尿素和生物炭施用对菜地土壤氨氧化作用的影响

研究将生物炭(40000 kg hm~(-2))和不同用量的尿素(0, 150, 300, 450 kg hm~(-2))施用于酸性红壤中,连续种植四季作物后采集菜地土壤样品,通过定量PCR方法测定添加硝化抑制剂后土壤氨氧化微生物数量和土壤氨氧化潜势的变化,并分析氨氧化古菌(AOA)和氨氧化细菌(AOB)对土壤氨氧化潜势的相对贡献,深入探讨生物炭和氮肥添加对菜地土壤氨氧化微生物和氨氧化潜势的影响。结果表明,与未添加生物炭相比,添加生物炭处理土壤容重降低了7.1%～11.5%,pH值提高了0.20～0.56个单位,有机质含量增加了13.5%～19.1%;与未施氮肥处理相比,无机氮的含量增加了38.5%～77.8%(未添加生物炭)和17.1%～59.5%(添加生物炭)。添加生物炭和氮肥处理AOA的基因拷贝数没有显著差异(P 0.05),氮肥添加提高了AOB的基因拷贝数147.5%～385.6%(未添加生物炭)和69.5%～514.0%(添加生物炭)。添加生物炭处理,随氮肥施用量的增加,氨氧化潜势降低了13.4%～20.7%。因此,本研究中氮肥添加使AOB的amoA基因拷贝数显著增加、氨氧化潜势显著下降,对AOA没有显著影响(P 0.05);AOA对氨氧化潜势起到了主导作用;生物炭和尿素添加通过改变土壤的无机氮含量、pH、有机质含量影响土壤氨氧化过程。     

脱硫废弃物改良宁夏盐渍化土壤对细菌和氨氧化微生物丰度的影响

为探明脱硫废弃物改良盐渍化土壤对微生物群落的影响效果,在2009~2010年,采用田间试验,施用不同量的脱硫废弃物(0、0.74、1.49、2.25、3.00 kg·m-2),研究了脱硫废弃物对盐渍化土壤细菌、氨氧化细菌和氨氧化古菌的影响。试验结果表明:0~20 cm土层,Ca2+和NO-3-N含量随着施用量增加而增加;土壤p H值、电导率值显著下降。实时荧光定量PCR(q PCR)分析结果表明,微生物丰度随着脱硫废弃物的施用发生变化,但这种变化并不与脱硫废弃物的施用量呈线性关系。在0~20 cm土壤层,施脱硫废弃物使得细菌16S rRNA基因拷贝数处理组显著高于对照组。氨氧化古菌与氨氧化细菌基因拷贝数在T2和T4处理高于其它处理。20~40 cm土层各处理间微生物群落没有显著变化,或没有出现规律的变化趋势。因此,脱硫废弃物增加了土壤细菌和氨氧化功能基因丰度,且对上层土壤影响更为显著。本研究中施用脱硫废弃物1.49 kg·m-2(T2)是引起细菌和氨氧化功能基因丰度增加的施用量。     

氮肥施加条件下增温对硝化菌活性和丰度的影响

温度在多种生物地球化学过程中起到关键的调节作用,是影响土壤硝化作用和微生物分布的重要因素之一。硝化过程的第1个步骤由氨氧化细菌(AOB)和氨氧化古菌(AOA)催化,然而,不同施氮量下,增温对硝化菌活性和丰度的影响尚不清楚。本研究基于2008年10月起设立于太行山山前平原的长期增温试验平台(高于地表2m的红外加热器使土壤温度升高1.5℃),于2018年5月对不施氮(N0)和施氮[N1,240kg(N)·hm-2·a-1]下增温分别对0～10 cm和10～20 cm土壤硝化潜势(PNR)、AOA和AOB丰度的影响进行了研究。硝态氮(NO3--N和铵态氮(NH4+-N)含量用分光光度法测量,应用缓冲液培养法测定土壤PNR,提取土壤DNA后用实时荧光定量PCR技术测定功能基因AOA和AOB的丰度。结果表明:温度升高显著增加N1条件下PNR和NO3--N含量(P0.05),降低了N0条件下PNR和NO3--N含量,但差异不显著。N1条件下,增温土壤AOB丰度显著提高(P0.05); N0条件下,增温土壤AOA丰度显著降低(P0.05)。与N0相比, N1条件下的AOA/AOB比值明显降低,表明增温加氮肥处理对AOB的生长刺激更强烈。在增温加施氮条件下,细菌(AOB)表现显著的正反应,在增温不施氮条件下,古菌(AOA)和AOB表现显著的负反应。本研究结果可为全球增温背景下进一步了解硝化活性和氨氧化微生物对增温和氮有效性的响应提供科学依据。     

