梁作盼 李立青,2 萬(wàn)方浩 劉萬(wàn)學(xué)**
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土壤微生物對(duì)紫莖澤蘭生長(zhǎng)與競(jìng)爭(zhēng)的反饋:不同滅菌方法的比較*
梁作盼1李立青1,2萬(wàn)方浩1劉萬(wàn)學(xué)1**
(1. 中國(guó)農(nóng)業(yè)科學(xué)院植物保護(hù)研究所/植物病蟲(chóng)害生物學(xué)國(guó)家重點(diǎn)實(shí)驗(yàn)室 北京 100193; 2. 貴州大學(xué)生命科學(xué)學(xué)院 貴陽(yáng) 550025)
土壤微生物去除是驗(yàn)證土壤微生物反饋調(diào)節(jié)入侵植物競(jìng)爭(zhēng)排斥本地植物群落的重要手段。為了確定土壤微生物反饋效應(yīng)的最佳土壤微生物去除方法, 以及土壤微生物對(duì)紫莖澤蘭與本地植物競(jìng)爭(zhēng)中的反饋?zhàn)饔? 本試驗(yàn)比較了添加蛭石和未添加蛭石下, 3種常見(jiàn)土壤微生物滅菌方式(干熱滅菌、濕熱滅菌、輻照滅菌)處理的紫莖澤蘭單優(yōu)群落根際土壤對(duì)紫莖澤蘭與本地植物香茶菜生長(zhǎng)的影響。結(jié)果表明: 與未滅菌處理土壤相比, 3種滅菌處理土壤均顯著抑制了紫莖澤蘭和香茶菜的生長(zhǎng); 添加蛭石滅菌的土壤相對(duì)于未添加蛭石的滅菌土壤顯著促進(jìn)了2種植物的生長(zhǎng); 滅菌土壤添加蛭石的情況下輻照滅菌土壤的兩種植物的生物量顯著地高于干熱滅菌和濕熱滅菌土壤兩種植物的生物量, 其中輻照滅菌下紫莖澤蘭的生物量分別比干熱滅菌和濕熱滅菌條件下增加30.8%和66.5%, 香茶菜生物量分別顯著增加109.5%和63.4%。輻照滅菌土壤添加蛭石的處理方式最接近真實(shí)地反映土壤微生物對(duì)植物生長(zhǎng)的反饋效應(yīng)。進(jìn)一步進(jìn)行輻照滅菌土壤添加蛭石處理與未滅菌土壤添加蛭石處理的紫莖澤蘭與香茶菜混種的盆栽試驗(yàn), 結(jié)果顯示, 土壤微生物顯著增強(qiáng)了紫莖澤蘭對(duì)香茶菜的競(jìng)爭(zhēng)優(yōu)勢(shì), 相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度增加16.0%, 說(shuō)明土壤微生物在紫莖澤蘭競(jìng)爭(zhēng)排斥本地植物的入侵過(guò)程中具有正反饋偏利調(diào)節(jié)作用
入侵植物 紫莖澤蘭 土壤微生物 滅菌方法 反饋?zhàn)饔?/p>
土壤微生物群落作為植物地下生態(tài)系統(tǒng)的重要生物因子, 在生態(tài)系統(tǒng)中組成了一個(gè)強(qiáng)大的動(dòng)力資源庫(kù)。大量研究已表明, 生態(tài)系統(tǒng)的地上和地下部分緊密聯(lián)系、互為依存; 植物與土壤微生物群落的互作可以決定植物群落的競(jìng)爭(zhēng)演替方向和進(jìn)程[1-4]。外來(lái)入侵植物一旦在入侵地成功定殖, 就可通過(guò)種群競(jìng)爭(zhēng)性擴(kuò)張而迅速形成單優(yōu)群落, 不僅造成入侵地生境地上植物群落結(jié)構(gòu)改變和生物多樣性喪失, 而且對(duì)地下土壤微生物群落和功能產(chǎn)生深遠(yuǎn)的影響[5-6],這一生態(tài)過(guò)程和生態(tài)系統(tǒng)深層次的變化也必然會(huì)反過(guò)來(lái)直接或間接地影響外來(lái)入侵植物與本地植物的競(jìng)爭(zhēng)[4]。因此, 外來(lái)植物與入侵地土壤微生物互作及其在促進(jìn)入侵植物競(jìng)爭(zhēng)替代本地植物的作用, 成為近年來(lái)國(guó)際上備受關(guān)注的焦點(diǎn)和研究熱點(diǎn)[7-14]。
