孫 鋒, 趙燦燦, 何瓊杰, 呂會(huì)會(huì), 管奕欣, 谷艷芳,2,*

1 河南大學(xué)生命科學(xué)學(xué)院, 開(kāi)封 475004 2 河南大學(xué)生態(tài)科學(xué)和技術(shù)研究所, 開(kāi)封 475004

施肥和雜草多樣性對(duì)土壤微生物群落的影響

孫 鋒1, 趙燦燦1, 何瓊杰1, 呂會(huì)會(huì)1, 管奕欣1, 谷艷芳1,2,*

1 河南大學(xué)生命科學(xué)學(xué)院, 開(kāi)封 475004 2 河南大學(xué)生態(tài)科學(xué)和技術(shù)研究所, 開(kāi)封 475004

常年使用化肥和除草劑以及農(nóng)業(yè)新技術(shù)的高投入，使我國(guó)糧食主產(chǎn)區(qū)耕地出現(xiàn)了生產(chǎn)力降低、土壤生物多樣性失調(diào)和污染嚴(yán)重等生態(tài)問(wèn)題。采用磷脂脂肪酸(PLFA)方法來(lái)評(píng)估施肥和雜草多樣性對(duì)冬小麥土壤微生物群落結(jié)構(gòu)的影響。實(shí)驗(yàn)采用裂區(qū)實(shí)驗(yàn)設(shè)計(jì)，施肥作為主因素，雜草多樣性作為次因素?；屎陀袡C(jī)肥兩個(gè)施肥處理，在兩個(gè)施肥處理中進(jìn)行雜草多樣性設(shè)置，實(shí)驗(yàn)盆中心種植作物(冬小麥8株)，四周種植雜草(8株)，雜草種類選擇野燕麥、苜蓿、菊苣、播娘蒿。雜草多樣性處理設(shè)為0、1、2、4種雜草處理，0種雜草處理僅種植作物，有6盆；1種雜草處理為每盆種1種雜草，有12盆；2種雜草處理為每盆種兩種雜草，有12盆；4種雜草處理為每盆種4種雜草，有6盆。結(jié)果表明：在兩種施肥處理中，增加雜草多樣性顯著增加了土壤碳氮比和pH值，碳氮比都是在4種雜草處理中最高。施化肥處理中，增加雜草多樣性顯著影響真菌和細(xì)菌比，真菌和細(xì)菌比在4種雜草處理中最大，顯著高于0、1、2種雜草處理。在施有機(jī)肥處理中，增加雜草多樣性顯著影響陽(yáng)性菌和陰性菌比，陽(yáng)性菌和陰性菌比在0種雜草處理中最低，顯著低于1、2、4種雜草處理。在兩個(gè)施肥處理中，土壤碳氮比與各類群微生物量顯著相關(guān)，雜草多樣性通過(guò)改變土壤碳氮比改變微生物群落構(gòu)成，并且微生物群落結(jié)構(gòu)轉(zhuǎn)變方式不同。

磷脂脂肪酸(PLFA); 施肥; 雜草多樣性; 主要農(nóng)作物

土壤生物在增加土壤碳儲(chǔ)存、提高土壤肥力和調(diào)節(jié)植物生長(zhǎng)中起著重要作用。尤其土壤微生物，它是土壤生態(tài)系統(tǒng)的關(guān)鍵成份和土壤功能(如物質(zhì)循環(huán)，能量流動(dòng))的驅(qū)動(dòng)者[1]。微生物之間通過(guò)競(jìng)爭(zhēng)和其它相互作用可以降低真菌類疾病[2]，而微生物與植物根系共生形成菌根真菌能提高植物對(duì)氮和磷的吸收[3]。因此，土壤微生物在提高土壤生態(tài)系統(tǒng)功能方面起著重要作用。

