李昌明，王曉玥，孫 波*

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基于固態(tài)13C核磁共振波譜研究植物殘?bào)w分解和轉(zhuǎn)化機(jī)制的進(jìn)展①

李昌明1,2，王曉玥1，孫 波1*

(1土壤與農(nóng)業(yè)可持續(xù)發(fā)展國(guó)家重點(diǎn)實(shí)驗(yàn)室(中國(guó)科學(xué)院南京土壤研究所)，南京 210008；2 中國(guó)科學(xué)院大學(xué)，北京 100049)

植物殘?bào)w在土壤中的分解和轉(zhuǎn)化影響了其養(yǎng)分歸還和有機(jī)質(zhì)形成過(guò)程。由于缺乏高分辨率的分析方法，對(duì)不同氣候、植被和土壤類型條件下植物殘?bào)w在分解過(guò)程中化學(xué)結(jié)構(gòu)組成的演變特征和機(jī)制仍不清楚。核磁共振波譜技術(shù)在解析自然有機(jī)物化學(xué)組成方面具有獨(dú)特的優(yōu)勢(shì)，本文綜述了基于固態(tài)13C核磁共振波譜(solid-state13C-NMR spectroscopy)技術(shù)評(píng)價(jià)植物殘?bào)w的基質(zhì)質(zhì)量、解析植物殘?bào)w的分解速率及其官能團(tuán)組成的變化特征、揭示土壤腐殖質(zhì)特性等方面的主要進(jìn)展。未來(lái)針對(duì)植物殘?bào)w分解和有機(jī)質(zhì)形成機(jī)制的研究，應(yīng)該結(jié)合穩(wěn)定性同位素質(zhì)譜和掃描電鏡分析方法，綜合分析植物殘?bào)w中的有機(jī)化合物組成和物理結(jié)構(gòu)；從多時(shí)空尺度揭示不同類型植物殘?bào)w中有機(jī)碳官能團(tuán)的降解路徑；結(jié)合高通量測(cè)序和基因芯片分析方法，深入研究土壤微生物群落與植物殘?bào)w化學(xué)結(jié)構(gòu)的協(xié)同演變機(jī)制，提出不同氣候–土壤–植被類型區(qū)促進(jìn)土壤有機(jī)質(zhì)形成的調(diào)控措施。

核磁共振波譜；植物殘?bào)w；分解；有機(jī)碳官能團(tuán)；土壤有機(jī)質(zhì)

土壤有機(jī)質(zhì)是陸地生態(tài)系統(tǒng)的重要碳庫(kù)[1]，也是土壤肥力的基礎(chǔ)[2]，而植物殘?bào)w是土壤有機(jī)質(zhì)的重要來(lái)源[3]。植物吸收土壤養(yǎng)分，通過(guò)光合作用合成有機(jī)物，部分光合產(chǎn)物最終以凋落物和根茬形式進(jìn)入土壤分解，這一過(guò)程是土壤養(yǎng)分元素歸還以及腐殖質(zhì)形成的主要途徑[4]，也是養(yǎng)分元素生物地球化學(xué)循環(huán)的關(guān)鍵環(huán)節(jié)。以往針對(duì)不同氣候、植被和土壤類型條件下的植物殘?bào)w分解開(kāi)展了大量研究，但主要集中在分解速率及其影響因素方面[5-10]，對(duì)于其化學(xué)結(jié)構(gòu)特征和組成變化規(guī)律仍不清楚[11-12]。固態(tài)13C核磁共振波譜(solid-state13C-NMR spectroscopy)具有同時(shí)定性、定量分析有機(jī)物質(zhì)化學(xué)組成的優(yōu)勢(shì)，已經(jīng)廣泛應(yīng)用于研究天然有機(jī)化合物的結(jié)構(gòu)特征，近十年來(lái)才開(kāi)始應(yīng)用于研究植物殘?bào)w的分解機(jī)制。本文綜述了基于固態(tài)13C核磁共振波譜評(píng)價(jià)植物殘?bào)w基質(zhì)質(zhì)量、研究植物殘?bào)w官能團(tuán)的組成變化和分解速率、解析植物殘?bào)w分解進(jìn)入土壤腐殖質(zhì)路徑等方面的進(jìn)展，以期為陸地生態(tài)系統(tǒng)碳循環(huán)過(guò)程模擬提供參數(shù)支撐，為建立合理的農(nóng)田秸稈還田措施和土壤有機(jī)質(zhì)培育措施提供理論基礎(chǔ)。

