黃土區(qū)溝道泥沙微生物群落變化特征及其影響因素

侯芳彬,王 蕊,Salman Ali,高 鑫,郭勝利,3*

黃土區(qū)溝道泥沙微生物群落變化特征及其影響因素

侯芳彬1,王 蕊1,Salman Ali2,高 鑫1,郭勝利1,3*

(1.西北農(nóng)林科技大學(xué)水土保持研究所,黃土高原土壤侵蝕與旱地農(nóng)業(yè)國家重點(diǎn)實驗室,陜西 楊凌 712100；2.西北農(nóng)林科技大學(xué)資源與環(huán)境學(xué)院,陜西 楊凌 712100；3.中國科學(xué)院、水利部水土保持研究所,陜西 楊凌 7 12100)

在黃土高原溝壑區(qū),通過16S rRNA基因片段和ITS高通量測序,研究溝道泥沙中細(xì)菌和真菌群落在上-中-下游的變化特征.結(jié)果表明:與溝頭相比,把口站的細(xì)菌群落中擬桿菌門(Bacteroidetes)與厚壁菌門(Firmicutes)的相對豐度分別增加6.6%和10.5%,而變形菌門(Proteobacteria)的相對豐度降低15.1%;真菌群落中擔(dān)子菌門(Basidiomycota)的相對豐度增加7.7%,而子囊菌門(Ascomycota)降低30.2%;泥沙中黏粒含量與細(xì)菌豐富度(Chao1指數(shù))和多樣性(Shannon指數(shù))之間顯著負(fù)相關(guān)(<0.05),與真菌的豐富度和多樣性無顯著相關(guān)性;細(xì)菌和真菌群落多樣性和豐富度的空間差異與SOC、Olsen-P的變化有關(guān)(<0.05).因此,泥沙中顆粒組成物和養(yǎng)分含量可能是影響溝道微生物群落變化的主要因素.

溝道泥沙；空間重分布；細(xì)菌；真菌；顆粒組成

陸地表面每年有高達(dá)75Gt的土壤發(fā)生遷移和重新分布,其中70%在陸地表面或相鄰流域低洼處沉積[1-3].土壤的重新分布極大地影響了陸地生態(tài)系統(tǒng)的凈初級生產(chǎn)力[4-6]以及空間異質(zhì)性[3,7-10].土壤中棲息的微生物是陸地表面中最豐富與活躍的一類生物[11-13],是生物地球化學(xué)循環(huán)的重要驅(qū)動力[14].地表物質(zhì)的側(cè)向移動使得地貌[15-16]、土壤結(jié)構(gòu)[10]、土壤養(yǎng)分[17-20]、微生物特性[21]等發(fā)生變化.

黃土高原溝壑區(qū)總面積3.56萬km2,水土流失面積為3.06萬km2,地形支離破碎,溝壑縱橫,大體分為塬面、坡地和溝道,坡面和溝道合稱為溝壑,例如高原溝壑區(qū)齊家川示范區(qū)內(nèi)溝壑的面積可以占到56%以上[22].溝道不僅是坡面泥沙進(jìn)入河流和湖泊的主要通道,也是泥沙沉積的主要區(qū)域.黃土高原溝道系統(tǒng)的產(chǎn)沙量高達(dá)整個黃土高原總侵蝕量的80%,坡面泥沙經(jīng)過運(yùn)移進(jìn)入溝道系統(tǒng)[23-24],使得溝道中泥沙含沙量大于1000kg/m3 [25].溝道不僅是坡面泥沙進(jìn)入河流和湖泊的主要通道,也是泥沙沉積的主要區(qū)域.黃土高原溝道系統(tǒng)的產(chǎn)沙量高達(dá)整個黃土高原總侵蝕量的80%,坡面泥沙經(jīng)過運(yùn)移進(jìn)入溝道系統(tǒng)[23-24],使得溝道中泥沙含沙量大于1000kg/m3[26].泥沙遷移過程中輕(低密度)和細(xì)(黏粒和粉粒)的顆粒優(yōu)先發(fā)生運(yùn)移[25,27-28],更容易遷移到更遠(yuǎn)的地方[3,29-30].同時,泥沙顆粒的遷移、分布對土壤有機(jī)碳礦化和積累具有顯著影響[5-6,31-32].

微生物是影響陸地表面生物地球化學(xué)循環(huán)的重要因素,已有研究表明微生物群落在坡位間存在顯著差異[21,33],這主要是與坡位間底物供應(yīng)和水分條件有關(guān)[21].Mohammadi等發(fā)現(xiàn)下坡位較高的土壤微生物量和活性與其較高的土壤水分和碳氮底物供應(yīng)有關(guān)[34].坡面侵蝕-沉積區(qū)的土壤微生物量以及酶活性對土壤有機(jī)碳含量、濕度等因素的敏感程度不同[35-36].因此,侵蝕地形對水分和底物產(chǎn)生的變化會對坡面土壤微生物群落產(chǎn)生顯著影響,但是,目前對溝道重分布過程中微生物群落分布的研究不清楚.因此,本文探討的溝道泥沙微生物群落變化及其影響因素將有助于理解溝道泥沙的遷移分布對陸地生態(tài)系統(tǒng)物質(zhì)循環(huán)的影響.

本研究選擇黃土高原溝壑區(qū)典型治理小流域,基于該流域主溝道,從王東村到把口站等間距采集泥沙樣品,利用高通量測序等技術(shù)獲取不同位置泥沙中微生物群落的信息,分析泥沙中細(xì)菌和真菌群落的變化特征;在此基礎(chǔ)上探討了溝道中微生物群落變化的影響因素.