農(nóng)田管理方式(如施化肥、除草劑等)直接或間接地影響土壤微生物群落構(gòu)成。當(dāng)前，大量化肥施用于農(nóng)田用來(lái)滿足人類食物需求[4]。人為的氮輸入是100年前的10倍[5]。從1996年到2005年，中國(guó)的谷物產(chǎn)量增加了10%，但化肥施用量增加了51%[6]。土壤微生物群落結(jié)構(gòu)和施肥有密切關(guān)系。長(zhǎng)期施氮肥能減少總微生物量和真菌生物量[7-8]，改變土壤氨氧化細(xì)菌群落構(gòu)成[9]。長(zhǎng)期施磷肥能顯著減少真菌生物量[8,10]。因此，長(zhǎng)期施化肥對(duì)微生物有不利影響。除草劑的大量使用，使農(nóng)田雜草多樣性急劇降低。農(nóng)田雜草是棲息在農(nóng)田中鳥(niǎo)類、昆蟲(chóng)和傳粉動(dòng)物的食物來(lái)源[11-12]，同時(shí)也是地上地下生態(tài)系統(tǒng)密切聯(lián)系的紐帶，影響分解者生物群落組成(微生物、線蟲(chóng)、螨類)、養(yǎng)分利用和土壤生態(tài)過(guò)程的穩(wěn)定性[13-14]。大量研究集中于雜草對(duì)作物產(chǎn)量的影響，而農(nóng)田雜草如何影響土壤微生物群落結(jié)構(gòu)的相關(guān)研究還比較少[15]，且結(jié)果不一致[15-17]。微生物群落構(gòu)成和多樣性的改變對(duì)植被生產(chǎn)力的影響是未來(lái)的主要挑戰(zhàn)[18]。

磷脂脂肪酸(PLFA)法不僅可以檢測(cè)活體微生物群落結(jié)構(gòu)而且可以估計(jì)微生物生物量。磷脂脂肪酸組成的改變被認(rèn)為是微生物群落結(jié)構(gòu)轉(zhuǎn)變的敏感標(biāo)記，廣泛用來(lái)比較不同的土地利用系統(tǒng)、作物管理模式和營(yíng)養(yǎng)壓力下微生物群落的差異[19-20]，是目前較可靠的研究方法。

常年使用化肥和農(nóng)藥以及農(nóng)業(yè)新技術(shù)的高投入，使我國(guó)糧食主產(chǎn)區(qū)耕地出現(xiàn)了生產(chǎn)力降低、土壤生物多樣性失調(diào)和污染嚴(yán)重等生態(tài)問(wèn)題。保護(hù)生物多樣性被認(rèn)為是應(yīng)對(duì)未來(lái)農(nóng)業(yè)風(fēng)險(xiǎn)的重要戰(zhàn)略[21]。本研究采用盆栽模擬試驗(yàn)探索施化肥和有機(jī)肥措施下增加雜草多樣性是否改變冬小麥土壤微生物群落構(gòu)成，以及該變化方式是否相同。旨在為農(nóng)田土壤環(huán)境保持健康穩(wěn)定提供一定的科學(xué)依據(jù)?；谠撗芯刻岢黾僭O(shè)：(1)增加雜草多樣性通過(guò)影響土壤C/ N改變微生物群落，(2)增加雜草多樣性在兩種施肥處理中改變微生物群落結(jié)構(gòu)方式不同。

1 研究區(qū)域

試驗(yàn)地點(diǎn)位于河南省開(kāi)封市河南大學(xué)試驗(yàn)田，地理位置為34°48′ N、114°18′ E，暖溫帶氣候，受季風(fēng)影響顯著，四季分明，年均氣溫14 ℃，年均日照2267.6 h，年均降雨量為634.2 mm，屬于半濕潤(rùn)偏干旱型，土壤為黃河沖積物母質(zhì)發(fā)育而成，土層深厚，土質(zhì)疏松。

2 研究方法

2.1 實(shí)驗(yàn)設(shè)計(jì)