為了驗(yàn)證土壤微生物對(duì)植物群落競(jìng)爭(zhēng)演替的影響, 設(shè)置土壤微生物對(duì)植物生長(zhǎng)與競(jìng)爭(zhēng)的反饋效應(yīng)試驗(yàn)時(shí)(如溫室盆栽試驗(yàn)), 其中常見(jiàn)的重要手段是通過(guò)特定的方法去除土壤微生物以進(jìn)行比較研究, 即帶菌土壤與無(wú)菌土壤種植的植物生長(zhǎng)情況相比較,才能真正反映土壤微生物對(duì)植物的反饋?zhàn)饔谩T趯?duì)土壤進(jìn)行滅菌的過(guò)程中, 最理想的方法是滅殺了所有微生物且不改變土壤理化性質(zhì)[15]。迄今為止, 去除土壤微生物的主要方法有高溫干熱滅菌法[16-17]、高壓蒸氣濕熱滅菌法[10,18]、γ射線的輻照滅菌法[18-20]和化學(xué)熏蒸法[16,18]等。顯然, 不同土壤微生物去除方法會(huì)影響土壤微生物反饋的實(shí)際強(qiáng)度[19], 從而形成研究結(jié)果或結(jié)論的差異, 但鮮有研究比較土壤微生物的不同去除方法的優(yōu)劣。
我國(guó)是外來(lái)生物入侵最為嚴(yán)重的國(guó)家之一, 其中入侵植物種類(lèi)占51%[21]。紫莖澤蘭[(Sprengel) R. King & H. Robinson] (Synonym:Sprengel)是我國(guó)危害最嚴(yán)重的外來(lái)入侵植物之一, 也是世界性入侵雜草[21-23]; 現(xiàn)已在我國(guó)云南、貴州、四川、重慶、廣西等地區(qū)廣泛分布, 并正向東和向北繼續(xù)迅速擴(kuò)散[24-25]。紫莖澤蘭可迅速競(jìng)爭(zhēng)排擠當(dāng)?shù)刂参镄纬蓡畏N優(yōu)勢(shì)群落, 不僅嚴(yán)重降低了入侵地的生物多樣性, 導(dǎo)致生態(tài)系統(tǒng)功能退化, 而且對(duì)入侵地的農(nóng)、林、畜牧業(yè)生產(chǎn)造成了嚴(yán)重經(jīng)濟(jì)損失[22-23,26]。前期的研究已經(jīng)發(fā)現(xiàn), 土壤微生物在紫莖澤蘭的競(jìng)爭(zhēng)擴(kuò)張中具有重要作用[27-37]。本研究目的是以紫莖澤蘭入侵土壤作為案例, 一是比較研究3種常見(jiàn)土壤微生物去除方法(干熱滅菌法、濕熱滅菌法、輻照滅菌法)對(duì)植物生長(zhǎng)的影響, 為相關(guān)研究的微生物去除方法的采用提供借鑒; 同時(shí), 進(jìn)一步解析土壤微生物在紫莖澤蘭競(jìng)爭(zhēng)排斥本地植物的入侵?jǐn)U張中的作用。為進(jìn)一步了解紫莖澤蘭在入侵地的種群建立和擴(kuò)張的微生物學(xué)機(jī)制提供理論依據(jù), 為研究紫莖澤蘭的控制策略和紫莖澤蘭入侵生境的生態(tài)修復(fù)奠定基礎(chǔ), 同時(shí)對(duì)其他外來(lái)入侵植物的研究也具有重要的參考價(jià)值。
1 材料與方法
1.1 紫莖澤蘭土壤的采集
