李奇松 雷衛(wèi)星 劉江西 朱捷文 史凌珊 蔡普默 張見明 賈小麗
摘要:【目的】分析間作麥冬對(duì)春季茶園土壤養(yǎng)分、酶活性和微生物群落結(jié)構(gòu)的影響,探討不同種植模式條件下,茶園土壤環(huán)境、微生物群落間的互作機(jī)制,為茶園間作模式提供理論依據(jù)?!痉椒ā恳陨降靥萏锊鑸@為研究對(duì)象,通過(guò)16S rDNA高通量測(cè)序技術(shù)等,分析茶樹單作、茶樹—麥冬間作及茶園空地土壤(CK)的土壤養(yǎng)分含量、土壤酶活性及細(xì)菌群落結(jié)構(gòu)多樣性與豐富度差異?!窘Y(jié)果】相對(duì)于單作,間作麥冬能顯著提高茶園土壤含水量與有機(jī)質(zhì)、速效氮、速效磷和速效鉀含量(P<0.05,下同),以及脲酶、蛋白酶、纖維素酶和酸性磷酸酶活性,而pH無(wú)明顯變化。相對(duì)于單作和CK,間作麥冬對(duì)茶園土壤細(xì)菌群落的多樣性和豐富度無(wú)明顯影響,但群落結(jié)構(gòu)發(fā)生顯著變化;其土壤變形菌門(Proteobacteria)、放線菌門(Actinobacteria)和芽單胞菌門(Gemmatimonadetes)的相對(duì)豐度顯著提高,而綠彎菌門(Chloroflexi)的相對(duì)豐度顯著降低。相關(guān)分析結(jié)果表明,變形菌門和放線菌門與土壤速效營(yíng)養(yǎng)、有機(jī)質(zhì)和土壤相關(guān)酶呈顯著正相關(guān);芽單胞菌門與速效氮、速效磷呈顯著正相關(guān);綠灣菌門與有機(jī)質(zhì)呈顯著負(fù)相關(guān)。LEfSe分析結(jié)果表明,變形菌門中的根瘤菌目(Rhizobiales)、黃單胞菌目(Xanthomonadales)、羅丹諾桿菌科(Rhodanobacteraceae)、褚氏桿菌屬(Chujaibacter)、伯克氏菌科未分類菌屬(unidentified_Burkholderiaceae),以及放線菌門中的放線菌門未分類菌綱(unidentified_ Actinobacteria)為間作茶園土壤樣本的標(biāo)志性微生物,且相對(duì)豐度顯著高于CK和單作處理?!窘Y(jié)論】茶園間作麥冬可誘導(dǎo)土壤細(xì)菌群落結(jié)構(gòu)發(fā)生變化,能富集更多參與土壤營(yíng)養(yǎng)循環(huán)和拮抗病原菌的有益細(xì)菌,有利于提高土壤養(yǎng)分供給能力和茶樹的抗病性。
關(guān)鍵詞: 間作;細(xì)菌多樣性;微生物群落結(jié)構(gòu);茶園;高通量測(cè)序
中圖分類號(hào):S154? ? ? ? ? ? ? ? ? ? ? ? ? ? ?文獻(xiàn)標(biāo)志碼: A 文章編號(hào):2095-1191(2021)12-3366-09
Effects of intercropping Ophiopogon japonicus into tea plantation on its soil physicochemical properties and
microbial community structure
LI Qi-song1,2, LEI Wei-xing1, LIU Jiang-xi1, ZHU Jie-wen1, SHI Ling-shan1,
CAI Pu-mo1, ZHANG Jian-ming1, JIA Xiao-li1,2 *
(1College of Tea and Food Science, Wuyi University, Wuyishan,F(xiàn)ujian 354300, China; 2Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring/College of Life Sciences,F(xiàn)ujian
Agriculture and Forestry University, Fuzhou? 350002, China)