1 核磁共振技術(shù)的理論基礎(chǔ)

核磁共振(nuclear magnetic resonance，NMR)是指自旋的原子核在磁場(chǎng)中吸收一定頻率的電磁波而產(chǎn)生的能級(jí)躍遷的現(xiàn)象。原子質(zhì)量數(shù)為奇數(shù)的原子具有自旋特性，被稱為磁性核，如1H、13C、31P和15N。當(dāng)自旋的原子核放入外加磁場(chǎng)時(shí)，其原子核偶極子產(chǎn)生與外加磁場(chǎng)方向相同的低能態(tài)(順磁)或相反的高能態(tài)(逆磁)兩種趨向，在通過(guò)外加電磁波誘導(dǎo)原子核從原來(lái)的順磁(低能態(tài))變?yōu)槟娲?高能態(tài))的過(guò)程中，原子核會(huì)吸收能量從低能級(jí)躍遷至高能級(jí)，即核磁共振現(xiàn)象。通常原子核周圍均包含有電子云，它對(duì)原子本身磁場(chǎng)接受外加磁場(chǎng)具有一定的屏蔽作用，使得原子核對(duì)電磁波的吸收峰相對(duì)于原子核基準(zhǔn)物質(zhì)發(fā)生偏移。這種相對(duì)于基準(zhǔn)物質(zhì)的偏離程度便是出峰位置，也即化學(xué)位移，一般用d表示，單位是ppm。13C-NMR的位移范圍一般為0 ~ 250 ppm。不同類型官能團(tuán)結(jié)構(gòu)中，由于C(13C的自然豐度約為1.01%，可指示或代表總碳，即13C視為總碳的標(biāo)記物)所處的化學(xué)環(huán)境不同，其周圍電子云的密度不同，所產(chǎn)生的屏蔽作用也不同，因此產(chǎn)生的化學(xué)位移也存在差異。反之則可根據(jù)不同位移值判別13C所處的化學(xué)環(huán)境，即官能團(tuán)的種類。13C-NMR核磁共振波譜通?？梢越馕?大類官能團(tuán)，這些官能團(tuán)指征特定種類的生物大分子化合物(表1)。此外，由于13C原子所吸收的電磁波能量會(huì)隨原子核數(shù)量的增多(濃度高)而正比例變強(qiáng)，即峰面積呈正比例增大，因此核磁共振光譜技術(shù)不僅能給出有機(jī)化合物化學(xué)結(jié)構(gòu)的定性結(jié)果，還能夠通過(guò)計(jì)算得到其官能團(tuán)的半定量信息[13-14]。

表113C固態(tài)核磁共振波譜分析的有機(jī)碳官能團(tuán)種類及對(duì)應(yīng)的生物大分子化合物[18, 35, 67]

注：①含氧烷基碳總體上指征著碳水化合物種類。

2 13C固態(tài)核磁共振波譜技術(shù)的優(yōu)缺點(diǎn)

