Changes in the activities of key enzymes and the abundance of functional genes involved in nitrogen transformation in rice rhizosphere soil under different aerated conditions

Soil microorganisms play important roles in nitrogen transformation. The aim of this study was to characterize changes in the activity of nitrogen transformation enzymes and the abundance of nitrogen function genes in rhizosphere soil aerated using three different methods(continuous flooding(CF), continuous flooding and aeration(CFA), and alternate wetting and drying(AWD)). The abundances of amoA ammonia-oxidizing archaea(AOA) and ammonia-oxidizing bacteria(AOB), nirS, nirK, and nifH genes, and the activities of urease, protease, ammonia oxidase, nitrate reductase, and nitrite reductase were measured at the tillering(S1), heading(S2), and ripening(S3) stages. We analyzed the relationships of the aforementioned microbial activity indices, in addition to soil microbial biomass carbon(MBC) and soil microbial biomass nitrogen(MBN), with the concentration of soil nitrate and ammonium nitrogen. The abundance of nitrogen function genes and the activities of nitrogen invertase in rice rhizosphere soil were higher at S2 compared with S1 and S3 in all treatments. AWD and CFA increased the abundance of amoA and nifH genes, and the activities of urease, protease, and ammonia oxidase, and decreased the abundance of nirS and nirK genes and the activities of nitrate reductase and nitrite reductase, with the effect of AWD being particularly strong. During the entire growth period, the mean abundances of the AOA amoA, AOB amoA, and nifH genes were 2.9, 5.8, and 3.0 higher in the AWD treatment than in the CF treatment, respectively, and the activities of urease, protease, and ammonia oxidase were 1.1, 0.5, and 0.7 higher in the AWD treatment than in the CF treatment, respectively. The abundances of the nirS and nirK genes, and the activities of nitrate reductase and nitrite reductase were 73.6, 84.8, 10.3 and 36.5% lower in the AWD treatment than in the CF treatment, respectively. The abundances of the AOA amoA, AOB amoA, and nifH genes were significantly and positively correlated with the activities of urease, protease, and ammonia oxidase, and the abundances of the nirS and nirK genes were significantly positively correlated with the activities of nitrate reductase. All the above indicators were positively correlated with soil MBC and MBN. In sum, microbial activity related to nitrogen transformation in rice rhizosphere soil was highest at S2. Aeration can effectively increase the activity of most nitrogen-converting microorganisms and MBN, and thus promote soil nitrogen transformation.

Microbial community structure and functional metabolic diversity are associated with organic carbon availability in an agricultural soil

Exploration of soil environmental characteristics governing soil microbial community structure and activity may improve our understanding of biogeochemical processes and soil quality. The impact of soil environmental characteristics especially organic carbon availability after 15-yr different organic and inorganic fertilizer inputs on soil bacterial community structure and functional metabolic diversity of soil microbial communities were evaluated in a 15-yr fertilizer experiment in Changping County, Beijing, China. The experiment was a wheat-maize rotation system which was established in 1991 including four different fertilizer treatments. These treatments included： a non-amended control（CK）, a commonly used application rate of inorganic fertilizer treatment（NPK）; a commonly used application rate of inorganic fertilizer with swine manure incorporated treatment（NPKM）, and a commonly used application rate of inorganic fertilizer with maize straw incorporated treatment（NPKS）. Denaturing gradient gel electrophoresis（DGGE） of the 16 S r RNA gene was used to determine the bacterial community structure and single carbon source utilization profiles were determined to characterize the microbial community functional metabolic diversity of different fertilizer treatments using Biolog Eco plates. The results indicated that long-term fertilized treatments significantly increased soil bacterial community structure compared to CK. The use of inorganic fertilizer with organic amendments incorporated for long term（NPKM, NPKS） significantly promoted soil bacterial structure than the application of inorganic fertilizer only（NPK）, and NPKM treatment was the most important driver for increases in the soil microbial community richness（S） and structural diversity（H）. Overall utilization of carbon sources by soil microbial communities（average well color development, AWCD） and microbial substrate utilization diversity and evenness indices（H＇ and E） indicated that long-term inorganic fertilizer with organic amendments incorporated（NPKM, NPKS） could significantly stimulate soil microbial metabolic activity and functional diversity relative to CK, while no differences of them were found between NPKS and NPK treatments. Principal component analysis（PCA） based on carbon source utilization profiles also showed significant separation of soil microbial community under long-term fertilization regimes and NPKM treatment was significantly separated from the other three treatments primarily according to the higher microbial utilization of carbohydrates, carboxylic acids, polymers, phenolic compounds, and amino acid, while higher utilization of amines/amides differed soil microbial community in NPKS treatment from those in the other three treatments. Redundancy analysis（RDA） indicated that soil organic carbon（SOC） availability, especially soil microbial biomass carbon（Cmic） and Cmic/SOC ratio are the key factors of soil environmental characteristics contributing to the increase of both soil microbial community structure and functional metabolic diversity in the long-term fertilization trial. Our results showed that long-term inorganic fertilizer and swine manure application could significantly improve soil bacterial community structure and soil microbial metabolic activity through the increases in SOC availability, which could provide insights into the sustainable management of China＇s soil resource.