1 材料與方法

1.1 研究區(qū)概況

位于陜甘交界處的長武縣王東溝小流域 (東經(jīng)107°40′30″~107°42′30″,北緯35°12′~35°16′) (圖1).該流域為“陜西長武農(nóng)田生態(tài)系統(tǒng)國家野外科學(xué)觀測研究站”的所在地,是我國重點(diǎn)水土流失治理小流域.土地面積8.3km2,塬、坡、溝約各占土地面積的1/3(27.7%36.4%35.9%)[37],溝壑密度為2.78km/km2,屬典型的黃土高原溝壑類型區(qū).塬面海拔1220m,從塬面到溝底的最大高差為280m.屬于大陸季風(fēng)氣候,年均氣溫9.1℃,310℃積溫3029℃,多年平均雨量584mm,但季節(jié)性分布不均,降雨的60%以上都集中在6~9月,多以短期暴雨形式出現(xiàn).該流域的主要土壤類型為黃墡土和黑壚土,母質(zhì)為深厚的中壤質(zhì)馬蘭黃土,土層深厚,土質(zhì)疏松,質(zhì)地均一,可蝕性高,為本實驗的開展提供了條件.

1.2 溝道泥沙樣品的采集

2018年5月中旬,沿王東溝流域主溝道(全長6.3km)等間距采樣,間距2.1km左右(圖1);選定的點(diǎn)依次為王東村(上游)、范家梁(中游)、杜家坪(中游)和把口站(下游).在溝道中隨機(jī)采樣,重復(fù)3次,共12個樣品,考慮到溝道中的泥沙層較淺,每個采樣點(diǎn)取0~10cm的泥沙樣本.

圖1 王東溝流域采樣位置示意

各樣品混合均勻后分成兩份:一份在室外置于4℃的保溫箱內(nèi),之后立即轉(zhuǎn)移至試驗室?20℃的冷藏箱保存,以用于高通量測序;另一份樣品風(fēng)干,用于測試土壤顆粒、養(yǎng)分等理化指標(biāo).

1.3 DNA提取和高通量測序

采用Fast DNA SPIN Kit for soil試劑盒和MP FastPrep-24核酸提取儀提取土壤中的DNA.通過1%瓊脂糖凝膠電泳和分光光度法(260nm/280nm處的光密度比)檢查提取的DNA質(zhì)量.將所有提取的DNA樣品儲存在?20℃下用于進(jìn)一步分析.根據(jù)測序區(qū)域的選擇,使用帶 Barcode 的特異引物進(jìn)行PCR擴(kuò)增:338F (5'-ACTCCTACGGGAGGCAG-CAG-3')和806R(5'-GGACTACHVGGGTWTCTAAT-3')[38]擴(kuò)增細(xì)菌16S rRNA基因的V3-V4區(qū)域,同時使用ITS1 (5'-CTTGGTCATTTAGAGGAAGTAA- 3')和ITS2(5'-GCTGCGTTCTTCATCGATGC-3')引物通過PCR擴(kuò)增真菌ITS基因區(qū)域[39].

從2%瓊脂糖凝膠中提取擴(kuò)增子,并使用AxyPrep DNA凝膠提取試劑盒(Axygen Biosciences, Union City, CA, USA).根據(jù)制造商的說明純化,然后使用GeneJET (Thermo Scientific公司)定量.將純化的擴(kuò)增子以等摩爾量合并,然后根據(jù)標(biāo)準(zhǔn)方案在Illumina MiSeq平臺上進(jìn)行配對末端測序(2′300).

首先使用QIIME包 (Quantitative Insights Into Microbial Ecology, v1.2.1)進(jìn)行高質(zhì)量序列的提取.之后使用以下標(biāo)準(zhǔn)對原始FASTQ文件進(jìn)行解復(fù)用和質(zhì)量過濾: (i)在10bp滑動窗口上獲得平均質(zhì)量分?jǐn)?shù)<20的任何位點(diǎn)截短300bp,并丟棄短于50bp的讀數(shù); (ii)精確條形碼匹配,引物匹配中的兩個核苷酸錯配,并除去含有模糊特征的讀數(shù); (iii)僅根據(jù)它們的重疊序列組裝長于10bp的重疊序列.無法組裝的讀數(shù)被丟棄.使用UCLUST將唯一序列集分類為具有97%相似性閾值的操作分類單位(OTU).使用Usearch (版本8.0.1623)鑒定并除去嵌合序列.使用UCLUST對Silva119 16S rRNA數(shù)據(jù)庫分析每個16S rRNA和ITS基因序列的分類,使用90%的置信度閾值.將細(xì)菌和真菌的原始讀數(shù)共同存入NCBI序列讀取存檔(SRA)數(shù)據(jù)庫.

1.4 理化性質(zhì)分析

風(fēng)干土樣磨細(xì),一部分過2mm篩(10目),分析土壤顆粒組成(MS-2000馬爾文激光粒度儀)和pH值 (在土壤與溶液(1mol/L KCl)之比為1 : 2.5 (/)的上清懸浮液中測量).一部分過0.25mm篩(65目),測定樣品中的有機(jī)碳含量(H2SO4-K2Cr2O7外加熱法[40])和速效磷(Olsen法[41-42]).