與傳統(tǒng)化學(xué)提取方法相比，固態(tài)核磁共振波譜有如下優(yōu)點(diǎn)。首先，固態(tài)核磁共振波譜可以直接分析植物樣品中表征木質(zhì)素和纖維素等的官能團(tuán)組成[15]，避免了提取過(guò)程所帶來(lái)的結(jié)構(gòu)變化問(wèn)題[16]，其分析結(jié)果更接近于真實(shí)狀態(tài)[17]。例如傳統(tǒng)方法(如Proxi-mate analysis, Van Soest serial extraction, temperature- programmed pyroanalysis)在分析前對(duì)原始樣品所進(jìn)行的熱裂解等有針對(duì)性提取過(guò)程，會(huì)破壞樣品的結(jié)構(gòu)組成信息，如在對(duì)類木質(zhì)素-單寧蛋白質(zhì)復(fù)合體的分析中，全局方法由于化學(xué)提取、熱反應(yīng)破壞了氮含量高的多肽類化合物等的檢測(cè)結(jié)果偏低，但13C-NMR波譜方法可以無(wú)損地在147和151 ppm波段上可以檢測(cè)到對(duì)應(yīng)峰[18]。另外，傳統(tǒng)提取方法在提取過(guò)程中會(huì)形成原始樣品所沒(méi)有的復(fù)雜物質(zhì)，例如傳統(tǒng)方法提取的木質(zhì)素會(huì)被大量脂類包裹，導(dǎo)致其難以定量分析[16]。其次，核磁共振光譜技術(shù)適合分析以烷基為主的復(fù)雜大分子化合物結(jié)構(gòu)，能夠很好地區(qū)分烷基(聚亞甲基)和含氧烷基(碳水化合物或者脂基相連的)碳之間結(jié)構(gòu)的差異[19]。此外，13C-NMR波譜所需樣品量小[20]，因此適合于分析經(jīng)過(guò)長(zhǎng)時(shí)間分解后剩余量低的植物殘?bào)w樣品[21]。

盡管核磁共振技術(shù)有諸多優(yōu)點(diǎn)，但其使用成本高、技術(shù)要求復(fù)雜，制約了該方法的廣泛應(yīng)用[20]。同時(shí)，13C-NMR波譜僅能獲取碳骨架信息，無(wú)法獲得分子單體信息。而且13C-NMR波譜僅能以半定量的形式給出各碳官能團(tuán)所占的比例。此外，在研究植物殘?bào)w分解過(guò)程中有機(jī)質(zhì)的來(lái)源時(shí)，需要借助其他d13C同位素、質(zhì)譜等手段綜合分析[22]。

3 研究植物殘?bào)w基質(zhì)質(zhì)量和分解速率

植物殘?bào)w的分解速率決定著生態(tài)系統(tǒng)中養(yǎng)分循環(huán)的快慢，在一定程度上決定著土壤養(yǎng)分有效性的高低[23]。除氣候、土壤性質(zhì)等外部因素以外，植物殘?bào)w自身的基質(zhì)質(zhì)量(氮、磷、木質(zhì)素、纖維素、C/N、C/P、木質(zhì)素/N)也是影響凋落物分解速率的重要因素[24]。利用13C-NMR波譜可以通過(guò)區(qū)分植物殘?bào)w中不同類別的官能團(tuán)來(lái)分析凋落物的基質(zhì)質(zhì)量，并預(yù)測(cè)腐解過(guò)程中的有機(jī)碳分解速率和殘余量[25]。

13C-NMR波譜解析的官能團(tuán)中，含氧烷基碳代表容易被分解者微生物代謝利用的碳水化合物，即易分解碳；烷基碳和芳香族碳等則表征難以被利用的木質(zhì)素、單寧等，即難分解碳[25]。研究表明，難分解碳的含量越高，有機(jī)物的分解速率越慢[25]。例如，Lorenz等[26]發(fā)現(xiàn)山毛櫸葉片中烷基碳含量高于橡樹(shù)葉，而松木針葉中表征木質(zhì)素的芳香族碳含量高于櫻木葉，高含量的難分解碳降低了山毛櫸葉片和松針的分解速率。此外，進(jìn)一步計(jì)算難分解碳和易分解碳的比值，如含氧烷基/烷基，含氧烷基/甲氧基等，可以更敏感地反映植物殘?bào)w的可分解性和分解速率，即其比值越高，植物殘?bào)w越容易被分解，分解速率越高[27-28]，并且其相關(guān)性高于C/N和木質(zhì)素/N與植物殘?bào)w分解速率相關(guān)性[28]。植物殘?bào)w初始化學(xué)組成對(duì)其分解量的預(yù)測(cè)受到腐解時(shí)間的影響，例如，Prescott等[29]發(fā)現(xiàn)在腐解初期(1年)，木質(zhì)素或者含氧烷基含量與腐解速率顯著相關(guān)；但在腐解后期(4 ~ 5年)，不同類別植物殘?bào)w的殘余量趨于相似。