Straw and biochar strongly affect functional diversity of microbial metabolism in paddy soils

The application of straw and biochar is widely practiced for the improvement of soil fertility.However,its impact on microbial functional profiles,particularly with regard to paddy soils,is not well understood.The aim of this study was to investigate the diversity of microbial carbon use patterns in paddy soils amended with straw or straw-derived biochar in a 3-year field experiment in fallow soil and at various development stages of a rice crop(i.e.,tillering and blooming).We applied the community level physiological profiling approach,with 15 substrates(sugars,carboxylic and amino acids,and phenolic acid).In general,straw application resulted in the greatest microbial functional diversity owing to the greater number of available C sources than in control or biochar plots.Biochar amendment promoted the use of α-ketoglutaric acid,the mineralization of which was higher than that of any other substrate.Principal component analyses indicated that microbial functional diversity in the biochar-amended soil was separated from those of the straw-amended and control soils.Redundancy analyses revealed that soil organic carbon content was the most important factor regulating the pattern of microbial carbon utilization.Rhizodeposition and nutrient uptake by rice plants modulated microbial functions in paddy soils and stimulated the microbial use of N-rich substances,such as amino acids.Thus,our results demonstrated that the functional diversity of microorganisms in organic amended paddy soils is affected by both physicochemical properties of amendment and plant growth stage.

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.

Soil functional indicators in mixed beech forests are clearly species-specifi c

Beech stands are considered part of the ancient forest ecosystems in the northern hemisphere.In mixed stands in beach forest ecosystems,the type of associated tree species can signifi cantly aff ect soil functions,but their infl uence on microbial activity,nutrient cycling and belowground properties is unknown.Here,we considered forest patches in northern Iran that are dominated by diff erent tree species:Fagus orientalis Lipsky,Quercus castaneifolia C.A.Mey.,Pterocarya fraxinifolia(Lam.),Tilia begonifolia Stev.,Zelkova carpinifolia Dippe,Acer cappadocicum Gled,Acer velutinum Boiss.,Fraxinus excelsior L.,Carpinus betulus L.,and Alnus subcordata C.A.Mey.For each forest patch–tree species,litter and soil samples(25×25×10 cm,100 of each)were analyzed for determine soil and litter properties and their relationship with tree species.The litter decomposition rate during a 1-year experiment was also determined.A PCA showed a clear diff erence between selected litter and soil characteristics among tree species.F.orientalis,Q.castaneifolia,P.fraxinifolia,T.begonifolia,Z.carpinifolia,A.cappadocicum,and A.velutinum enhanced soil microbial biomass of carbon,whereas patches with F.excelsior,C.betulus and A.subcordata had faster litter decomposition and enhanced biotic activities and C and N dynamics.Thus,soil function indicators were species-specifi c in the mixed beech forest.A.subcordata(a N-fi xing species),C.betulus and F.excelsior were main drivers of microbial activities related to nutrient cycling in the old-growth beech forest.

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.