紫莖澤蘭單優(yōu)群落土壤采集樣地位于云南省玉溪市澄江縣麒麟橋附近的山谷帶(24°42′N(xiāo), 102°52′E),海拔1 840~1 873 m, 年平均降水量869 mm。該地區(qū)為中亞熱帶、北亞熱帶、南溫帶和中溫帶4個(gè)氣候類(lèi)型的氣候, 土壤類(lèi)型屬于南方紅壤, 是滇中地區(qū)主要的土壤類(lèi)型, 是紫莖澤蘭最適生長(zhǎng)區(qū)和嚴(yán)重發(fā)生的區(qū)域。
于2013年9月上旬, 參照Niu等[28]和肖博等[35]的土壤采集方法, 在上述區(qū)域的紫莖澤蘭單優(yōu)群落中進(jìn)行20點(diǎn)取樣。于采樣區(qū)選定20個(gè)條件較為均一的樣點(diǎn), 每樣點(diǎn)面積約3 m×3 m, 樣點(diǎn)間相隔約10 m。去除采樣點(diǎn)地表雜草和枯枝落葉后, 取0~10 cm的表土; 每個(gè)樣點(diǎn)取土約4 L。將所有土壤過(guò)20目篩, 充分混合后作為植物盆栽的基質(zhì)土壤備用。
1.2 溫室盆栽反饋試驗(yàn)
1.2.1 供試植物
紫莖澤蘭種子和本地植物香茶菜[(Benth.) Hara]種子均取自云南省澄江縣, 香茶菜為紫莖澤蘭發(fā)生區(qū)常見(jiàn)伴生植物。
1.2.2 盆栽土壤的處理設(shè)置
設(shè)置為8種紫莖澤蘭土壤的處理方式, 分別為: 不滅菌處理、干熱滅菌處理、濕熱滅菌處理、輻照滅菌處理; 不滅菌添加蛭石處理、干熱滅菌添加蛭石處理、濕熱滅菌添加蛭石處理、輻照滅菌添加蛭石處理。后4種處理即添加滅菌蛭石的目的是考慮到土壤滅菌可能會(huì)對(duì)土壤理化特性(尤其是土壤通透性)產(chǎn)生影響, 從而影響土壤微生物反饋效應(yīng)的實(shí)際強(qiáng)度。不滅菌處理即土壤不作任何處理, 視為含有土壤微生物的對(duì)照處理; 干熱滅菌處理參考Trevors[16]方法, 將土壤分裝于托盤(pán)后置于烘箱中, 于180 ℃下加熱4 h, 其間2 h后用潔凈的鐵鏟翻土一次; 濕熱滅菌處理參考Callaway等[10]的方法, 將土壤裝入布袋后置于高壓蒸汽滅菌鍋, 在121 ℃、0.105 MPa條件下濕熱滅菌3次, 每次30 min, 間隔時(shí)間為24 h; 輻照滅菌處理參考Berns等[20]的方法, 將土壤裝袋置于BFT-Ⅱ型60Co-γ輻照裝置中, 輻照源為60 Co-γ射線, 輻照劑量為36 kGy (4 kGy?h-1, 持續(xù)9 h)。添加蛭石的4種處理為前4種處理的土壤分別與輻照滅菌蛭石充分混合; 蛭石添加量為土壤︰蛭石(質(zhì)量比)=9︰1。
1.2.3 盆栽試驗(yàn)設(shè)計(jì)
為了驗(yàn)證土壤微生物及滅菌方式對(duì)植物生長(zhǎng)的反饋效應(yīng)以及對(duì)紫莖澤蘭與本地植物競(jìng)爭(zhēng)效應(yīng)的影響, 溫室盆栽分別設(shè)置紫莖澤蘭與香茶菜分別單種和二者混種2類(lèi)盆栽類(lèi)型。每處理均重復(fù)10個(gè)。
植物單種設(shè)置, 即將上述8種處理土壤分別盆栽種植紫莖澤蘭和香茶菜。紫莖澤蘭單種, 于盆栽試驗(yàn)開(kāi)始前1個(gè)月進(jìn)行紫莖澤蘭種子播種育苗, 播種前以3% H2O2溶液浸泡紫莖澤蘭種子3 min, 用無(wú)菌水沖洗3次后播種于經(jīng)濕熱滅菌的河沙中, 適時(shí)澆水, 保證光照適度, 待苗高3 cm左右時(shí)按每盆1株移栽入盆缽(直徑12 cm, 高10 cm, 下同)中央?yún)^(qū)域。香茶菜單種, 將消毒后的香茶菜種子按每盆5粒均勻撒播于盆缽中央?yún)^(qū)域, 然后覆蓋對(duì)應(yīng)處理的薄土一層, 出苗后不連續(xù)間苗至每盆1株。