Abstract:【Objective】The effects of Ophiopogon japonicus intercropping with tea plantation in springon soil nu-trient, enzyme activity and microbial community structure were analyzed to study the interaction mechanism between soil environment and microorganism under different culture mode conditions, and provide theoretical basis for intercropping practice of tea plantation. 【Method】The tea plantation located at mountain terrace was used as the research objective to analyze the nutrient content, enzyme activity, bacterial community structure and diversity in soilunder tea monoculture, tea-O. japonicus intercropping and tea plantation soil(CK) by using 16S rDNA high-throughput sequencing technology. 【Result】Compared to monoculture, O. japonicus intercropping significantly increased soil water content, organic matter, available nitrogen(N), available? phosphorus(P), available potassium(K), urease, protease, cellulase and acid phosphatase(P<0.05,the same below), while pH was not evidently changed. The diversity and richness of soil bacterial community in tea plantation were not greatly influenced by intercropping as compared with that of monoculture and? CK, whereas the community structure was significantly changed. The relative abundances of Proteobacteria, Actinobacteria and Gemmatimonadetes were significantly increased in the intercropping treatment, while Chloroflexi was significantly decreased. The correlation analysis showed that Proteobacteria and Actinomycetes were significantly positively correlated with the soil available nutrients, soil organic matter and enzymes;Gemmatimonadetes were significantly positively correlated with available N and available P;Chloroflexi had negative correlation with soil organic matter. LEfSe analysis results showed that Rhizobiales, Xanthomonadales, Rhodanobacteraceae, Chujaibacter and unidentified Burkholderiaceae from Proteobacteria,and unidentified Actinobacteria from Actinobacteria were the biomark microorganisms in soil of intercropping tea plantation, and their abundance were significantly higher than that of CK and monoculture treatment. 