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。     

水氮耦合对设施农田土壤自养和异养硝化作用的影响

水氮措施影响设施土壤氮素的转化及硝化微生物活性,但水氮耦合对设施土壤自养和异养硝化作用差异的影响尚不明确。以连续8年设施水氮耦合田间定位试验土壤为研究对象,控制不同土壤田间持水量(WHC)(40%WHC、60%WHC和80% WHC)进行室内微宇宙培养试验,通过添加乙炔抑制剂抑制自养硝化途径,研究水氮耦合对设施土壤自养和异养硝化速率及参与自养硝化的氨氧化微生物的影响,分析氨氧化微生物氨氧化古细菌(AOA)和氨氧化细菌(AOB)对自养硝化作用的贡献。结果表明,水氮耦合下,不同硝化途径NH4+-N、NO^3--N含量以及参与自养硝化的AOA amoA和AOB amoA基因拷贝数均有显著差异。无乙炔培养7 d后,NO^3--N含量显著增加,而NH4+-N含量显著降低,AOA amoA和AOB amoA的基因丰度显著增加。添加乙炔后,NO^3--N、NH4+-N含量基本保持恒定,AOA amoA和AOB amoA基因丰度显著减少。水氮耦合显著影响自养和异养硝化速率,冗余分析(RDA)表明,NH4+-N含量、AOB amoA、NO^3--N-C2H2、AOA amoA可分别解释自养和异养硝化速率变异的68.9%、34.9%、32.8%和24.4%。设施土壤存在自养硝化和异养硝化两种途径,60%～80%WHC各施氮处理均以自养硝化为主,占总硝化速率的65%～86%;仅40%WHC下,氮纯养分量300和525 kg·hm-2处理以异养硝化为主,占总硝化速率的61%～77%。AOB和AOA共同驱动自养硝化,且AOB贡献更大。     

硝化微生物在土壤团聚体中的分布及其对种植方式的响应

【目的】硝化微生物在农田土壤氮转化过程发挥重要作用，深入开展团聚体中硝化微生物分布研究，有助于揭示土壤结构-微生物-土壤营养元素循环间的相互影响机制。【方法】选取旱地黄棕壤为研究对象，比较了玉米连作（M-M）和玉米/花生轮作（M-P）两种种植方式下土壤团聚体的性质和硝化潜势（NP）的变化，并通过荧光定量PCR和高通量测序研究了团聚体中不同类型硝化微生物功能基因的丰度和群落组成差异。【结果】与M-M相比，M-P能够显著提高团聚体pH、NH4+和全碳（TC）含量。M-P使NP显著提高，但团聚体粒径对NP无显著影响。氨氧化细菌（AOB）amoA基因丰度在M-P中高于M-M，且在较小粒级团聚体中分布更多，而氨氧化古菌（AOA）和全程氨氧化细菌（Comammox）amoA基因的分布模式与AOB大致相反，表明AOB更能适应较小团聚体环境，而AOA和Comammox倾向在较大团聚体中占据竞争优势。此外，与M-M相较，M-P团聚体间AOA/AOB和Comammox/AOB比值的差异减小，表明轮作促使土壤硝化微生物在不同粒级间的分布更加均匀。进一步对属水平土壤团聚体硝化菌群落组成分析，结果显示M-P提高了Nitrolancea属亚硝酸盐氧化细菌（NOB）和Candidatus Nitrosocosmicus属AOA的占比，降低了Nitrospira属NOB的占比，对AOB各属无显著影响。而团聚体粒径仅对Nitrosospira属AOB的占比产生显著影响。NH4+含量和pH是影响土壤团聚体NP和硝化微生物群落变化的最主要因子。NP与AOB amoA基因丰度显著正相关，与AOA amoA基因丰度负相关。但在群落组成上，Nitrosospira属AOB，Candidatus Nitrosocosmicus属AOA和Nitrospira属NOB均与NP呈现正相关。【结论】土壤团聚体粒径和种植方式能较大程度影响硝化微生物的分布，然而，不同硝化微生物在团聚体间分异机制具有明显差异，该研究为完善禾豆轮作下土壤硝化微生物在微域环境的生态适应机制提供了理论支持。     