1.5 數(shù)據(jù)分析方法

采用SAS (8.0, SAS Inst. 1998) 軟件GLM程序包對溝道不同處理間的理化性質(zhì)和微生物群落的Alpha、Beta多樣性指數(shù)進(jìn)行方差分析(ANOVA),當(dāng)F檢驗顯著時,再對四個位置處理間均值進(jìn)行比較 (Duncan)檢驗(<0.05).通過Sigmaplot (12.5)軟件繪制四個處理排名前十的微生物群落在門、綱、目、科、屬水平的相對豐度圖.采用R語言(3.5.1)對微生物數(shù)據(jù)進(jìn)行整理,通過ape包和ggplot2包繪制主坐標(biāo)分析圖 (Principal Co-ordinates Analysis; PCoA),了解不同處理間門水平(phylum)上細(xì)菌和真菌群落的差異;通過vegan包繪制UPGMA聚類樹(Unweighted Pair-group Method with Arithmetic Mean);通過vegan包和packfor包繪制冗余分析圖(Redundancy Analysis; RDA).

2 結(jié)果與分析

2.1 溝道泥沙理化性狀的變化特征

溝道泥沙顆粒的理化性狀存在顯著的空間差異(表1).溝道上游 (王東村) 泥沙的粉粒含量為68.4%,分別較中游(59.0%)、下游(53.3%)高出16%、28%.泥沙中黏粒含量變化最為明顯,下游較上游增加54%(下游.上游:42.3%. 27.4%);砂粒含量無差異.土壤有機(jī)碳(SOC)含量從7.4g/kg (上游)增加到9.1g/kg (下游),增加幅度近23%.速效磷(Olsen-P)的變化趨勢與SOC相似,與上游(17.3mg/kg)相比,中游(22.8mg/kg)和下游(27.2mg/kg)分別增加24.1%和36.4%.

表1 溝道泥沙顆粒理化性狀含量

注:同行不同字母表示空間位置變化差異性顯著(<0.05).

2.2 不同空間位置細(xì)菌和真菌群落的組成差異

溝道泥沙樣本中細(xì)菌和真菌群落分別獲得34186和38902個高質(zhì)量序列.從上游到下游,泥沙細(xì)菌群落的OTU數(shù)顯著降低了23.2%,而真菌群落則呈現(xiàn)先降低后增加的趨勢,且無顯著性差異.溝道不同空間位置泥沙細(xì)菌的Chao1指數(shù)與Shannon指數(shù)具有顯著差異(0.05)(表2),均表現(xiàn)為:上游(王東村)>中游(范家梁、杜家坪)>下游(把口站),表明從上游到下游,細(xì)菌群落的豐富度與多樣性分別降低13.5%和10.4%.而真菌群落的Chao1指數(shù)與Shannon指數(shù)從王東村到把口站增加9.0%和5.4%,但均未達(dá)到顯著水平.

表2 溝道泥沙微生物群落豐富度、多樣性和OTU數(shù)(細(xì)菌和真菌有效序列分別為34186和38902條)

注:同行不同字母表示空間位置變化差異性顯著(<0.05).

2.3 溝道泥沙細(xì)菌和真菌群落的變化特征

溝道內(nèi)不同位置泥沙細(xì)菌和真菌群落在門、綱、目、科、屬水平上的相對豐度存在一定差異 (圖2、3).在細(xì)菌群落的門水平上,變形菌(Proteobacteria)、擬桿菌(Bacteroidetes)和厚壁菌(Firmicutes)在溝道不同處理中均為優(yōu)勢菌門,其中變形菌門的相對豐度降低了15.1%,但未達(dá)到顯著水平;擬桿菌門和厚壁菌門較上游相比,相對豐度分別增加了6.6%和10.5%,但均未達(dá)到顯著水平(圖2a).綱水平上,-變形菌綱 (Gammaproteobacteria)在溝道不同位置的相對豐度占比最高且始終保持在35%以上.下游與上游相比,擬桿菌綱(Bacteroidia)增加幅度為6% (18.6%24.2%);-變形菌綱 (Alphaproteobacteria) 的相對豐度降低近3倍(19.1%6.9%);梭狀芽孢桿菌綱 (Clostridia) 的相對豐度增加近3倍 (3.3%9.4%) (圖2b).科水平上,把口站處黃單胞菌科(Xanthomonadaceae)和甲殼蟲菌科(Chitinophagaceae)的相對豐度均較上-中游顯著降低(0.05) (圖2d).

圖3 溝道不同處理在門,綱,目,科,屬水平上真菌群落的相對豐度 (P < 0.05)

真菌群落中,子囊菌門(Ascomycota)、擔(dān)子菌門(Basidiomycota)和羅茨菌門(Rozellomycota)為優(yōu)勢菌門且均存在較大的變異性.子囊菌門在下游的相對豐度僅為上游相對豐度的41%(21.3%51.5%).與之相反,下游擔(dān)子菌門的相對豐度為上游的2.18倍(14.2%6.5%),羅茨菌門為上游的1.62倍(3.1%1.2%).壺菌門(Chytridiomycota)和鞭毛菌門(Mortierellomycota)在溝道不同位置中有所差異,但平均相對豐度較小,分別為1.5%和1.1%(圖3a).另外,除綱水平上座囊菌(Dothideomycetes)的相對豐度較上-中游顯著降低外(0.05) (圖3b),真菌群落在其它水平上均無顯著差異.