长期偏施氮肥对桑园土壤氨氧化微生物的影响

氮肥能够影响土壤氨氧化细菌(AOB)和氨氧化古菌(AOA)的丰度和种群结构。利用实时荧光定量PCR(RT-PCR)和变性梯度凝胶电泳(PCR-DGGE)技术研究不同氮肥施用年限(4年,4Y;17年,17Y;32年,32Y;0年,0Y)桑园土壤氨氧化微生物丰度及种群结构变化。结果发现,长期施用氮肥导致桑园土壤酸化,与4Y土壤相比,32Y土壤p H降低0.88。4Y处理土壤AOB amoA基因的拷贝数最高,而在32Y土壤中AOA amoA基因拷贝数最高。各处理AOB amoA基因拷贝数为每克干土6.46×10~5～8.32×10~7,明显高于AOA amoA基因拷贝数每克干土1.70×10~4～1.20×10~5。AOB种群丰度与潜在硝化速率(PNR)呈显著正相关,而AOA种群丰度与土壤pH和PNR的相关性不显著,表明AOB在硝化作用中发挥更为重要的作用。DGGE条带分析表明,氮肥施用年限对AOB种群结构影响较大,而对AOA种群结构影响较小。结果表明,桑园中AOB种群在氮循环中占主导地位,并且长期施用氮肥对桑园土壤AOB丰度和种群结构影响较大,而对AOA影响最小。     

华北平原中部夏玉米农田不同施氮水平氨挥发规律

以华北平原中部地区潮土为对象,研究了撒施不同水平尿素对夏玉米季氨挥发的影响,为合理施用氮肥和减少农田氨挥发损失提供依据。结合当地农民种植与施氮习惯,试验设置8个施氮水平,分别为0(N0)、50(N1)、100(N2)、150(N3)、200(N4)、250(N5)、300(N6)、400(N7)kg·hm~(-2),利用田间试验原位测定-密闭室连续抽气法测定氨挥发。结果表明,夏玉米种植体系在施入氮肥后发生了明显的氨挥发,且氨挥发主要发生在施肥后5 d内,在施肥后1～3 d出现氨挥发速率峰值,基肥与追肥后氨挥发通量最大分别达到N 2.35、5.30 kg·hm~(-2)·d~(-1),基肥期氨挥发量在N 3.76～9.82 kg·hm~(-2),追肥期氨挥发量在N 5.79～27.29 kg·hm~(-2)。在整个夏玉米生长期间,氨挥发量随着氮肥施用量的增加而增加。施氮量为200 kg·hm~(-2)条件下,氨挥发量相对较低,夏玉米产量为10 721.87 kg·hm~(-2),高于其他施氮水平处理的玉米产量。可见,合理的氮肥用量能够兼顾产量和生态环境,京郊夏玉米田间土壤在200 kg·hm~(-2)的氮肥水平下,玉米产量最高且氨挥发损失较低。     