實(shí)驗(yàn)始于2010年10月，采用盆栽模擬方式(盆長(zhǎng)75 cm，盆寬50 cm，盆高50 cm)種植作物為冬小麥(Triticumaestivum)和玉米(Zeamays)輪作，土壤取自撂荒地，原土壤化學(xué)性質(zhì)全氮為0.30 g/ kg，銨態(tài)氮為16.1 mg/ kg，全磷為0.61 g/ kg，有效磷10.5 mg/ kg，有機(jī)碳3.2 g/ kg，pH為7.41。采用施肥作為主因素、雜草多樣性作為次因素的裂區(qū)實(shí)驗(yàn)設(shè)計(jì)，化肥(NPK)和有機(jī)肥(OM)兩個(gè)施肥處理，施化肥時(shí)間為冬小麥播前(10月，基肥)和拔節(jié)期(次年3月，追肥)，施肥量如表1；有機(jī)肥為雞糞經(jīng)堆制發(fā)酵后作基肥施用(無(wú)追肥)，施用前先分析氮養(yǎng)分含量，以和施化肥處理等氮量為標(biāo)準(zhǔn)，同長(zhǎng)期定位試驗(yàn)[22]。在兩個(gè)施肥處理中進(jìn)行雜草多樣性設(shè)置，雜草和冬小麥作物同時(shí)種植，玉米不種植雜草。實(shí)驗(yàn)盆中心種植作物(冬小麥8株)，四周種植雜草(8株)，雜草種類選擇野燕麥(Avenafatua)、苜蓿(Medicagosativa)、菊苣(Cichoriumintybus)、播娘蒿(DescurainiaSophia)。雜草多樣性處理設(shè)為0、1、2、4種雜草處理，0種雜草處理僅種植作物(冬小麥16株)；1種雜草處理為每盆種1種雜草(8株)；2種雜草處理為每盆種兩種雜草、每種4株；4種雜草處理為每盆種4種雜草、每種2株。0種雜草處理有6個(gè)重復(fù)；1種雜草處理有4個(gè)組合(a, b, c, d)，各3個(gè)重復(fù)共12盆；2種雜草有6種組合(ab, ac, ad, bc, bd, cd)，各2個(gè)重復(fù)共12盆；4種雜草處理有一種組合(abcd)6個(gè)重復(fù)。共計(jì)72 (2種施肥處理×4種雜草不同組合的36個(gè)重復(fù))個(gè)實(shí)驗(yàn)盆。

2.2 土壤樣品采集及處理

在2013年(連續(xù)3a種植冬小麥，第3年取樣)冬小麥開(kāi)花期(4月30號(hào))，用直徑2 cm土鉆在實(shí)驗(yàn)盆中按五點(diǎn)法取0—20 cm土層土樣，用鑷子揀出根、凋落物碎屑及小石粒，混勻過(guò)2 mm土篩。分成兩份，用無(wú)菌塑料袋裝好，一份貯于-20 ℃冰箱用于微生物磷脂脂肪酸分析，一份自然風(fēng)干用于測(cè)定土壤化學(xué)特性。

2.3 測(cè)定方法

2.3.1 土壤微生物量測(cè)定方法

采用磷脂脂肪酸(PLFA)生物標(biāo)記法[23]。稱量相當(dāng)8 g干重的鮮土樣，用23 mL含有氯仿、甲醇、磷酸鹽緩沖液(1∶2∶0.8)的混合提取液萃取脂質(zhì)，N2氣體下濃縮萃取液。對(duì)磷脂進(jìn)行分離，把脂肪酸恢復(fù)成甲酯，脂肪酸甲酯溶解在200 mL包含有十九烷酸甲酯(19:0)己烷溶劑中，19:0作為內(nèi)部標(biāo)準(zhǔn)。采用安捷倫6890氣相色譜儀分析磷脂脂肪酸樣本，磷脂脂肪酸(PLFA)的鑒定采用細(xì)菌脂肪酸標(biāo)準(zhǔn)和MIDI峰鑒別軟件。認(rèn)定單一不飽和脂肪酸和環(huán)丙基脂肪酸為革蘭氏陰性菌[24]，a/ i支鏈脂肪酸為革蘭氏陽(yáng)性菌[25]，脂肪酸14:0、15:0、16:0、17:0、18:0、革蘭氏陰性菌和革蘭氏陽(yáng)性菌總和為細(xì)菌；16:1ω5c為菌根真菌標(biāo)記[25]；18:1ω9c和18:2ω6,9c為真菌標(biāo)記[26]。

2.3.2 土壤化學(xué)特性測(cè)定方法

pH值分析采用0.01 mol/ L的CaCl2溶液浸提pH計(jì)法；土壤有機(jī)碳分析采用重鉻酸鉀氧化外加熱法；土壤全氮分析采用半微量凱氏定氮法；銨態(tài)氮分析采用2 mol/ L的KCl浸提連續(xù)流動(dòng)分析儀測(cè)定法。