2.4 細(xì)菌和真菌群落的Beta多樣性分析及RDA分析

采用PCoA分析對溝道上-中-下游的泥沙樣本進(jìn)行分析,結(jié)果表明溝道微生物群落在分析結(jié)果中具有一定的空間差異(圖4a、4b).細(xì)菌群落排序軸第1軸的貢獻(xiàn)率為41.3%,排序軸第2軸的貢獻(xiàn)率為15.6%,前2軸累計解釋了變量的57.0%.其中,第一主成分軸上王東村、范家梁與杜家坪三點(diǎn)聚類明顯,但與把口站差距明顯.真菌群落排序軸第1軸的貢獻(xiàn)率為21.1%,排序軸第2軸的貢獻(xiàn)率為17.2%,前2軸累計解釋了變量的38.3%.王東村、范家梁、杜家坪和把口站在第一與第二成分軸上均有差距.

構(gòu)建UPGMA聚類樹對溝道樣品進(jìn)行聚類分析,研究四個處理間的相似性.細(xì)菌群落的UPGMA聚類樹表明:除杜家坪2外,把口站與其他3個處理的細(xì)菌群落區(qū)系明顯屬于兩個不同的組(圖4a);但是,真菌群落的UPGMA聚類樹顯示4個處理間的真菌群落區(qū)系區(qū)分不明顯(圖4b).

采用RDA分析對各環(huán)境因子(黏粒、粉粒、SOM和Olsen-P)與不同處理的泥沙微生物群落組成進(jìn)行相關(guān)性分析(圖5a、5b).結(jié)果顯示細(xì)菌和真菌群落的分布與粒級含量、SOM和Olsen-P有較強(qiáng)的相關(guān)性.此外,在微生物群落,尤其是細(xì)菌群落的RDA分析中能夠區(qū)分出把口站和上-中游兩個明顯的地理群.

圖5 溝道泥沙細(xì)菌和真菌群落在不同處理中的RDA分析

3 討論

3.1 溝道泥沙顆粒分布的空間變化對微生物群落的影響

泥沙或土壤是微生物的棲息地,隨著泥沙或土壤的運(yùn)動,微生物群落會產(chǎn)生相應(yīng)變化[43].從王東村(上游)到把口站(下游),溝道泥沙中黏粒比例增加,粉粒含量降低(表1);細(xì)菌和真菌群落的豐富度和多樣性也存在差異(表2).通過粒級含量與Alpha多樣性指數(shù)的回歸分析發(fā)現(xiàn):黏粒含量與細(xì)菌Chao1、Shannon指數(shù)顯著負(fù)相關(guān)(<0.05);粉粒含量與細(xì)菌Chao1、Shannon指數(shù)顯著正相關(guān)(<0.05).這些結(jié)果表明溝道細(xì)菌群落的空間分布差異可能與顆粒分布的空間變化有關(guān).溝道內(nèi)泥沙顆粒在遷移的過程中不斷分選,黏粒含量不斷提高,非毛管孔隙比例增加,使得細(xì)菌在該孔隙中活動困難[44],因而把口站處細(xì)菌群落的豐富度和多樣性降低.除此之外,Yang等[45]在研究天然草地時發(fā)現(xiàn)與0.25~1mm和<0.25mm的顆粒相比, 2~4mm和1~2mm顆粒的細(xì)菌多樣性更大;Sessitsch等[46]發(fā)現(xiàn)細(xì)砂、淤泥和黏土中相關(guān)細(xì)菌種群的組成、結(jié)構(gòu)主要受粒徑影響,細(xì)菌多樣性呈現(xiàn)隨粒徑減小而增加的趨勢.

與細(xì)菌不同,黏粒含量與真菌Chao1、Shannon指數(shù)顯著正相關(guān)(<0.05);粉粒含量與真菌Chao1、Shannon指數(shù)顯著負(fù)相關(guān)(<0.05).與細(xì)菌群落相關(guān)結(jié)果相比,泥沙粒級與真菌群落豐富度、多樣性變化的相關(guān)性較弱,這是由于真菌菌絲的生長形式使它們比細(xì)菌具有更強(qiáng)的轉(zhuǎn)移營養(yǎng)物和克服不良生長條件的能力[47-49].

3.2 溝道泥沙中微生物群落與養(yǎng)分含量的相關(guān)性

微生物群落的動態(tài)變化與侵蝕導(dǎo)致的土壤養(yǎng)分含量的改變密切相關(guān)[9,50-55].泥沙顆粒向下游分選的過程中黏粒含量比例增加,SOC、Olsen-P含量也有所提高.由RDA分析,SOC和Olsen-P沿溝道上-中-下游的含量變化是影響細(xì)菌與真菌群落組成和活性的因素(圖5a、5b).SOC、Olsen-P與細(xì)菌豐富度、多樣性顯著相關(guān)(<0.05),表明SOC和Olsen-P能夠影響細(xì)菌群落的組成.根據(jù)微生物營養(yǎng)對策分類,富營養(yǎng)菌可利用活性較高的碳源快速生長,寡養(yǎng)菌對貧瘠養(yǎng)分條件抗性能力更強(qiáng)[56].本研究中變形菌門[57]和擬桿菌門[56]均屬于富養(yǎng)菌,因此這兩種菌在養(yǎng)分含量豐富的把口站相對豐度較高.