【Conclusion】Intercropping O. japonicus in tea plantation can alter the community structure of soil bacteria and enrich more beneficial bacteria that involve in nutrient cycling and antagonistic pathogens, which is conducive to improve soil nutrient supply capacity and tea disease resistance.
Key words: intercropping;bacterial diversity;microbial community structure; tea plantation; high-throughput sequencing
Foundation item: Fujian Natural Science Foundation (2020J05217); Project of the Central Government Guided Local Science and Technology Development(2019L3012); Project of Fujian Young and Middle-aged Teachers Education Research(JAT190787); Open Fund Project of Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring(NYST-2019-02)
0 引言
【研究意義】茶樹是多年生常綠木本植物,是我國(guó)南方地區(qū)重要的特色經(jīng)濟(jì)作物。近年來(lái),隨著種植時(shí)間的推移,單一化栽培帶來(lái)的茶園土壤生態(tài)系統(tǒng)失衡問(wèn)題日益凸顯(Arafat et al.,2017)。一方面,南方地區(qū)地形崎嶇,多為山地,茶樹多采用梯田種植,同時(shí)降水量大且不均勻,實(shí)際生產(chǎn)中極少種植護(hù)坡植物,造成茶園土壤中鈣、鎂、鉀等堿基離子嚴(yán)重流失,進(jìn)而導(dǎo)致水體污染和土壤酸化;另一方面,茶樹自毒分泌物不斷累積導(dǎo)致土壤微生物群落失衡,植物病原菌群數(shù)量增加,茶園病害頻發(fā)(Arafat et al.,2017;王海斌等,2018)。間作是一種可持續(xù)的耕作方式,能有效提高農(nóng)田的生物多樣性,修復(fù)和維持土壤微生物群落結(jié)構(gòu)和功能多樣性,抑制田間雜草和病蟲害(林文雄和陳婷,2019)。麥冬是多年生耐陰耐旱的常綠草本藥用植物,有一定的經(jīng)濟(jì)價(jià)值。將麥冬間作于茶園梯面和梯壁上,具有提高茶園生物多樣性水平,減少土壤及養(yǎng)分流失和抑制茶園雜草的潛力(李洋洋等,2011)。因此,探討間作麥冬對(duì)茶園土壤微生物群落結(jié)構(gòu)、土壤養(yǎng)分和土壤酶活性的影響,闡明茶樹—土壤環(huán)境—微生物之間的互作機(jī)制,可為茶園復(fù)合配置提供理論依據(jù),對(duì)建設(shè)可持續(xù)生態(tài)茶園具有重要意義?!厩叭搜芯窟M(jìn)展】近年來(lái),越來(lái)越多的學(xué)者認(rèn)為,對(duì)作物生長(zhǎng)發(fā)育及產(chǎn)量形成機(jī)制的研究應(yīng)回歸根際(Philippot et al.,2013)。