长期施肥与覆膜对土壤细菌、泉古菌和氨氧化微生物丰度的影响

施肥与覆膜等农田管理措施能够改变土壤的物理化学性质,这直接影响着驱动氨氧化过程的氨氧化微生物,而氨氧化过程是硝化作用的限速步骤。以沈阳农业大学棕壤长期施肥与覆膜试验站为平台,采用荧光定量PCR技术,研究了5种施肥制度下[不施肥(CK)、氮肥(N)、氮磷肥(NP)、有机肥(M)和有机无机配施(MNP)]土壤细菌、泉古菌和氨氧化微生物数量的变化。结果表明,不同施肥处理细菌、泉古菌、氨氧化细菌和氨氧化古菌的基因拷贝数平均值分别为0.52×109～4.20×109、2.14×108～9.69×108、0.21×107～6.89×107和0.26×107～74.70×107copies g-1干土。与CK相比,有机肥处理(M、MNP)能显著增加土壤细菌的丰度,化肥处理(N、NP)则相反;施肥尤其是化肥处理(N、NP)均能降低泉古菌和氨氧化古菌的丰度;有机肥处理(M、MNP)显著增加了氨氧化细菌的丰度。细菌、泉古菌、氨氧化细菌和氨氧化古菌丰度均与pH值存在显著正相关关系(P0.05),细菌和氨氧化细菌丰度则主要受全碳含量的影响,而细菌、泉古菌和氨氧化细菌丰度与铵态氮、硝态氮含量存在极显著负相关关系(P0.01)。研究结果可为进一步探讨农田生态系统中氨氧化微生物对不同管理措施的响应机制及其在氮素转化中的作用提供科学依据。     

模拟氮沉降下施石灰对休耕红壤优势植物根际土壤微生物群落的影响

氮沉降引起红壤酸化加剧和土壤生态系统功能退化。采用休耕植物自然演替恢复土壤生物多样性和生态系统功能;同时,针对氮沉降造成的土壤酸化,通过施石灰来调控土壤pH,以期加速土壤生态恢复进程。土壤微生物群落结构的改变能够指示土壤恢复措施的影响。为探究氮沉降背景下,石灰施用措施对休耕红壤生态功能的恢复效果,以高强度农作休耕地上最初出现的优势植物狗尾草(Setaria viridis(L.)Beauv)根际为研究对象,研究模拟氮沉降(0kg·hm~(–2)、45kg·hm~(–2)和90kg·hm~(–2))下施石灰(0 kg·hm~(–2)和110 kg·hm~(–2))对根际土壤微生物群落的影响。结果表明,模拟氮沉降降低了各类群微生物磷脂脂肪酸(PLFA)量、革兰氏阴/阳性细菌比及香农多样性指数。在没有额外施氮的处理中,施石灰降低了各类群微生物PLFA量。而氮和石灰交互作用下,各类群微生物PLFA量均随氮沉降量增加而增加。结构方程模型显示,石灰对微生物群落的影响最为强烈;模拟氮沉降和施石灰通过综合影响土壤pH、养分有效性及植物—微生物养分竞争而改变微生物群落结构和多样性。总之,模拟氮沉降下施用石灰措施能够改善休耕红壤生境,降低因氮沉降造成的酸化对根际微生物群落的危害,加速土壤生态系统恢复。     

硝化抑制剂和秸秆对潮棕壤碳氮转化和微生物群落特征的短期影响

氮是植物和微生物生长繁殖的必需营养元素,而氮矿化表征了土壤供氮能力。通过盆栽实验,采用同位素稀释法和磷脂脂肪酸(PLFA)法,研究了添加硝化抑制剂和秸秆条件下,潮棕壤碳氮矿化和微生物群落组成变化特征。结果表明,与施氮量N 0.1 g·kg~(-1)的单施氮肥处理(NF)相比,氮肥配施1%硝化抑制剂(NFI)的土壤铵态氮提高32%,而硝态氮降低53%。氮肥与施用量为5 g·kg~(-1)的秸秆配施(NS),土壤氮素总矿化速率增加36%,微生物生物量碳提高51%,β-葡萄糖苷酶活性提高36%,同时显著增加了土壤总PLFA以及细菌、真菌、真菌/细菌和革兰式阴性菌(P0.05),土壤呼吸熵降低50%。与氮肥配施秸秆处理(NS)相比,氮肥、秸秆和硝化抑制剂配施处理(NSI),土壤铵态氮提高33%,硝态氮下降47%。综上所述,氮肥和秸秆配施可以提高土壤微生物生物量,改变土壤微生物群落组成,配施1%(N)硝化抑制剂后降低土壤硝化速率,增加土壤供氮能力。     

