張俊華　張　翼　李　明

(1.寧夏大學(xué)環(huán)境工程研究院， 銀川 750021； 2.寧夏大學(xué)教育學(xué)院， 銀川 750021)

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寧夏枸杞園土壤線蟲和微生物群落多樣性研究

張俊華1張翼2李明1

(1.寧夏大學(xué)環(huán)境工程研究院， 銀川 750021； 2.寧夏大學(xué)教育學(xué)院， 銀川 750021)

為了揭示寧夏枸杞園土壤質(zhì)量變化趨勢(shì)，以寧夏枸杞之鄉(xiāng)——中寧縣為研究區(qū)，選取不同樹齡寧夏枸杞園土壤，分析不同季節(jié)、土層和樹齡條件下土壤線蟲和微生物群落特征變化規(guī)律。結(jié)果表明，隨樹齡的增加，枸杞園0～20 cm土壤線蟲總數(shù)先增加后減少，6 a樹齡時(shí)達(dá)最大值。不同樹齡表層土壤均為食細(xì)菌線蟲所占比例最大(夏季和秋季平均分別為57.23%和61.19%)，植物寄生線蟲次之；亞表層植物寄生線蟲比例顯著提高。夏季表層土壤總磷脂脂肪酸(PLFA)和細(xì)菌PLFA濃度隨樹齡呈減小-增大-減小的趨勢(shì)，9 a樹齡各菌群PLFA濃度普遍最大。隨樹齡的增加，夏季0～20 cm土壤線蟲多樣性和豐富度指數(shù)先增大后減小，但土壤微生物多樣性指數(shù)、均勻度指數(shù)都逐漸減小，線蟲和微生物群落優(yōu)勢(shì)度指數(shù)都逐漸增大；20～40 cm土壤線蟲和微生物數(shù)量、多樣性指數(shù)和優(yōu)勢(shì)度指數(shù)變化趨勢(shì)一致。土壤EC與微生物總PLFA濃度、細(xì)菌PLFA濃度達(dá)顯著負(fù)相關(guān)；土壤有機(jī)質(zhì)、全氮、速效磷含量與土壤各線蟲數(shù)量和微生物濃度相關(guān)性普遍達(dá)顯著或極顯著水平。土壤線蟲總數(shù)、食細(xì)菌線蟲數(shù)量與細(xì)菌、真菌和放線菌PLFA濃度均顯著或極顯著相關(guān)。總之，季節(jié)、土層和樹齡對(duì)土壤線蟲和微生物群落均有不同程度的影響，但樹齡對(duì)其影響相對(duì)最?。患竟?jié)、土層和樹齡對(duì)土壤微生物群落的影響比對(duì)土壤線蟲群落更顯著。在相同季節(jié)和土層條件下，土壤微環(huán)境質(zhì)量隨著樹齡的增加呈現(xiàn)出先改善后退化的趨勢(shì)。

寧夏枸杞； 土壤線蟲群落； 磷脂脂肪酸； 生態(tài)指數(shù)； 土壤理化性狀

引言

土壤生物作為土壤生態(tài)功能的關(guān)鍵驅(qū)動(dòng)者，其群落結(jié)構(gòu)的變化在農(nóng)業(yè)生態(tài)系統(tǒng)服務(wù)功能中占據(jù)重要的地位[1]。其中，線蟲作為土壤食物網(wǎng)的重要組成部分，是農(nóng)田土壤中多樣性最為豐富的土壤動(dòng)物，能夠靈敏地反映環(huán)境變化時(shí)土壤生態(tài)系統(tǒng)的綜合狀況[2]，在評(píng)價(jià)農(nóng)田土壤生態(tài)系統(tǒng)變化方面具有很大的優(yōu)勢(shì)[3-4]；而土壤微生物在生態(tài)系統(tǒng)營(yíng)養(yǎng)物質(zhì)循環(huán)過(guò)程，特別是碳、氮循環(huán)過(guò)程中扮演著重要的角色[5-6]。