間套作已被證實(shí)能對(duì)土壤微生物群落結(jié)構(gòu)及多樣性產(chǎn)生顯著影響,能提高有益菌群數(shù)量和減少病原微生物數(shù)量,對(duì)改良土壤環(huán)境和提高植物抗病能力具有積極作用(Li et al.,2014)。目前,關(guān)于茶園間作模式的研究主要集中在豆科植物間作和農(nóng)林間作等。茶園間作三葉草促進(jìn)了土壤可培養(yǎng)細(xì)菌的碳源代謝多樣性,改良茶園土壤理化性狀(徐華勤等,2008);大豆間作可增加茶園土壤中可培養(yǎng)細(xì)菌、真菌和放線菌的數(shù)量(韋持章等,2018),提高茶園土壤中有效氮含量,尤其是銨態(tài)氮含量,進(jìn)而影響茶葉主要理化成分的組成及茶葉的口感和香氣(Duan et al.,2019);間作豆科植物(大豆和紫云英)不僅能改善茶園土壤營(yíng)養(yǎng)環(huán)境,還能提高土壤中參與碳循環(huán)相關(guān)微生物的豐度,有利于促進(jìn)茶樹對(duì)旱澇的多重抗性(Wang et al.,2021)。對(duì)于農(nóng)林間作,Ma等(2017)研究發(fā)現(xiàn),間作板栗提高了茶園土壤養(yǎng)分的可用性和土壤酶活性,利于茶葉產(chǎn)量和質(zhì)量的提高;Zhang等(2021)比較了桂花—含笑—茶、含笑—茶和桂花—茶3種間作模式,發(fā)現(xiàn)桂花—含笑—茶間作模式最優(yōu),可有效提高茶園土壤中擬桿菌門和厚壁菌門的豐度,菌群的變化與茶園土壤營(yíng)養(yǎng)環(huán)境改善密切相關(guān)??梢姡g作模式具有緩解單一化茶樹栽培帶來(lái)的土壤微生態(tài)惡化的作用?!颈狙芯壳腥朦c(diǎn)】梯田茶園間作配置中,與豆科植物相比,麥冬為多年生低矮草本,不會(huì)影響茶園通風(fēng),具有一次種植產(chǎn)生長(zhǎng)期效益的特點(diǎn),可降低勞力成本;與農(nóng)林間作相比,麥冬能有效降低林下土壤水肥流失。系統(tǒng)了解茶園土壤微生物對(duì)麥冬間作的響應(yīng)機(jī)制,是維持茶葉產(chǎn)量和土壤養(yǎng)分可持續(xù)性的基本前提。然而,目前尚缺乏相關(guān)研究?!緮M解決的關(guān)鍵問(wèn)題】通過(guò)高通量測(cè)序技術(shù),分析茶樹與麥冬間作模式下土壤微生物群落結(jié)構(gòu)的變化,明確茶樹麥冬間作模式下土壤微生物群落結(jié)構(gòu)與土壤環(huán)境因子的相關(guān)性,為茶園間作模式的科學(xué)構(gòu)建提供理論支撐。
1 材料與方法
1. 1 研究區(qū)概況
試驗(yàn)在國(guó)家水土保持科技示范園(武夷學(xué)院)進(jìn)行(東經(jīng)118°00′35″,北緯27°44′25″),該地區(qū)屬中亞熱帶季風(fēng)濕潤(rùn)氣候區(qū),年平均日照時(shí)數(shù)1629.5 h,年平均降水量1926.9 mm,年平均氣溫18.3 ℃,有效積溫在5000 ℃以上,相對(duì)濕度在80%左右,適合茶樹生長(zhǎng)。茶園基礎(chǔ)土壤肥力(0~20 cm):pH 4.6,全氮0.61 g/kg,全磷0.37 g/kg,全鉀9.97 g/kg,有機(jī)質(zhì)12.36 g/kg。
1. 2 試驗(yàn)設(shè)計(jì)
供試茶樹均為6年樹齡的肉桂茶樹(Camellia sinensis L. Rougui)。茶園為梯田式,總面積為13.3 ha,大行間距為1.5 m,雙行單株條列式種植,小行距×株距為0.4 m×0.3 m。分別隨機(jī)設(shè)茶樹單作和茶樹—冬麥間作2個(gè)處理,每處理5個(gè)小區(qū)樣地,每小區(qū)樣地面積為5.0 m×20.0 m。麥冬于2018年3月6日種植于間作小區(qū)的梯面和梯壁(圖1),與茶樹最小距離為0.3 m,種植行株距為0.18 m×0.18 m。不同處理茶園的栽培管理措施保持一致。
1. 3 土壤樣品采集
