陳 娜,劉 毅,黎 娟,袁 婧,葛體達(dá),吳金水,孫志龍,徐華勤*

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長期施肥對稻田不同土層反硝化細(xì)菌豐度的影響

陳 娜1,2,劉 毅2,黎 娟1,袁 婧2,葛體達(dá)2,吳金水2,孫志龍3,徐華勤1*

(1.湖南農(nóng)業(yè)大學(xué)農(nóng)學(xué)院,湖南 長沙 410128；2.中國科學(xué)院亞熱帶農(nóng)業(yè)生態(tài)研究所亞熱帶農(nóng)業(yè)生態(tài)過程重點(diǎn)實(shí)驗(yàn)室,湖南 長沙 410125；3.湖南省寧鄉(xiāng)市回龍鋪鎮(zhèn)農(nóng)業(yè)綜合服務(wù)中心,湖南 寧鄉(xiāng) 410606)

為了探討長期施肥對稻田不同土層關(guān)鍵反硝化功能種群豐度的影響及核心驅(qū)動(dòng)因子,以湖南寧鄉(xiāng)長期施肥定位試驗(yàn)田為平臺,選取不施肥(CK)、全量化肥(NPK)和秸稈還田(ST)3個(gè)處理,結(jié)合實(shí)時(shí)熒光定量PCR(qPCR)技術(shù),系統(tǒng)分析了稻田不同土層(0~10,10~20,20~30,30~40cm)關(guān)鍵反硝化功能基因(和)的豐度及其與土壤理化性質(zhì)的內(nèi)在聯(lián)系.結(jié)果表明,相比于不施肥處理(CK),施肥處理(NPK和ST)在0~40cm土層土壤SOC、TN、NO3--N、NH4+-N和Olsen-P分別顯著增加了2.2%~83.6%,3.5%~58.3%,70.8%~222.1%,0.9%~83.7%和16.5%~94.5%,pH值下降了0.31~0.67個(gè)單位;長期施用化肥和秸稈使和基因豐度分別增加0.75~7.18倍,1.57~3.02倍和0.53~3.81倍,其中秸稈還田對反硝化細(xì)菌數(shù)量的影響比單施化肥更顯著;稻田、和反硝化型細(xì)菌的豐度隨土層深度增加而逐漸降低,具有明顯的垂直分布特征;RDA分析結(jié)果顯示,土壤養(yǎng)分如SOC和TN是影響水稻土、和反硝化型細(xì)菌垂直分布的關(guān)鍵因子,而pH值是調(diào)控反硝化細(xì)菌在稻田底土分布的核心驅(qū)動(dòng)因子.研究結(jié)果可為提升稻田土壤肥力和減少稻田氮素?fù)p失和溫室氣體排放提供理論依據(jù).

水稻土；長期施肥；不同土層；反硝化細(xì)菌；種群豐度

農(nóng)田土壤為N2O排放的主要人為源,年均排放量約為4.2Tg,占全球總釋放量的70%[1].我國是世界上最大的水稻生產(chǎn)國,稻田耕種面積占世界水稻生產(chǎn)面積的27%.因此,我國稻田N2O的排放日益受到關(guān)注[3].稻田土壤N2O的排放主要由土壤微生物參與的硝化和反硝化作用所驅(qū)動(dòng)[2].由于稻田土壤長期處于淹水厭氧環(huán)境,因此反硝化作用被認(rèn)為是稻田N2O產(chǎn)生的主要途徑[3].其中,基因編碼的硝酸還原酶是反硝化過程的第一步反應(yīng)酶,和基因編碼的亞硝酸還原酶控制著關(guān)鍵的限速步驟,因此,、和常用作標(biāo)記基因用以研究土壤反硝化細(xì)菌[4-5].大量研究結(jié)果表明[6-8],反硝化功能種群豐度的增加會導(dǎo)致反硝化作用的增強(qiáng),進(jìn)而引起N2O排放增多.因此,明確稻田土壤關(guān)鍵反硝化功能種群的豐度變化規(guī)律,對于減少稻田土壤氮素?fù)p失及N2O排放具有重要的意義.