單一植物長(zhǎng)期種植會(huì)引起土壤微生物多樣性減少，細(xì)菌數(shù)量減少，真菌數(shù)量增加，土壤類型從細(xì)菌型向真菌型轉(zhuǎn)變，土壤線蟲結(jié)構(gòu)也會(huì)向不利于土壤質(zhì)量的方向發(fā)展[7]。隨樹齡的增加，土壤細(xì)菌、微生物碳、氮生物量均先增大后減小，但真菌數(shù)量呈一直增大的趨勢(shì)[8]。海南省澄邁縣香蕉園土壤中植物寄生線蟲的數(shù)量隨樹齡的增加而增加，食細(xì)菌線蟲、食真菌線蟲和捕食-雜食性線蟲的數(shù)量則表現(xiàn)出相反趨勢(shì)，香蕉園土壤的生態(tài)環(huán)境遭到破壞[9]。在樹齡較小的果樹根圍線蟲群落的多樣性指數(shù)和均勻度指數(shù)均高于樹齡較大的果樹，而優(yōu)勢(shì)度指數(shù)相反；且植物線蟲更易于侵襲幼齡果樹[10]。隨著線蟲群落的改變，細(xì)菌和真菌都有顯著變化[11]，且隨植物生長(zhǎng)年限的增長(zhǎng), 土壤線蟲總數(shù)及屬數(shù)、密度、多樣性指數(shù)和土壤微生物數(shù)量呈相似變化趨勢(shì)[12-13]。食細(xì)菌線蟲數(shù)量與細(xì)菌生物量呈極顯著正相關(guān)關(guān)系[14]，并且能夠顯著提高土壤氮和有效磷[15]。土壤總碳能夠顯著影響土壤微生物生物量，土壤pH值能顯著影響土壤線蟲總數(shù)。此外，施用氮肥能夠顯著降低土壤微生物碳代謝功能群多樣性指數(shù)、真菌/細(xì)菌(F/G)和食真菌線蟲數(shù)量[16-17]，同時(shí)提高食細(xì)菌線蟲數(shù)量[18]；施用磷肥則能顯著提高食細(xì)菌和食真菌線蟲的數(shù)量[19]。胡鋒等[20]指出食微動(dòng)物雖然在某些條件下可抑制微生物種群，但總體上起著激活、增殖“培養(yǎng)”微生物的作用。

寧夏枸杞(LyciumbarbarumL.)為茄科枸杞屬多年生落葉灌木，具有極高的藥用價(jià)值和營(yíng)養(yǎng)價(jià)值。因獨(dú)特的地理氣候條件，寧夏成為枸杞的原產(chǎn)地和最佳生態(tài)區(qū)。近年來(lái)由于過(guò)量施肥、頻繁采摘和噴灑農(nóng)藥等，局部地區(qū)出現(xiàn)枸杞產(chǎn)量減少、品質(zhì)下降的問(wèn)題，為了揭示該現(xiàn)象的根本原因，本文選擇對(duì)土壤環(huán)境變化敏感的土壤線蟲和微生物群落進(jìn)行研究，分析不同季節(jié)、土層和樹齡寧夏枸杞園土壤微生物和線蟲群落多樣性、相互作用及其與土壤理化性狀的關(guān)系，旨在探討寧夏枸杞園土壤質(zhì)量動(dòng)態(tài)變化規(guī)律，為改善枸杞園土壤質(zhì)量、推進(jìn)寧夏枸杞產(chǎn)業(yè)的可持續(xù)發(fā)展提供理論依據(jù)。

1　材料與方法

1.1研究區(qū)概況

寧夏回族自治區(qū)中衛(wèi)市中寧縣(105°15′～106°05′E，36°49′～37°47′N)是全國(guó)枸杞生產(chǎn)基地縣、中國(guó)枸杞之鄉(xiāng)，也是寧夏枸杞的主產(chǎn)區(qū)。該地區(qū)年平均氣溫9.5℃，年降水量202.1 mm；日平均氣溫大于等于0℃積溫3 200～3 300℃。本研究在中寧縣寧安鎮(zhèn)南橋村分別選擇樹齡為當(dāng)年(小于1 a)、3、6、9、12 a枸杞地各3塊(各塊面積大于660 m2)，共15塊地。該地區(qū)土壤以灌淤土為主, 質(zhì)地為砂壤土。