于2019年4月25日進(jìn)行田間調(diào)查,麥冬株高為18.21 cm,單株葉片數(shù)83.59片,覆蓋度56.73%。按五點(diǎn)采樣法采集距茶樹主干15 cm,深度10~20 cm的土壤,將5個(gè)點(diǎn)的樣品均勻混合,每處理有3次重復(fù)。以茶園內(nèi)的空地土壤作為空白對(duì)照(CK)。每個(gè)土壤樣品分為兩部分,一部分儲(chǔ)存在-80 ℃用于提取土壤DNA,另一部分儲(chǔ)存在4 ℃用于測(cè)定土壤酶活性和土壤養(yǎng)分含量。
1. 4 土壤理化性質(zhì)及酶活性測(cè)定
土壤速效氮含量用堿解擴(kuò)散法測(cè)定,速效磷含量用磷鉬藍(lán)比色法測(cè)定,速效鉀含量用火焰原子吸收光譜法測(cè)定,土壤pH采用酸度計(jì)測(cè)定,土壤有機(jī)質(zhì)含量采用重鉻酸鉀—硫酸消化法測(cè)定(鮑士旦,2000)。參考關(guān)松蔭(1986)的方法測(cè)定脲酶、蛋白酶、轉(zhuǎn)化酶、纖維素酶、過(guò)氧化物酶、酸性磷酸酶和過(guò)氧化物酶等7種土壤酶的活性。
1. 5 土壤總DNA提取
采用BioFast Soil Genomic DNA Extraction Kit試劑盒(BioFlux,杭州,中國(guó))提取土壤總DNA,并以1%瓊脂糖凝膠電泳檢測(cè)其純度,再用NanoDrop 2000C Spectrophotometer(Thermo Scientific,馬薩諸塞州,USA)測(cè)定DNA濃度,質(zhì)量合格的DNA用于根際細(xì)菌群落高通量測(cè)序分析。
1. 6 16S rDNA高通量測(cè)序分析
采用Illumina Hiseq測(cè)序方法對(duì)茶園土壤微生物群落的豐度和結(jié)構(gòu)進(jìn)行評(píng)價(jià)。采用引物341F和806R對(duì)16S DNA中V3~V4區(qū)域進(jìn)行擴(kuò)增,檢測(cè)細(xì)菌的群落結(jié)構(gòu)與多樣性。使用TruSeq?DNA PCR-free Sample Preparation Kit試劑盒將純化的PCR產(chǎn)物進(jìn)行文庫(kù)構(gòu)建。經(jīng)過(guò)Qubit和Q-PCR驗(yàn)證文庫(kù)合格后,使用NovaSeq6000對(duì)DNA文庫(kù)進(jìn)行測(cè)序。測(cè)序數(shù)據(jù)通過(guò)Qiime V1.9.1去除平均質(zhì)量分?jǐn)?shù)低(Q<20)和長(zhǎng)度短(<100 bp)的低質(zhì)量序列,得到最終的有效數(shù)據(jù)(Effective Tags)。利用Uparse對(duì)所有樣本的全部Effective Tags進(jìn)行聚類,默認(rèn)以97%的一致性序列聚類成為OTUs。進(jìn)一步用Qiime V1.9.1中的blast方法與Unit(v7.2)數(shù)據(jù)庫(kù)對(duì)OTUs序列進(jìn)行物種注釋,獲得不同分類水平微生物豐度數(shù)據(jù)。
1. 7 統(tǒng)計(jì)分析
采用DPS 7.05進(jìn)行單因素方差分析(LSD test,P<0.05)。利用Qiime V1.9.1在OTU水平計(jì)算Alpha多樣性指數(shù)和構(gòu)建UPGMA樣本聚類樹。使用LEfSe(Line discriminant analysis effect size)分析不同樣本組間顯著差異的標(biāo)志性微生物。使用R軟件分析并制作稀釋曲線、NMDS圖和Spearman相關(guān)系數(shù)熱圖。
2 結(jié)果與分析
2. 1 麥冬間作對(duì)茶園土壤理化性質(zhì)和酶活性的影響
從表1可看出,茶園梯面和梯壁間作麥冬后,茶園土壤的含水量、有機(jī)質(zhì)、速效氮、速效磷、速效鉀含量均顯著高于單作(P<0.05,下同),其含水量、有機(jī)質(zhì)、速效鉀含量也顯著高于CK。單作茶園土壤有機(jī)質(zhì)含量顯著高于CK,但速效氮、速效磷和速效鉀含量與CK無(wú)顯著差異(P>0.05,下同)。不同處理間的土壤pH無(wú)顯著差異。除過(guò)氧化物酶和纖維素酶外,不同處理間其他5種土壤酶的活性變化趨勢(shì)一致,表現(xiàn)為間作>單作>CK。與單作處理相比,間作顯著提高了茶園土壤脲酶、蛋白酶、纖維素酶和酸性磷酸酶活性;與CK相比,單作茶樹顯著提高了脲酶和蛋白酶活性。