硝化抑制剂与尿素配施对旱地土壤温室气体排放及硝化微生物的影响

为明确施肥措施对旱地土壤温室气体排放的综合效应及微生物机理,采集典型麦田土壤进行室内微宇宙培养,研究了双氰胺(DCD)和烯丙基硫脲(ATU)分别与尿素配施对旱地土壤氮素转化及N2O、CO2和CH4排放的影响,同时监测了不同类型微生物群落的动态变化.结果表明氨氧化细菌(AOB)主导了施氮麦田土壤硝化过程及N2O排放.单施...     

长期施肥对稻田土壤微生物群落结构及氮循环功能微生物数量的影响

  【目的】   稻田是陆生生态系统中重要的氮库之一,在氮素生物地球化学循环中具有重要地位。研究不同施肥处理对稻田土壤微生物群落结构及其功能的影响具有重要意义。   【方法】   田间试验位于江苏省金坛市,在取样时试验已进行了6年。施肥处理包括:不施肥对照 (CK)、施化肥 (CF)、化肥+猪粪混施 (CMF)、化肥+秸秆混施 (CSF)。采用高通量测序和定量PCR方法测定稻田土壤微生物群落结构及氮循环相关功能微生物数量。   【结果】   在施用肥料6年后,土壤全碳、可溶性有机碳、全氮、铵态氮和硝态氮含量均不同程度地提高。与CF相比,CSF和CMF处理土壤pH升高,全碳、可溶性有机碳与养分含量升高。CK与施肥处理的土壤细菌群落结构差异明显,不同施肥处理的细菌群落结构之间有明显差别。聚类结果显示,CK与CMF处理细菌群落聚类更接近,CF处理和CSF处理细菌群落结构更为接近;与CK相比,CF、CMF、CSF处理土壤中氨氧化细菌 (AOB) 和铁氨氧化微生物Feammox A6的丰度显著提高,其中Feammox A6分别增长87.6%、158%和157%。冗余分析结果表明,施肥过程及其对土壤化学性质的改变显著影响土壤细菌群落的组成和分布。   【结论】   施肥导致的反应底物 (NH₄+、NO₃–含量) 及土壤理化性质的差异,是土壤微生物群落结构和功能微生物数量响应的主要决定因素。不施肥与化肥配施猪粪的土壤细菌群落聚类更接近,施化肥与化肥配施秸秆的细菌群落结构更为接近。施肥对氨氧化细菌AOA数量影响不明显,但显著提高氨氧化古菌AOB和厌氧铁氨氧化功能微生物Feammox A6的数量,特别是有机肥 (猪粪、秸秆) 提高Feammox A6数量的效果大于化肥。长期单施化肥土壤中厌氧氨氧化细菌丰度显著降低,反硝化功能基因nirK、nosZ丰度显著增高;化肥配施猪粪土壤中的厌氧氨氧化细菌丰度变化不明显,反硝化功能基因narG、nirK、nosZ丰度显著增高;化肥配施秸秆处理厌氧氨氧化细菌丰度变化不明显,反硝化功能基因nirK、nosZ丰度显著增高。     

Responses of bacterial and archaeal ammonia oxidisers of an acidic luvisols soil to different nitrogen fertilization rates after 9?years