研究區(qū)枸杞地每年灌水3～4次，翻地1～2次，除草4～5次，采摘8～10次；施用化肥約2次(多為春施和秋施)，每年噴灑農(nóng)藥8～11次。

1.2樣品采集

分別于夏季(盛果期，7月14日)和秋季(落葉期，10月25日)采集土壤樣品。在樹冠投影范圍外，先除去表層枯枝落葉后，用土鉆取表層(0～20 cm)和亞表層(20～40 cm)土壤。樣品采集時(shí)每塊地選擇9個(gè)點(diǎn)分別分層采樣，然后將同一地塊相同層次的土壤充分混勻，將新鮮土樣分成2份，一份低溫冷藏帶回實(shí)驗(yàn)室，在-20℃下冷凍保存，用于土壤線蟲的分離和鑒定以及土壤微生物磷脂脂肪酸的提取、測(cè)定，另一份在室內(nèi)風(fēng)干用于測(cè)定土壤pH值、電導(dǎo)率(EC)、有機(jī)質(zhì)及養(yǎng)分含量。

1.3樣品分析

1.3.1土壤樣品理化性狀測(cè)定

土壤pH值采用酸度計(jì)法測(cè)定；EC采用電導(dǎo)率法測(cè)定；有機(jī)質(zhì)采用外加熱法測(cè)定；全氮采用凱氏定氮法測(cè)定；堿解氮采用堿解擴(kuò)散法測(cè)定；速效磷采用Oslen法測(cè)定；速效鉀采用乙酸銨提取-火焰光度計(jì)法測(cè)定[21]。

1.3.2土壤線蟲分離和鑒定

每個(gè)樣品稱取土樣100 g，利用改良的淺盤法[22]對(duì)土壤線蟲進(jìn)行分離提取。線蟲總數(shù)通過(guò)解剖鏡直接計(jì)數(shù)，然后在光學(xué)顯微鏡下參照BONGERS的分類圖進(jìn)行科屬鑒定[23-24]。

1.3.3土壤PLFA測(cè)定

采用修正的Bligh-Dyer方法提取脂類[25]。利用HP6890氣相色譜-HP5973質(zhì)譜聯(lián)用儀。內(nèi)標(biāo)為19: 0用于定量。峰面積通過(guò)計(jì)算機(jī)自動(dòng)積分，各脂肪酸的識(shí)別與定量分別參照 BAME (Bacterial acid methyl esters) Mix 和Supelcoe 37 Component FAME Mix。

1.3.4生態(tài)指數(shù)計(jì)算

土壤線蟲和微生物生態(tài)指數(shù)公式[26-27]為：

多樣性指數(shù)(Diversity index)

H′=-∑(pilnpi)

均勻度(Evenness)

J′=H′/lnS

豐富度(Species richness)

SR=(S-1)/lnN

優(yōu)勢(shì)度指數(shù)(Dominance index)

式中pi——第i個(gè)分類單元中個(gè)體所占的比例

S——所鑒定分類單元的個(gè)數(shù)

N——鑒定的線蟲或微生物磷脂脂肪酸(PLFA)生物標(biāo)記的個(gè)體數(shù)量

1.4數(shù)據(jù)處理

利用SAS中Duncan法檢驗(yàn)不同樹齡、季節(jié)和土層枸杞園土壤線蟲及微生物數(shù)量差異顯著性，用MANOVA法研究季節(jié)、土層和樹齡對(duì)土壤線蟲和微生物指標(biāo)的交互影響，采用Pearson相關(guān)進(jìn)行土壤理化性狀與土壤線蟲和微生物數(shù)量間的相關(guān)性分析。

2　結(jié)果與分析

2.1寧夏枸杞園土壤線蟲群落特征

本研究夏季和秋季共獲得土壤線蟲2 145條，個(gè)體密度平均107條/(100 g干土)，分屬于2綱6目11科38屬，基本情況見表1。

夏季共分離得到土壤線蟲36屬904條，個(gè)體密度平均90條/(100 g干土)，其中螺旋屬Helicotylenchus、擬麗突屬Acrobeloides和小桿屬Rhabditidae為優(yōu)勢(shì)屬，個(gè)體數(shù)量占所有已知個(gè)體總數(shù)的44.82%；13個(gè)常見屬共占所有已知屬個(gè)體總數(shù)的48.91%；23個(gè)稀有屬僅占所有已知屬個(gè)體總數(shù)的6.34%。秋季共分離得到土壤線蟲30屬1 241條，個(gè)體密度平均124條/(100 g干土)，其中擬麗突屬、小桿屬和螺旋屬為優(yōu)勢(shì)屬，占所有已知屬個(gè)體總數(shù)的43.40%；17個(gè)常見屬占所有已知屬個(gè)體屬總數(shù)的51.49%；15個(gè)稀有屬占所有已知屬個(gè)體總數(shù)5.11%。