2. 2 間作麥冬對(duì)茶園土壤細(xì)菌群落多樣性影響
經(jīng)過(guò)高通量測(cè)序和Qiime V1.9.1質(zhì)控處理,9個(gè)土壤樣品共得到577276條有效序列,每個(gè)樣品平均有效序列為64142條。稀釋曲線可反映測(cè)序深度及合理性,也能反映樣本中物種的豐富程度。結(jié)果顯示,在測(cè)序數(shù)達(dá)到40000后曲線趨向平坦,說(shuō)明測(cè)序數(shù)據(jù)量漸進(jìn)合理,測(cè)序深度足夠滿足后續(xù)分析要求(圖2-A)。有效序列經(jīng)過(guò)聚類,間作處理得到3544個(gè)OTUs,單作處理獲得3574個(gè)OTUs,CK獲得3225個(gè)OTUs(圖2-B)。不同處理間共有的OTUs為2394個(gè),即不同處理間至少有66.98%的OTUs是共有的。分別有96.29%、88.27%、72.16%、54.62%、33.75%、4.88%的OTUs成功注釋到35門、46綱、102目、185科、388屬和192種。
由表2可知,樣本的文庫(kù)覆蓋度在99.0%以上,說(shuō)明注釋所獲得的種群數(shù)據(jù)基本能代表土壤細(xì)菌群落的真實(shí)情況。間作處理的菌群豐富度(物種數(shù)、Chao1指數(shù)、ACE指數(shù))和多樣性指數(shù)(香農(nóng)指數(shù)、辛普森指數(shù))均略高于單作處理,但未達(dá)到顯著水平。間作處理和單作處理的菌群豐富度和多樣性均顯著高于CK,說(shuō)明種植茶樹能提高土壤細(xì)菌多樣性和豐富度,但間作麥冬無(wú)法顯著改變茶園土壤的細(xì)菌群落多樣性和豐富度。
2. 3 茶園土壤細(xì)菌群落組成與群落結(jié)構(gòu)
為明確不同處理土壤細(xì)菌群落結(jié)構(gòu)的差異,對(duì)不同處理的土壤細(xì)菌群落結(jié)構(gòu)進(jìn)行非度量多維尺度NMDS和UPGMA聚類分析(圖3),結(jié)果表明,間作處理土壤微生物群落結(jié)構(gòu)顯著區(qū)別于單作處理和CK(圖3-A);與CK相比,單作處理和間作處理的土壤微生物群落結(jié)構(gòu)一致性更高(圖3-B),說(shuō)明種植茶樹可構(gòu)建茶樹特有的土壤細(xì)菌群落結(jié)構(gòu),間作麥冬進(jìn)一步影響了土壤細(xì)菌群落組成。
從門水平看,前十大菌門涵蓋了土壤樣品中超過(guò)95.37%的細(xì)菌,其中酸桿菌門(Acidobacteria)、變形菌門(Proteobacteria)、綠彎菌門(Chloroflexi)、放線菌門(Actinobacteria)為優(yōu)勢(shì)菌門,占比超過(guò)87.98%(圖3-B)。與CK相比,茶樹單作顯著降低土壤中酸桿菌門的相對(duì)豐度,提高變形菌門和擬桿菌門(Bacteroidetes)的相對(duì)豐度。與單作茶樹相比,間作麥冬茶園土壤中變形菌門、放線菌門和芽單胞菌門(Gemmatimonadetes)的相對(duì)豐度顯著提高,而綠彎菌門、擬桿菌門和疣微菌門(Verrucomicrobia)的相對(duì)豐度降低。
2. 4 不同處理間顯著性差異菌群
LEfSe分析可用于不同樣本組之間微生物群落的比較,能在組與組間獲取具有統(tǒng)計(jì)學(xué)顯著差異的標(biāo)志性微生物種類(Segata et al.,2011)。圖4結(jié)果顯示,當(dāng)LDA Score>4時(shí),不同處理間酸桿菌門、酸桿菌綱(Acidobacteriia)和酸桿菌目(Acidobacteriales)為CK樣本標(biāo)志性微生物,且相對(duì)豐度顯著高于單作和間作處理;單作茶園土壤樣本中,擬桿菌門、擬桿菌綱(Bacteroidia)、纖線桿菌科(Ktedonobactera-ceae)為標(biāo)志性微生物,且相對(duì)豐度顯著高于CK和間作處理;變形菌門、γ-變形菌綱(Gammaproteobacteria)、伯克氏菌科未分類菌屬(unidentified_Burkholderiaceae)、黃單胞菌目(Xanthomonadales)、羅丹諾桿菌科(Rhodanobacteraceae)、褚氏桿菌屬(Chujaibacter)、放線菌門、放線菌門未分類菌綱(unidentified_Actinobacteria)、根瘤菌目(Rhizobiales)為間作茶園土壤樣本標(biāo)志性微生物,且相對(duì)豐度顯著高于CK和單作處理。