基于前期的預(yù)備試驗(yàn), 采用不滅菌土壤添加蛭石和輻照土壤滅菌添加蛭石的2種土壤處理方式分別混合種植紫莖澤蘭與香茶菜。即在盆缽直徑并離缽邊1/3的位置栽植1株紫莖澤蘭幼苗, 再在紫莖澤蘭相對(duì)離缽邊1/3的位置均勻撒播5粒香茶菜種子(出苗后不連續(xù)間苗至每盆1株香茶菜)。紫莖澤蘭單種、香茶菜單種以及紫莖澤蘭與香茶菜混種一共18個(gè)種植處理。
上述各盆栽處理在溫室內(nèi)隨機(jī)擺放。植物生長(zhǎng)期內(nèi)溫室溫度在25 ℃左右, 光周期14 L︰10 D, 根據(jù)植物生長(zhǎng)情況澆水, 植物生長(zhǎng)3個(gè)月后收獲。
1.2.4 測(cè)定指標(biāo)及測(cè)定方法
土壤理化性質(zhì): 為了明確土壤滅菌方式對(duì)土壤理化特性的影響, 分別測(cè)定了用于盆栽試驗(yàn)的4種處理(不滅菌、干熱滅菌、濕熱滅菌與輻照滅菌)的土壤理化指標(biāo)。土壤pH用電極法(WTWpH340)測(cè)定, 土壤懸濁液為水土比1︰2.5(質(zhì)量比); 土壤有機(jī)碳用重鉻酸鉀法測(cè)定; 土壤全氮采用凱氏定氮法測(cè)定; 土壤硝態(tài)氮含量采用硫酸銅澄清-紫外分光光度法; 銨態(tài)氮含量采用氯化鉀浸提-靛藍(lán)吸光光度法, 用流動(dòng)分析儀(Zellwegger Analytical Milwaukee WI)測(cè)定; 全磷采用氫氧化鈉熔融-鉬銻抗比色法; 土壤速效磷含量采用碳酸氫鈉浸提-鉬銻抗比色法; 全鉀采用氫氧化鈉熔融-火焰光度法; 土壤速效鉀含量采用醋酸銨浸提-火焰光度法。每個(gè)處理隨機(jī)選取3個(gè)重復(fù)。
植株生物量: 植株生長(zhǎng)3個(gè)月后, 分別完整取出盆缽中植物, 洗凈泥土, 置于烘箱70 ℃烘干72 h直至恒重后稱(chēng)重。混合種植處理的紫莖澤蘭和香茶菜的生物量分開(kāi)測(cè)定。為了獲得紫莖澤蘭對(duì)本地植物香茶菜的競(jìng)爭(zhēng)強(qiáng)度, 用紫莖澤蘭的相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度(%)來(lái)表示紫莖澤蘭的競(jìng)爭(zhēng)力, 計(jì)算公式[38]:
紫莖澤蘭競(jìng)爭(zhēng)相對(duì)優(yōu)勢(shì)度=紫莖澤蘭生物量/兩種植物總生物量×100%(1)
1.3 數(shù)據(jù)統(tǒng)計(jì)分析方法
紫莖澤蘭相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度采用單因子方差分析(one-way ANOVA), 微生物不同去除方法的土壤養(yǎng)分含量比較采用單因子多重比較方差分析(one-way ANOVA: Fisher LSD test), 微生物不同去除方式以及有無(wú)蛭石的各個(gè)處理紫莖澤蘭、香茶菜的生物量比較采用雙因子多重比較方差分析(two-way ANOVA: Fisher LSD test)。統(tǒng)計(jì)分析軟件為SAS10.0(Inc. Chicago USA)。
2 結(jié)果與分析
2.1 土壤不同滅菌方法下土壤理化性質(zhì)的比較