植物殘?bào)w在腐解過(guò)程中的殘余量變化符合一階指數(shù)衰減模型(方程1)，能夠被很好地?cái)M合并計(jì)算得到腐解常數(shù)(k constant)[30]：

W=0×exp(-) (1)

式中：0是初始時(shí)間的植物殘?bào)w重量(g)，W是時(shí)間的植物殘?bào)w重量(g)。植物殘?bào)w分解過(guò)程中，有機(jī)碳官能團(tuán)絕對(duì)含量的變化與殘留量變化一致[21]，不同官能團(tuán)的變化速率特征可以采用一階指數(shù)衰減模型描述[31-33]。

4 解析植物殘?bào)w腐解過(guò)程中官能團(tuán)的變化途徑和模式

了解植物殘?bào)w在分解過(guò)程中各有機(jī)碳官能團(tuán)的動(dòng)態(tài)變化是精確估算陸地生態(tài)系統(tǒng)碳循環(huán)和平衡的基礎(chǔ)[34]。在植物殘?bào)w分解過(guò)程中，其化學(xué)組成不斷改變，進(jìn)而影響了殘余物的分解速率隨著植物殘?bào)w的分解進(jìn)程。植物殘?bào)w在分解過(guò)程中，其含氧烷基碳豐度逐漸降低，而芳香基碳、烷基碳豐度升高[35-36]。同時(shí)，植物殘?bào)w的分解程度可以用烷基/氧烷基(alkyl/O- alkyl)[37]、芳香率(aromaticity)[38]和炔基碳與甲氧基碳比值(carbonhydrate C : methoxyl C)[39]表征，其比值越高表明植物殘?bào)w的腐解程度越大。

由于植物殘?bào)w的組成差異，在腐解過(guò)程中其有機(jī)碳官能團(tuán)化學(xué)結(jié)構(gòu)轉(zhuǎn)化路徑不同。一方面，轉(zhuǎn)化路徑的不同表現(xiàn)在不同植物殘?bào)w中官能團(tuán)的分解順序不同。例如，對(duì)意大利南部林地刺槐、黑松凋落葉中6種官能團(tuán)腐解速率的研究表明，在刺槐凋落葉中官能團(tuán)的分解順序?yàn)榉臃蓟?含氧烷基碳=苯環(huán)基碳>羰基碳=烷基碳>甲氧基碳，而在黑松凋落葉中官能團(tuán)的分解順序則表現(xiàn)為含氧烷基碳>烷基碳>羰基碳=酚芳基碳>苯環(huán)基碳>甲氧基碳[40]。又如，硬木類凋落物中的芳香基碳比烷基碳更容易分解，而針葉林凋落物中卻相反[32, 41]。

另一方面，轉(zhuǎn)化路徑的不同表現(xiàn)在一些植物殘?bào)w在分解過(guò)程中沒(méi)有表現(xiàn)出易分解物質(zhì)下降而難分解物質(zhì)積累的規(guī)律。某些植物殘?bào)w分解過(guò)程中含氧烷基官能團(tuán)的豐度變化不大，可能是由于其來(lái)源復(fù)雜性。例如，亞熱帶人工馬尾松林根部的含氧烷基豐度沒(méi)有顯著下降，這是由于根部的含氧烷基不僅來(lái)源于易分解的多糖，也源于氧化后的丙烷基側(cè)鏈以及甲氧基基團(tuán)，使含氧烷基在分解過(guò)程中處于合成和分解的動(dòng)態(tài)平衡[31]。另外，分解樹(shù)木殘?bào)w的白腐菌對(duì)不同組分碳的無(wú)選擇性分解也是各官能團(tuán)豐度變化不顯著的原因之一[42]。例如，澳大利亞南洋杉葉、莖混合凋落物在2年腐解過(guò)程中，氧烷基含量先減后增，而烷基含量則先增后減，其他各個(gè)官能團(tuán)豐度無(wú)顯著變化，并沒(méi)有出現(xiàn)烷基、芳香基顯著積累的現(xiàn)象[42]。同樣，烷基/氧烷基比值的變化也與植物殘?bào)w種類有關(guān)，木材中烷基/氧烷基比值并沒(méi)有隨分解進(jìn)程而升高[40]，利用烷基/氧烷基指征分解進(jìn)程時(shí)，需要有一定限制條件，即相同植物來(lái)源，并不是腐解質(zhì)量損失越高對(duì)應(yīng)的化學(xué)結(jié)構(gòu)變化越大[43]。

