硝態(tài)氮異化還原機(jī)制及其主導(dǎo)因素研究進(jìn)展

楊　杉，吳勝軍，蔡延江，周文佐，朱同彬，王　雨，黃　平,*

1 中國科學(xué)院水庫水環(huán)境重點(diǎn)實(shí)驗(yàn)室，中國科學(xué)院重慶綠色智能技術(shù)研究院，重慶　400714

2 西南大學(xué)地理科學(xué)學(xué)院，重慶　400715

3 中國科學(xué)院水利部成都山地災(zāi)害與環(huán)境研究所中國科學(xué)院山地表生過程與生態(tài)調(diào)控重點(diǎn)實(shí)驗(yàn)室，成都　610041

4 南京師范大學(xué)地理科學(xué)學(xué)院，南京　210046

硝態(tài)氮異化還原機(jī)制及其主導(dǎo)因素研究進(jìn)展

楊杉1,2，吳勝軍1，蔡延江3，周文佐2，朱同彬4，王雨1，黃平1,*

1 中國科學(xué)院水庫水環(huán)境重點(diǎn)實(shí)驗(yàn)室，中國科學(xué)院重慶綠色智能技術(shù)研究院，重慶400714

2 西南大學(xué)地理科學(xué)學(xué)院，重慶400715

3 中國科學(xué)院水利部成都山地災(zāi)害與環(huán)境研究所中國科學(xué)院山地表生過程與生態(tài)調(diào)控重點(diǎn)實(shí)驗(yàn)室，成都610041

4 南京師范大學(xué)地理科學(xué)學(xué)院，南京210046

摘要:硝態(tài)氮)異化還原過程通常包含反硝化和異化還原為銨(DNRA)兩個方面，是土壤氮素轉(zhuǎn)化的重要途徑，其強(qiáng)度大小直接影響著硝態(tài)氮的利用和環(huán)境效應(yīng)(如淋溶和氮氧化物氣體排放)。反硝化和DNRA過程在反應(yīng)條件、產(chǎn)物和影響因素等方面常會呈現(xiàn)出協(xié)同與競爭的交互作用機(jī)制。綜述了反硝化和DNRA過程的研究進(jìn)展及其二者協(xié)同競爭的作用機(jī)理，并闡述了在、pH、有效C、氧化還原電位(Eh)等環(huán)境條件和土壤微生物對其發(fā)生強(qiáng)度和產(chǎn)物的影響，提出了今后應(yīng)在產(chǎn)生機(jī)理、土壤環(huán)境因素、微生物學(xué)過程以及與其他氮素轉(zhuǎn)化過程耦聯(lián)作用等方面亟需深入研究，以期增進(jìn)對氮素循環(huán)過程的認(rèn)識以及為加強(qiáng)氮素管理利用提供依據(jù)。

關(guān)鍵詞：硝態(tài)氮異化還原；反硝化；硝態(tài)氮異化還原成銨(DNRA)；N2O；協(xié)同競爭機(jī)制

1硝態(tài)氮異化還原的機(jī)理過程

(4)時間進(jìn)程不同在條件適宜的情況下，土壤反硝化速度較快，1—2 d就可全部完成；DNRA過程一般要在2—5 d之后才發(fā)生[1, 24]。但為何出現(xiàn)DNRA過程相對滯后的現(xiàn)象，其機(jī)制目前尚不清楚[1]。

圖1　硝態(tài)氮異化還原過程及其主要機(jī)理Fig.1　The scheme of dissimilatory nitrate reduction process and its main mechanisms(Nar,Nor,Nos,dNir,dnra-Nir表示參與硝態(tài)氮異化還原過程的還原酶；narG /napA,nirB/nirC/cysG, nirK/nirS,norC/norB,nosZ/nosR/nosD-FYL表示參與硝態(tài)氮異化還原過程的還原酶所對應(yīng)的功能基因

2硝態(tài)氮異化還原的協(xié)同競爭機(jī)制

3硝態(tài)氮異化還原過程主導(dǎo)因素及其對協(xié)同與競爭的調(diào)節(jié)機(jī)制

3.1土壤環(huán)境條件

3.1.2氧化還原電位(Eh)