不同滅菌方式對(duì)土壤理化特性有一定影響, 濕熱滅菌的影響最大, 干熱滅菌次之, 而輻照滅菌的影響最小(表1)。與未滅菌土壤相比, 干熱滅菌的土壤pH和速效鉀含量顯著性降低, 分別降低4.5%和11.5%; 濕熱滅菌的土壤總氮、總鉀、硝態(tài)氮、銨態(tài)氮、速效鉀的含量顯著降低, 分別降低9.7%、2.6%、7.1%、18.7%和20.1%; 輻照滅菌的土壤僅是總氮含量顯著降低, 降低9.7%。4種土壤處理中, 干熱滅菌的土壤pH最低, 顯著低于其他3個(gè)處理; 干熱處理的土壤速效鉀含量相對(duì)于土壤未滅菌處理、輻照滅菌的土壤顯著降低, 相對(duì)于濕熱滅菌的土壤顯著增加; 濕熱滅菌的土壤總鉀、硝態(tài)氮和銨態(tài)氮在4個(gè)處理間含量最低, 相對(duì)于未滅菌、干熱滅菌的土壤顯著降低, 但與輻照滅菌的土壤無(wú)顯著差異, 濕熱滅菌的土壤速效鉀顯著低于其他3個(gè)處理; 有機(jī)碳、總磷、速效磷在4種土壤處理間無(wú)顯著差異。
表1 不同土壤滅菌方法對(duì)土壤理化性質(zhì)的影響
同行數(shù)據(jù)中不同字母表示不同滅菌方式之間在5%水平上差異顯著, 下同。Different letters in the same line indicate significant differences among different sterilization methods at 0.05 level (Fisher’s LSD test). The same below.
2.2 土壤不同滅菌方法、蛭石添加對(duì)紫莖澤蘭和香茶菜生物量的影響
紫莖澤蘭單優(yōu)群落土壤無(wú)論是不添加蛭石還是添加蛭石, 3種滅菌方式(干熱滅菌、濕熱滅菌、輻照滅菌)均顯著降低入侵植物紫莖澤蘭和本地植物香茶菜的生物量, 但3種滅菌方式之間對(duì)紫莖澤蘭和香茶菜生物量的影響存在種間差異和是否添加蛭石的影響(圖1)。
SNS: 未滅菌; SDS: 干熱滅菌; SAS: 濕熱滅菌; SIS:輻照滅菌。不同大寫(xiě)字母表示相同的蛭石因子下滅菌方式之間在5%水平上差異顯著; 不同小寫(xiě)字母表示相同的土壤滅菌處理下添加蛭石與未添加蛭石之間在5%水平上差異顯著(Two-way ANOVA, Fisher’s LSD test)。SNS: non-sterilized soil; SDS: soil subjected to dry-heating sterilization; SAS: soil subjected to autoclaving sterilization; SIS: soil subjected to gamma irradiation sterilization; SAV: soil plus vermiculite; SNV: soil without vermiculite. Different capital letters indicate significant differences among soil sterilization methods with the same vermiculite addition treatment at 0.05 level (Fisher’s LSD test). Different lowercase letters indicate significant differences between adding vermiculite and none-adding vermiculite for the same soil sterilization method at 0.05 level (Fisher’s LSD test).