It is still not clear which group of ammonia-oxidizing microorganisms plays the most important roles in nitrification in soils. Change in abundances and community compositions of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) under long-term different nitrogen (N) fertilization rates were investigated in an acidic luvisols soil using real-time polymerase chain reaction and denaturing gradient gel electrophoresis, respectively, based on the ammonia monooxygenase a-subunit gene. The experimental plan included the following treatments: control without N fertilization (N_CK), low N fertilization rate, middle N fertilization rate, and high N fertilization rate as 0, 100, 150, and 250?kg urea-N?ha^?1, respectively. Long-term different N fertilization rates did not significantly alter the total C and N contents of soil while it significantly decreased soil pH, which ranged from 5.60 to 5.20. The AOB abundance was more abundant in the N fertilization treatments than the N_CK treatment; the AOA abundance decreased by the increasing N fertilization rates, as did the ratios of AOA/AOB. The large differences in the potential nitrification rates among four treatments depended on the changes in AOA abundance but not to changes in AOB abundance. Phylogenetic analysis showed that the AOB communities were dominated by Nitrosospira clusters 1, 3, and 9 while all AOA sequences were grouped into soil/sediment cluster except for one sequence. Taken together, these results indicated that AOB and AOA preferred different soil N conditions and AOA were functionally more important in the nitrification than AOB in the acidic luvisols soil.     

Influence of nitrogen fertilization on soil ammonia oxidizer and denitrifier abundance,microbial biomass,and enzyme activities in an alpine meadow

Terrestrial ecosystems are predicted to experience an increasing level of atmospheric nitrogen (N) deposition, which may cause significant shifts in plant community composition and concomitantly stimulate soil acidification. However, little is known concerning the effects of N deposition on belowground microbial communities in alpine grassland ecosystems such as on the Tibetan Plateau. This study examined the responses of soil N-transforming microbes (measured after DNA extraction and quantitative PCR), soil microbial biomass C (SMBC) and N (SMBN), and soil enzyme activities to different forms (NH₄ ⁺-N, NO₃ ^?-N, and NH₄NO₃-N) and rates (1.5 and 7.5 g N m^?2 year^?1, denoted as low and high N, respectively) of N fertilization (addition) in two successive plant growing seasons. The N rate, not N form, influenced the abundance of ammonia-oxidizing archaea (AOA). High N addition significantly increased ammonia-oxidizing bacteria (AOB) abundance which differed across different N form treatments. Nitrogen addition had no significant impact on the abundance of soil denitrifiers. The SMBC and SMBN were significantly decreased by high N additions, but no difference was found among different N forms. Despite higher urease activities being detected in the late plant growing season, the activities of invertase and alkaline phosphomonoesterase stayed unchanged irrespective of the different N amendments and plant growing season. Significant positive correlations were found between potential nitrification rates and AOB abundances. These results highlight that AOB seemed to respond more sensitively to different N fertilization and might have prominent roles in soil N cycling processes in this Tibetan Plateau alpine meadow than AOA.     

