreased Proteobacteria. Principal component analysis demonstrated that only 7% LDPE was positively correlated with Actinobacteria, indicating that higher concentrations of LDPE contributed to the growth of this phylum. The findings of this study imply that MP contamination could affect soil chemical properties and microbial activity and that these effects primarily depend on MP concentrations in soil.     

Interactive effects of elevation and land use on soil bacterial communities in the Tibetan Plateau

The Tibetan Plateau of China is uniquely vulnerable to the global climate change and anthropogenic disturbances. As soil bacteria exert a considerable influence on the ecosystem function, understanding their response to different climates and land-use types is important. Here, we characterized the bacterial community composition and diversity across three major ecosystems (cropland, forest, and grassland) in the Sygera Mountains of Tibet, along a typical elevational gradient (3 300-4 600 m). The abundance of taxa that preferentially inhabit neutral or weak alkaline soil environments (such as Actinobacteria, Thermoleophilia, and some non-acidophilus Acidobacteria) was significantly greater in the cropland than in the forest and grassland. Furthermore, the diversity of soil bacterial communities was also significantly greater in the cropland than in the forest and grassland. We observed a unimodal distribution of bacterial species diversity along the elevation gradient. The dominant phyla Acidobacteria and Proteobacteria exhibited consistent elevational distribution patterns that mirrored the abundance of their most abundant classes, while different patterns were observed for Acidobacteria and Proteobacteria at the class level. Soil pH was the primary edaphic property that regulated bacterial community composition across the different land-use types. Additionally, soil pH was the main factor distinguishing bacterial communities in managed soils (i.e., cropland) from the communities in the natural environments (i.e., forest and grassland). In conclusion, land use (particularly anthropogenic disturbances such as cropping) largely controlled soil environment, played a major role in driving bacterial community composition and distribution, and also surpassed climate in affecting bacterial community distribution.     

Effects of organic and other management practices on soil nematode communities in tea plantation: a case study in southern China

Four major tea management practices (organic, pollution‐free, conventional, and semi‐natural) are employed in Chinese tea plantations at present. These practices can induce changes in the physiochemical parameters, microorganism community and enzyme activity in tea plantation soil. However, understanding of their effects on soil nematodes is still scarce. This study aimed to investigate whether and how different management practices affect the biodiversity, function, and structure of soil nematode communities in tea plantation habitats. The soil nematode community structures and ecological indices were determined from the soil samples collected more than 6 y after their respective farming practices were first applied, and different management practices did not greatly affect soil nematode community evenness or species diversity, but organic practice increased nematode trophic diversity, common species diversity, and species richness. Pollution‐free practice considerably increased fungivorous nematodes, and both pollution‐free and conventional practice decreased bacterivorous nematodes markedly in the subsurface layers of soil. Predator and omnivorous nematodes were found to be more abundant in semi‐natural plantation. Organic practice was more sustainable and suitable for tea cultivation, with the greatest biodiversity, best nutrient conditions, higher and more stable C/N ratio and lower interference in the food web.     

不同秸秆还田方式对和田风沙土土壤微生物 多样性的影响

秸秆还田是有效利用秸秆资源的重要途径,能够提高土壤养分含量、调节土壤微生物的群落结构和多样性,但目前还缺乏不同秸秆还田方式对新疆沙化土壤肥力和微生物多样性影响的系统报道。为探索新疆沙化土壤肥力可持续提升模式,于2010—2012年在和田风沙土土壤上设置秸秆直接还田(NPKS)、过腹还田(NPKM,15.0 t×hm~(-2))和炭化还田(NPKB1,2.5 t×hm~(-2);NPKB2,15.0 t×hm~(-2))定位试验,研究不同秸秆还田处理对和田风沙土土壤养分、微生物数量、土壤酶活性和Biolog碳源利用的影响。结果表明:1)与单施化肥(NPK)相比,不同秸秆还田方式均能显著提高风沙土土壤养分含量,其中NPKM处理效果最好,其次是NPKB2处理,NPKS和NPKB1处理分别为第3和第4。2)不同秸秆还田方式对土壤微生物数量影响差异显著,均增加了土壤中细菌、放线菌和生理菌群的数量,与NPK处理相比,细菌数量NPKB2处理最高,放线菌数量NPKM处理最高,分别显著提高了413.16%和574.19%。但NPKB1和NPKB2处理对生理菌群数量的提升效果好于NPKS处理和NPKM处理。土壤酶活性,不同秸秆还田方式总体好于NPK处理,NPKM处理的提升效果最好。3)Biolog碳源利用分析表明不同秸秆还田方式均能提高风沙土土壤微生物活性和丰富度指数。主成分分析表明,不同秸秆还田方式土壤微生物群落明显不同,起分异作用的碳源主要为羧酸类和糖类。聚类分析显示NPKB2和NPKM处理之间、NPKB1和NPKS处理之间土壤微生物功能相似。由此可以看出,不同秸秆还田方式均能显著提高和田沙化土壤微生物活性和功能多样性,但不同方式的增效不同。从3年定位试验结果看,秸秆过腹还田和炭化还田的效果较好,秸秆直接粉碎还田有增加土传病害的风险。该结果将为南疆沙化土壤肥力可持续提升提供一定的理论指导。     