紫莖澤蘭單種時(shí)(圖1a), 未添加蛭石的紫莖澤蘭土壤經(jīng)干熱滅菌、濕熱滅菌、輻照滅菌后紫莖澤蘭生物量比未滅菌土壤分別顯著降低98.9%、99.1%和97.8%; 添加蛭石的土壤經(jīng)干熱滅菌、濕熱滅菌、輻照滅菌后紫莖澤蘭的生物量相對(duì)于未滅菌添加蛭石的土壤處理分別顯著降低84.8%、80.7%和74.7%。在未添加蛭石的紫莖澤蘭土壤中, 3種滅菌方式之間的紫莖澤蘭生物量沒(méi)有顯著差異; 而在添加蛭石的土壤中, 3種滅菌方式之間的紫莖澤蘭生物量有顯著差異, 輻照滅菌處理土壤的紫莖澤蘭生長(zhǎng)最好, 分別比干熱滅菌、濕熱滅菌顯著增加30.8%和66.5%, 濕熱滅菌次之, 比干熱滅菌增加27.3%。
香茶菜單種時(shí)(圖1b), 未添加蛭石的紫莖澤蘭土壤經(jīng)3種方法滅菌后, 香茶菜在種植后1個(gè)月相繼死亡; 添加蛭石的土壤經(jīng)干熱滅菌、濕熱滅菌、輻照滅菌后, 香茶菜生物量相比于添加蛭石的未滅菌土壤處理分別顯著降低81.2%、75.9%和60.7%。在添加蛭石的土壤中, 3種滅菌方式對(duì)香茶菜生物量有顯著影響, 輻照滅菌處理的香茶菜生長(zhǎng)最好, 分別比干熱滅菌、濕熱滅菌顯著增加109.5%和63.4%, 香茶菜生物量在濕熱滅菌土壤雖然比干熱滅菌土壤增加28.2%, 但沒(méi)有顯著差異。
從4種滅菌方法處理的土壤是否添加蛭石的結(jié)果比較來(lái)看(圖1), 在未滅菌土壤中, 是否添加蛭石對(duì)紫莖澤蘭和香茶菜生物量均無(wú)顯著影響; 而在3種滅菌處理土壤中, 添加蛭石分別顯著提高了紫莖澤蘭和香茶菜的生物量, 經(jīng)干熱滅菌、濕熱滅菌和輻照滅菌后添加蛭石土壤的紫莖澤蘭生物量比未添加蛭石的土壤分別顯著增加12.9倍、20.1倍和10.5倍, 香茶菜在未添加蛭石的3種滅菌土壤中相繼死亡, 但在添加蛭石的3種滅菌土壤中則緩慢生長(zhǎng)。
土壤不同滅菌方式和是否添加蛭石間存在顯著的交互作用(紫莖澤蘭:=3.59,=3,=0.001 5; 香茶菜:=4.59,=3,=0.005 6), 交互作用對(duì)紫莖澤蘭和香茶菜的生物量產(chǎn)生顯著影響(表2)。
表2 土壤不同滅菌方式和是否添加蛭石以及兩者交互作用對(duì)紫莖澤蘭、香茶菜生物量影響的方差分析
2.3 土壤微生物對(duì)紫莖澤蘭與香茶菜競(jìng)爭(zhēng)的影響
未滅菌添加蛭石的土壤處理和輻照滅菌添加蛭石的土壤處理之間紫莖澤蘭相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度具有顯著性差異(=7.31,=1,=0.014 5), 輻照滅菌添加蛭石的土壤處理的紫莖澤蘭相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度為52.54%, 未滅菌添加蛭石的土壤處理(對(duì)照組)紫莖澤蘭相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度為60.94%, 未滅菌添加蛭石的土壤處理比輻照滅菌添加蛭石的土壤處理紫莖澤蘭相對(duì)競(jìng)爭(zhēng)優(yōu)勢(shì)度增加了16.0%(圖2), 表明土壤滅菌后降低了紫莖澤蘭的競(jìng)爭(zhēng)優(yōu)勢(shì)度。
SNSAV: 未滅菌土壤添加蛭石; SISAV: 輻照滅菌添加蛭石。不同字母表示5%水平差異顯著(Fisher’s LSD test). SNSAV: non-sterilized soil plus vermiculite; SISAV: soil subjected to gamma irradiation sterilization plus vermiculite. Different letters indicate significant difference at the 0.05 level (Fisher’s LSD test).