真菌群落同樣與土壤養(yǎng)分含量密切相關(guān).SOC、Olsen-P與真菌豐富度、多樣性正相關(guān)(<0.05).這可能與真菌具有良好的分解能力有關(guān):子囊菌門和擔(dān)子菌門能夠分解大多數(shù)有機(jī)物質(zhì)和植物殘骸[58-59],因而溝道真菌群落的豐富度和多樣性與養(yǎng)分含量有關(guān).另外,PCoA分析中(圖4b),隨養(yǎng)分含量的增加,不同處理間真菌群落差距明顯也可以印證這一點(diǎn).另外,Trivedi等[50]研究發(fā)現(xiàn)侵蝕區(qū)SOC的流失能夠抑制土壤微生物群落(特別是真菌)的快速生長;Thormann[51]發(fā)現(xiàn)門水平上不同真菌群落在泥炭地碳循環(huán)中發(fā)揮重要作用.因此,研究認(rèn)為細(xì)菌和真菌群落在溝道泥沙中的動態(tài)變化與養(yǎng)分含量變化有關(guān).

3.3 溝道的厭氧環(huán)境對微生物群落的影響

厭氧環(huán)境能夠影響細(xì)菌群落的豐富度和多樣性[55].由PCoA分析和UPGMA聚類樹,把口站與王東村、范家梁、杜家坪3個處理差距明顯(圖4a),表明把口站由于長期積水產(chǎn)生的厭氧環(huán)境影響了細(xì)菌群落.由圖2b,-變形菌綱(好氧菌)[60]在把口站的相對豐度較其他3個處理降低了近2/3(6.9% vs18.0%),擬桿菌綱(厭氧菌)[61]則增加6%(24.2% vs. 18.6%).由此,厭氧環(huán)境使把口站與上-中游細(xì)菌群落差異明顯.

此外,結(jié)合王東溝流域塬面與坡面的已有研究成果,溝道Chao1指數(shù)(2408.2)和Shannon指數(shù)(8.45)顯著低于塬面(4732.0, 10.09)和坡面(4589.4, 9.84) (< 0.05)[21,33],表明細(xì)菌群落的Alpha多樣性指數(shù)在塬-坡-溝的地形變化中呈降低趨勢.塬面和坡面的優(yōu)勢菌門中除變形菌(兼性厭氧菌)外,酸桿菌和放線菌均為好氧菌[60,62];溝道的優(yōu)勢菌門中,變形菌(兼性厭氧菌),擬桿菌(厭氧菌)和厚壁菌(厭氧菌)等厭氧菌富集(圖2a)[61].從黃土高原溝壑區(qū)地貌組成角度來看,塬面和坡面是來水來沙區(qū)[63-65],溝道是水流和泥沙的匯集區(qū)[24],因而溝道中水分條件良好,形成的厭氧環(huán)境有利于厭氧菌的生存,進(jìn)而影響了溝道細(xì)菌群落的分布.

溝道的厭氧環(huán)境盡管對細(xì)菌影響顯著,但對真菌群落的影響不顯著.對真菌群落而言,坡面土壤中的優(yōu)勢菌門為接合菌門(Zygomycota)、擔(dān)子菌門和子囊菌門[21];溝道中為子囊菌門、擔(dān)子菌門和羅茨菌門(圖3a).有學(xué)者在接合菌門,子囊菌門和擔(dān)子菌門中發(fā)現(xiàn)了17種需氧真菌種[66].但是,也有研究發(fā)現(xiàn)子囊菌門中有些菌綱,如糞殼菌能夠適應(yīng)厭氧環(huán)境 (圖3b)[67-69];羅茨菌門也可以同時生存于土壤、淡水以及海洋沉積物等環(huán)境(圖3a)[70-71].同時,UPGMA聚類樹(圖4b)聚類不明顯可以證明這一點(diǎn).

4 結(jié)論

4.1 門水平上,與上游相比,把口站的細(xì)菌群落中擬桿菌門與厚壁菌門的相對豐度分別增加6.6%、10.5%,變形菌門降低15.1%;真菌群落中擔(dān)子菌門的相對豐度增加7.7%,而子囊菌門降低30.2%.

4.2 細(xì)菌群落的豐富度、多樣性降低,而真菌群落增加,這可能與顆粒的空間分布有關(guān).

4.3 溝道的理化環(huán)境影響微生物群落的分布.除此以外,溝道內(nèi)厭氧環(huán)境在一定程度上影響了細(xì)菌群落的分布.

[1] Robert F Stallard. Terrestrial sedimentation and the carbon cycle: Coupling weathering and erosion to carbon burial [J]. Global Biogeochemical Cycles, 1998,12(2):231-257.

[2] Chaplot V, Jean Poesen. Sediment, soil organic carbon and runoff delivery at various spatial scales [J]. Catena, 2012,88(1):46-56.

[3] Asemeret Asefaw Berhe, Rebecca T Barnes, Johan Six, et al. Role of soil erosion in biogeochemical cycling of essential elements: carbon, nitrogen, and phosphorus [J]. Annual Review of Earth and Planetary Sciences, 2018,46(1):521-548.

[4] Harden J W, Sharpe J M, Parto W J, et al. Dynamic replacement and loss of soil carbon on eroding cropland [J]. Global Biogeochemical Cycles, 1999,13(4):885-901.

[5] Lal R. Soil erosion and carbon dynamics [J]. Soil & Tillage Research, 2005,81:137-142.

[6] Berhe A A, Harte J, Harden J W, et al. The significance of the erosion-induced terrestrial carbon sink [J]. Bioscience, 2007,57(4): 337-346.

[7] Gregorich E G, Greerb K J, Anderson D W, et al. Carbon distribution and losses — erosion and deposition effects [J]. Soil & Tillage Research, 1998,47:291-302.

[8] Nannipieri P, Ascher J, Ceccherini M T, et al. Microbial diversity and soil functions [J]. European Journal of Soil Science, 2003,54:655-670.