2.4 數(shù)據(jù)處理與分析

用單因素方差分析判定雜草多樣性對(duì)土壤化學(xué)性質(zhì)、微生物生物量和群落比的影響；把植物初級(jí)生產(chǎn)量作為協(xié)變量，用協(xié)方差分析判定植物多樣性對(duì)以上指標(biāo)的影響；用LSD法表示顯著性差異；Origin 8.0進(jìn)行作圖。

表1 試驗(yàn)地肥料使用量

3 結(jié)果

3.1 施肥和雜草多樣性對(duì)土壤化學(xué)性質(zhì)的影響

由表2可知：施化肥處理中，土壤全氮、銨態(tài)氮、有機(jī)碳、碳氮比和pH值均低于施有機(jī)肥。在施化肥處理中，雜草多樣性對(duì)土壤全氮、銨態(tài)氮、有機(jī)碳和pH值無(wú)顯著影響，碳氮比在4種雜草處理中最高，比1種雜草處理高8.6%，且有顯著差異。在施有機(jī)肥處理中，雜草多樣性顯著影響土壤碳氮比和pH值；碳氮比在4種雜草處理中顯著高于1種雜草和2種雜草處理；pH值在4種雜草處理中最高，在0種雜草處理中最低，且兩處理間有顯著差異。

表2 冬小麥開(kāi)花期土壤養(yǎng)分

數(shù)據(jù)為平均值加標(biāo)準(zhǔn)誤，0種草和4種草處理重復(fù)6次，1種草和2種草處理重復(fù)12次

3.2 施肥和雜草多樣性對(duì)初級(jí)生產(chǎn)量的影響

由表3可知：在兩個(gè)施肥處理中，雜草多樣性對(duì)初級(jí)生產(chǎn)量無(wú)顯著影響。施有機(jī)肥各個(gè)雜草多樣性處理初級(jí)生產(chǎn)量均高于施化肥處理。

3.3 施肥和雜草多樣性對(duì)土壤微生物的影響

由表4可見(jiàn)：在NPK施肥處理中，雜草多樣性顯著影響真菌和細(xì)菌比；在OM處理中，雜草多樣性顯著影響陽(yáng)性菌和陰性菌比；在兩個(gè)施肥處理中，把初級(jí)生產(chǎn)量作為協(xié)變量后，仍有顯著差異。

由圖1可知：在施有機(jī)肥處理中，土壤總微生物量和各類群微生物量遠(yuǎn)高于施化肥處理；在施有機(jī)肥各個(gè)雜草多樣性處理中，總微生物量是施化肥各個(gè)雜草多樣性處理的4.0、4.2、4.1、4.5倍；施有機(jī)肥處理中陽(yáng)性菌和陰性菌比、真菌和細(xì)菌比高于施化肥處理。

表3 施肥和雜草多樣性處理下初級(jí)生產(chǎn)量(g/ 盆)

數(shù)據(jù)為平均值±標(biāo)準(zhǔn)誤，0種和4種雜草處理重復(fù)6次，1種和2種雜草處理重復(fù)12次

在施化肥處理中，雜草多樣性對(duì)總微生物量、細(xì)菌生物量無(wú)顯著影響；真菌和菌根真菌生物量在1種雜草處理中最低(1.0 nmol/ g干土和0.4 nmol/ g干土)，在4種雜草處理中最高(1.3 nmol/ g干土和0.6 nmol/ g干土)，且兩處理間有顯著性差異，其他處理之間無(wú)顯著差異；陽(yáng)性菌和陰性菌比在各處理間無(wú)顯著差異；真菌和細(xì)菌比在0種雜草處理中最低，4種雜草處理中最高，且與0種雜草、1種雜草和2種雜草處理有顯著性差異。

在施有機(jī)肥處理中，雜草多樣性對(duì)總微生物量、細(xì)菌生物量、真菌生物量無(wú)顯著影響；菌根真菌生物量在1種雜草處理中最低，為1.5 nmol/ g干土；在4種雜草處理中最高，為1.8 nmol/ g干土，且兩處理間有顯著性差異；陽(yáng)性菌和陰性菌比在0種雜草處理中最低，在4種雜草處理中最高，0種雜草處理與有雜草處理間都有顯著差異；真菌和細(xì)菌比在各雜草處理間無(wú)顯著性差異。