隨著樹齡的增加，夏季0～20 cm土壤線蟲總數(shù)先增加后減少，6 a樹齡達(dá)到最大值(比當(dāng)年樹齡增加47.85%)，樹齡為12 a時(shí)線蟲總數(shù)低于當(dāng)年樹齡33.91%(圖1)。秋季不同樹齡表層土壤線蟲變化趨勢(shì)與夏季相同，但當(dāng)年樹齡線蟲總數(shù)最小。隨著樹齡的增加，20～40 cm夏季土壤線蟲總數(shù)無(wú)明顯變化規(guī)律，秋季則先減少后增加。秋季表層土壤線蟲總數(shù)比夏季平均增加24.49%，亞表層增加33.36%；不同樹齡秋季表層線蟲總數(shù)平均值最大。

不同樹齡表層土壤均為食細(xì)菌線蟲所占比例最大(夏季和秋季平均分別為57.23%和61.19%)，植物寄生線蟲次之(夏季和秋季平均分別為25.67%和21.64%)，食真菌線蟲和捕食-雜食性線蟲比例平均小于10%(圖2)。亞表層植物寄生線蟲比例顯著提高(夏季和秋季分別為41.68%和40.04%)，尤其在秋季，樹齡為小于1、6、9 a時(shí)植物寄生線蟲比例高于食細(xì)菌線蟲。隨樹齡的增加，食真菌線蟲所占比例先增大后減小，而捕食-雜食性線蟲變化普遍與之相反。

隨著樹齡的增加，夏季和秋季0～20 cm土壤線蟲多樣性和豐富度指數(shù)先增大后減??；優(yōu)勢(shì)度指數(shù)則呈一直增大趨勢(shì)。線蟲各生態(tài)指數(shù)表層與亞表層無(wú)明顯差異。秋季線蟲豐富度指數(shù)高于夏季，而其他3種生態(tài)指數(shù)普遍略低于夏季；秋季各生態(tài)指數(shù)間差異相對(duì)較小，如表2所示。

表1　寧夏枸杞園0～20 cm土壤線蟲屬優(yōu)勢(shì)度和功能類群Tab.1　Dominance and functional group of soil nematodes in 0～20 cm soil of Lycium barbarum L.orchard

注：*表示未查到其中文名。BF、PP、FF和OP分別表示食細(xì)菌線蟲、植物寄生線蟲、食真菌線蟲和捕食-雜食性線蟲。+，為稀有屬比例小于1%；++，為常見屬比例1%～10%；+++，為優(yōu)勢(shì)屬比例大于10%[28]。

圖1　寧夏枸杞園0～20 cm土壤線蟲總數(shù)Fig.1　Abundance of nematodes in 0～20 cm soil of Lycium barbarum L. orchard

從多因素方差分析結(jié)果來(lái)看(表3)，季節(jié)對(duì)線蟲總數(shù)、優(yōu)勢(shì)度和豐富度指數(shù)有顯著和極顯著影響；除植物寄生線蟲數(shù)量、優(yōu)勢(shì)度指數(shù)和均勻度指數(shù)外，土層對(duì)其他土壤線蟲指標(biāo)均有極顯著或顯著影響；樹齡可以顯著影響食細(xì)菌線蟲數(shù)量、捕食-雜食線蟲數(shù)量和線蟲優(yōu)勢(shì)度指數(shù)。在季節(jié)、土層和樹齡多因素交互中，只有土層和樹齡2因子交互對(duì)食細(xì)菌線蟲樹齡有顯著影響，其他2因子或3因子交互對(duì)土壤線蟲各指標(biāo)均無(wú)顯著影響。

2.2寧夏枸杞園土壤微生物群落特征

2.2.1土壤各菌群PLFA質(zhì)量摩爾濃度

供試土壤中細(xì)菌PLFA濃度占微生物總PLFA質(zhì)量摩爾濃度(以下簡(jiǎn)稱濃度)的70%～82%，真菌占8%～15%，放線菌占6%～11%(圖3，圖中不同字母表示相同季節(jié)和土層不同樹齡土壤總PLFA濃度間的差異性)。隨著枸杞樹齡的增加，夏季表層

圖2　不同季節(jié)和樹齡枸杞園土壤0～20 cm不同營(yíng)養(yǎng)類群線蟲比例Fig.2　Proportions of different trophic groups of nematodes in different seasons and planting ages in surface soil of Lycium barbarum L. orchard

表2　不同樹齡土壤線蟲群落多樣性指數(shù)Tab.2　Characteristics of diversity of soil nematode communities at different stand ages

表3　季節(jié)、土層、樹齡及其交互作用影響枸杞園土壤線蟲因子的多因素方差分析結(jié)果Tab.3　Results from three-way ANOVA testing effects of season, layer, planting age, and their interactions on soil nematode index in orchard of Lycium barbarum L.