不同生育期苹果园土壤氨氧化微生物丰度研究

【目的】大量施氮引起的土壤酸化问题已严重制约苹果的安全生产。氨氧化微生物驱动的土壤硝化作用是土壤氮素循环的重要环节,探析苹果园土壤中氨氧化微生物氨单加氧酶基因(amoA)丰度与土壤硝化强度(Potential Nitrification,PN)和土壤理化性质的相关性,有助于评价土壤氨氧化微生物类群在苹果园土壤生态系统中的作用。【方法】本研究以辽宁省丹东东港地区‘寒富’苹果园土壤为研究对象,采用实时荧光定量PCR(Real-time PCR)技术,检测苹果树不同生育时期, 4月28日(萌芽期)、 7月24日(新梢停长期)、 10月23日(落叶期)的两个苹果园(分别编号为D1和D2)的土壤理化性质、 土壤硝化强度、 氨氧化古菌(Ammonia-oxidizing archaea, AOA)和氨氧化细菌(Ammonia-oxidizing bacteria, AOB)的amoA基因丰度,并分析了氨氧化微生物丰度与土壤理化性质和土壤硝化强度之间的关系。【结果】不同生育时期‘寒富’苹果园土壤理化因子差异较大。所有供试土壤的硝态氮(NO-3-N)、 速效磷(AP)和速效钾(AK)含量在4月份最高,铵态氮(NH+4-N)含量在7月最高,NO-3-N、 NH+4-N、 AP和AK含量在10月多为最低。且所有供试土壤pH值均在4.25~6.09之间。同一生育时期内,D2土壤pH均显著高于D1土壤,但其NO-3-N和NH+4-N含量则不同程度地低于D1土壤。不同采样时期的果园土壤硝化强度随季节变化表现出先降后增的趋势,除7月D2土壤硝化强度显著高于D1土壤外,4月与10月D2土壤硝化强度均显著低于D1土壤。尽管不同采样时期的土壤AOA与AOB丰度随生育期而各异,所有供试土壤中AOA丰度均显著高于AOB丰度。同一时期内,D2土壤AOA和AOB丰度均显著高于D1土壤。尽管土壤pH、 NO-3-N与AOA、 AOB均表现出显著相关性,土壤PN仅与AOA丰度明显正相关。【结论】长期施肥导致苹果园土壤pH值降低,pH值的改变是影响AOA与AOB丰度的重要因子,果园土壤的硝化过程主要由AOA来完成,土壤硝化强度与季节变化引起的温度和土壤环境因子等的改变密切相关。苹果园无机氮肥混合有机肥的施入,同时结合自然生草、 人工刈割等管理制度,在一定程度上可改变土壤氮素的含量与种类,减缓土壤酸化。     

Effects of flue gas desulfurization gypsum by-products on microbial biomass and community structure in alkaline–saline soils

Purpose

For an alkaline?Csaline region in Northwest China, we examined the responses of soil microbial communities to flue gas desulfurization gypsum by-products (FGDB), a new ameliorant for alkaline?Csaline soils. In 2009 and 2010, we collected soils from 0?C20?cm and 20?C40?cm depths along an experimental FGDB gradient (0, 0.74, 1.49, 2.25, and 3.00?kg FGDB m^?2).

Materials and methods

As a measure of microbial community composition and biomass, we analyzed phospholipid fatty acids (PLFAs). We used real-time quantitative polymerase chain reaction (qPCR) to measure abundance of bacterial 16?S rRNA copy numbers. Additionally, physicochemical soil parameters were measured by common laboratory methods.

Results and discussion

Microbial community composition differed along the FGDB gradient; however, the microbial parameters did not follow a linear response. We found that, in 2009, total PLFA concentrations, and concentrations of total bacterial and Gram-negative bacterial PLFAs were slightly higher at intermediate FGDB concentrations. In 2010, total PLFA concentrations, and concentrations of total bacterial, Gram-positive bacterial, Gram-negative bacterial, and fungal PLFAs as well as the fungal:bacterial PLFA ratio were highest at 1.49?kg FGDB m^?2 and 3.00?kg FGDB m^?2. PLFA concentrations often differed between 2009 and 2010; however, the patterns varied across the gradient and across microbial groups. For both years, PLFA concentrations were generally higher at 0?C20?cm depth than at 20?C40?cm depth. Similar results were obtained for the 16?S rRNA copy numbers of bacteria at 0?C20?cm depth. FGDB addition resulted in an increase in soil Ca²⁺ and NO ₃ ^? ?CN and a decrease in pH and electrical conductivity (EC). Shifts in PLFA-based microbial community composition and biomass could partly be explained by pH, soil organic carbon, total nitrogen (TN), soil moisture, EC, inorganic nitrogen, C/N, and Ca²⁺. Indirect effects via shifts in abiotic soil properties, therefore, seem to be an important pathway through which FGDB affect soil microbial communities.

Conclusions

Our results demonstrate that addition of FGDB leads to significant changes in soil physicochemical and microbial parameters. As such, addition of FGDB can have large impacts on the functioning of soil ecosystems, such as carbon and nitrogen cycling processes.     