2. 5 細(xì)菌群落結(jié)構(gòu)與土壤理化性質(zhì)的相關(guān)性
土壤環(huán)境變量與優(yōu)勢(shì)菌門的相關(guān)分析結(jié)果(圖5)表明,變形菌門、放線菌門、藍(lán)藻門與速效鉀、有機(jī)質(zhì)、含水量、脲酶、蛋白酶、纖維素酶、轉(zhuǎn)化酶、酸性磷酸酶、多酚氧化酶均呈顯著正相關(guān),綠灣菌門與有機(jī)質(zhì)呈顯著負(fù)相關(guān),芽單胞菌門與速效氮、速效磷呈顯著正相關(guān),硝化螺旋菌門(Nitrospirae)與速效鉀、含水量、轉(zhuǎn)化酶呈顯著負(fù)相關(guān)。
3 討論
植物多樣性已被證實(shí)能改變土壤生物區(qū)系的組成和功能(Eisenhauer et al.,2017)。間作是植物多樣性在農(nóng)業(yè)實(shí)踐中的具體應(yīng)用,有利于保持土壤微生態(tài)穩(wěn)定性和提高土壤養(yǎng)分利用率(Li et al.,2014)。土壤酶是土壤中重要的生物活性物質(zhì),與土壤物質(zhì)循環(huán)和養(yǎng)分供應(yīng)能力緊密相關(guān),是評(píng)價(jià)土壤肥力和土壤環(huán)境質(zhì)量的重要指標(biāo)(Dindar et al.,2015)。間作麥冬能否對(duì)茶園土壤環(huán)境產(chǎn)生影響還未知。據(jù)此,本研究對(duì)單作、間作茶園土壤理化性質(zhì)進(jìn)行分析,結(jié)果表明,間作麥冬能顯著提高茶園土壤的含水量、有機(jī)質(zhì)、速效氮、速效磷和速效鉀含量;同時(shí),其脲酶、蛋白酶、纖維素酶和酸性磷酸酶活性也顯著上升,與其他茶園間作體系相似(韋持章等,2018;Duan et al.,2019)。
茶園土壤酸化是茶樹種植中面臨的重要問(wèn)題。前人對(duì)不同茶園間作模式的研究中,部分學(xué)者發(fā)現(xiàn)間作不能顯著提高土壤pH(李艷春等,2019);而黎健龍等(2008)、邢瑤等(2020)研究發(fā)現(xiàn),茶園間作大豆和玉米后,將其秸稈還田后能顯著提高土壤有機(jī)質(zhì)和pH。本研究中,間作麥冬對(duì)茶園土壤pH未產(chǎn)生影響,但提高了土壤的有機(jī)質(zhì)含量。這可能與麥冬間作過(guò)程中,凋落的葉片和根系的不斷輸入,并被土壤纖維素酶降解有關(guān)。但本研究中麥冬間作的時(shí)長(zhǎng)僅為1年,因而對(duì)土壤pH的影響還不顯著,有待今后開展長(zhǎng)期定位試驗(yàn)進(jìn)行驗(yàn)證。綜合麥冬間作茶園土壤理化及酶活性結(jié)果,麥冬和茶樹間作下,地下部相互作用提高了土壤酶活性,促進(jìn)了土壤物質(zhì)循環(huán),改善了土壤的水肥條件。土壤酶主要來(lái)源于微生物,其活性與土壤微生物群落的變化密切相關(guān)(Dindar et al.,2015)。土壤細(xì)菌參與植物生長(zhǎng)發(fā)育中的營(yíng)養(yǎng)吸收、生長(zhǎng)調(diào)節(jié)和拮抗病原微生物等生態(tài)學(xué)過(guò)程(Lladó et al.,2017;Maron et al.,2018)。間作條件下,不同植物來(lái)源的根系分泌物能介導(dǎo)土壤中微生物群落結(jié)構(gòu)及功能發(fā)生變化(Li et al.,2018;Zhang et al.,2019)。