除了植物殘?bào)w的化學(xué)組成，分解過(guò)程中的生物和非生物因素也影響了有機(jī)碳官能團(tuán)的轉(zhuǎn)化路徑。生物因素中，土壤生物顯著影響了植物殘?bào)w的分解過(guò)程，如大型土壤動(dòng)物蚯蚓等的進(jìn)食促進(jìn)了植物殘?bào)w分解，經(jīng)消化道排泄后使植物殘?bào)w與其他小型微生物接觸更均勻，增加了植物殘?bào)w的腐解面積，并增強(qiáng)了其對(duì)微生物的口適性[17, 44]。土壤微生物群落組成與植物殘?bào)w化學(xué)結(jié)構(gòu)是協(xié)同演變的，但其協(xié)同演變的機(jī)制仍有待進(jìn)一步研究[45-46]。目前的研究表明，在低C/N的植物殘?bào)w中芳香基碳與微生物群落結(jié)構(gòu)的變化相關(guān)性最強(qiáng)，而在高C/N植物殘?bào)w中則表現(xiàn)為氧烷基碳與微生物群落結(jié)構(gòu)顯著相關(guān)[45, 47]。另外，不同分解時(shí)期，微生物與有機(jī)組分的相關(guān)性也不同；例如，對(duì)小麥、桉樹(shù)、豌豆腐解過(guò)程的研究表明，在腐解60 d時(shí)小麥葉和根中的烷基碳與革蘭氏陽(yáng)性菌含量顯著正相關(guān)，腐解150 d時(shí)3種植物殘?bào)w的雙氧烷基碳與微生物豐度的相關(guān)性最強(qiáng)[47]。

非生物因素中，氣候條件和土壤性質(zhì)均是影響植物殘?bào)w分解過(guò)程中化學(xué)結(jié)構(gòu)變化的重要因素。例如，由于Ca是微生物生長(zhǎng)代謝的重要元素，Mn是木質(zhì)素分解酶的重要組成成分，因此土壤中的Ca，Mn等元素含量也會(huì)影響植物殘?bào)w中化學(xué)組成的變化[31,48]。對(duì)綠肥腐解過(guò)程的研究表明，不同種類綠肥腐解12周后，土壤微生物群落與綠肥有機(jī)碳化學(xué)結(jié)構(gòu)同時(shí)發(fā)生變化，綠肥基質(zhì)質(zhì)量和土壤性質(zhì)共同影響了綠肥的分解過(guò)程，但其相對(duì)影響隨腐解進(jìn)程而變化[49]。另外，由于在一定范圍內(nèi)，土壤中高含水量促進(jìn)微生物活性，因此含氧烷基碳的豐度與受降雨量影響的土壤濕度顯著正相關(guān)[31]?；诓煌瑲夂驇У牟煌寥李愋偷闹脫Q試驗(yàn)研究表明，氣候等地點(diǎn)因素對(duì)腐解過(guò)程中化學(xué)結(jié)構(gòu)變化的影響顯著高于土壤類型的影響[50-51]。溫度升高，通過(guò)促進(jìn)植物殘?bào)w分解，促進(jìn)了易分解物質(zhì)向難分解物質(zhì)轉(zhuǎn)化。同時(shí)，植物殘?bào)w的化學(xué)組成也影響了其分解的溫度敏感性。研究表明，難分解碳組分的溫度敏感性高于易分解碳組分。這是由于溫度–質(zhì)量(temperature-quality)假說(shuō)認(rèn)為難分解碳組分需要更多的反應(yīng)勢(shì)能，反應(yīng)勢(shì)能越高，反應(yīng)隨溫度變化越明顯[52]。Erhagen等[52]發(fā)現(xiàn)凋落物分解的溫度系數(shù)(10)與凋落物中烷基和含氧烷基成正比，凋落物化學(xué)組成解釋了10變異的90%。因此，13C-NMR獲取的植物殘?bào)w化學(xué)組成信息，可用于描述凋落物腐解的溫敏性，為模擬全球氣候變化條件下生態(tài)系統(tǒng)碳循環(huán)的反饋機(jī)制提供理論依據(jù)。