长期施肥对水稻土剖面氨氧化古菌和细菌丰度及组成的影响

长期施肥影响稻田土壤理化性质和硝化微生物群落,但长期施肥对稻田不同土层氨氧化古菌(AOA)和氨氧化细菌(AOB)群落结构的影响尚不明确.以湖南宁乡稻田不同施肥制度长期定位试验为平台,选取不施肥(CK)、施秸秆有机肥(ST)、有机-无机肥配施(OM)和施全量化肥(NPK)4个处理,采用实时荧光定量PCR和Illumina...     

Different roles of rhizosphere effect and long-term fertilization in the activity and community structure of ammonia oxidizers in a calcareous fluvo-aquic soil

Ammonia oxidation is a critical step in the soil nitrogen (N) cycle and can be affected by the application of mineral fertilizers or organic manure. However, little is known about the rhizosphere effect on the function and structure of ammonia-oxidizing bacterial (AOB) and archaeal (AOA) communities, the most important organisms responsible for ammonia oxidation in agricultural ecosystems. Here, the potential nitrification activity (PNA), population size and composition of AOB and AOA communities in both the rhizosphere and bulk soil from a long-term (31-year) fertilizer field experiment conducted during two seasons (wheat and maize) were investigated using the shaken slurry method, quantitative real-time polymerase chain reaction and denaturing gradient gel electrophoresis. N fertilization greatly enhanced PNA and AOB abundance, while manure application increased AOA abundance. The community structure of AOB exhibited more obvious shifts than that of AOA after long-term fertilization, resulting in more abundant AOB phylotypes similar to Nitrosospira clusters 3 and 4 in the N-fertilized treatments. Moreover, PNA was closely correlated with the abundance and community structure of AOB rather than that of AOA among soils during both seasons, indicating that AOB play an active role in ammonia oxidation. Conversely, the PNA and population sizes of AOB and AOA were typically higher in the rhizosphere than the bulk soil, implying a significant rhizosphere effect on ammonia oxidation. Cluster and redundancy analyses further showed that this rhizosphere effect played a more important role in shaping AOA community structure than long-term fertilization. Overall, the results indicate that AOB rather than AOA functionally dominate ammonia oxidation in the calcareous fluvo-aquic soil, and that rhizosphere effect and fertilization regime play different roles in the activity and community structures of AOB and AOA.     

长期施肥对棕壤氨氧化细菌和古菌丰度的影响

【目的】氨氧化是氮转化过程的限速步骤,其由氨氧化微生物所驱动。本研究旨在探明 37 年玉米–大豆轮作施肥条件下影响棕壤氨氧化微生物丰度的主要影响因子及变化规律。【方法】以沈阳农业大学棕壤肥料长期定位试验耕层土壤 (0—20 cm) 为材料,选取其中 9 个施肥处理进行取样分析:不施肥 (CK)、低量氮肥 (N₁)、高量氮肥 (N₂)、氮磷肥 (N₁P)、氮磷钾肥 (N₁PK)、高量有机肥 (M₂)、高量有机肥 + 低量氮肥 (M₂N₁)、高量有机肥 + 氮磷肥 (M₂N₁P)、高量有机肥 + 氮磷钾肥 (M₂N₁PK)。采用实时荧光定量 PCR 技术测定其氨氧化微生物丰度,通过对土壤基本化学性质和氨氧化微生物丰度的冗余分析找出影响氨氧化微生物丰度的主要因素。【结果】施用有机肥处理的土壤 pH、有机质、全氮、碱解氮、速效钾、速效磷、铵态氮、硝态氮含量明显高于不施肥和单施化肥处理。各施肥处理土壤有机质、全氮、碱解氮、速效钾、速效磷的含量总体呈现有机肥处理 > 化肥处理 > CK;与不施肥处理 (CK) 相比,单施化肥处理显著降低了土壤 pH 值,施用有机肥处理显著提高了土壤 pH 值,其中 N₂ 处理的土壤 pH 最低,M₂ 处理的土壤 pH 最高。不同施肥处理氨氧化细菌 (AOB) 的丰度为 0.94 × 106～5.77 × 106 copies/g 干土,氨氧化古菌 (AOA) 的丰度为 3.56 × 106～1.22 × 107 copies/g 干土;施用有机肥处理 AOB 和 AOA 丰度显著高于不施肥和单施化肥处理,其中 M₂ 处理的 AOB 和 AOA 丰度最高,单施氮肥处理的 AOB 和 AOA 丰度最低。冗余分析 (RDA) 表明,影响棕壤 AOB 和 AOA 丰度的主要环境因子有土壤 pH、有机质、全氮、碱解氮、速效磷、速效钾,且与 AOB 和 AOA 丰度呈正相关关系。【结论】长期轮作施肥显著改变了棕壤的化学性质,从而对氨氧化微生物的丰度产生了显著影响。长期施用有机肥显著提高了土壤养分含量及 AOB 和 AOA 的丰度,对维持土壤氨氧化微生物的数量起到十分重要的作用;同时试验结果也为今后通过改变土壤 pH、有机质、全氮、碱解氮、速效磷、速效钾等性质对 AOB 和 AOA 进行调节提供了依据。     