近年來,由于稻田增值高產(chǎn)的需要,施肥成為保障糧食安全和產(chǎn)量的關(guān)鍵措施.但研究發(fā)現(xiàn),長期不同施肥會引起稻田土壤理化性質(zhì)出現(xiàn)差異,進(jìn)而影響反硝化微生物,從而影響稻田土壤反硝化作用及N2O的排放[9-10].因此,關(guān)于稻田土壤反硝化微生物對長期施肥響應(yīng)的研究逐漸成為國內(nèi)外學(xué)者關(guān)注的熱點(diǎn).研究發(fā)現(xiàn)[11-12],施用化肥和有機(jī)肥均顯著提高反硝化細(xì)菌豐度,且施用有機(jī)肥處理與化肥處理間反硝化細(xì)菌豐度和群落結(jié)構(gòu)差異顯著.這些研究表明不同施肥制度顯著影響反硝化微生物,然而到目前為止,關(guān)于長期施肥對稻田土壤反硝化微生物分布影響的研究主要集中在耕作層(0~20cm)土壤,而深層土壤反硝化微生物對長期不同施肥制度的響應(yīng)的研究少有報(bào)道.因此,非常有必要針對長期施肥對稻田土壤剖面不同深度反硝化微生物的分布特征開展研究.

為了探究長期施肥對稻田不同土層關(guān)鍵反硝化功能種群豐度的影響,本研究依托湖南省寧鄉(xiāng)縣長期定位試驗(yàn)田,選取無肥對照、全化肥、秸稈還田3種不同施肥處理,采集0~10,10~20,20~30,30~40cm土層土壤樣品,運(yùn)用熒光定量PCR(qPCR)技術(shù),系統(tǒng)分析了和等3種關(guān)鍵反硝化功能基因在不同施肥處理中沿土壤剖面的豐度變化特征及其核心驅(qū)動(dòng)因子.研究結(jié)果可為提高稻田氮素利用效率和溫室氣體減排提供理論依據(jù).

1 材料與方法

1.1 供試樣點(diǎn)及樣品采集

采樣地點(diǎn)位于湖南省寧鄉(xiāng)縣農(nóng)業(yè)技術(shù)推廣中心,地理位置為113°00′20″E,北緯28°25′16″N,海拔36.1m,年平均氣溫為17.5℃,年均降雨量為1300mm,年均無霜期在274d左右,年日照為1663h.該地區(qū)為典型雙季稻產(chǎn)區(qū),于1986年設(shè)立田間試驗(yàn),為長期定位施肥實(shí)驗(yàn)田.本研究采用其中3個(gè)施肥處理:①無肥對照(CK):不施加任何肥料;②全化肥處理(NPK):僅施氮磷鉀化肥,按每公頃施60kg氮((NH4)2SO4)、30kg磷(P2O5)和60kg鉀(K2O)的比例進(jìn)行施肥;③秸稈還田處理(ST):施用上一季度收割的水稻秸稈為主(早季稻秸稈還田量為2775.0kg/hm2,晚季稻秸稈還田量為3600.0 kg/hm2),若與處理②比,總氮磷鉀量不足則用化肥補(bǔ)足.試驗(yàn)小區(qū)面積為28.22m2,每個(gè)處理3次重復(fù),隨機(jī)區(qū)組排列.

土壤樣品采集于2017年5月中旬,在每個(gè)小區(qū)采用五點(diǎn)法采集,土壤剖面0~40cm范圍內(nèi)按10cm間距分段采樣.采樣時(shí)將鮮土分為2份:一份用錫箔紙包好立即用液氮速凍,存放于-80℃冰箱用于分子生物學(xué)實(shí)驗(yàn);另一部分室內(nèi)剔除石塊和植物殘?bào)w后,存于4℃冰箱,進(jìn)行理化指標(biāo)的測定.土壤的基本理化性質(zhì)見表1.

表1 供試土壤基本理化性質(zhì) Table 1 Characteristics of the soil in this study

1.2 樣品理化指標(biāo)測定及方法

土壤pH值按水土比2.5:1用Mettler- toledo320 pH計(jì)測定;土壤有機(jī)碳(SOC)和全氮(TN)采用碳氮元素分析儀(VARIO MAX C/N,德國)測定(干燒法);土壤速效磷(Olsen-P)含量采用Olsen法;硝態(tài)氮(NO3--N)和銨態(tài)氮(NH4+-N)用連續(xù)流動(dòng)分析儀(Flastar 5000Analyzer)測定.