玉米秸秆生物炭对褐土微生物功能多样性及 细菌群落的影响

生物炭施入土壤被认为是一种有效的固碳减排措施,可增加土壤有机碳及矿质养分含量,提高土壤的持水能力及保肥能力。为探明其施入土壤后对土壤微生物活性及多样性的影响,本文在盆栽试验条件下,采用Biolog与高通量测序相结合的方法,研究了CK(不施生物炭)和施用5 g·kg~(-1)、10 g·kg~(-1)、30 g·kg~(-1)、60 g·kg~(-1)玉米秸秆生物炭对土壤微生物碳源利用能力(AWCD)、功能多样性指数以及土壤细菌的丰度和多样性的影响。结果表明,随着生物炭施用量的增加,表征土壤微生物活性的AWCD值呈下降趋势,表现为:5 g·kg~(-1)处理≈CK10 g·kg~(-1)处理30 g·kg~(-1)处理60 g·kg~(-1)处理,其中CK和5 g·kg~(-1)处理间差异不显著(P0.05),而10 g·kg~(-1)、30 g·kg~(-1)和60 g·kg~(-1)处理在整个培养期间的AWCD值显著低于CK处理(P0.05);土壤微生物群落代谢功能多样性指数(H′)、碳源利用丰富度指数(S)均随生物炭施用量的增加而呈下降趋势,但均匀度指数(E)表现出相反趋势,5g·kg~(-1)、10 g·kg~(-1)、30 g·kg~(-1)、60 g·kg~(-1)各处理的H′较CK处理分别增加0.16%、-0.88%、-3.14%、-11.09%,S分别增加-2.82%、-11.27%、-18.31%、-47.89%,E分别增加1.14%、3.00%、3.73%和13.76%。主成分分析表明,与CK处理比较,5 g·kg~(-1)处理对土壤微生物群落碳源利用方式没有显著影响(P0.05),而10 g·kg~(-1)、30 g·kg~(-1)和60g·kg~(-1)处理对土壤微生物群落碳源利用方式影响显著(P0.05)。随着生物炭施用量的增加,土壤细菌OTU数目及丰富度指数(Chao1)呈增加趋势,5 g·kg~(-1)处理与CK处理差异不显著,而10 g·kg~(-1)、30 g·kg~(-1)、60 g·kg~(-1)处理的OTU数目较CK处理分别增加1.09%、5.26%、24.42%,Chao1分别增加5.73%、10.21%、37.68%。土壤中施用生物炭后土壤细菌变形菌门(Proteobacteria)的丰度在CK处理和5 g·kg~(-1)处理间差异不显著(P0.05),而10g·kg~(-1)、30 g·kg~(-1)、60 g·kg~(-1)处理较CK处理分别增加32.3%、21.1%、16.7%,拟杆菌门(Bacteroidetes)的丰度随着生物炭施用量的增加各处理较CK处理分别减少22.1%、55.3%、66.8%、50.5%。生物炭施入土壤后降低了土壤可培养微生物的活性,减少或改变了土壤微生物碳源利用的种类,使土壤原有微生物群落组分发生改变,生物炭也影响了土壤细菌各菌群在土壤中的丰度,使其分布的均匀性降低。为了不影响微生物群落结构和功能,石灰性褐土上生物炭一次还田量不能超过5 g·kg~(-1)(干土)。     