注：*、 **和***分別表示在0.05、0.01和0.001水平上的顯著性，ns表示不顯著，下同。

土壤細(xì)菌PLFA濃度先減小后增大，到9 a樹齡時(shí)達(dá)到最大值，樹齡為12 a時(shí)又有所減?。欢鴣啽韺油寥兰?xì)菌PLFA濃度先增大后減??；秋季表層土壤細(xì)菌PLFA濃度變化與夏季亞表層相似，但各樹齡間無(wú)顯著差異；秋季亞表層土壤細(xì)菌PLFA濃度先減小后增大，6 a樹齡時(shí)最小， 當(dāng)年樹齡相對(duì)最大。隨樹齡的增加，土壤真菌和放線菌PLFA濃度變化趨勢(shì)與細(xì)菌相似。夏季表層總PLFA濃度大于亞表層及秋季0～40 cm土層，其中9 a樹齡最高，依次分別高于其他樹齡32.97%、50.45%、13.72%和10.67%。秋季亞表層總PLFA濃度最小，平均值只有39.70 nmol/g，且除6 a樹齡外，其他4個(gè)樹齡間均無(wú)顯著差異。

圖3　不同種植年限土壤微生物磷脂脂肪酸質(zhì)量摩爾濃度Fig.3　Soil microbial PLFAs contents at different stand ages of Lycium barbarum L.

2.2.2土壤微生物群落生態(tài)指數(shù)

隨著樹齡的增加，夏季表層土壤微生物多樣性、均勻度和豐富度指數(shù)都逐漸減小(表4)，而優(yōu)勢(shì)度指數(shù)變化與之相反，所以12 a樹齡的土壤微生物群落多樣性最差。隨樹齡的增加，夏季和秋季亞表層多樣性指數(shù)呈增大-減小的趨勢(shì)；秋季表層多樣性指數(shù)有減小-增大的現(xiàn)象，9 a和12 a樹齡各指數(shù)基本相等。

相對(duì)于線蟲各指標(biāo)來(lái)講，季節(jié)、土層和樹齡對(duì)土壤微生物的影響更顯著(表5)。除F/G和均勻度指數(shù)外，季節(jié)對(duì)微生物PLFA濃度和各生態(tài)指數(shù)的影響都達(dá)到極顯著或顯著水平。土層對(duì)土壤微生物PLFA濃度和生態(tài)指數(shù)也普遍達(dá)到顯著和極顯著水平，但對(duì)土壤G-/G+及微生物多樣性指數(shù)無(wú)顯著影響。樹齡對(duì)放線菌PLFA濃度、優(yōu)勢(shì)度、均勻度和豐富度均無(wú)顯著影響，但對(duì)其他微生物指標(biāo)都產(chǎn)生顯著或極顯著影響。季節(jié)、土層和樹齡每2個(gè)因子交互對(duì)微生物總PLFA濃度、細(xì)菌、真菌PLFA濃度和多樣性指數(shù)都有顯著或極顯著影響。整體而言，3個(gè)因子對(duì)土壤微生物的影響程度由大到小依次為：季節(jié)、土層、樹齡。季節(jié)、土層和樹齡3因子交互對(duì)微生物多樣性能夠產(chǎn)生極顯著影響。

表4　不同樹齡土壤微生物群落多樣性指數(shù)Tab.4　Characteristics of diversity of soil microbe communities at different stand ages

表5　季節(jié)、土層、樹齡及其交互作用影響枸杞園土壤微生物因子的多因素方差分析結(jié)果Tab.5　Results from three-way ANOVA testing effects of season, layer, planting age, and their interactions on soil microbe index in orchard of Lycium barbarum L.