1.3 土壤DNA的提取和實(shí)時(shí)熒光定量PCR

土壤DNA的提取方法參考陳哲[13]方法,并稍作修改:取0.5g經(jīng)液氮速凍的土壤.DNA濃度測定使用核酸蛋白測定儀(Nanodrop ND-1000UV-Vis分光光度計(jì)),并取2μL用1%瓊脂糖膠進(jìn)行電泳檢測,DNA樣品保存于-20℃冰箱.

實(shí)時(shí)熒光定量PCR所用儀器為ABI 7900 (Applied Biosystem),標(biāo)準(zhǔn)曲線的建立參照陳哲[13]的方法:、和PCR反應(yīng)體系均為10μL,含有5μL SYBR GREEN Ⅰ (Takara),0.7μL ROX (Takara),0.3μL引物,1μL濃度為5ng的DNA模板,加水補(bǔ)至10μL.基因引物對為-571F-773R[13],引物序列為CCGATYCCGGCVAT- GTCSAT/GGNACGTTNGADCCCCA,反應(yīng)條件為95℃預(yù)變性30s,95℃變性5s,60℃退火30s,共40個(gè)循環(huán);基因引物對為-1aCuF/K-3CuR[14],引物序列為ATCATGCTSCTGCCGCG/GCCTCGA- TCAGRTTGTGGTT,反應(yīng)條件為95℃預(yù)變性30s, 95℃變性5s,56℃退火30s,共40個(gè)循環(huán);基因引物對為-cd3aF/-R3cd[15],引物序列為GTSAACGTSAAGGARACSGG/GASTTCGGRTGSGTCTTGA,反應(yīng)條件為95℃預(yù)變性30s,95℃變性5s,56℃退火20s,72℃延伸30s,共40個(gè)循環(huán).溶解曲線均為95℃ 15s,60℃ 15s,90℃ 15s.

1.4 數(shù)據(jù)處理與分析

qPCR數(shù)據(jù)的導(dǎo)出采用SDS 2.3軟件,數(shù)據(jù)處理與統(tǒng)計(jì)分析采用Microsoft Excel 2016和SPSS 20.0,圖形繪制采用ORIGIN 9.0.不同處理顯著性用One-way ANOVA(單因素方差分析)進(jìn)行檢驗(yàn),采用Duncan多重比較分析組間差異.冗余分析(RDA)用Canoco 5.0實(shí)現(xiàn).

2 結(jié)果與討論

2.1 長期施肥對稻田土壤基本理化性質(zhì)的影響

如圖1所示,經(jīng)長期施肥后,各處理間0~40cm土層土壤SOC、TN、NO3--N、NH4+-N、Olsen-P含量和pH值差異顯著.同時(shí)多重比較(表2)結(jié)果發(fā)現(xiàn),施肥和土壤深度及其交互作用均對土壤SOC、TN、NO3--N、NH4+-N和Olsen-P含量及pH值有極顯著影響(<0.01).相比于CK處理,施肥處理(NPK和ST)在0~40cm土層土壤SOC、TN、NO3-- N、NH4+-N和Olsen-P分別增加了2.2%~83.6%, 3.5%~58.3%,70.8%~222.1%,0.9%~83.7%和16.5%~ 94.5%, pH值下降了0.31~0.67個(gè)單位;相比于全化肥處理,秸稈還田使0~30cm土層土壤SOC、TN、NO3--N和NH4+-N含量分別增加了20.3%~26.6%、18.1%~25.0%、3.2%~85.3%和22.8%~78.4%,pH值下降0~0.16個(gè)單位,使20~40cm土層土壤Olsen-P含量增加6.0%~34.4%.長期施肥增加土壤養(yǎng)分,降低pH值,這一結(jié)論在施肥試驗(yàn)中具有普遍性,如Zhao等[16]在稻麥種植制度的施肥試驗(yàn)中發(fā)現(xiàn)所有施肥處理包括化肥及化肥配施秸稈處理土壤有機(jī)質(zhì)、有效磷和全氮含量均增加;孟紅旗等[17]和于冰等[18]的研究表明施用化肥及秸稈配施化肥處理較不施肥處理pH值降低,秸稈配施化肥處理的有機(jī)質(zhì)、TN、NH4+-N、NO3--N和有效磷含量高于其他處理.