3 討論
大量的研究業(yè)已證實(shí), 土壤微生物在調(diào)節(jié)和促進(jìn)外來(lái)入侵植物對(duì)本地植物的群落競(jìng)爭(zhēng)演替中具有重要的作用[10,39-43], 土壤微生物的去除以及去除后添加特定微生物是驗(yàn)證土壤微生物反饋?zhàn)饔玫闹匾芯渴侄蝃44-46]。本文的結(jié)果顯示, 土壤微生物對(duì)紫莖澤蘭與本地植物香菜的生長(zhǎng)均具有顯著的正反饋效應(yīng), 且土壤微生物有助于增強(qiáng)紫莖澤蘭對(duì)本地植物的競(jìng)爭(zhēng)優(yōu)勢(shì), 這也與前人的結(jié)果一致[27-28,35], 從而進(jìn)一步說(shuō)明了土壤微生物在促進(jìn)紫莖澤蘭的競(jìng)爭(zhēng)性入侵?jǐn)U張中具有重要作用。
國(guó)際上, 驗(yàn)證土壤微生物總體反饋效應(yīng)的土壤微生物去除方式有干熱滅菌、濕熱滅菌、輻照滅菌和化學(xué)熏蒸等, 其中濕熱滅菌由于操作簡(jiǎn)單、成本較低而被廣泛應(yīng)用, 其次為輻照滅菌。本文的結(jié)果顯示, 不同的滅菌方式對(duì)植物的生長(zhǎng)產(chǎn)生顯著影響, 以輻照滅菌的方式為最佳, 干熱滅菌不可取。一方面, 可能由于滅菌降低土壤營(yíng)養(yǎng)有關(guān), 如干熱處理降低速效鉀含量, 濕熱處理降低可利用氮含量和速效鉀, 但輻照滅菌對(duì)可利用肥力無(wú)顯著性影響。前人發(fā)現(xiàn), 濕熱高壓滅菌可改變土壤理化性質(zhì)[47], 包括降低土壤pH和土壤團(tuán)聚體、增加可溶性離子錳含量、降低鐵含量、產(chǎn)生有毒的有機(jī)物等[16]; 也有報(bào)道, γ射線滅菌法也會(huì)改變土壤的理化性質(zhì), 例如硝態(tài)氮與銨態(tài)氮的比例[48]; McNamara等[19]通過(guò)對(duì)ISI (Institute for Scientific Information)數(shù)據(jù)庫(kù)涉及輻照滅菌和高壓滅菌的試驗(yàn)結(jié)果比較后認(rèn)為, 高壓滅菌方法對(duì)理化性質(zhì)和生物活性影響較大, γ射線滅菌法對(duì)土壤和土壤有機(jī)質(zhì)影響較小; Berns等[20]研究發(fā)現(xiàn)γ射線滅菌法對(duì)土壤的理化性質(zhì)和生物活性影響相對(duì)于高溫滅菌方式具有較小的影響。另一方面, 可能主要與不同滅菌方式改變土壤的物理特性有關(guān), 干熱易造成土壤顆粒干化[16], 濕熱滅菌增加了土壤的緊密度[20,48-49], 而輻照滅菌則影響小[19,47,50]。如Smith等[51]通過(guò)將高溫滅菌和沒(méi)有處理過(guò)的土壤混合之后與沒(méi)有處理的土壤進(jìn)行比較, 發(fā)現(xiàn)高溫滅菌土壤對(duì)植物生長(zhǎng)以及菌根真菌侵染有顯著性影響。本文結(jié)果顯示, 土壤滅菌后添加蛭石的土壤植物生物量顯著大于滅菌土壤未添加蛭石的處理, 這可能主要是因?yàn)樘砑域问岣咄寥赖氖杷沙潭群屯ㄍ感? 從而有利于植物的生長(zhǎng)。
由于滅菌方式影響植物的生長(zhǎng)或生物量, 因此不合適的土壤微生物去除方式(如干熱滅菌、濕熱滅菌相對(duì)于輻照滅菌)可能會(huì)造成土壤微生物對(duì)植物生長(zhǎng)和競(jìng)爭(zhēng)的反饋?zhàn)饔帽桓吖馈1驹囼?yàn)結(jié)果顯示, 輻照滅菌為土壤滅菌處理的最佳方式, 同時(shí), 由于未滅菌土壤是否添加蛭石對(duì)植物的生長(zhǎng)無(wú)影響, 因此, 為了驗(yàn)證或更真實(shí)反映土壤微生物在外來(lái)植物競(jìng)爭(zhēng)替代本地植物中的作用和作用強(qiáng)度, 應(yīng)該優(yōu)先采用輻照滅菌添加蛭石的方式。未滅菌土壤是否添加蛭石對(duì)植物的生長(zhǎng)無(wú)影響, 則可能是由于土壤微生物的活動(dòng)具有改善土壤物理特性(通透性)的作用, 從而抵消了蛭石對(duì)土壤通透性的提升作用。
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Feedback of soil biota ongrowth and competitiveness with native plant: A comparison of different sterilization methods*
LIANG Zuopan1, LI Liqing1,2, WAN Fanghao1, LIU Wanxue1**
(1. State Key Laboratory for Biology of Plant Diseases and Insect Pests / Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China; 2. School of Life Sciences, Guizhou University, Guiyang 550025, China)