Microbial Activity in a Temperate Forest Soil as Affected by Elevated Atmospheric CO_2

Microorganisms play a key role in the response of soil ecosystems to the rising atmospheric carbon dioxide (CO2) as they mineralize organic matter and drive nutrient cycling. To assess the effects of elevated CO2 on soil microbial C and N immobilization and on soil enzyme activities, in years 8 (2006) and 9 (2007) of an open-top chamber experiment that begun in spring of 1999, soil was sampled in summer, and microbial biomass and enzyme activity related to the carbon (C), nitrogen (N) and phosphorus (P) cycling were measured. Although no effects on microbial biomass C were detected, changes in microbial biomass N and metabolic activity involving C, N and P were observed under elevated CO2. Invertase and dehydrogenase activities were significantly enhanced by different degrees of elevated CO2. Nitrifying enzyme activity was significantly (P < 0.01) increased in the August 2006 samples that received the elevated CO2 treatment, as compared to the samples that received the ambient treatment. Denitrifying enzyme activity was significantly (P < 0.04) decreased by elevated CO2 treatments in the August 2006 and June 2007 (P < 0.09) samples. β-N-acetylglucosaminidase activity was increased under elevated CO2 by 7% and 25% in June and August 2006, respectively, compared to those under ambient CO2. The results of June 2006 samples showed that acid phosphatase activity was significantly enhanced under elevated CO2. Overall, these results suggested that elevated CO2 might cause changes in the belowground C, N and P cycling in temperate forest soils.

Microbial Development in Soils Under Intensively Managed Bamboo (Phyllostachys praecox) Stands

Phyllostachys praecox C. D. Chu et C. S. Chao, a favored bamboo shoot species, has been widely planted in recent years. Four stands with different historical management practices were selected for this study to understand the evolution of soil microbial ecology by determining the effects of a new mulching and heavy fertilization practice on soil quality using microbiological parameters. Compared with the traditional practice (index 1), microbial biomass carbon (MBC) and soil microbial respiration carbon (MRC) with the new management practice significantly decreased (P ＜ 0.01 and P ＜ 0.05,respectively) with 1-2 years of mulching (index 2) and then for continued mulching significantly increased (P ＜ 0.05). The ratios of MBC/TOC (total organic carbon) and MRC/TOC also significantly diminished (P ＜ 0.05) with mulching. The average well color development (AWCD) and Shannon index decreased with mulching time, and the significant decrease(P ＜ 0.05) in Shannon index occurred from index 2 to index 3. The results from a principal components analysis (PCA)showed that the scores of the first principal component for indexes 1 and 2 were significantly larger (P ＜ 0.05) than soils mulched 3-4 years or 5-6 years. Also, the second principal component scores for index 1 were larger than those for index 2, suggesting that the ability of soil microorganisms to utilize soil carbon was decreasing with longer use of the new management practice and causing a deterioration of soil biological properties.

土壤含水率对豫中植烟土壤微生物群落多样性及氮循环功能基因丰度的影响

为揭示豫中典型浓香型烤烟产区植烟土壤氮素矿化动态变化、土壤微生物多样性以及氮素循环功能基因对水分条件的响应特征,通过室内培养法研究50%(H-50%)、65%(H-65%)和80%(H-80%)持水量条件下,河南许昌植烟土壤细菌和真菌群落功能多样性的差异。结果表明,H-65%处理土壤的无机氮矿化量及矿化速率均高于其他处理。在土壤细菌中,变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、绿弯菌门(Chloroflexi)、厚壁菌门(Firmicutes)、酸杆菌门(Acidobacteria)、浮霉菌门(Planctomycetes)、芽单胞菌门(Gemmatimonadetes)为优势菌门(相对丰度>3%),其中,H-80%处理中变形菌门的相对丰度显著高于其他处理,而厚壁菌门的相对丰度显著低于其他处理;H-50%处理中放线菌门、绿弯菌门的相对丰度显著高于其他处理。在土壤真菌中,子囊菌门(Ascomycota)占土壤真菌总OTU(operational taxonmic units)数的90%以上,其相对丰度随土壤含水率增加呈倒“V”的变化趋势。LEfSe(LDA effect size)分析结果表明,各处理在细菌属水平共检测出6种活性生物标志物(LDA值>3.5)。细菌群落具有丰富的功能多样性,一级功能层表现为代谢方面较活跃,二级功能层的功能基因丰度在不同含水率条件下发生明显变化;与固氮过程相关的固氮酶基因nifK、nifD、nifH的相对丰度在不同处理中表现为H-50%>H-65%>H-80%,反硝化过程相关基因norB、nirK、nosZ的相对丰度均在H-65%处理最高。综合来看,合理调控土壤含水率可以有效调节豫中烟区土壤氮素矿化动态、土壤微生物群落功能多样性以及氮循环相关功能基因的丰度。