表2 施肥處理和土壤深度對土壤理化性質(zhì)的多重比較Table 2 Effects of fertilization and soil depth on soil properties

注:數(shù)值及*號為值和顯著水平.**為極顯著(<0.01).

由于耕作層土壤養(yǎng)分的向下遷移,使得土壤養(yǎng)分具有垂直分布特征.圖1中土壤C、N、P含量均在0~10cm土層中最高,與土層深度呈顯著負(fù)相關(guān).杜林森等[19]通過38a的長期培肥試驗(yàn)發(fā)現(xiàn),土壤碳氮含量隨土壤深度增加而逐漸降低,且施用秸稈和化肥處理是不施肥處理的1.1~13.7倍,單艷紅等[20]研究發(fā)現(xiàn)0~30cm土層土壤Olsen-P含量與土層深度呈負(fù)相關(guān),這與本研究結(jié)果一致.長期施肥稻田土壤養(yǎng)分垂直分布在水稻生產(chǎn)上具有雙重意義[21]:一方面,養(yǎng)分適度下移,可以豐富稻田底土養(yǎng)分含量,對于培育稻田土壤肥力極為有利;另一方面,當(dāng)養(yǎng)分下移超過水稻根系所能吸收的范圍,將造成養(yǎng)分的淋失,進(jìn)而造成地下水的污染.由此可見,長期施化肥或秸稈秸稈對提高稻田土壤肥力和促進(jìn)稻田可持續(xù)性具有顯著的效果,同時(shí)需對施肥可能導(dǎo)致的環(huán)境問題引起注意.

2.2 不同施肥處理對土壤narG、nirK和nirS型反硝化型細(xì)菌豐度的影響

、和型反硝化細(xì)菌基因拷貝數(shù)如圖2所示,、和基因豐度分別在1.20′107~5.02′109,5.10′106~3.36′109,4.71′106~2.75′109拷貝數(shù)/g干土,其在不同土壤深度土層的分布對不同施肥的響應(yīng)趨勢較相似.長期施肥提高了土壤、和型反硝化細(xì)菌基因豐度,相比較于不施肥處理,施用秸稈和化肥使基因豐度增加0.75~7.18倍,基因豐度增加1.57~3.02倍,基因豐度增加0.53~3.81倍.這與之前的研究結(jié)論基本一致,如解開治等[22]指出無機(jī)肥和無機(jī)有機(jī)肥配施均能顯著提高稻田土壤和基因豐度;靳振江等[26]也發(fā)現(xiàn)施用化肥和化肥配施秸稈處理的基因豐度較無肥處理提高了0.51倍和0.80倍.其原因?yàn)?反硝化微生物主要為異養(yǎng)厭氧型微生物,在稻田土壤長期的淹水厭氧環(huán)境下,土壤養(yǎng)分的增加能極大地滿足反硝化微生物生長繁殖對養(yǎng)分的需求,從而刺激反硝化微生物的大量繁殖.同時(shí),從圖中可得,秸稈還田處理中、和基因豐度較僅施用化肥高,表明長期施用秸稈對稻田反硝化微生物數(shù)量的促進(jìn)作用更顯著.這與很多國內(nèi)外研究結(jié)果相似[23-24],如尹昌等[25]研究表明施用有機(jī)肥顯著促進(jìn)型反硝化細(xì)菌的生長,而施用化肥需配施有機(jī)肥才促進(jìn)反硝化微生物的生長;Chen[30]等發(fā)現(xiàn)有機(jī)肥處理、和反硝化細(xì)菌數(shù)量顯著高于無機(jī)肥處理.其原因?yàn)?首先,秸稈有機(jī)肥的長期輸入為反硝化細(xì)菌和其他微生物提供了大量生物有效性碳源,促進(jìn)微生物的大量繁殖,微生物活性的提高反過來又促進(jìn)有機(jī)物的降解,從而增加土壤中速效養(yǎng)分,為微生物的生長繁殖提供適宜的環(huán)境[26];其次,NO3--N是反硝化作用的底物,NO3--N顯著增加(圖1)為其提供了豐富的反應(yīng)底物[27];最后,有機(jī)質(zhì)增加刺激了土壤微生物活性,呼吸作用強(qiáng),加速了厭氧環(huán)境的形成[28].化肥雖然也能為反硝化微生物直接快速地提供NO3--N底物,但并不能直接增加土壤碳養(yǎng)分,而是通過促進(jìn)植株根系生長和產(chǎn)生根系分泌物來保障土壤反硝化微生物對碳源的需求[29].