2.3土壤理化性質(zhì)與土壤線蟲和微生物間的相關(guān)性

供試區(qū)域土壤有機(jī)質(zhì)含量與全氮、堿解氮、速效磷含量之間呈極顯著或顯著正相關(guān)，堿解氮含量與全氮、速效磷含量呈極顯著正相關(guān)關(guān)系，速效鉀含量與pH值、EC呈顯著性負(fù)相關(guān)(表4)。土壤pH值與EC和線蟲數(shù)量、微生物數(shù)量普遍呈負(fù)相關(guān)關(guān)系，其中EC與微生物總PLFA濃度和細(xì)菌PLFA濃度達(dá)顯著相關(guān)。除植物寄生線蟲外，土壤有機(jī)質(zhì)、全氮含量與各線蟲數(shù)量和微生物濃度均呈顯著或極顯著正相關(guān)關(guān)系。除植物寄生線蟲和食真菌線蟲外，土壤速效磷含量與土壤各線蟲數(shù)量和微生物濃度相關(guān)性均達(dá)顯著或極顯著。土壤速效鉀含量與微生物總PLFA濃度、細(xì)菌PLFA濃度呈顯著正相關(guān)關(guān)系。線蟲總數(shù)與細(xì)菌、真菌和放線菌PLFA濃度呈顯著和極顯著相關(guān)，食細(xì)菌線蟲數(shù)量與總PLFA、細(xì)菌、真菌和放線菌均顯著或極顯著相關(guān)，捕食-雜食性線蟲數(shù)量與放線菌PLFA濃度顯著相關(guān)。

土壤EC與微生物多樣性和優(yōu)勢(shì)度分別呈極顯著負(fù)相關(guān)和正相關(guān)(表7)。土壤有機(jī)質(zhì)含量與線蟲豐富度指數(shù)、微生物均勻度呈顯著性正相關(guān)；全氮、堿解氮、速效磷含量與微生物豐富度呈極顯著和顯著負(fù)相關(guān)；速效鉀含量與微生物多樣性、優(yōu)勢(shì)度指數(shù)呈顯著負(fù)相關(guān)和正相關(guān)關(guān)系。土壤線蟲豐富度與微生物均勻度間呈顯著性正相關(guān)。

表6　土壤理化性狀與土壤線蟲和微生物數(shù)量的相關(guān)性分析Tab.6　Correlation between soil PLFAs and soil physicochemical properties

注：P0.05=0.602，P0.01=0.735，下同。

表7　土壤理化性狀與土壤線蟲和微生物生態(tài)指數(shù)的相關(guān)性分析Tab.7　Correlation between soil PLFAs and soil physicochemical properties

注：表中-N和-M分別代表土壤線蟲和土壤微生物。

3　討論

研究區(qū)地處衛(wèi)寧平原引黃灌區(qū)，土壤有不同程度的次生鹽漬化，土壤線蟲和微生物群落在不同季節(jié)、土層和樹齡都有其獨(dú)特的變化規(guī)律。本研究得到不同樹齡土壤線蟲類群屬數(shù)2綱6目11科38屬，個(gè)體密度平均107條/(100 g干土)，低于其他果園的報(bào)道結(jié)果[29-30]。

夏季枸杞園表層土壤食細(xì)菌線蟲所占比例最大，植物寄生線蟲次之，亞表層植物寄生線蟲數(shù)量顯著增加，秋季樹齡為小于1、6、9 a的土壤植物寄生線蟲比例居各營(yíng)養(yǎng)類群最高值。植物寄生線蟲是引起連作障礙的原因之一[31]，可誘發(fā)或加重某些病害的發(fā)生，造成經(jīng)濟(jì)損失[32]，所以需要抑制這幾個(gè)樹齡秋季土壤植物寄生線蟲的繁殖。使用除草劑和化肥會(huì)抑制植物寄生線蟲的生長(zhǎng)[33]。但食細(xì)菌線蟲也可以顯著提高木本植物對(duì)土壤氮和磷的吸收[34]，促進(jìn)植物根系生長(zhǎng)[35]，提高植物對(duì)污染/退化土壤的忍耐力[36]，所以土壤食細(xì)菌線蟲還應(yīng)該保留合理的數(shù)量。