古尔班通古特沙漠不同区域藻类结皮微生物结构和潜在功能

藻类结皮形成和发育,能够提高土壤稳定性并增加土壤有机质含量,为微生物生长、繁殖和草本植物拓殖创造条件。因此,藻类结皮潜在功能对后续生物结皮及生态系统演替具有重要意义。然而,古尔班通古特沙漠藻类结皮营养循环相关微生物及潜在功能机制尚不清楚。以古尔班通古特沙漠不同区域藻类结皮为研究对象,采用宏基因组测序技术,研究藻类结皮微生物群落及碳氮循环功能基因特征。研究结果表明蓝藻菌门、变形菌门、放线菌门是藻类结皮中主要微生物类群,在沙漠固碳和氮循环中起到重要作用。微生物α多样性结果显示仅物种丰富度指数在三个区域内存在显著差异。β多样性结果显示藻类结皮未因沙漠局部气候及理化因子差异产生微生物群落分化。而微生物群落功能基因对环境变化响应要比微生物群落更为敏感,沙漠东部和西部藻类结皮功能基因产生显著分化。三个区域微生物功能基因中还原型三羧酸循环是自养生物固碳主要途径,而卡尔文循环是光合生物固碳的主要途径,其中rpiA和rbcS基因更易受到降水影响。鞘脂单胞菌属、念珠藻属和伪枝藻属在参与固碳过程中表现出的差异,可能是导致固碳功能基因产生分化的原因之一。氮循环主要途径以硝酸盐还原为主,大部分氮素通过硝酸盐同化作用被土壤微生物转化为铵盐,少量氮素被反硝化为一氧化二氮和一氧化氮流失。沙漠藻类结皮固氮作用较弱,仅有念珠藻属和伪枝藻属参与,且存在nifH、nifD、nifK三个功能基因。这些固氮功能基因更易受到土壤中硝态氮含量的影响。硝化过程仅注释到氨单加氧酶或甲烷单加氧酶编码pmoABC-amoABC基因,而hao和nxrA、nxrB基因均未注释获得。

土壤碳循环微生物作用研究进展

土壤碳是全球碳循环的重要组成部分,其碳循环过程在气候调节中发挥着重要作用,而微生物是土壤碳循环的关键驱动力。土壤微生物能与植物共生间接促进植物光合作用与土壤碳的输入,可直接参与土壤碳的固定与转化。微生物残体及其分泌物在矿物质结合态有机质和土壤团聚体的形成中发挥关键作用,有利于土壤有机碳的长期稳定。微生物介导的激发效应对土壤有机质分解具有调控作用,可影响土壤CO_(2)和CH_(4)等温室气体的排放。通过微生物作用提升土壤的固碳潜力或碳汇功能,可助力我国实现“碳达峰、碳中和”的重大战略目标。本文综述了微生物在土壤有机碳输入、有机质形成与稳定、有机质分解矿化等过程中的作用与机制,以及土壤性质、气候条件、植物因素与人类活动对微生物介导的土壤碳循环的影响,尤其是相关研究的最新进展与理论更新。未来可加强微生物介导的土壤有机碳稳定化与碳储过程的作用机制研究,关注土壤微生物群落结构功能与碳循环之间的复杂关系及其对全球变化的响应。

微塑料参与下的土壤碳循环过程评述

土壤有机碳固定是驱动土壤肥力演变和陆地生态系统碳平衡的关键过程。鉴于微塑料在土壤生态系统中的持久性和生态环境风险,其对土壤性质和过程的影响日益受到关注,但基于土壤碳循环视角关注微塑料介导作用的研究仍相对匮乏。赋存于土壤中的微塑料能够通过间接影响土壤理化性质和直接参与碳循环的方式影响土壤有机碳固存、矿化与消长,这进一步加剧了土壤有机碳循环过程的不确定性,也突出了相关研究的迫切性。以此为背景,本文概述了土壤有机碳固定途径的理论发展,总结了土壤中微塑料的来源特征,阐述了微塑料对不同土壤碳库的影响,并深入探讨了微塑料调控土壤碳循环的可能机制,最后对微塑料参与下的土壤有机碳循环相关研究进行了展望。结果表明微塑料能够通过影响土壤物理结构、微生物群落结构多样性、酶活性与功能基因、生物膜的形成、动物的繁殖与生长、植物的生长和根系沉积等对土壤碳的平衡起到介导作用,同时通过自身参与到土壤全链条生物地球化学循环中而直接影响土壤有机碳循环。但相关研究仍处于起步阶段,如何选取科学方法将微塑料周转与有机碳循环过程进行区分与耦合是未来研究的难点。因此,在现有研究基础上,通过先进土壤学研究手段的嵌套与改良,以及研究思路的革新与交叉,可进一步精准区分微塑料源碳在不同有机碳库中的贡献潜力,探明微塑料直接和间接影响土壤有机碳循环的耦合作用机制,并推进多因素影响下微塑料参与土壤碳循环过程的研究。