圖2 不同施肥處理下不同土壤深度反硝化細(xì)菌基因豐度 Fig.2 Gene Abundance of denitrifying bacteria in soil profile with different fertilizer application

之前有報(bào)道指出,土壤養(yǎng)分的垂直分布也會引起土壤微生物具有垂直分布特征[30].如Taylor等[31]發(fā)現(xiàn)農(nóng)田土壤表層細(xì)菌數(shù)量遠(yuǎn)高于底層;Fierer等[32]指出草地土壤微生物數(shù)量隨土壤深度的增加而減少.圖2中隨著土壤深度的增加,不同施肥處理、和基因豐度均顯著降低,具有明顯的垂直分布特征, 類似結(jié)果在森林土壤中也有發(fā)現(xiàn)[33].造成這種變化趨勢的主要原因可能為土壤表層受耕作等影響較大,肥料和凋落物等直接施入表土,土壤表層養(yǎng)分如有機(jī)碳、硝態(tài)氮和速效磷等含量較高(圖1),因而土壤表層微生物更易于獲取足夠的養(yǎng)分和底物;隨著深度增加,土壤養(yǎng)分含量逐漸減少(圖1),微生物生長受限,微生物數(shù)量減少.另外,本研究表明,相對于施用化肥處理,秸稈還田處理中不同土層反硝化微生物的豐度都要更高(圖2),類似試驗(yàn)結(jié)果在長期定位施肥的旱地(菜地)土壤中也有所發(fā)現(xiàn)[34].水稻田不同于旱地土,其土壤養(yǎng)分向下遷移速率和滲漏損失量相對較小,大多沉積于底底土中,因此不同施肥處理所引起的稻田耕作層養(yǎng)分含量的差異,其類似特征也能反映在底土上.正是因?yàn)椴煌┓侍幚黹g土壤養(yǎng)分垂直分布的差異,導(dǎo)致了、和反硝化型細(xì)菌在不同施肥處理中垂直分布存在差異.

2.3 narG、nirK和nirS型反硝化型細(xì)菌豐度與土壤理化性質(zhì)的關(guān)系

RDA排序結(jié)果(圖3)表明,第一和第二排序軸占總特征值的72.76%,表明這6項(xiàng)環(huán)境因子能解釋大部分反硝化細(xì)菌基因豐度的變化.土壤SOC、TN、NH4+-N、NO3--N、Olsen-P和pH值均極顯著影響反硝化功能種群豐度(蒙特卡羅檢驗(yàn)值分別為=0.002,0.002,0.002,0.002,0.006,0.002),其中土壤SOC和TN在第一排序軸上的投影長度較長, NH4+-N、NO3--N和pH值次之,Olsen-P最短,表明在6項(xiàng)理化因子中SOC和TN對土壤反硝化基因豐度的影響較大.因此,土壤養(yǎng)分如SOC和TN是影響稻田土壤、和反硝化型細(xì)菌垂直分布的關(guān)鍵因子,尤其對稻田耕作層的影響更為顯著(圖3).類似的結(jié)果在其他生態(tài)系統(tǒng)也有發(fā)現(xiàn),如Fierer等[32]認(rèn)為土壤微生物數(shù)量隨土壤深度的增加而減少主要是由于土壤碳的有效性降低;Liu等[35]認(rèn)為在森林土壤中,土壤DOC、DON、NH4+和NO3-垂直分布是、和型反硝化細(xì)菌呈垂直分布特征的關(guān)鍵驅(qū)動(dòng)因子.同時(shí)RDA結(jié)果顯示,pH值與20~30cm和30~40cm土層反硝化細(xì)菌的豐度緊密相關(guān),暗示pH值可能是驅(qū)動(dòng)、和型反硝化細(xì)菌在稻田底土分布的核心驅(qū)動(dòng)因子. pH值對反硝化細(xì)菌具有選擇效應(yīng),因而在不同的土壤環(huán)境中反硝化細(xì)菌對pH值的響應(yīng)不同[36]. Dandie等[37]發(fā)現(xiàn),農(nóng)田土壤中pH值是限制型反硝化細(xì)菌群落結(jié)構(gòu)的唯一影響因子;而王亞男等[43]在設(shè)施菜地中的研究和Enwall[38]在稻田的研究發(fā)現(xiàn)pH值與反硝化細(xì)菌豐度并沒有相關(guān)性.本研究pH值顯著影響反硝化基因豐度,與前者研究結(jié)果相似.0~20cm施肥處理、10~ 20cm、20~30cm和30~40cm土層處理基因豐度在二維排序圖中彼此分離,表明土壤深度影響反硝化基因豐度.在0~ 30cm土層中,全化肥處理、秸稈還田處理與不施肥處理彼此分離,表明施用化肥及秸稈還田顯著影響土壤反硝化細(xì)菌基因豐度.