氧化還原電位(Eh)能間接地反映土壤的含氧狀態(tài)，從而影響硝態(tài)氮異化還原過程，其主要取決于土壤中的氧分壓或溶解態(tài)氧的濃度[17]。Eh通過氧分壓來調(diào)控硝態(tài)氮異化還原過程，氧化和還原條件均能進(jìn)行反硝化作用[34, 37]，但相較于還原條件，在氧化條件下反硝化速率明顯降低[37]；而強(qiáng)還原性會更有利于DNRA過程的發(fā)生[1, 18, 38]。Eh<300 mV 的厭氧條件是反硝化進(jìn)行的必要條件；若Eh較高，氧分壓就會成為反硝化作用的主要限制因子[1, 37]。也有研究表明，還原性較弱的環(huán)境中也能進(jìn)行DNRA過程[12, 39]，Pseudomonasputrefaciens在Eh為0mv時能進(jìn)行DNRA過程，而Eh為-100mV時受到極大抑制[1]。此外，Eh還能決定硝態(tài)氮異化還原的途徑[34]，通過對兩個過程產(chǎn)生條件的比較，DNRA過程對氧分壓變化較不敏感[39- 40]。當(dāng)氧分壓從0升高到2%的過程中，反硝化均呈現(xiàn)降低的趨勢。但DNRA過程則呈現(xiàn)不同的趨勢，當(dāng)氧分壓為0—0.5%時，DNRA過程顯著增加；為0.5%—1%時，DNRA過程沒有變化；繼續(xù)上升到1%—2%時，DNRA的強(qiáng)度減小[40]。這些研究結(jié)果為通過調(diào)控氧化還原狀況有效管理氮素轉(zhuǎn)化與利用提供了重要依據(jù)。

3.1.3土壤pH

3.1.4有效C

3.2土壤微生物

土壤微生物在其新陳代謝過程中能對有機(jī)質(zhì)進(jìn)行分解、轉(zhuǎn)化，是硝態(tài)氮異化還原過程的參與者。

3.2.1硝態(tài)氮異化還原過程土壤微生物

土壤微生物的種類、數(shù)量、種群結(jié)構(gòu)與時空動態(tài)變化等都會對硝態(tài)氮異化還原過程有一定的影響。硝態(tài)氮異化還原微生物是一個大的生理類群，而反硝化和DNRA過程存在著不同的微生物類型(表1)。

表1　硝態(tài)氮異化還原過程的微生物類型

細(xì)菌功能基因是影響硝態(tài)氮異化還原過程動態(tài)變化及產(chǎn)物組成的關(guān)鍵因子，故借助編碼硝態(tài)氮異化還原過程關(guān)鍵基因的菌群是研究硝態(tài)氮異化還原過程微生物的重要方法。研究表明，土壤反硝化菌中，nosZ基因最為穩(wěn)定，不易受到環(huán)境影響；nirK基因?qū)Νh(huán)境因子的響應(yīng)比nirS基因敏感[33]。分別施用有機(jī)肥和無機(jī)氮肥，土壤narG基因的優(yōu)勢種群有明顯差異(無機(jī)肥處理含優(yōu)勢種群EU873052，有機(jī)肥處理則沒有)[32]。

3.2.2影響硝態(tài)氮異化還原過程土壤微生物多樣性的因素

硝態(tài)氮異化還原過程的影響因素較多，且影響作用并不是單一的，而是交互聯(lián)系作用的。除以上幾種主導(dǎo)因素外，土壤質(zhì)地[35]、土壤含水量[35]和土壤溫度[7, 44]等土壤環(huán)境的其他因素也會對硝態(tài)氮異化還原過程產(chǎn)生影響。在對不同土壤質(zhì)地與硝態(tài)氮異化還原關(guān)系的研究中，與粘土相比，砂土的DNRA過程速率低，N2O的排放量少[35]。這主要是由于粘土所含的土壤水分多，厭氧環(huán)境較適宜硝態(tài)氮異化還原過程的發(fā)生[35]。