表4 不同雜草多樣處理間土壤微生物量和群落比的方差分析

圖1 施肥和雜草多樣性處理對(duì)土壤微生物量的影響Fig.1 Effects of fertilization and weeds diversity on microbial biomass at anthesis stage of winter wheatG+/ G-: Gram-positive bacteria biomass/Gram-negative bacteria biomass; F/ B: Fungi biomass/ bacterial biomass

3.4 相關(guān)分析

由表5可知：在兩個(gè)施肥處理中，碳氮比與總微生物量和各類群微生物量顯著相關(guān)，銨態(tài)氮和pH值與微生物量無(wú)顯著相關(guān)性。在施化肥處理中，有機(jī)碳與細(xì)菌、真菌、菌根真菌生物量顯著相關(guān)；而在施有機(jī)肥處理中，有機(jī)碳與總微生物量和真菌生物量顯著相關(guān)。

表5 微生物量與土壤化學(xué)性質(zhì)相關(guān)分析

3.5 雜草物種對(duì)土壤微生物群落的影響

由表6可知：對(duì)含1種雜草處理進(jìn)行方差分析，結(jié)果表明物種專一性對(duì)各類群土壤微生物量和類群比無(wú)顯著影響。

4 討論

施有機(jī)肥提高了土壤養(yǎng)分，更有利于增加土壤微生物量。結(jié)果表明施有機(jī)肥處理土壤總微生物量和各類群微生物量多于施化肥處理 (圖1)，因?yàn)橛袡C(jī)肥處理中有機(jī)碳含量高于施化肥處理(表2)，微生物量依賴于土壤有機(jī)碳[27]；有機(jī)肥本身含有微生物，這也是增加土壤微生物量的原因。施肥顯著改變了土壤微生物群落結(jié)構(gòu)，施化肥處理中陽(yáng)性菌與陰性菌比低于施有機(jī)肥 (圖1)。Marschner 等[28]在長(zhǎng)期施肥研究中結(jié)果也表明陽(yáng)性菌與陰性菌比在施化肥處理中顯著低于施有機(jī)肥處理。施有機(jī)肥處理有較高的真菌和細(xì)菌比 (圖1)，增加真菌和細(xì)菌比被認(rèn)為增強(qiáng)了生態(tài)系統(tǒng)效率和食物網(wǎng)復(fù)雜性[29-30]。是農(nóng)田生態(tài)系統(tǒng)更加可持續(xù)發(fā)展的標(biāo)志并且對(duì)環(huán)境有較低的影響[31]。而且，施有機(jī)肥處理碳氮比高于施化肥處理(表2)，碳氮比在一定范圍內(nèi)可以作為養(yǎng)分肥力的指標(biāo)。因此，施有機(jī)肥更有利于土壤生態(tài)系統(tǒng)穩(wěn)定性。

雜草多樣性顯著改變了土壤養(yǎng)分，在兩個(gè)施肥處理中，4種雜草多樣性處理中碳氮比和pH值最高(表2)。碳氮比和pH值是重要的環(huán)境因子，會(huì)影響微生物群落構(gòu)成，盡管在施有機(jī)肥4種雜草處理中pH值有顯著增加(表2)，但pH值變化范圍比較窄，且與各類群微生物量無(wú)顯著相關(guān)(表5)，而各類群微生物量和與碳氮比顯著相關(guān)(表5)，所以增加雜草多樣性通過(guò)改變土壤碳氮比改變微生物群落結(jié)構(gòu)，證明了第一個(gè)假設(shè)。這和Marschner等[28]研究結(jié)果相同，細(xì)菌和真菌群落結(jié)構(gòu)顯著地受碳氮比影響。