圖3 影響反硝化細(xì)菌基因豐度因素的RDA分析 Fig.3 RDA analysis of influencing factors to gene abundance of denitrifying bacteria

3 結(jié)論

3.1 長期施肥顯著提升水稻土不同土層碳、氮、磷等含量,降低土壤pH值.

3.2 稻田、和反硝化型細(xì)菌的豐度隨土層深度增加而逐漸降低.長期施肥顯著增加水稻土不同土層、和反硝化型細(xì)菌的豐度,其中秸稈還田對反硝化細(xì)菌數(shù)量的影響比施用化肥更顯著.

3.3 土壤養(yǎng)分如SOC和TN是影響水稻土、和反硝化型細(xì)菌垂直分布的關(guān)鍵因子,而pH值是調(diào)控反硝化細(xì)菌在稻田底土分布的核心驅(qū)動(dòng)因子.

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Effects of long-term fertilization on the abundance of the key denitrifiers in profile of paddy soil profiles.

CHEN Na1,2, LIU Yi2, LI Juan1, YUAN Jing2, GE Ti-da2, WU Jin-shui2, SUN Zhi-long3, XU Hua-qin1*

(1.College of Agronomy, Hunan Agriculture University, Changsha 410128, China；2.Key Laboratory of Subtropical Agriculture Ecology, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China；3.Integrated Service for Agriculture Ningxiang County Huilongpu Town, Ningxiang 410606, China)., 2019,39(5)：2154~2160

The aims of this study were to explore the effect of long-term fertilization on the abundance of the key denitrifiers in paddy soil profiles (0~40cm), and the core factors driving denitrifiers. Soils with non-fertilization (CK), inorganic fertilizer (NPK) and organic fertilizer (ST) were collected in Ning xiang County, Hunan Province, and real-time fluorescent quantitative PCR technology was used to analyze the abundance of-,- and-containing communities in paddy soil profile (0~10cm, 10~20cm, 20~30cm, 30~40cm) and their relationship with soil properties. The results showed that compared with CK, SOC、TN、NO3--N、NH4+-N and Olsen-P in soil profile under NPK and ST increased by 2.2%~83.6%、3.5%~58.3%、70.8%~222.1%、0.9%~ 83.7% and 16.5%~94.5% respectively, and pH decreased by 0.31~0.67 units. Long-term application of inorganic fertilizer and organic fertilizer increased,, andgene abundance by 0.75~7.18 times, 1.57~3.02 times, and 0.53~3.81 times, respectively. And the effect of organic fertilizer on the abundance of denitrifiers was more significant than that of inorganic fertilizer application; The abundance of-,- and-containing communities decreased gradually with soil depth increasing, which presented an obvious vertical distribution; RDA analysis showed that soil nutrients such as SOC and TN were the core factors affecting the vertical distribution of-,- and-containing populations in paddy soil, especially in the cultivated horizon, while pH was the core driving factor regulating the distribution of denitrifying bacteria in paddy field subsoil. The results can provide theoretical basis for improving soil fertility and reducing nitrogen loss and greenhouse gas emission in paddy soils.

paddy soil；long-term fertilization；soil profile；denitrifying bacteria；abundance

X172

A

1000-6923(2019)05-2154-07

陳 娜(1994-),女,湖南婁底人,湖南農(nóng)業(yè)大學(xué)碩士研究生,主要從事環(huán)境生態(tài)修復(fù).發(fā)表論文1篇.

2018-10-14

國家自然基金資助項(xiàng)目(41771300,41301274)

*責(zé)任作者, 副教授, xu7541@163.com