4研究展望

以往對硝態(tài)氮異化還原過程的研究主要集中于反硝化，但由于DNRA過程生成了有效性高且淋溶性較差的銨態(tài)氮，進(jìn)而增強(qiáng)土壤氮的可利用性，近年來關(guān)于DNRA過程的研究逐漸受到了充分重視。目前，DNRA過程的研究對象多為海水或淡水沉積物[10, 18]，而對陸地土壤研究較少，已有的研究也主要集中于森林和農(nóng)田等土壤，且多為室內(nèi)培養(yǎng)結(jié)果[15, 25]，自然生境中的硝態(tài)氮異化還原狀況還未知。在全球變化的背景下，有必要對不同氣候、土壤和耕作施肥制度下的硝態(tài)氮異化還原強(qiáng)度深入研究。鑒于硝態(tài)氮異化還原過程研究中存在影響因素多、時空變異大、測定難度大等限制條件，今后應(yīng)亟需加強(qiáng)以下幾個方面的研究。

(2)加強(qiáng)土壤環(huán)境因素對硝態(tài)氮異化還原過程反饋機(jī)制的研究。硝態(tài)氮異化還原過程的研究多數(shù)局限在對單一土壤環(huán)境因素的控制或模擬，而主導(dǎo)硝態(tài)氮異化還原過程的土壤環(huán)境因素有很多，存在復(fù)雜的交互作用，且不同生境下各因子的影響強(qiáng)度差異較大。如不同海拔高度、不同立地條件，土壤水熱條件和有機(jī)C庫有所不同，勢必影響到硝態(tài)氮異化還原的強(qiáng)度。決定土壤中反硝化和DNRA過程平衡的環(huán)境因素亦未見報道。此外，在硝態(tài)氮異化還原過程對環(huán)境因子的響應(yīng)研究中，探討如何選擇并調(diào)節(jié)土壤環(huán)境因子參數(shù)。同時，考慮在土壤環(huán)境因子復(fù)合影響下，土壤氮素和其他土壤元素之間的綜合效應(yīng)，明確土壤氮素閾值，提高氮肥利用率的同時，確保土壤的其他養(yǎng)分的固持。諸如，若Eh<200 mV，土壤中的鐵錳化合物會被還原為不同價態(tài)的錳、硫、鐵，土壤出現(xiàn)潛育化，導(dǎo)致O2分壓減小，影響土壤中的氮素形態(tài)及供應(yīng)情況[17]；硝態(tài)氮異化還原過程能在此范圍中發(fā)生，如何協(xié)調(diào)各土壤養(yǎng)分固持與供給平衡，以獲得最高產(chǎn)量或最大收益時最佳氮素投入量，保持土壤優(yōu)良性狀，利于作物生長。

(3)加強(qiáng)硝態(tài)氮異化還原過程的微生物學(xué)過程的研究。當(dāng)前，參與硝態(tài)氮還原的微生物中，反硝化菌的數(shù)量、區(qū)系組成及其活性報道較多[3]，而對于DNRA菌組成和數(shù)量等的研究較少，但已越來越受到研究者們的關(guān)注。土壤環(huán)境和農(nóng)業(yè)措施，能夠影響土壤中微生物的活性、豐度及群落組成。研究不同生態(tài)系統(tǒng)土壤微生物量及活性對反硝化和DNRA兩個過程的影響，對于完善土壤氮素內(nèi)循環(huán)機(jī)制，提高土壤肥力，具有十分重要的作用。對于滿足反硝化和DNRA雙重性質(zhì)的細(xì)菌，今后可在同一個細(xì)胞中開展反硝化與DNRA競爭機(jī)理的研究[3]。同時，考慮厭氧氨氧化細(xì)菌對硝態(tài)氮異化還原過程的影響。研究表明，厭氧氨氧化菌能同時表現(xiàn)出反硝化和厭氧氨氧化的能力，兩個反應(yīng)可在同一種微生物體內(nèi)進(jìn)行[46- 47]。

參考文獻(xiàn)(References):

[1]殷士學(xué). 淹水土壤中硝態(tài)氮異化還原成銨過程的研究[D].江蘇: 南京農(nóng)業(yè)大學(xué), 2000.