5 分析植物殘?bào)w腐解過(guò)程中形成進(jìn)入土壤的有機(jī)質(zhì)的組成特征

植物殘?bào)w在土壤中分解后，一部分以CO2形式排放至大氣，另一部分通過(guò)土壤生物參與的腐殖化作用以及與土壤膠體的蓄留固定作用形成土壤有機(jī)質(zhì)[53]。植物殘?bào)w的化學(xué)結(jié)構(gòu)組成深刻影響著土壤有機(jī)質(zhì)的化學(xué)組成[54]。建立植物殘?bào)w化學(xué)組成與有機(jī)質(zhì)性質(zhì)之間的關(guān)系，可通過(guò)植物殘?bào)w屬性的變化預(yù)測(cè)植物腐解過(guò)程中土壤有機(jī)質(zhì)屬性的變化[55]。例如，與硬木樹(shù)種相比，針葉樹(shù)凋落物中的芳香基碳分解速率較慢，而烷基碳分解較快，導(dǎo)致針葉林下土壤中芳香基碳積累速率更快[33, 41]。橡樹(shù)林下土壤有機(jī)質(zhì)以羰基碳為主，針葉林下土壤有機(jī)質(zhì)以烷基碳為主，而石蘭科常綠灌木(manzanita)下土壤有機(jī)質(zhì)則以氧烷基碳為主[56]。此外，Johnson等[57]認(rèn)為多年生木本植物南杉木(hoop pine)的凋落物(枝、莖、葉)在兩年的分解過(guò)程中并沒(méi)有出現(xiàn)難分解類型碳的大量積累，因此不適合作為長(zhǎng)期固碳類型的樹(shù)種。

此外，植物殘?bào)w的化學(xué)組成也影響了腐殖化進(jìn)程及土壤中有機(jī)質(zhì)的積累速率[40-41]。植物殘?bào)w分解過(guò)程中，一部分碳被微生物利用進(jìn)而轉(zhuǎn)化為難分解物質(zhì)持留在土壤中，另一部分碳轉(zhuǎn)化為CO2排放到大氣中[19]。近年的研究結(jié)果表明，微生物分解后的有機(jī)碳更容易被土壤黏粒吸附，是土壤穩(wěn)定有機(jī)碳的重要組成成分[58]。易分解碳對(duì)土壤中穩(wěn)定有機(jī)碳貢獻(xiàn)更大的可能原因之一是，利用難分解碳的微生物以k-生長(zhǎng)型微生物為主，它們的碳源利用率低，因此更多比例的碳以CO2的形式消耗，而不是形成穩(wěn)定的土壤有機(jī)質(zhì)[58-59]。

此外，由于烷基碳和芳香基碳比較穩(wěn)定，種植富含此類有機(jī)碳官能團(tuán)的植被或者輸入其植物殘?bào)w可以促進(jìn)土壤有機(jī)質(zhì)的積累[57, 60-61]。Rumpel[62]發(fā)現(xiàn)在法國(guó)小麥種植區(qū)植物殘?bào)w經(jīng)火燒后會(huì)產(chǎn)生芳香基(Aromatics)含量較高的黑炭(black carbon)，并與土壤中的黏土礦物等無(wú)機(jī)組分結(jié)合，加之年降雨量低，侵蝕和淋失作用弱，從而增加了土壤長(zhǎng)期碳固定的潛能。由于13C-NMR可以揭示植物殘?bào)w腐解過(guò)程中土壤有機(jī)質(zhì)的積累過(guò)程和特征，因此可以為建立培肥土壤的間作體系[61]、人工林[63]和經(jīng)濟(jì)作物[64]提供物種選擇的科學(xué)依據(jù)。