大部分土壤微生物是依賴外源碳的非自養(yǎng)生物，根代謝物增加了土壤有機(jī)碳，有利于微生物生長(zhǎng)。本文結(jié)果表明地上雜草多樣性和地下微生物群落緊密相關(guān)(表4)。在施化肥處理中，雜草多樣性顯著影響真菌和細(xì)菌比(表4)，4種雜草處理中，真菌和細(xì)菌比最高(圖1)，因?yàn)樵?種雜草處理中真菌生物量最多(圖1)。真菌能分解大量的植物殘?bào)w釋放營(yíng)養(yǎng)，促進(jìn)土壤團(tuán)聚提高土壤質(zhì)量，且能增加土壤碳儲(chǔ)存。因此，在施化肥處理中物種豐富的植物群落的生態(tài)位互補(bǔ)作用、積極的交互作用和較多的可利用資源[32-33]更有利于真菌生長(zhǎng)。4種雜草處理增強(qiáng)了生態(tài)系統(tǒng)效率的另一個(gè)原因是菌根真菌生物量最大，菌根真菌能增強(qiáng)宿主對(duì)氮和磷的吸收，也可以減少宿主土傳病蟲(chóng)害[34]；而且4種雜草處理中有較多的原生動(dòng)物和小型節(jié)肢動(dòng)物(未發(fā)表)，土壤動(dòng)物與微生物交互作用刺激分解作用[35-36]，提高作物對(duì)土壤中氮的吸收并且減少害蟲(chóng)的危害[37-38]。因此，施化肥處理中增加雜草多樣性通過(guò)改變真菌和細(xì)菌比影響微生物群落，并且有助于改善土壤生態(tài)系統(tǒng)。在施有機(jī)肥處理中，雜草多樣性顯著影響陽(yáng)性菌和陰性菌比(表4)，陰性菌生物量在4種雜草處理中最高。陰性菌傾向于利用根圍來(lái)源的碳[39]，大量的陰性菌被認(rèn)為是從貧營(yíng)養(yǎng)到富營(yíng)養(yǎng)的轉(zhuǎn)變[40]。植物通過(guò)改變根分泌液質(zhì)量和數(shù)量影響陰性菌生物量，因?yàn)楦置谝菏俏⑸锢玫闹匾荚矗腋置谝汉统练e物可以刺激微生物生長(zhǎng)[41]。在有機(jī)肥處理中，雜草多樣性對(duì)真菌和細(xì)菌比無(wú)顯著影響(表4)，因此，在有機(jī)肥處理中增加雜草多樣性對(duì)改善土壤生態(tài)系作用不大，可能因?yàn)樵诜饰趾蜕飳W(xué)健康的土壤中，雜草處于競(jìng)爭(zhēng)弱勢(shì)地位。在兩種施肥處理中增加雜草多樣性改變微生物群落結(jié)構(gòu)的方式不同。證明了第二個(gè)假設(shè)。因此，植物物種豐富度是影響微生物交互的重要因子。盡管在雜草多樣性處理間微生物群落結(jié)構(gòu)差別較小，但這些微小差別對(duì)微生物驅(qū)動(dòng)的生態(tài)系統(tǒng)過(guò)程(如營(yíng)養(yǎng)循環(huán))會(huì)有重要的積累效應(yīng)。

Milcu等[42]研究表明豆科物種的存在對(duì)土壤微生物量有積極的作用。實(shí)驗(yàn)中，卻沒(méi)有得出此結(jié)論，在含有豆科、菊科、禾本科和十字花科雜草物種處理中，物種專一性對(duì)土壤微生物量和類群比都無(wú)顯著影響(表6)。因此，是物種多樣性而不是物種專一性影響微生物群落構(gòu)成。Eisenhauer等[43]研究結(jié)果也表明是植物多樣性而不是植物功能組驅(qū)動(dòng)土壤食物網(wǎng)的結(jié)構(gòu)和功能。建議在農(nóng)田中施有機(jī)肥，以增加土壤微生物量；在施化肥農(nóng)田中要保持一定的雜草多樣性，用于調(diào)節(jié)土壤微生物群落結(jié)構(gòu)，改善土壤生態(tài)系統(tǒng)。

5 結(jié)論

本文結(jié)果顯示施有機(jī)肥能較大的增加土壤微生物量和增加土壤養(yǎng)分。雜草多樣性通過(guò)改變土壤碳氮比顯著影響微生物群落構(gòu)成，施化肥處理中增加雜草多樣性顯著增加了真菌和細(xì)菌比和土壤碳氮比，提高了土壤生態(tài)系統(tǒng)穩(wěn)定性；而在肥沃的有機(jī)肥處理中，增加雜草多樣性顯著增加了陽(yáng)性菌和陰性菌比、pH值。

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Effects of fertilization and diversity of weed species on the soil microbial community

SUN Feng1, ZHAO Cancan1, HE Qiongjie1, Lü Huihui1, GUAN Yixin1, GU Yanfang1,2,*

1CollegeofLifescience,HenanUniversity,Kaifeng475004,China2InstituteofEcologicalScienceandTechnology,HenanUniversity,Kaifeng475004,China