培肥措施对复垦土壤微生物碳氮代谢功能多样性的影响

土壤复垦是矿区生态环境恢复和耕地总量平衡及质量提升的根本要求。本研究依托山西襄垣采煤塌陷区复垦定位试验基地,采用Biolog-ECO方法和荧光定量PCR技术,研究了不施肥（CK）、单施化肥（CF）、单施有机肥（M）和有机无机培肥（MCF）4种培肥措施下复垦4年和8年土壤微生物碳代谢功能多样性及氮代谢功能基因丰度的变化特征。结果表明,随复垦年限增加,单施有机肥较其他处理可显著提高复垦土壤微生物的总碳源利用能力;不同处理复垦土壤微生物碳源相对利用率总体表现为氨基酸类>糖类>聚合物类>羧酸类>双亲化合物类>胺类,其中单施有机肥更大程度上提高了羧酸类、氨基酸类和胺类碳源的利用率;复垦年限和培肥措施没有改变复垦土壤微生物优势度指数,但有机无机配施较其他处理可显著提高香浓指数（H′）和Pielou均匀度指数;不同处理复垦土壤氮转化功能基因丰度总体表现为amoA（AOA）> amoA（AOB）>nisS、nirK> nifH,5种功能基因丰度均为以有机无机培肥处理最高,且随复垦时间增加而增加;复垦土壤有机质含量与nirS、nirK、nifH基因丰度以及AWCD值存在显著相关性,相关系数在0.707～0.807,同时5种氮转化功能基因丰度均与玉米产量存在显著或极显著的相关性,相关系数在0.824～0.949。综上所述,单施有机肥可提高土壤有机质含量,进而增强了复垦土壤碳代谢强度,有机无机培肥则更有利于复垦土壤碳氮代谢功能多样性的提升,并促进作物产量形成。     

The influence of different types of urban land use on soil microbial biomass and functional diversity in Beijing,China

Soil microbes in urban ecosystems are affected by a variety of abiotic and biotic factors resulting from changes in land use. However, the influence of different types of land use on soil microbial properties and soil quality in urban areas remains largely unknown. Here, by comparing five types of land use: natural forest, park, agriculture, street green and roadside trees, we examined the effects of different land uses on soil microbial biomass and microbial functional diversity in Beijing, China. We found that soil properties varied with land uses in urban environments. Compared to natural forest, soil nutrients under the other four types of urban land use were markedly depleted, and accumulation of Cu, Zn, Pb and Cd was apparent. Importantly, under these four types of land use, there was less microbial biomass, but it had greater functional diversity, particularly in the roadside‐tree soils. Furthermore, there were significant correlations between the microbial characteristics and physicochemical properties, such as organic matter, total nitrogen and total phosphorus (P < 0.05), suggesting that lack of nutrients was the major reason for the decrease in microbial biomass. In addition, the larger C/N ratio, Ni concentration and pool of organic matter together with a higher pH contributed to the increase in microbial functional diversity in urban soils. We concluded that different land uses have indirect effects on soil microbial biomass and microbial community functional diversity through their influence on soil physicochemical properties, especially nutrient availability and heavy metal content.     

清水灌溉在消除土壤多环芳烃中的作用及对土壤微生物特征的影响: 以沈抚灌区为例

To evaluate the effect of groundwater irrigation on the polycyclic aromatic hydrocarbons(PAHs) pollution abatement and soil microbial characteristics,a case study was performed in the Shenfu irrigation area of Shenyang,Northeast China,where the irrigation with petroleum wastewater had lasted for more than fifty years,and then groundwater irrigation instead of wastewater irrigation was applied due to the gradually serious PAHs pollution in soil.Soil chemical properties,including PAHs and nutrients contents,and soil microbial characteristics,including microbial biomass carbon,substrateinduced respiration,microbial quotient(qM),metabolic quotient(qCO2),dehydrogenase(DH),polyphenol oxidase(PO),urease(UR) and cellulase(CE) in surface and subsurface were determined.Total organic C,total N,total P,and available K were significantly different between the sites studied.The PAHs concentrations ranged from 610.9 to 6362.8 μg kg-1 in the surface layers(0-20 cm) and from 404.6 to 4318.5 μg kg-1 in the subsurface layers(20-40 cm).From the principal component analysis,the first principal component was primarily weighed by total PAHs,total organic C,total N,total P and available K,and it was the main factor that influencing the soil microbial characteristics.Among the tested microbial characteristics,DH,PO,UR,CE,qM and qCO2 were more sensitive to the PAHs stress than the others,thus they could serve as useful ecological assessment indicators for soil PAHs pollution.     

Culture-based and culture-independent assessment of the impact of mixed and single plant treatments on rhizosphere microbial communities in hydrocarbon contaminated flare-pit soil

Phytoremediation is a novel treatment option for weathered, hydrocarbon contaminated, flare-pit soil in prairie ecosystems. The remediation potential of six different naturalized prairie plants was assessed by examining their impact on the degradation potential of indigenous bacterial communities. Culture-based and culture-independent microbiological methods were used to determine if mixed plant treatments stimulate different microbial communities and catabolic genotypes in comparison to individual plant species that comprise the mix. DGGE analysis of PCR-amplified 16S rRNA genes revealed that alfalfa (Medicago sativa) had a dominant effect on the structure of rhizosphere microbial communities in mixed plant treatments, stimulating relative increases in specific Bacteroidetes and Proteobacteria populations. Alfalfa and mixes containing alfalfa, while supporting 100 times more culturable PAH degraders than other treatments, exhibited only 10% TPH reduction, less than all planted treatments except perennial rye grass (Lolium perenne). Total petroleum hydrocarbon (TPH) reduction was greatest in single-species grass treatments, with creeping red fescue (Festuca rubra) reducing the TPH concentration by 50% after 4.5 months. Overall TPH reduction throughout the study was positively correlated (p<0.001) to culturable n-hexadecane degraders.     