围垦对崇明东滩湿地全程氨氧化微生物的影响

全程氨氧化微生物（comammox）的发现根本改变了学术界对硝化过程的认识，但其地理分异规律及对氮转化过程的贡献仍不清楚。本研究选择长江口崇明东滩不同围垦年限（0、27、51、86年）稻田表层耕作土壤，采用好氧培养试验测定土壤硝化潜力；通过标靶功能基因amoA实时荧光定量硝化微生物的数量变异特征，包括全程氨氧化细菌（comammox）、氨氧化细菌（AOB）和古菌（AOA）。结果表明，与围垦0年的自然滩涂湿地相比，围垦27、51、86年的水稻土净硝化速率从2.24mg N /(kg·d)分别增加至19.3、11.6和11.4mg N /(kg·d)，增幅高达5.1-8.7倍。土壤氨氧化古菌AOA的丰度与围垦年限显著正相关。自然滩涂湿地中氨氧化古菌AOA和AOB的数量分别为0.34×107 copies/g和1.14×107 copies/g，围垦86年后增幅最高可达27.9倍。自然滩涂湿地中comammox Clade A和Clade B amoA基因拷贝数高于围垦稻田土壤，且Clade A随着围垦年限增加其丰度显著增加。统计分析发现，氨氧化细菌AOB与土壤硝化速率显著正相关，可能在围垦水稻土氨氧化过程中发挥了重要作用；而全程硝化细菌comammox Clade A和Clade B与土壤总有机碳（TOC）、铵含量（NH4+）呈显著负相关关系，可能更适应于营养贫瘠的滩涂自然湿地土壤。     

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。     

稻虾共作模式下稻田土壤氨氧化微生物丰度和群落结构的特征

【目的】研究稻虾共作模式下土壤氨氧化微生物数量、群落多样性及群落结构,深入了解该模式下的土壤微生态环境的演变。【方法】试验点在湖北省荆州市长江大学农学院基地,设置稻虾共作模式 (CR) 与常规中稻种植模式 (MR),借助荧光定量PCR技术与Illumina Miseq高通量测序平台,分析了土壤氨氧化细菌 (AOB) 与古菌 (AOA) 丰度、多样性及群落结构。【结果】与MR模式相比,CR模式显著提高了土壤硝态氮、总碳及总氮含量,对土壤pH、碱解氮及土壤碳氮比无显著影响。CR模式土壤AOA与AOB amoA基因拷贝数为3.13 × 105和7.01 × 105 copies/g干土,MR模式土壤AOA、AOB amoA基因拷贝数为1.41 × 105和3.87 × 105 copies/g干土,两个模式土壤AOB的数量均显著高于AOA,CR模式土壤AOA、AOB的数量均显著高于MR模式 (P < 0.05)。α群落多样性指数表明,相比MR,CR模式显著降低了土壤AOA群落多样性,对AOB群落多样性无显著影响。Venn结果分析,CR模式增加了AOA amoA基因的物种,改变了AOB amoA基因的物种组成,且AOB amoA物种数量下降。在属水平上,norank_c_environmental_samples_p_Thaumarchaeota、unclassified_k_norank_d_Archaea、norank_c_environmental_samples_p_Crenarchaeota、norank_p_environmental_samples_k_norank为AOA的优势类群,相对丰度占AOA amoA基因总序列的99.25%～99.46%,CR模式显著提高了norank_c_environmental_samples_p_Crenarchaeota在AOA群落属水平的相对丰度;unclassified_k_norank_d_Bacteria、norank_f_environmental_samples、norank_o_environmental_samples_c_Betaproteobacteria、unclassified_o_Nitrosomonadales为AOB的优势类群,相对丰度共占97.78%～98.49%,且CR模式显著增加了norank_o_environmental_samples_c_Betaproteobacteria与unclassified_o_Nitrosomonadales在AOB群落属水平的相对丰度。冗余分析 (RDA) 结果显示,土壤基本理化性质对于土壤AOA、AOB群落结构影响有着相似的趋势,其中对AOA、AOB群落结构影响最大的因子是硝态氮,其次分别为总碳、铵态氮、碱解氮、pH。根据RDA投影距离分析,稻虾共作模式对土壤AOA群落结构的影响大于AOB,且MR与稻虾共作模式土壤AOB的群落结构具有一定的相似度。【结论】稻虾共作模式显著降低了AOA群落多样性,而对AOB群落无显著影响;稻虾共作模式显著增加了AOA与AOB的丰度并显著影响了群落结构组成。土壤硝态氮、总碳、铵态氮、碱解氮、pH含量是导致土壤微生物数量、多样性及群落结构变化的主要原因。     