石油污染土壤微生物修复技术及机理研究进展

综述了环境微生物技术在石油污染土壤修复中的应用方法,介绍了人为干预提高石油降解微生物治理油污土壤的原位和异位修复技术和微生物去除石油组分的作用机理。针对微生物修复的研究热点多为石油降解微生物的选取及多种微生物的复合菌对石油组分的去除效果,但对微生物技术的实际应用和机理研究相对较少。提出了未来微生物技术修复石油污染土壤的研究和发展方向,包括特定材料对微生物的固定化、利用宏组学与示踪技术进一步明确微生物的降解机理和质粒拼接手段构建高效基因工程菌。

球形赖氨酸芽孢杆菌WH07对潜育化水稻土的改良效果和土壤微生态的影响

为建立潜育化稻田微生物改良技术,采用MWMM(modified wolfe’s mineral medium)培养基富集微好氧FeOB,结合16S rRNA测序等技术鉴定菌株种类,分别采用100 mL 10^(6)(T1)、10^(7)(T2)、10^(8)(T3)CFU/mL菌株发酵液处理潜育化水稻土,评价菌株对潜育化水稻土壤的还原性物质、土壤养分、氮循环功能基因丰度和水稻秧苗生长的影响,并利用16S rRNA高通量测序技术评价该菌株对土壤微生态的影响。结果显示:筛选到的对Fe^(2+)具有较强氧化作用的FeOB为球形赖氨酸芽孢杆菌WH07(Lysinibacillus sphaericus WH07);相比于CK,土壤氧化还原电位(Eh)显著提高(P<0.05),并由负电位转为正电位;T1、T2、T3处理土壤还原性物质总量分别减少26.47%、41.53%、53.19%,亚铁含量分别减少0.37%、21.50%、50.09%,亚锰含量分别减少7.84%、21.57%、37.25%。土壤碱解氮含量分别显著增加15.50%、27.38%、48.90%(P<0.05),速效磷分别显著增加12.52%、17.34%、27.38%(P<0.05),速效钾分别显著增加11.56%、17.20%、19.34%(P<0.05),有机质分别显著增加8.66%、22.22%、45.05%(P<0.05),pH显著分别增加3.40%、8.94%、16.99%(P<0.05)。土壤AOAamoA基因丰度分别增加11.94%、14.68%、33.83%,nosZ基因丰度分别增加42.97%、75.78%、118.75%,nifH基因丰度分别增加38.29%、51.05%、216.13%,UreC基因丰度分别增加16.74%、54.51%、60.94%。水稻株高分别增加5.44%、10.98%、36.00%,叶龄分别增加10.21%、23.42%、36.94%,鲜质量增加分别12.61%、22.52%、28.38%,白根数分别增加10.14%、32.92%、46.81%。土壤微生物多样性指数Chao1和Shannon指数相比于CK均显著降低(P<0.05)。门水平上相对丰度前10的土壤细菌中,有8个显著下调(P<0.05),如Proteobacteria等、2个(Bacteroidetes和Firmicutes)显著上调。在相对丰度前50的属中,3个处理分别有20、19、22个属显著上调(P<0.05),包括Macellibacteroides等6个FeOB;25个属在3个处理中均显著下调(P<0.05),包括MBNT15等4个铁还原菌。调控网络分析显示菌株WH07潜在地与FeOB协同改善土壤理化性质和生物活性,最终促进了秧苗生长。结果表明,应用菌株WH07显著改善了潜育化水稻土壤理化性质,改变了土壤微生物群落结构和功能。