Effects of modified Pb-, Zn-, and Cd- availability on the microbial communities and on the degradation of isoproturon in a heavy metal contaminated soil

The effects of modified heavy metal (HM) availability on the microbial community structure and on the microbe-mediated degradation of herbicide isoproturon (IPU) were evaluated in soil with a long-term HM contamination. The fate of ¹⁴C-ring labelled IPU was investigated for over 60 days under controlled microcosm conditions. Phosphate mineral apatite and a water solution of Pb, Zn, and Cd salts were previously homogeneously mixed into the soil material to reduce and to increase the proportion of bioavailable HM, respectively. The availability of Pb, Zn, and Cd was determined by HM fractionation and plant uptake 110 days after the addition of amendments, shortly before IPU addition. Apatite treatment reduced the availability of HM, but did not affect the microbial biomass and the microbial community structure on the genotype level (total soil DNA-RAPD). However, it changed the microbial community structure on the phenotype level, based on the composition of phospholipid fatty acids (PLFA) at the end of the degradation experiment. The degradation of IPU did not change. In contrast to apatite treatment, HM supplementation increased the bioavailability of Pb, Zn and Cd, which resulted in biomass reduction and changes of microbial community structure on the genotypic (total soil DNA-RAPD) and phenotypic (PLFA) level. Increased bioavailability of HM also significantly reduced the rate of IPU degradation and mineralisation. The total mineralisation over a period of 60 days decreased from 12 to 5% of initial ¹⁴C. Increased HM bioavailability did not influence the degradation pathways and kinetics of IPU.     

Soil microbial biomass and community composition as affected by cover crop diversity in a short‐term field experiment on a podzolized Stagnosol‐Cambisol

Background: Cover cropping appears as a useful land management practice with numerous benefits for ecosystem functions. Aim: The objectives of this study were to determine the effects of different winter cover crops on soil microbial biomass, activity, and community composition in intensively managed agriculture systems as function of cover crop diversity. Methods: For this purpose, an on‐farm experiment was conducted at a podzolized Stagnosol‐Cambisol during seven months growing oil radish as single cover crop and five different cover crop mixtures comprising 5 to 13 plant species. A fallow treatment was used as control. Phospholipid fatty acids were used to determine the soil microbial biomass and soil microbial community composition. Basal respiration of the soil microorganisms was measured as a proxy for microbial activity. Results: The results show that none of the cover crop mixture could increase soil organic carbon or total nitrogen content. Three cover crop mixtures and oil radish as single cover crop significantly increased soil microbial biomass by about 50% and all of the investigated cover crops significantly increased microbial respiration and metabolic quotient by 50–150%. Only highly diverse cover crop mixtures significantly increased individual microbial groups such as Gram‐positive and Gram‐negative bacteria, actinobacteria, and saprotropic and mycorrhizal fungi by about 20% compared to the control. However, the ratio of fungi to bacteria was not influenced by any of the cover crop mixtures under study. Conclusion: These findings corroborate that aboveground plant diversity is linked to belowground microbial diversity.     

黑土区基准坡长和LS算法对地形因子的影响

该文结合小区实测坡长资料及Mc Cool数据,对地形因子算法中涉及的基准坡长影响和不同算法计算值的特征进行了讨论。研究表明,在坡长较小的情况下,20和22.13 m基准坡长计算得到的坡长因子相差不大,但随着坡度增加,在坡长指数的复合影响下,两者的差异渐趋增大。理论分析表明,坡长指数采用与坡度相关的变值更为合理。通过与实测数据对比发现,修正版通用土壤侵蚀模型(RUSLE)算法中的坡长因子与其更为接近,结合与Mc Cool数据的对比分析表明,研究区坡长指数更适合细沟和细沟间侵蚀比率中等的情形,或者采用RUSLE模型算法计算得到。同时研究发现,张宪奎算法、Moore算法、Desmet算法和B?hner算法计算得到的LS因子值都要比参照值小,而且4种算法与参照值的接近程度依次降低。空间分布特征而言,栅格累计算法总体较为破碎,并在平直坡面出现较多平行分布条带,而含有面积指标的其他3种算法则总体呈现光滑连续特性,但有无数据区域的存在。该结果对于研究区土壤侵蚀模型地形因子算法选择具有一定的现实意义。