黑土区农田土壤氮循环关键过程微生物基因丰度的分布特征

土壤微生物作为碳氮循环过程的主要驱动者与作物生产和生态环境安全关系密切。目前,仅有少数基于单一氮循环过程的研究报导了功能基因的空间分布特征,缺乏关于氮循环关键过程微生物分布特征的耦联分析。本研究采用实时荧光定量PCR技术,对东北黑土农田土壤氮循环关键过程的固氮、氨氧化和反硝化过程功能基因丰度特征及对土壤因子的响应进行关联分析。研究发现,在低pH（4.5?5.0）土壤中,不同氮循环基因丰度均显著低于其他pH土壤样本。种植大豆的土壤nifH基因丰度显著高于种植玉米的土壤样本（分别高于60%和83%）。AOA amoA基因丰度显著高于AOB amoA基因丰度,AOA amoA与AOB amoA基因丰度的比值为3.1到91.0。氮循环功能基因丰度与土壤pH和TC之间存在显著的正相关关系（P < 0.01）。非度量多维尺度分析（NMDS）结果显示主要表征黑土区氮循环基因组成的NMDS1与土壤pH和TC显著正相关。方差分解分析（VPA）和随机森林分析（RF）结果显示土壤pH和TC是氮循环微生物基因丰度空间分布的最主要驱动因子。本研究发现除了土壤因子外,地理距离对农田土壤氮循环关键过程微生物分布也产生重要影响,为认识土壤微生物参与的农田生态系统的生物地球化学循环过程提供理论基础。     

亚硝化球菌属(Nitrososphaera)可能是酸性土壤硝化作用的重要驱动者

选择初始pH相近的两个酸性土壤(JX-3和JX-7)样品进行培养试验,探讨了氨氧化古菌(ammonia-oxidizing archaea,AOA)和氨氧化细菌(ammonia-oxidizing bacteria,AOB)在酸性土壤硝化过程中所发挥的作用。结果显示,经过50 d的培养,JX-7样品硝化速率显著高于JX-3,且明显降低土壤pH。培养后,两个土壤样品AOB丰度均增加,但样品间没有显著差异;JX-7土壤AOA丰度显著增加,而JX-3无显著变化。两个土壤样品AOA群落组成本身存在分异,但对于同一样品培养前后均无显著分异;AOB群落组成在两土壤间没有分异,但培养前后分别有分异。培养后,JX-7样品中AOA优势属Nitrososphaera和某些未知微生物的个别OTUs绝对丰度显著增加,而两样品AOB中Nitrosospira属的一些OTUs的绝对丰度均显著增加。因此,所研究的酸性土壤样品中AOA是硝化作用的主要贡献者,而且AOA主要通过提高Nitrososphaera属中个别OTUs的丰度,而不是整个群落来调控硝化作用。     

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。     

有机碳氮添加对酸性森林土壤氨氧化过程的影响

以亚热带酸性森林土壤为研究对象,开展了微宇宙室内培养实验,设置了有机碳和有机氮添加处理,分析了土壤硝化活性和氨氧化古菌(Ammonia-oxidizing archaea,AOA)、氨氧化细菌(Ammonia-oxidizing bacteria,AOB)的功能基因丰度,研究了外源有机碳和有机氮对酸性森林土壤氨氧化过程的影响规律。结果表明:外源有机氮添加显著刺激了酸性森林土壤硝化活性,乙炔抑制实验表明自养氨氧化对酸性森林土壤硝化过程的贡献率90%。有机碳添加对土壤硝化活性未有显著影响,同时添加有机碳和无机铵态氮也未显著提高土壤硝化活性,而外源有机氮添加提高了土壤矿化速率并导致土壤NH3浓度升高,可能是土壤硝化活性、AOA和AOB数量显著增加的主要原因。     

水稻生育期内红壤稻田氨氧化微生物数量和硝化势的变化

利用荧光定量PCR(Real-timePCR)技术,通过特异引物检测amoA基因拷贝数分析了水稻不同生育期红壤稻田土壤中氨氧化细菌(Ammonia oxidizing bacteria,AOB)和氨氧化古菌(Ammonia oxidizing archaea,AOA)的数量变化,并测定了土壤潜在硝化势。结果显示:红壤稻田土壤中AOA数量显著高于AOB,二者比例在1.6～120.7之间;红壤稻田根层土中AOA数量显著高于表土,随水稻生长根层和表土中AOA数量均逐渐增加,且根层土中增加幅度更大;在水稻生长前期表土中AOB数量较多,孕穗期后根层土中AOB数量显著增加且高于表土。水稻生长期内土壤潜在硝化势也具有逐渐增加趋势,且根层土潜在硝化势增加幅度更大。根层土中潜在硝化势与AOB和AOA数量均呈显著正相关,而表土中潜在硝化势只与AOA数量存在显著正相关。研究表明,红壤稻田土壤中AOA数量更为丰富,且与硝化作用的关联程度更为密切,证实了氨氧化微生物在红壤稻田土壤微生物组成及其生态系统功能中的重要性。     