Farmland ecosystems are primary producers of food, feed, fiber, and other natural products. Species diversity constitutes an important foundation in farmland ecosystems, but human activities are greatly accelerating the loss rate of species. Considerable evidence shows that agricultural management threatens biodiversity and negatively affects species richness and abundance of taxa. In major grain-producing areas, reductions in productivity and soil biodiversity and serious pollution problems occur as a result of fertilizer and pesticide use as well as new agricultural technologies. Conservation of biological diversity is considered to be an important strategy to reduce risks to agriculture in the future. Phospholipid fatty acid (PLFA) analysis was employed to examine the effects of fertilization and diversity of weed species on soil microbial community structure in a winter wheat plantation. The experiment used a split-plot design and was established in October 2010. Two fertilization treatments (including chemical fertilizer and organic manure) were applied to the main plots and diversity of weed species (0, 1, 2 and 4 species) were sown in the sub-plots. Wheat was grown in the center of plots and weeds were grown around the wheat plants (all eight plants). The weed species wereAvenafatua,Medicagosativa,Cichoriumintybus, andDescurainiasophia. For the zero species weed treatments, six plots were grown of wheat plants only. For the 1-species weed treatments, one kind of weed was grown with the wheat in 12 plots. For the 2-species weed treatments, two weed species were grown with the wheat in 12 plots. For the 4-species weed treatments, four weed species were grown with the wheat in six plots. Increased weed diversity significantly increased the soil carbon(C)∶nitrogen(N) ratio and pH in both fertilizer treatments, and the C∶N ratio was the highest in the 4-species treatment. In the chemical fertilizer treatment, weed diversity significantly affected the fungi:bacteria ratio, which was highest in the 4-species treatment. Fungal and mycorrhizal fungal biomass were lowest in the 1-species treatment (1.0 nmol/g dry soil and 0.4 nmol/g dry soil, respectively), and significantly lower than in the 4-species treatment (1.3 nmol/g dry soil and 0.6 nmol/g dry soil, respectively). In the organic manure treatments, the gram-positive:gram-negative bacterial ratio was lowest in the 0-species treatment compared with the 1-, 2-and 4-species treatments. Mycorrhizal fungal biomass was lowest in the 1-species treatment (1.5 nmol/g dry soil), and significantly lower than in the 4-species treatment (1.8 nmol/g dry soil). In both fertilizer treatments, weed species diversity affected microbial community composition by changing the soil C∶N ratio, which was correlated with biomass of various functional groups of soil microbes. Moreover, the shift of the microbial community composition in a different way. Plant species richness is an important factor affecting microbial interactions. Despite the small differences in microbial community structure between different weed diversity treatments, these minor differences will have an important cumulative effect on microbial-driven ecosystem processes. For legumes,Asteraceae,Poaceae, and cruciferous weed species treatments, species specificity had no significant effects on soil microbial biomass and taxa. Thus, species diversity affects microbial community composition. We recommend applying manure to increase soil microbial biomass in farmlands and maintain diversity of weed species. This will lead to changes in microbial community structure to regulate and improve soil ecosystem stability in chemically fertilized farmland. This study is of practical and theoretical significance for 1) our understanding of how plant diversity affects soil microbial community composition and the development of soil ecosystem health, 2) exploring microbial ecological function in maintaining soil ecosystem stability, and 3) revealing plant-soil-microbial interactions and feedback mechanisms.

PLFA; fertilization; weed diversity; main crop

國(guó)家自然科學(xué)基金項(xiàng)目(31070394); 河南省科技攻關(guān)項(xiàng)目(142102110034)

2014-01-09;

日期:2014-11-19

10.5846/stxb201401090071

*通訊作者Corresponding author.E-mail: guyanfang@henu.edu.cn

孫鋒, 趙燦燦, 何瓊杰, 呂會(huì)會(huì), 管奕欣, 谷艷芳.施肥和雜草多樣性對(duì)土壤微生物群落的影響.生態(tài)學(xué)報(bào),2015,35(18):6023-6031.

Sun F, Zhao C C, He Q J, Lü H H, Guan Y X, Gu Y F.Effects of fertilization and diversity of weed species on the soil microbial community.Acta Ecologica Sinica,2015,35(18):6023-6031.