[9] Stavi I, Lal R. Variability of soil physical quality in uneroded, eroded, and depositional cropland sites [J]. Geomorphology, 2011,125: 85-91.

[10] Zhang J H, Wang Y, Jia L Z, et al. An interaction between vertical and lateral movements of soil constituents by tillage in a steep-slope landscape [J]. Catena, 2017,152:292-298.

[11] Whitman W B, Coleman D C, William J Wiebe. Prokaryotes: The unseen majority [J]. Proc. Natl. Acad. Sci., 1998,5: 6578-6583.

[12] Torsvik V, ?vre?s L, Frede T Thingstad. Prokaryotic diversity- magnitude, dynamics, and controlling factors [J]. Science, 2002, 296(5570):1064-1066.

[13] Craig J Venter, Remington Karin, Heidelberg John F, et al. Environmental genome shotgun sequencing of the Sargasso Sea [J]. Science, 2004,304(5667):66-74.

[14] Paul G Falkowski, Tom Fenchel and Edward F Delong. The microbial engines that drive Earth’s biogeochemical cycles [J]. Science, 2008,320(5879):1034-1039.

[15] Liu Huanyao, Zhou Jiaogen, Feng Qingyu, et al. Effects of land use and topography on spatial variety of soil organic carbon density in a hilly, subtropical catchment of China [J]. Soil Research, 2017,55(2): 134.

[16] Dialynas Y G, Bastola S, Bras R L, et al. Topographic variability and the influence of soil erosion on the carbon cycle [J]. Global Biogeochemical Cycles, 2016,30(5):644-660

[17] Berhe A A, Barnes R T, Six J, et al. Erosional redistribution of topsoil controls soil nitroge dynamics [J]. Biogeochemistry, 2017,132:37-54.

[18] Hu Yaxian, Berhe Asmeret Asefaw, Fogel Marilyn L, et al. Transport-distance specific SOC distribution: Does it skew erosion induced C fluxes [J]. Biogeochemistry, 2016,128(3):339-351.

[19] Zhang Haicheng, Liu Shuguang, Yuan Wenping, et al. Inclusion of soil carbon lateral movement alters terrestrial carbon budget in China [J]. Science Reports, 2014,4(7247):1-6.

[20] Kirkels F M S A, Cammeraat L H, Kuhn N J. The fate of soil organic carbon upon erosion, transport and deposition in agricultural landscapes — A review of different concepts [J]. Geomorphology, 2014,226:94-105.

[21] Sun Qiqi, Hu Yaxian, Wang Rui, et al. Spatial distribution of microbial community composition along a steep slope plot of the Loess Plateau [J]. Applied Soil Ecology, 2018,130:226-236.

[22] 畢華興,劉立斌,劉斌.黃土高塬溝壑區(qū)水土流失綜合治理范式 [J]. 中國水土保持科學(xué), 2010,8(4):27-33. Bi Huaxing, Liu Libin, Liu Bin. Paradigm of integrated management on soil and water losses in LoessPlateau-gullyRegion [J]. Science of Soil and Water Conservation, 2010,8(4):27-33.

[23] 費(fèi)祥俊,邵學(xué)軍.泥沙源區(qū)溝道輸沙能力的計算方法 [J]. 泥沙研究, 2004,1:1-8. Fei Xiangjun, Shao Xuejun. Sediment transport capacity of gullies in small watersheds [J]. Journal of Sediment Research, 2018,130:226- 236.

[24] 王光謙,李鐵鍵,薛 海,等.流域泥沙過程機(jī)理分析 [J]. 應(yīng)用基礎(chǔ)與工程科學(xué)學(xué)報, 2006,14(4):455-462. Wang Guangqian, Li Tiejian, Xue Hai, et al. Mechanism analysis of watershed sedmient processes [J]. Journal of Basic Science and Engineering, 2006,14(4):455-462.

[25] 錢 婧,張麗萍,王文艷.紅壤坡面土壤團(tuán)聚體特性與侵蝕泥沙的相關(guān)性 [J]. 生態(tài)學(xué)報, 2018,38(5):1590-1599. Qian Jing, Zhang Liping, Wang Wenyan. The relationship between soil aggregates and eroded sediments from sloping vegetated red soils of South China [J]. Acta Ecologica Sinica, 2018,38(5):1590-1599.

[26] 王興奎,錢 寧,胡維德.黃土丘陵溝壑區(qū)高含沙水流的形成及匯流過程 [J]. 水利學(xué)報, 1982,7(4):26-35. Wang Xingkui, Qian Ning, Hu Dewei. The formation and process of confluence of the flow with hyperconcentration in the Gullied- Hilly Loess Areas of the Yellow River Basin [J]. Shuili Xuebao, 1982,7(4): 26-35.

[27] Bajracharya R M, Lal R, Kimble J M. Erosion effects on carbon dioxide concentration and carbon flux from an ohio alfisol [J]. Soil Science Society of America Journal, 2000,64(2):694-700.

[28] Walling D E. The sediment delivery problem [J]. Journal of Hydrology, 1983,65:209-237.

[29] Beusen A H W, Dekkers A L M, Bouwman A F, et al. Estimation of global river transport of sediments and associated particulate C, N, and P [J]. Global Biogeochemical Cycles, 2005,7(5):345-361.

[30] G C Starr, R Lal, R Malone, et al. Modeling soil carbon transported by water erosion processes [J]. Land Degrad. Dev., 2000,11:83-91.