隨樹齡的增加，表層土壤線蟲總數(shù)與微生物PLFA濃度變化并不一致：土壤線蟲總數(shù)先增加后減少，6 a樹齡土壤線蟲總數(shù)最多；但土壤微生物總PLFA濃度先減小后增大再減小，9 a樹齡土壤總PLFA濃度最大。這是由于線蟲攝食的細(xì)菌通過(guò)腸道后大部分仍保持活性[37]，而且這些細(xì)菌可能在腸道內(nèi)獲得某些激素和限制性營(yíng)養(yǎng)物質(zhì)，因而當(dāng)排出后生長(zhǎng)加快；此外，線蟲的分泌和排泄物為細(xì)菌生長(zhǎng)提供了更易于利用的基質(zhì)及無(wú)機(jī)營(yíng)養(yǎng)，這對(duì)非根際土壤環(huán)境中細(xì)菌的增殖尤為重要，因此食細(xì)菌線蟲能夠促進(jìn)微生物種群的增長(zhǎng)[20]。陳小云等[38]指出食細(xì)菌線蟲顯著增加了土壤細(xì)菌、真菌和放線菌的數(shù)量，且對(duì)真菌和放線菌數(shù)量的促進(jìn)作用比對(duì)細(xì)菌更為明顯，與本研究結(jié)論完全一致，這種現(xiàn)象可能是由于速生型細(xì)菌和慢生型真菌存在較激烈的資源競(jìng)爭(zhēng)[39]。食細(xì)菌線蟲對(duì)細(xì)菌的捕食(減弱細(xì)菌對(duì)資源的競(jìng)爭(zhēng))給真菌(或放線菌)提供了生長(zhǎng)的競(jìng)爭(zhēng)優(yōu)勢(shì)[40]。相對(duì)于線蟲各指標(biāo)來(lái)講，季節(jié)、土層和樹齡對(duì)該地區(qū)枸杞園土壤微生物的影響更顯著，且這3個(gè)因素的交互對(duì)土壤微生物多樣性有顯著影響，這也反映了微生物群落組成對(duì)外部環(huán)境影響的敏感性。

土壤EC和微生物PLFA總濃度、細(xì)菌PLFA濃度、微生物多樣性呈顯著負(fù)相關(guān)關(guān)系，說(shuō)明土壤鹽分會(huì)抑制土壤微生物的多樣性，但會(huì)促進(jìn)適合高鹽分環(huán)境微生物的繁殖使其成為優(yōu)勢(shì)種群。土壤有機(jī)質(zhì)與各線蟲數(shù)量和微生物濃度均呈顯著或極顯著正相關(guān)關(guān)系，可以提高土壤線蟲豐富度和微生物群落的均勻度[41-42]。土壤速效氮含量與線蟲數(shù)量呈極顯著正相關(guān)，這是由于土壤氮能夠直接通過(guò)新陳代謝、銨態(tài)氮釋放或間接通過(guò)侵染和(或)食用細(xì)菌、真菌來(lái)增加土壤線蟲數(shù)量[43]。除食真菌線蟲和植物寄生線蟲外，土壤速效磷與各線蟲數(shù)量和微生物PLFA濃度均存在顯著或極顯著正相關(guān)關(guān)系，但本地區(qū)枸杞園長(zhǎng)期大量施用復(fù)合肥，土壤氮磷鉀含量均處于較高水平，故與低磷水平下土壤菌根真菌數(shù)量與土壤磷含量呈顯著負(fù)相關(guān)關(guān)系的結(jié)論相反[44]。枸杞園通過(guò)施肥來(lái)顯著影響土壤微環(huán)境，土壤速效氮和速效磷與線蟲總數(shù)和食細(xì)菌線蟲呈顯著和極顯著整相關(guān)，與LIU等[45]研究結(jié)論完全一致。本研究發(fā)現(xiàn)枸杞園土壤微生物學(xué)性質(zhì)和養(yǎng)分含量與土壤線蟲群落組成表現(xiàn)出密切的關(guān)系，這表明樹齡的增加改變了土壤資源有效性及微生物群落，進(jìn)而對(duì)土壤線蟲群落或土壤碎屑食物網(wǎng)的結(jié)構(gòu)和功能產(chǎn)生影響[46]。本試驗(yàn)結(jié)果表明，不同樹齡枸杞園土壤線蟲生態(tài)指數(shù)和微生物生態(tài)指數(shù)變化趨勢(shì)并不一致。線蟲豐富度指數(shù)與微生物均勻度指數(shù)呈顯著正相關(guān)，這一現(xiàn)象也與線蟲和微生物群落生長(zhǎng)、取食密切相關(guān)[20]。