6 結(jié)語(yǔ)與展望

植物殘?bào)w在土壤中的腐解過(guò)程是生物地球化學(xué)循環(huán)的重要環(huán)節(jié)，也是陸地碳循環(huán)和平衡的核心[23]。13C-NMR分析可以評(píng)價(jià)植物殘?bào)w基質(zhì)質(zhì)量、分解程度，全面分析分解過(guò)程中各組分官能團(tuán)的腐解速率，解析化學(xué)結(jié)構(gòu)的分解轉(zhuǎn)化模式，進(jìn)而確定進(jìn)入土壤的有機(jī)質(zhì)組成特征。目前仍需加強(qiáng)以下3個(gè)方面的研究：

1) 結(jié)合d13C質(zhì)譜分析[65-66]和掃描電鏡[66]等方法，綜合研究植物殘?bào)w中的生物大分子化合物結(jié)構(gòu)和物理結(jié)構(gòu)，全面評(píng)價(jià)植物殘?bào)w的基質(zhì)質(zhì)量，預(yù)測(cè)植物殘?bào)w的腐解速率。

2) 從團(tuán)聚體-土體-景觀-區(qū)域的空間尺度和不同的時(shí)間尺度，加強(qiáng)多時(shí)空尺度下植物殘?bào)w有機(jī)碳官能團(tuán)降解路徑的研究，闡明植物殘?bào)w屬性和環(huán)境因子對(duì)其腐解進(jìn)程中化學(xué)結(jié)構(gòu)變化的影響。

3) 結(jié)合高通量測(cè)序(illumina)和基因芯片(geo-chip)等方法，加強(qiáng)土壤微生物群落結(jié)構(gòu)演替與植物殘?bào)w化學(xué)結(jié)構(gòu)變化之間協(xié)同關(guān)系的研究，明確控制植物殘?bào)w腐解的關(guān)鍵功能微生物及其網(wǎng)絡(luò)結(jié)構(gòu)，提出不同區(qū)域土壤微生物功能的調(diào)控措施。針對(duì)我國(guó)不同農(nóng)區(qū)土壤有機(jī)質(zhì)提升問(wèn)題，借助區(qū)域尺度的聯(lián)網(wǎng)土壤置換實(shí)驗(yàn)，開(kāi)展10年以上尺度的長(zhǎng)期研究，綜合研究不同氣候、土壤、植被類型下植物殘?bào)w分解和有機(jī)質(zhì)積累的生物學(xué)機(jī)制[67-69]。

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Advances in Studying Mechanisms of Plant Residue Decomposition and Turnover Based on Solid-State13C Nuclear Magnetic Resonance Spectroscopy

LI Changming1, 2, WANG Xiaoyue1, SUN Bo1*

(1 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; 2 University of Chinese Academy of Sciences, Beijing 100049)

Decomposition and turnover of plant residues in soil play critical roles in the nutrient release and organic matter formation. Due to the deficit of high-resolution detection method, the characteristics and mechanisms of chemical structure of plant residues changing with climate, vegetation and soil conditions during their decomposition process remain unclear. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool to elucidate direct information on chemical composition of nature organic matter. The recent progresses were reviewed in evaluating the quality of plant residues, predicting the decomposition rate and the transformation of functional groups of organic carbon, and analyzing the characteristics of soil humus by using the solid-state13C NMR spectroscopy. To deepen our understanding of mechanisms of plant residue decomposition and organic matter formation, the composition and structure of biological macromolecules in plant residues should be comprehensively analyzed by using combinedd13C mass spectrometry and scanning electron microscopy. Then the decomposition pathway of functional groups of organic carbon could be studied at different temporal and spatial scales. And the synergetic change of microbial community composition and chemical structure of plant residues could be revealed by using high-throughput sequencing and gene chip methods. These will be helpful to put forwards the best management practices to promote the soil organic matter formation under different climate, soil and plant conditions.

Nuclear magnetic resonance; Plant residue; Decomposition; Organic carbon components; Soil organic matter

10.13758/j.cnki.tr.2017.04.003

154；Q958

A

國(guó)家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2016YFD0200300)和國(guó)家自然科學(xué)基金項(xiàng)目(41271258)資助。

(bsun@issas.ac.cn)

李昌明(1987—)，男，甘肅蘭州人，博士研究生，主要從事土壤生態(tài)學(xué)方面的研究。E–mail：cmli@issas.ac.cn