[2]殷士學(xué), 沈其榮. 缺氧土壤中硝態(tài)氮還原菌的生理生化特征. 土壤學(xué)報, 2003, 40(4): 624- 630.

[3]陳麗敏. 淹水土壤中反硝化菌和硝酸還原菌數(shù)量、生理類群及其還原特點(diǎn)的研究[D].江蘇: 揚(yáng)州大學(xué), 2001.

[4]Canfield D E, Glazer A N, Falkowski P G. The evolution and future of earth′s nitrogen cycle. Science, 2010, 330(6001): 192- 196.

[5]蔡祖聰. 尿素和KNO3對水稻土無機(jī)氮轉(zhuǎn)化過程和產(chǎn)物的影響無機(jī)氮轉(zhuǎn)化過程. 土壤學(xué)報, 2003, 40(2): 239- 245.

[6]Tiedje J M, Sexstone A J, Myrold D D, Robinson J A. Denitrification: ecological niches, competition and survival. Antonie Van Leeuwenhoek, 1982, 48(6): 569-583.

[7]朱兆良, 文啟孝. 中國土壤氮素. 南京: 江蘇科學(xué)技術(shù)出版社, 1992.

[8]張玉樹, 丁洪, 秦勝金. 農(nóng)業(yè)生態(tài)系統(tǒng)中氮素反硝化作用與N2O排放研究進(jìn)展. 中國農(nóng)學(xué)通報, 2010, 26(6): 253- 259.

[9]Woods D D. The reduction of nitrate to ammonia by Clostridium welchii. Biochemical Journal, 1938, 32(11): 2000- 2012.

[10]Giblin A E, Tobias C R, Song B, Weston N, Banta G T, RiveraMonroy V H. The importance of dissimilatory nitrate reduction to ammonium (DNRA)in the nitrogen cycle of coastal ecosystems. Oceanography, 2013, 26(3): 124- 131.

[11]Chen D L, Chalk P M, Freney J R. Distribution of reduced products of15N labelled nitrate in anaerobic soils. Soil Biology & Biochemistry, 1995, 27(12): 1539- 1545.

[12]Yin S X, Chen D, Chen L M, Edis R. Dissimilatory nitrate reduction to ammonium and responsible microorganisms in two Chinese and Australian paddy soils. Soil Biology & Biochemistry, 2002, 34(8): 1131- 1137.

[13]Lu W W, Zhang H L, Shi W M. Dissimilatory nitrate reduction to ammonium in an anaerobic agricultural soil as affected by glucose and free sulfide. European Journal of Soil Biology, 2013, 58: 98- 104.

[14]Bengtsson G, Bergwall C. Fate of15N labelled nitrate and ammonium in a fertilized forest soil. Soil Biology& Biochemistry, 2000, 32(4): 545- 557.

[15]Rütting T, Huygens D, Müller C, Van Cleemput O, Godoy R, Boeckx P. Functional role of DNRA and nitrite reduction in a pristine south ChileanNothofagusforest. Biogeochemistry, 2008, 90(3): 243- 258.

[16]Huygens D, Rüetting T, Boeckx P, Van Cleemput O, Godoy R, Müeller C. Soil nitrogen conservation mechanisms in a pristine south ChileanNothofagusforest ecosystem. Soil Biology & Biochemistry, 2007, 39(10): 2448- 2458.

[17]黃昌勇. 土壤學(xué). 北京: 中國農(nóng)業(yè)出版社, 2000.

[18]Ma H B, Aelion C M. Ammonium production during microbial nitrate removal in soil microcosms from a developing marsh estuary. Soil Biology & Biochemistry, 2005, 37(10): 1869- 1878.

[19]Burgin A J, Hamilton S K. Have we overemphasized the role of denitrification in aquatic ecosystems? A review of nitrate removal pathways. Frontiers in Ecology and the Environment, 2007, 5(2): 89- 96.

[20]蔡延江,丁維新,項(xiàng)劍. 土壤N2O和NO產(chǎn)生機(jī)制研究進(jìn)展. 土壤, 2012, 44(5): 712- 718.