石油污染土壤微生物群落结构及降污固碳潜力

为探究石油污染土壤中微生物群落结构特征及降污固碳潜力,该研究选取中国东部、中部、西北部、西南部4个典型油气田企业在役井场为研究区域,结合16S rRNA高通量测序及生物信息学技术,研究不同油田表层土壤(0~20 cm)潜在降污、固碳微生物群落结构变化规律及主要驱动环境因子,并针对降污、固碳相关代谢通路进行预测及功能注释。结果表明:(1)不同油田土壤全量养分及微生物生物量大致呈东部油田最高,西南部及西北部油田较为接近,中部油田最低的规律。(2)研究区土壤微生物优势菌为变形杆菌门、放线菌门、绿弯菌门、拟杆菌门,酸杆菌门。(3)基于VPA、RDA分析结果推测,微生物量碳、微生物量氮、RubisCO酶活性、总石油烃含量为影响污染土壤微生物群落结构变化的主要驱动环境因子,其中,TPH(r^(2)=0.67、P=0.001)、MBC(r^(2)=0.36、P=0.0042)、MBN(r^(2)=0.74、P=0.003)和RubisCO酶活性(r^(2)=0.37、P=0.0041)均与微生物群落结构具有显著相关性。(4)KEGG数据库功能注释结果表明,不同油田污染土壤中与微生物固碳过程相关的代谢通路相对丰度均显著高于与石油烃等有机物降解相关的代谢通路,且上述通路在不同油田间的相对丰度差异较小。研究结果为支撑新形势下石油石化行业减污增汇技术发展具有重要意义。

Disentangling the contributions of arbuscular mycorrhizal fungi to soil multifunctionality

Soil multifunctionality represents a range of soil processes driven by the interactions between soil abiotic and biotic components.As a group of ubiquitous fungi that form mutualistic symbiotic associations with a vast array of terrestrial plants,arbuscular mycorrhizal(AM)fungi may play a critical role in maintaining soil multifunctionality,but the characteristics of their contributions remain to be unraveled.This mini review aims to disentangle the contributions of AM fungi to soil multifunctionality.We provide a framework of concepts about AM fungi making crucial contributions to maintaining multiple soil functions,including primary productivity,nutrient cycling,water regulation and purification,carbon and climate regulation,habitat for biodiversity,disease and pest control,and pollutant degradation and detoxification,via a variety of pathways,particularly contributing to soil and plant health.This review contends that AM fungi,as a keystone component of soil microbiome,can govern soil multifunctionality,ultimately promoting ecosystem services.

Partial organic fertilizer substitution promotes soil multifunctionality by increasing microbial community diversity and complexity

Partial substitution of synthetic nitrogen(N)with organic fertilizers(PSOF)is of great significance in improving soil ecosystem functions in systems that have deteriorated due to the excessive application of chemical N fertilizer.However,existing studies typically focus on individual soil functions,neglecting the fact that multiple functions occur simultaneously.It remains unclear how PSOF influences multiple soil functions and whether these impacts are related to soil microbial communities.Here,we examined the impacts of partial substitutions(25%–50%)of chemical N fertilizer with organic form(pig manure or municipal sludge)in a vegetable field on soil multifunctionality,by measuring a range of soil functions involving primary production(vegetable yield and quality),nutrient cycling(soil enzyme activities,ammonia volatilization,N leaching,and N runoff),and climate regulation(soil organic carbon sequestration and nitrous oxide emission).We observed that PSOF improved soil multifunctionality,with a 50%substitution of chemical N fertilizer with pig manure being the best management practice;the result was strongly related to the diversities and network complexities of bacteria and fungi.Random forest analysis further revealed that soil multifunctionality was best explained by the bacterial-fungal network complexity,followed by available phosphorus level and bacterial diversity.The PSOF also shifted the composition of bacterial and fungal communities,with increased relative abundances of dominant bacteria phyla,such as Bacteroidetes,Gemmatimonadetes,and Myxococcota,and fungal phyla,such as Basidiomycota and Olpidiomycota.The observed increases in soil multifunctionality were consistent with significant increases in the relative abundances of keystone taxa such as Blastocladiomycota,Chaetomiaceae,and Nocardiopsaceae.Together,these findings indicate that PSOF can enhance interactions within and among microbial communities and that such practices have the potential to improve soil ecosystem multifunctionality and contribute to the development of sustainable agriculture.