Abundance and community structure of ammonia-oxidizing archaea and bacteria in an acid paddy soil

Nitrification is essential to the nitrogen cycle in paddy soils. However, it is still not clear which group of ammonia-oxidizing microorganisms plays more important roles in nitrification in the paddy soils. The changes in the abundance and composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were investigated by real-time PCR, terminal restriction fragment length polymorphism, and clone library approaches in an acid red paddy soil subjected to long-term fertilization treatments, including treatment without fertilizers (CT); chemical fertilizer nitrogen (N); N and potassium (NK); N and phosphorus (NP); N, P, and K (NPK); and NPK plus recycled crop residues (NPK+C). The AOA population size in NPK+C was higher than those in CT, while minor changes in AOB population sizes were detected among the treatments. There were also some changes in AOA community composition responding to different fertilization treatments. Still few differences were detected in AOB community composition among the treatments. Phylogenetic analysis showed that the AOA sequences fell into two main clusters: cluster A and cluster soil/sediment. The AOB composition in this paddy soil was dominated by Nitrosospira cluster 12. These results suggested that the AOA were more sensitive than AOB to different fertilization treatments in the acid red paddy soil.     

硝化抑制剂对毛竹林土壤N_2O排放和氨氧化微生物的影响

为了探索硝化抑制剂在毛竹生产中的施用技术,通过培养试验研究3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)两种硝化抑制剂对毛竹林施用尿素后土壤N2O排放、氮素转化和相关氨氧化细菌(AOB)、氨氧化古菌(AOA)群落结构和丰度的影响。试验设(1)对照(CK)、(2)单施尿素(Urea)、(3)尿素+1%DMPP(DMPP占总N的1%,下同);(4)尿素+1.5%DMPP;(5)尿素+10%DCD;(6)尿素+15%DCD等6个处理,测定N2O的排放动态以及气体排放转折点时的土壤特征指标。结果表明:与单施尿素相比,160 d的时间内两种DMPP用量处理的土壤N2O累积排放减排幅度均为54%,而10%DCD和15%DCD处理的土壤分别减少28%和41%。DMPP和DCD处理50 d和90 d时土壤的NH4+-N含量均显著高于(p0.05)单施尿素处理,而NO3--N含量和表观硝化率则恰好相反,但两种抑制剂间无差异。DMPP处理的AOB群落结构的变化从10 d开始显现,至50 d和90 d时仍保持明显的抑制状态,而DCD处理则至90 d时抑制作用基本消失。单施尿素AOB功能基因(amo A)的丰度均显著高于硝化抑制剂处理(90 d时尿素+10%DCD处理除外);在整个培养期内,尿素和对照土壤的AOA群落结构相似,硝化抑制剂反而增加了AOA功能基因的丰度,表明硝化抑制剂对AOA丰度无明显抑制作用。即两种硝化抑制剂主要通过抑制AOB起作用;调节土壤p H至中性范围,并在1%DMPP施用条件下,硝化抑制剂的抑制效果最显著。