[21]王瑩, 胡春勝. 環(huán)境中的反硝化微生物種群結(jié)構(gòu)和功能研究進(jìn)展. 中國生態(tài)農(nóng)業(yè)學(xué)報, 2010, 18(6): 1378- 1384.

[22]Stevens R J, Laughlin R J. Measurement of nitrous oxide and di- nitrogen emissions from agricultural soils. Nutrient Cycling in Agroecosystems, 1998, 52(2/3): 131- 139.

[23]Stevens R J, Laughlin R J, Malone J P. Soil pH affects the processes reducing nitrate to nitrous oxide and di-nitrogen. Soil Biology & Biochemistry, 1998, 30(8- 9): 1119- 1126.

[24]Schmidt C S, Richardson D J, Baggs E M. Constraining the conditions conducive to dissimilatory nitrate reduction to ammonium in temperate arable soils. Soil Biology & Biochemistry, 2011, 43(7): 1607- 1611.

[25]Fernandes S O, Bonin P C, Michotey V D, Garcia N, LokaBharathi P A. Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium. Scientific Reports, 2012, 2: 419.

[26]Hansen M, Clough T J, Elberling B. Flooding-induced N2O emission bursts controlled by pH and nitrate in agricultural soils. Soil Biology & Biochemistry, 2014, 69: 17- 24.

[27]賀紀(jì)正, 張麗梅. 土壤氮素轉(zhuǎn)化的關(guān)鍵微生物過程及機(jī)制. 微生物學(xué)通報, 2013, 40(1): 98- 108.

[28]鄒國元, 張福鎖. 根際反硝化作用與N2O釋放. 中國農(nóng)業(yè)大學(xué)學(xué)報, 2002, 7(1): 77- 82.

[29]Hom S S M, Hennecke H, Shanmugam K T. Regulation of nitrogenase biosynthesis inKlebsiellapneumoniaeeffect of nitrate. Journal of General Microbiology, 1980, 117(1): 169- 179.

[30]Koop-Jakobsen K, Giblin A E. The effect of increased nitrate loading on nitrate reduction via denitrification and DNRA in salt marsh sediments. Limnology and Oceanography, 2010, 55(2): 789- 802.

[31]Davis J H, Griffith S M, Horwath W R, Steiner J J, Myrold D D. Denitrification and nitrate consumption in an herbaceous riparian area and perennial ryegrass seed cropping system. Soil Science Society of America Journal, 2008, 72(5): 1299- 1310.

[32]陳哲, 袁紅朝, 吳金水, 魏文學(xué). 長期施肥制度對稻田土壤反硝化細(xì)菌群落活性和結(jié)構(gòu)的影響. 生態(tài)學(xué)報, 2009, 29(11): 5923- 5929.

[33]于涌杰. 土地利用方式對中國東南部紅壤微生物特性及氮轉(zhuǎn)化作用的影響[D].江蘇: 南京師范大學(xué), 2012.

[34]Matheson F E, Nguyen M L, Cooper A B, Burt T P, Bull D C. Fate of15Nnitrate in unplanted, planted and harvested riparian wetland soil microcosms. Ecological Engineering, 2002, 19(4): 249- 264.

[35]Sotta E D, Corre M D, Veldkamp E. Differing N status and N retention processes of soils under old-growth lowland forest in Eastern Amazonia, Caxiuan?, Brazil. Soil Biology & Biochemistry, 2008,40(3): 740- 750.

[36]Silver W L, Herman D J, Firestone M K. Dissimilatory nitrate reduction to ammonium in upland tropical forest soils. Ecology,2001, 82(9): 2410- 2416.

[37]倪吾鐘, 沈仁芳, 朱兆良. 不同氧化還原電位條件下稻田土壤中15N標(biāo)記硝態(tài)氮的反硝化作用. 中國環(huán)境科學(xué), 2000, 20(6): 519- 523.

[38]Rütting T, Boeckx P, Müller C, Klemedtsson L. Assessment of the importance of dissimilatory nitrate reduction to ammonium for the terrestrial nitrogen cycle. Biogeosciences, 2011, 8(7): 1779- 1791.