間作種植模式常被認(rèn)為可提高土壤微生物群落多樣性(Li and Wu,2018;Zhang et al.,2019)。在本研究中,間作麥冬沒(méi)有顯著提高茶園土壤細(xì)菌群落多樣性指數(shù),但顯著改變了茶園土壤微生物群落,與小麥/西瓜(Yu et al.,2019)、馬鈴薯/玉米(伏云珍等,2020)、靈芝/茶樹(李艷春等,2019)等間作組合的研究結(jié)果相似??梢?,細(xì)菌多樣性水平是否發(fā)生變化可能取決于間作類型和土壤環(huán)境條件,而土壤生態(tài)系統(tǒng)功能多樣性主要取決于功能微生物群落組成而非分類多樣性(Chaparro et al.,2012;Lakshmanan et al.,2014)。
本研究發(fā)現(xiàn),與單作茶樹相比,間作麥冬茶園土壤中的變形菌門、酸桿菌門、放線菌門和芽單胞菌門的豐度顯著提高,而綠彎菌門的豐度顯著降低。有報(bào)道表明,變形菌門是富營(yíng)養(yǎng)細(xì)菌,常在氮營(yíng)養(yǎng)較高的土壤環(huán)境中聚集(彭玉嬌等,2020);綠彎菌門生長(zhǎng)緩慢,通常聚集于低營(yíng)養(yǎng)環(huán)境(Nu?bel et al.,2001)。放線菌門廣泛分布于土壤中,在纖維素分解和腐殖質(zhì)形成中起到至關(guān)重要的作用(Ventura et al.,2007)。Lin等(2019)報(bào)道稱,有機(jī)肥的使用顯著增加了酸桿菌門和芽單胞菌門的相對(duì)豐度。由此可見,麥冬—茶樹間作體系中綠彎菌門減少的同時(shí)變形菌門、放線菌門和芽單胞菌門增加,從而促進(jìn)土壤養(yǎng)分循環(huán)和纖維素降解,與土壤速效養(yǎng)分和有機(jī)質(zhì)含量上升密切相關(guān)。土壤環(huán)境變量與優(yōu)勢(shì)菌門的相關(guān)分析進(jìn)一步證實(shí)了這一結(jié)果,即變形菌門和放線菌門與土壤速效營(yíng)養(yǎng)、有機(jī)質(zhì)和營(yíng)養(yǎng)循環(huán)相關(guān)酶呈顯著正相關(guān);芽單胞菌門與速效氮、速效磷呈顯著正相關(guān);綠灣菌門與有機(jī)質(zhì)呈顯著負(fù)相關(guān)。
根際促生菌在農(nóng)業(yè)生態(tài)系統(tǒng)中具有重要作用,可以抑制植物土傳病原微生物,提高速效養(yǎng)分濃度和促進(jìn)植物生長(zhǎng)(Khatoon et al.,2020)。在本研究中,LEfSe分析表明,變形菌門中的根瘤菌目、黃單胞菌目、羅丹諾桿菌科、褚氏桿菌屬和伯克氏菌科未分類菌屬,以及放線菌門中的放線菌門未分類菌綱為間作茶園土壤樣本標(biāo)志性微生物,且豐度顯著高于空白土壤和單作茶樹處理。根瘤菌目和褚氏桿菌屬與固氮、氨氧化和硝化作用有關(guān)(Cloutier et al.,2021)。伯克氏菌廣泛存在于健康土壤中,與植物生長(zhǎng)密切相關(guān),能有效控制土壤病害的發(fā)生,部分菌種具有解磷能力(Bontemps et al.,2010)。黃單胞菌目和所屬的羅丹諾桿菌科,以寡養(yǎng)單胞菌屬(Stenotrophomonas)為主(占菌科相對(duì)豐度的92%),該菌屬不僅能促進(jìn)植物生長(zhǎng),而且能代謝土壤中大量有機(jī)化合物(Robert et al.,2009)。放線菌門參與土壤中纖維素和腐殖質(zhì)代謝。綜上所述,麥冬間作茶樹可誘導(dǎo)土壤細(xì)菌群落結(jié)構(gòu)發(fā)生變化,富集更多參與物質(zhì)循環(huán)和拮抗植物病原菌的有益細(xì)菌。
4 結(jié)論
間作麥冬對(duì)茶園土壤細(xì)菌群落的多樣性和豐富度無(wú)明顯影響,但可誘導(dǎo)土壤細(xì)菌群落結(jié)構(gòu)發(fā)生變化,能富集更多參與土壤營(yíng)養(yǎng)循環(huán)和拮抗植物病原菌的有益細(xì)菌,有利于提高土壤養(yǎng)分供給能力和茶樹抗病性。
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(責(zé)任編輯 王 暉)