生物质炭-沼液配施条件下旱地红壤碳氮循环功能基因丰度主控因子与耦合关系

为研究生物质炭-沼液配施条件下碳氮生物地球化学循环特征,本研究以典型旱地红壤为对象,按0%和2%生物质炭添加量(C0和C1)与0%和100%沼液替代比例(B0和B1)配施,探究配施条件下4年间土壤基本理化性质、碳-氮循环功能基因丰度变化特征及其相互耦合关系。结果显示:与空白处理(CK)相比,生物质炭与沼液的联合施用处理(C1B1)土壤pH提升了1.92个单位,容重降低了19.2%,全氮含量则提高了268.6%。多元非线性回归模型显示,铵态氮(NH+4-N)、硝态氮(NO-3-N)和水溶性有机碳(WSOC)是影响碳氮循环功能基因丰度的主要因子。相关性热图则表明反硝化功能基因(narG、nirK、nirS和nosZ)与碳降解(chiA、pgu、naglu和gcd)、碳固定(rbcL、frdA、pccA和mct)、甲烷代谢功能基因(mxaF和pmoA)呈正相关关系。研究表明,生物质炭与沼液配施显著提升土壤质量,并通过影响土壤碳氮形态和含量改变碳氮循环功能基因丰度,最终调控土壤碳氮循环过程。

秸秆覆盖休耕对土壤C、N、P循环功能基因的影响

为了探索一种适于坡耕地的基于种养结合的耕作方式,采用田间试验结合基因芯片研究方法,探究了秸秆覆盖休耕技术[包括隔年秸秆覆盖休耕+旋耕(RF)、2年旋耕+1年秸秆覆盖休耕(RRF)]与常规耕作(CRT,秸秆移除后旋耕)对土壤C、N、P循环的影响。结果表明:外源C的投入激发了土壤微生物对有机物料的降解潜力,无论是RF处理,还是RRF处理,参与土壤C循环的降解功能基因(acsE、xylA和rbcL)丰度均有一定程度的增加,xylA基因平均相对丰度较CRT处理增加43.12%,而秸秆不还田的CRT处理中参与C同化基因(acsA)的丰度显著增加,平均增加33.03%;CRT处理参与N循环基因的丰度降低,而秸秆覆盖还田促进了土壤中N从NH4+-N向NO3--N的转化,gdh基因丰度增加;秸秆覆盖还田后土壤活性P的积累增强,碱性磷酸酶基因(phoD)丰度较CRT处理平均增加59.57%,phoD与速效P和phnk基因丰度呈显著正相关。研究表明,秸秆覆盖还田促进了土壤微生物C、N、P周转,进而促进外源有机C的转化和土壤有机C的积累,短期内秸秆当季覆盖休耕与上季覆盖休耕处理间差异不大。研究结果为东北黑土区坡耕地实施保护性耕作和防控土壤侵蚀提供了科学依据。

Effect of vegetation on soil bacteria and their potential functions for ecological restoration in the Hulun Buir Sandy Land,China

To date,much of research on revegetation has focused on soil microorganisms due to their contributions in the formation of soil and soil remediation process.However,little is known about the soil bacteria and their functions respond to the diverse vegetational types in the process of vegetation restoration.Effects of dominated vegetation,i.e.,Artemisia halodendron Turcz Ex Bess,Caragana microphylla Lam.,Hedysarum fruticosum Pall.and Pinus sylvestris L.on bacterial community structures and their potential functions in the Hulun Buir Sandy Land,China were determined using high-throughput 16S rRNA gene sequencing and phylogenetic investigation of communities by reconstruction of unobserved states(PICRUSt)in 2015.Although the dominant phyla of soil bacterial community among different types of vegetation,including Proteobacteria,Actinobacteria,Acidobacteria,Bacteroidetes and Firmicutes,were similar,the relative abundance of these dominant groups significantly differed,indicating that different types of vegetation might result in variations in the composition of soil bacterial community.In addition,functional genes of bacterial populations were similar among different types of vegetation,whereas its relative abundance was significantly differed.Most carbon fixation genes showed a high relative abundance in P.sylvestris,vs.recalcitrant carbon decomposition genes in A.halodendron,suggesting the variations in carbon cycling potential of different types of vegetation.Abundance of assimilatory nitrate reduction genes was the highest in P.sylvestris,vs.dissimilatory nitrate reduction and nitrate reductase genes in A.halodendron,indicating higher nitrogen gasification loss and lower nitrogen utilization gene functions in A.halodendron.The structures and functional genes of soil bacterial community showed marked sensitivities to different plant species,presenting the potentials for regulating soil carbon and nitrogen cycling.