[39]Pett-Ridge J, Silver W L, Firestone M K. Redox fluctuations frame microbial community impacts on N-cycling rates in a humid tropical forest soil. Biogeochemistry, 2006, 81(1): 95- 110.

[40]Fazzolarié, Nicolardot B, Germon J C. Simultaneous effects of increasing levels of glucose and oxygen partial pressures on denitrification and dissimilatory nitrate reduction to ammonium in repacked soil cores. European Journal of Soil Biology, 1998, 34(1): 47- 52.

[42]方芳, 高紅濤, 張曾宇, 孫志偉, 李哲, 郭勁松. 三峽庫區(qū)消落帶土壤N2O排放和反硝化影響因子分析. 重慶大學(xué)學(xué)報, 2013, 36(11): 93- 100.

[43]AzamF, Müller C, Weiske A, Benckiser G, Ottow J. Nitrification and denitrification as sources of atmospheric nitrous oxide-role of oxidizable carbon and applied nitrogen. Biology and Fertility of Soils, 2002, 35(1): 54- 61.

[44]Kelly-Gerreyn B A, Trimmer M, Hydes D J. A diagenetic model discriminating denitrification and dissimilatory nitrate reduction to ammonium in a temperate estuarine sediment. Marine Ecology Progress Series, 2001, 220: 33- 46.

[45]Baggs E M. Soil microbial sources of nitrous oxide: recent advances in knowledge, emerging challenges and future direction. Current Opinion in Environmental Sustainability, 2011, 3(5): 321- 327.

[46]Kartal B, Kuypers M M M, Lavik G, Schalk J, den Camp H J M O, Jetten M S M, Strous M. Anammox bacteria disguised as denitrifiers: nitrate reduction to dinitrogen gas via nitrite and ammonium. Environmental Microbiology, 2007, 9(3): 635- 642.

[47]黃孝肖, 陳重軍, 張蕊, 陳英旭, 吳偉祥. 厭氧氨氧化與反硝化耦合反應(yīng)研究進(jìn)展. 應(yīng)用生態(tài)學(xué)報, 2012, 23(3): 849- 856.

[48]周少奇. 厭氧氨氧化與反硝化協(xié)同作用化學(xué)計量學(xué)分析. 華南理工大學(xué)學(xué)報: 自然科學(xué)版, 2006, 34(5): 1- 4.

[49]沈李東, 鄭平, 胡寶蘭. 自然生態(tài)系統(tǒng)中的厭氧氨氧化. 生態(tài)學(xué)報, 2011, 31(15): 4447- 4454.

The synergetic and competitive mechanism andthe dominant factors of dissimilatory nitrate reduction processes: a review

YANG Shan1, 2, WU Shengjun1, CAI Yanjiang3, ZHOU Wenzuo2, ZHU Tongbin4, WANG Yu1, HUANG Ping1,*

1KeyLaboratoryofReservoirAquaticEnvironment,ChongqingInstituteofGreenandIntelligentTechnology,ChineseAcademyofScience,Chongqing400714,China2SchoolofGeographyScience,SouthwestUniversity,Chongqing400715,China3InstituteofMountainHazardsandEnvironment,ChineseAcademyofSciencesandMinistryofWaterResources;KeyLaboratoryofMountainEnvironmentEvolvementandRegulation,ChineseAcademyofSciences,Chengdu610041,China4CollegeofGeographyScience,NanjingNormalUniversity,Nanjing210046,China