pH regulates key players of nitrification in paddy soils

Increasing lines of evidence have suggested the functional importance of ammonia-oxidizing archaea (AOA) rather than bacteria (AOB) for nitrification in upland soils with low pH. However, it remains unclear whether niche specialization of AOA and AOB occurs in rice paddy wetlands constrained by oxygen availability. Using DNA-based stable isotope probing, we conclude that AOA dominated nitrification activity in acidic paddy soils (pH 5.6) while AOB dominated in alkaline soils (pH 8.2). Nitrification activity was stimulated by urea fertilization and accompanied by a significant increase of AOA in acid soils and AOB in alkaline soils. DNA-based stable isotope probing indicated significant assimilation of ¹³CO₂ for AOA only in acidic paddy soil, while AOB was the solely responsible for ammonia oxidation in the alkaline paddy soil. Phylogenetic analysis further indicated that AOA members within the soil group 1.1b lineage dominated nitrification in acid soils. Ammonia oxidation in the alkaline soil was catalyzed by Nitrosospira cluster 3-like AOB, suggesting that the physiological diversity of AOA is more complicated than previously thought, and soil pH plays important roles in shaping the community structures of ammonia oxidizers in paddy field.     

Nitrification activity and putative ammonia-oxidizing archaea in acidic red soils

Purpose  

Acidic red soils account for 21% of land area in China and contain low ammonia concentration due to ionization to ammonium. The unusual high affinity for ammonia of marine Nitrosopumilus maritimus and acidophilic soil Nitrosotalea devanaterra has suggested that ammonia-oxidizing archaea (AOA) may have greater selective advantage over ammonia-oxidizing bacteria (AOB) in ammonia-limited environment because ammonia rather than ammonium is thought to be the actual substrate for oxidation. The aim of this study was to assess whether nitrification activity can be attributed to AOA and/or AOB by relating community structures of AOA and AOB to nitrification activity in acidic red soils in southern China.     

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.     

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.     

生物硝化抑制剂对黔西南黄壤硝化作用及N2O排放的影响

为探索生物硝化抑制剂对贵州黔西南地区黄壤硝化作用及氧化亚氮(N2O)排放的影响,通过三周的室内培养试验,研究两种生物硝化抑制剂对羟基苯丙酸甲酯(MHPP)和丁香酸(SA)对黄壤中的无机态氮素含量、氨氧微生物功能基因以及N2O排放量的影响。结果表明,与对照CK相比,MHPP和SA在黄壤上均能明显抑制硝化作用,对土壤硝化速率的抑制率分别为6%~43%和5%~51%。MHPP和SA均抑制了黄壤氨氧化古菌AOA(12%~22%,27%~41%)与氨氧化细菌AOB(6%~19%,26%~46%)amoA基因的丰度。整个培养期内,黄壤的硝态氮含量与AOB的amoA基因丰度显著正相关,而与AOA的amoA基因丰度无显著相关,表明AOB对黄壤硝化作用起了主导作用。在N2O排放方面,MHPP和SA分别显著抑制了黄壤51%和21%的N2O排放积累量,MHPP的减排效果优于SA。MHPP降低了黄壤N2O排放的峰值,而SA主要延缓了黄壤N2O产生高峰的出现。总之,生物硝化抑制剂MHPP和SA在贵州黔西南黄壤上具有氮肥减施增效的潜力,这为今后烤烟新型绿色专用肥的开发提供了理论依据。     

亚热带松林中强酸性土壤自养和异养硝化作用的研究

The occurrence of nitrification in some acidic forest soils is still a subject of debate. Identification of main nitrification pathways in acidic forest soils is still largely unknown. Acidic yellow soil (Oxisol) samples were selected to test whether nitrification can occur or not in acidic subtropical pine forest ecosystems. Relative contributions of autotrophs and heterotrophs to nitrification were studied by adding selective nitrification inhibitor nitrapyrin. Soil NH₄⁺-N concentrations decreased, but NO₃^--N concentrations increased significantly for the no-nitrapyrin control during the first week of incubation, indicating that nitrification did occur in the acidic subtropical soil. The calculated net nitrification rate was 0.49 mg N kg^-1 d^-1 for the no-nitrapyrin control during the first week of incubation. Nitrapyrin amendment resulted in a significant reduction of NO₃^--N concentration. Autotrophic nitrification rate averaged 0.28 mg N kg^-1 d^-1 and the heterotrophic nitrification rate was 0.21 mg N kg^-1 d^-1 in the first week. Ammonia-oxidizing bacteria (AOB) abundance increased slightly during incubation, but nitrapyrin amendment significantly decreased AOB amoA gene copy numbers by about 80%. However, the ammonia-oxidizing archaea (AOA) abundance showed significant increases only in the last 2 weeks of incubation and it was also decreased by nitrapyrin amendment. Our results indicated that nitrification did occur in the present acidic subtropical pine forest soil, and autotrophic nitrification was the main nitrification pathway. Both AOA and AOB were the active biotic agents responsible for autotrophic nitrification in the acidic subtropical pine forest soil.