4　結(jié)束語(yǔ)

通過(guò)對(duì)土壤線蟲、微生物數(shù)量及其生態(tài)指數(shù)的分析，可知研究區(qū)寧夏枸杞園0～20 cm土壤線蟲和微生物數(shù)量多于20～40 cm，但二者生態(tài)指數(shù)變化規(guī)律不同；20～40 cm土壤線蟲和微生物在數(shù)量、多樣性指數(shù)和優(yōu)勢(shì)度指數(shù)變化趨勢(shì)一致。土壤有機(jī)質(zhì)、全氮、速效磷含量與土壤各線蟲數(shù)量和微生物濃度相關(guān)性普遍達(dá)顯著或極顯著水平，土壤線蟲總數(shù)、食細(xì)菌線蟲數(shù)量與細(xì)菌、真菌和放線菌PLFA濃度均顯著或極顯著相關(guān)。季節(jié)和土層對(duì)土壤線蟲和微生物群落多樣性的影響普遍大于樹齡；季節(jié)、土層和樹齡對(duì)微生物群落的影響較對(duì)線蟲群落更顯著。在相同季節(jié)、相同土層的前提下，寧夏枸杞園土壤微環(huán)境質(zhì)量隨樹齡的增加呈先改善后退化的趨勢(shì)。

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Soil Nematode and Microbial Community Diversity inLyciumbarbarumL. Orchard

Zhang Junhua1Zhang Yi2Li Ming1

(1.InstituteofEnvironmentalEngineering,NingxiaUniversity,Yinchuan750021,China2.CollegeofEducation,NingxiaUniversity,Yinchuan750021,China)

Soil nematode and microbes are essential and very sensitive to any upsets in terrestrial ecosystems. In order to reveal the tendency of soil quality of wolfberry (LyciumbarbarumL.) orchard, make the origin ofL.barbarumas the objective region, different stand ages of soil were selected in wolfberry orchard. The objective of the study was achieved by nematode and phospholipid fatty acid (PLFA) biomarker analysis of soil samples fromL.barbarumorchards in the objective region. The change rule of soil nematode and microbial community diversity with the change of season, soil layer and stand age was analyzed. The results showed that the abundance of nematode was increased and then decreased in 0～20 cm of soil, with the highest nematode at the stand age of 6. The proportion of bacterivores was the highest (57.23% and 61.19% in summer and autumn, respectively), and plant parasites nematode was next, fungivorous nematode and predators-omnivore had the lowest abundance. Plant parasites nematode was relatively higher at 20～40 cm than that at 0～20 cm. The average concentrations of total and bacterial PLFAs in the surface soil were initially decreased and then increased, and the highest microbial PLFA concentrations were obtained in 9thyear. The tendency change of total and bacterial PLFAs were similar to nematode abundance at 20～40 cm in summer. With longer stand age, Shannon diversity index (H′) and richness index (SR) of nematode were increased and then decreased, however,H′ andSRof microbial were decreased, and dominant index was increased. The change tendency of abundance,H′ andSRof soil nematode were similar to soil microbial. There was significant negative correlation between soil pH value, EC, microbial and bacteria PLFA. The organic matter, total nitrogen and available P were significantly positively correlated to the abundance of nematodes and concentration of microbial PLFA, respectively. Total abundance of nematode, bacterivores and bacteria, fungi and actinomyces PLFA were significantly positively correlated. On the whole, the season, layer and stand age had different effects on the nematode and microbial community, and the stand age had the least effect; the season, soil layer and stand age had more significant effect on microbe than nematode. Furthermore, the microenvironment of soil was improved and then declined gradually as the stand age increased in the same season as well as the soil layer.

LyciumbarbarumL.; soil nematode community; phospholipid fatty acid; ecological index; soil physicochemical characteristics

10.6041/j.issn.1000-1298.2016.09.024

2016-03-22

2016-04-11

國(guó)家自然科學(xué)基金項(xiàng)目(41261080)和寧夏自治區(qū)環(huán)保專項(xiàng)

張俊華(1977—)，女，副研究員，主要從事土壤質(zhì)量提升研究，E-mail: zhangjunhua728@163.com

S154.3； S154.5

A

1000-1298(2016)09-0161-10