[31] Lal R, Pimentel D. Soil erosion: a carbon sink or source [J]. Science, 2008,319:1040-1042.

[32] Jacinthe P A, Lal R. A mass balance approach to assess carbon dioxide evolution during erosional events [J]. Land Degradation & Development, 2001,12(4):329-339.

[33] Wang Rui, Sun Qiqi, Wang Ying, et al. Contrasting responses of soil respiration and temperature sensitivity to land use types: Cropland vs. apple orchard on the Chinese Loess Plateau [J]. Science of the Total Environment, 2018,621:425-433.

[34] Mohammadi M F, Jalali S G, Kooch Y, et al. The effect of landform on soil microbial activity and biomass in a hyrcanian oriental beech stand [J]. Catena, 2017,149:309-317.

[35] 楊佳佳,安韶山,張 宏,等.黃土丘陵區(qū)小流域侵蝕環(huán)境對土壤微生物量及酶活性的影響 [J]. 生態(tài)學(xué)報, 2015,35(17):5666-5674. Yang Jiajia, An Shaoshan, Zhang Hong, et al. Effect of erosion on soil microbial biomass and enzyme activity in the Loess Hills [J]. Acta Ecological Sinica, 2015,35(17):5666-5674.

[36] 覃 乾,朱世碩,夏 彬,等.黃土丘陵區(qū)侵蝕坡面土壤微生物量碳時空動態(tài)及影響因素 [J]. 環(huán)境科學(xué), 2019,40(4):1973-1980. Qin Qian, Zhu Shishuo, Xia Bin, et al. Temporal and spatial dynamics of soil microbial biomass carbon and its influencing factors on an eroded slope in the Hilly Loess Plateau Region [J]. Environmental Science, 2019,40(4):1973-1980.

[37] Li Y, Su S. Comprehensive Study of Efficient and ecological economic system in Wangdonggou of Changwu County [M]. Xinjiang: Science and Technology Document Press, 1991.

[38] Li Y, Zhang Qian, Zhang Fangfei, et al. Analysis of the microbiota of black stain in the primary dentition [J]. Plos One, 2015,10(9).

[39] Ruibo Sun, Melissa Dsouza, Jack A Gilbert, et al. Fungal community composition in soils subjected to long-term chemical fertilization is most influenced by the type of organic matter [J]. Environ Microbiol, 2016,18(12):5137-5150.

[40] Nelson D W, Sommers L E. Total carbon, organic carbon, and organic matter: laboratory method. Methods of Soil Analysis, Part 3 [M]. Madison:Soil Science Society of America, 1996:961-1010.

[41] Olsen S R, Cole V, Watenable F S, et al. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Cir. no. 939analysis, part 2 [J]. Am Soc Agron, 1954,9:914-926.

[42] Murphy J, Riley J P. A modified single solution method for the determination of phosphate in natural waters [J]. Anal. Chim. Acta, 1962,27:31-36.

[43] R K V?is?nen, Roberts M S, Garl, J L. Physiological and molecular characterisation of microbial communities associated with different water-stable aggregate size classes [J]. Soil biology & biochemistry, 2005,37(11):2007-2016.

[44] 耿增超,戴 偉.土壤學(xué) [M]. 北京:科學(xué)出版社, 2011:79-85. Geng Zengchao, Dai Wei. Soil Science [M]. Beijing: Science Press, 2011:79-85.

[45] Yang Chao, Liu Nan, Zhang Yingjun. Soil aggregates regulate the impact of soil bacterial and fungal communities on soil respiration [J]. Geoderma, 2019,337:444-452.

[46] Meagan E Schipanski, Elena M Bennett. The influence of agricultural trade and livestock production on the global phosphorus cycle [J]. Ecosystems, 2011,15(2):256-268.

[47] Jennings D H. Translocation of Solutes in fungi [J]. Bio. Rev., 1987, 62:215-243.

[48] Markus N T. Diversity and function of fungi in peatlands a carbon cycling perspective [J]. Soil. Sci., 2006,86:281-293.

[49] Yuste J C, En?unlas J P, Estiarte M, et al. Drought-resistant fungi control soil organic matter decomposition and its response to temperature [J]. Global Change Biology, 2011,17(3):1475-1486.

[50] Xiao Haibing, Li Zhongwu, Chang Xiaofeng, et al. The mineralization and sequestration of organic carbon in relation to agricultural soil erosion [J]. Geoderma, 2018,329:73-81.

[51] Huang Wei, Chen Xing, Jiang Xia, et al. Characterization of sediment bacterial communities in plain lakes with different trophic statuses [J]. Microbiologyopen, 2017,6(5).

[52] Lu Sidan, Sun Yujiao, Zhao Xuan, et al. Sequencing Insights into Microbial Communities in the Water and Sediments of Fenghe River, China [J]. Archives of Environmental Contamination & Toxicology, 2016,71(1):122-132.

[53] Diab W, Toufailya J, Villieras F, et al. Study of physicochemical properties of colloidal sediments of Litani River in Lebanon [J]. Physics Procedia, 2014,55:251-258.

[54] Terrence G, Acosta-Martinez V, Francisco J C. Pyrosequencing reveals bacteria carried in different wind-eroded sediments [J]. Journal of environmental quality, 2012,41(3):744-753.

[55] Jiang Hongchen, Dong Hailiang, Zhang Gengxin, et al. Microbial diversity in water and sediment of Lake Chaka, an athalassohaline lake in northwestern China [J]. Applied and environmental microbiology, 2006,72(6):3832-3845.