Abstract：The nitrate ion ), an important form of inorganic soil nitrogen, is susceptible to reduction under anaerobic conditions, and its reduction consists of both assimilatory and dissimilatory processes. The dissimilatory nitrate reduction process—of great significance in nitrogen transformation—includes denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Such reduction processes can directly affect the transformation of nitrates and the environmental consequences (such as leaching and N2O emission). During the processes of denitrification and DNRA, is utilized as a substrate, while N2O is generated synchronously. Nonetheless, there are significant differences between denitrification and DNRA, such as metabolic processes, the transformation mechanism, reductases, and the final products. For DNRA, the final product is ammonium ), which can continue to participate in other soil nitrogen transformation processes, such as crop uptake and nitrification. In agroecosystems, DNRA can consume 3.9%—25.4% of ; this process can decrease leaching and N2O emissions in comparison with denitrification.Both reducing pathways show a synergistic and competitive mechanism among the reaction conditions, products, and dominant regulators. The synergistic mechanism of denitrification and DNRA manifests itself as the similar suitable environmental conditions, the shared nitrate reductase (Nar), and an intermediate product (N2O), along with the similar soil parameters. Thus, according to the synergistic effect, the dissimilatory nitrate reduction process can be greatly enhanced without limiting factors such as the soil water regimen, temperature, and soil substrates. As for the competitive mechanism, it mainly involves competition for a substrate and energy supplies between denitrification and DNRA. In contrast, the direct competition for exists ubiquitouslybetween denitrification and DNRA. Nevertheless, regulation of soil parameters (such as available carbon,oxidation-reduction potential (Eh)) changes the concentration of accordingly; thus, the competition for between denitrification and DNRA should be rebalanced subsequently. Moreover, soil microorganisms that are related to denitrification and DNRA can compete for a carbon source for their growth and proliferation. The dissimilatory nitrate reduction process is influenced by a great number of factors, mainly environmental conditions and microorganisms. Sufficient soil and available carbon can significantly enhance the dissimilatory nitrate reduction process, whereas soil pH and Eh have their own suitable ranges for different dissimilatory nitrate reduction processes. The competition between denitrification and DNRA is regulated by these factors. With the changes in available carbon, soil pH, and Eh, the two pathways show different levels of activity. Bacteria can exist in the form of an advantageous microbial population during the dissimilatory nitrate reduction process. Nevertheless, different populations and genes are involved in denitrification and DNRA, and the diversity of soilmicroorganisms is in turn influenced by soil environmental factors. This review summarizes the synergistic and competitive mechanisms and the factors influencing denitrification and DNRA, for example, soil environmental conditions (soil , soil pH, available carbon and Eh) and microorganisms (population, diversity and genes). The mechanism of formation, soil environmental factors, microbiological processes, and the correlation with other nitrogen transformation processesurgently need further research on dissimilatory nitrate reduction processes. In DNRA, the mechanism of formation and analysis of N2O emissions, populations, diversity, and genes of a microorganism have not been established yet. In addition, the interactions of nitrogen transformation processes in soils—e.g., between denitrification and DNRA or between anaerobic ammonium oxidation and denitrification—should be investigated holistically. The knowledge about synergistic and competitive mechanisms and the factors influencing denitrification and DNRA should improve the understanding of the regulation of nitrogen transformation in soils; this knowledge is also necessary for the development of effective countermeasures and policies on soil nitrogen management.

Key Words:dissimilatorynitrate reduction process; denitrification; dissimilatory nitrate reduction to ammonium (DNRA); N2O; synergetic and competitive mechanism

基金項(xiàng)目:中國科學(xué)院西部行動計劃項(xiàng)目(KZCX2-XB3-14); 重慶市基礎(chǔ)與前沿研究項(xiàng)目(cstc2013jcyjA0302);中國科學(xué)院水庫水環(huán)境重點(diǎn)實(shí)驗(yàn)室開放基金(RAE2014BA06B)

收稿日期:2014- 07- 18; 網(wǎng)絡(luò)出版日期:2015- 07- 22

DOI:10.5846/stxb201407181464

*通訊作者Corresponding author.E-mail: huangping@cigit.ac.cn

楊杉，吳勝軍，蔡延江，周文佐，朱同彬，王雨，黃平.硝態(tài)氮異化還原機(jī)制及其主導(dǎo)因素研究進(jìn)展.生態(tài)學(xué)報,2016,36(5):1224- 1232.

Yang S, Wu S J, Cai Y J, Zhou W Z, Zhu T B, Wang Y, Huang P.The synergetic and competitive mechanism andthe dominant factors of dissimilatory nitrate reduction processes: a review.Acta Ecologica Sinica,2016,36(5):1224- 1232.