Soil sterilization is often used to explore feedback effects of soil microbes in community successions of competitive exclusion of native plants by invasive plants. In order to choose the most suitable soil sterilization method and to further analyze feedback effects of soil microbes on invasive plantcompetition with native plants, we compared the differences in biomass betweenand native plantcultured in sterilized soils. The tested soil sterilization methods in the study included dry-heating sterilization, autoclaving sterilization and irradiation sterilization. Non-sterilized soil was the control. In order to mitigate effects of sterilization on soil physico- chemical properties, vermiculite was added to soils sterilized with different methods. The results showed that sterilization by the three methods significantly decreasedandbiomass, regardless of vermiculite addition. For the three different sterilization methods, adding vermiculite to soil promoted the growth ofandwhereas plant biomass in non-sterilized soils was not affected by vermiculite addition.andbiomass under irradiation sterilization soils plus vermiculite was 30.8% and 66.5% higher than that under dry-heating and autoclaving sterilization soils with vermiculite, respectively. Thenbiomass under irradiation sterilization soils plus vermiculite increased by 109.5%and 63.4% compared with that in dry-heating sterilization or autoclaving sterilization soils plus vermiculite, respectively. Plants in gamma irradiated soils had the highest plant biomass among the soils subjected to the three sterilization treatments. Through mixed pot experiment ofandunder irradiation sterilization soils plus vermiculite and non-sterilized soils plus vermiculite, we found that soil microbes enhanced the competitive ability ofover the native plantand relative competitive advantage increased by 16%. These results indicated that irradiation sterilization soil plus vermiculite treatment was efficient in pot experiment studies on feedback effects of soil microbes on plants. Soil microbes exerted positive feedback during invading process of invasive plant.
Invasive plant;;Soil biota; Sterilization method; Feedback
10.13930/j.cnki.cjea.160040
S451.1
A
1671-3990(2016)09-1223-08
2016-01-11 接受日期: 2016-03-29
* 國(guó)家自然科學(xué)基金項(xiàng)目(31171907, 30871654)資助
**通訊作者:劉萬(wàn)學(xué), E-mail: liuwanxue@caas.cn
梁作盼, 研究方向?yàn)槿肭稚飳W(xué)和生態(tài)學(xué)。E-mail: liang1989qnd@163.com
* Funded by the National Natural Sciences Foundation of China (31171907, 30871654)
** Corresponding author, E-mail:liuwanxue@caas.cn
Received Jan. 11, 2016; accepted Mar. 29, 2016