[56] Noah Fierer Mark A Bradford, Robert B J. Toward an ecological classification of soil bacteria [J]. Ecology, 2007,88(6):1354-1364.

[57] Brajesh K S, Richard D B, Pete Smith, et al. Microorganisms and climate change: terrestrial feedbacks and mitigation options [J]. Nature Reviews Microbiology, 2010,8(11):779-790.

[58] Francois Lutzoni F, Frank Kauff, Cymon J Cox, et al. Assembling the fungal tree of life: Progress, classification and evolution of subcellular traits [J]. American Journal of Botany, 2004,91(10):1446-1480.

[59] Baldrian P, Kolarik M, Stursova M, et al. Active and total microbial communities in forest soil are largely different and highly stratified during decomposition [J]. The ISME Journal, 2012,6,248-258.

[60] Wells C L, Wilkins T D. Clostridia: Sporeforming Anaerobic Bacilli. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX) [M]. Galveston: University of Texas Medical Branch, 1996: Chapter 18.

[61] Flynn T M, Koval J C, Greenwald S M, et al. Parallelized, aerobic, single carbon-source enrichments from different natural environments contain divergent microbial communities [J]. Front Microbiol, 2017, 8:1-14.

[62] Eichorst S A, Breznak J A, Schmidt T M. Isolation and characterization of soil bacteria that define Terriglobus gen. nov., in the phylum Acidobacteria [J]. Appl Environ Microbiol, 2007,73(8): 2708-2717.

[63] 徐雪良.韭園溝流域溝間地、溝谷地來水來沙量的研究 [J]. 中國水土保持, 1987(8):23-26. Xu Xueliang. Study on the amount of water coming from the ditch and valley in the Gengyuangou Basin [J]. Soil and Water Conservation In China, 1987(8):23-26.

[64] 陳 浩.降雨特征和上坡來水對產(chǎn)沙的綜合影響 [J]. 水土保持學(xué)報, 1992,6(2):17-23. Chen Hao. The synthetic effect of rainfall characteristics and runoff from upper slope on sediment generation [J]. Journal of Soil and Water Conservation, 1992,6(2):17-23.

[65] 陳 浩,王開章.黃河中游小流域坡溝侵蝕關(guān)系研究 [J]. 地理研究, 1999,18(4):363-372. Chen Hao, Wang Kaizhang. A study on the slope-gully erosion relationship on small basins in the loess areas at the middle reaches of the Yellow River [J]. Geographical Research, 1999,18(4):363-372.

[66] Young D, Dollhofer V, Callaghan T M, et al. Isolation, identification and characterization of lignocellulolytic aerobic and anaerobic fungi in one- and two-phase biogas plants [J]. Bioresour Technol, 2018,268: 470-479.

[67] Spatafora J W. Ascomal evolution of filamentous ascomycetes: evidence from molecular [J]. Canadian Journal of Botany, 1995, 73(S1):811-815.

[68] Neuveglise C, Brygoo Y, Vercambre B, et al. Comparative-analysis of molecular and biological characteristics of strains of Beauveria brongniartii isolated from insects [J]. Mycological Research, 1994, 98(3):322-328.

[69] Berbee M L, Taylor J W. Two ascomycete classes based on fruiting- body characters and ribosomal DNA sequence [J]. Molecular Biology and Evolution, 1992,38(5):1590-1599.

[70] Turner M. The evolutionary tree of fungi grows a new branch [N]. Nature News, 2014-05-31.

[71] Ghosh P. Missing link fungi found in Devon pond [N]. BBC News, 2014-10-31.

致謝：本實驗的野外采樣工作由李偉佳、賀瑤等同學(xué)提供幫助,在此表示感謝.

Variations of soil microbial communities along a valley bottom of the loess plateau and the influencing factors.

HOU Fang-bin1, WANG Rui1, Salman Ali2, GAO Xin1, GUO Sheng-li1,3*

(1.State Key Laboratory of soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, China；2.College of Resource and Environment, Northwest A&F University, Yangling 712100, China；3.Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resource, Yangling 712100, China)., 2019,39(10)：4350~4359

Sediments were collected from up- to down-stream along a valley bottom on the Loess Plateau. Physicochemical properties of the collected sediments were measured and the characteristics of bacterial and fungal communities in the sediment samples were also determined using the high-throughput sequencing of 16S rRNA gene fragment and ITS. From up- to down-stream of the studied valley, the relative abundance of Bacteroidetes and Firmicutes in the collected sediments increased by 6.6% and 10.5% respectively, and the relative abundance of Proteobacteria decreased by 15.1%. The relative abundance of Basidiomycota increased by 7.7%, while the relative abundance of Ascomycota decreased by 30.2%. The bacterial richness (Chao1index) and diversity (Shannon index) were negatively correlated with sediment clay content (< 0.05), while the correlations between clay content and fungal were not significant. The richness and diversity of bacterial and fungal communities were also correlated with sediment SOC and Olsen-P (< 0.05). Therefore, sediment compositions and nutrient content appeared to be a crucial factor influencing the spatial variability of sediment microbial communities and diversity.

sediments；spatial re-distribution；bacteria；fungi；sediment compositions

X172

A

1000-6923(2019)10-4350-10

侯芳彬(1995-),女,河南新鄉(xiāng)人,西北農(nóng)林科技大學(xué)碩士研究生,主要研究方向為土壤生態(tài).

2019-03-07

國家自然科學(xué)基金資助項目(41371279)

* 責(zé)任作者, 研究員, slguo@ms.iswc.ac.cn