【作者】 唐晓红；

【导师】 魏朝富； 谢德体；

【作者基本信息】 西南大学 ， 农业资源利用， 2008， 博士

【摘要】 由于人口、经济、技术和社会压力而引起的土地利用变化加剧了全球气候变化的速度,寻求农业土壤增加和固定有机碳已经成为缓减大气CO₂浓度增加的有效途径之一。农业生态系统中的碳库不仅是全球碳库的一个重要组成部分,而且是其中最活跃的部分。农业生态系统中的物质循环,特别是C、N循环状况早已成为普遍关注的全球问题之一。稻田生态系统是农业生态系统的一个典型类型,其物质循环的状况和强度不仅强烈地影响该生态系统的生产力大小,而且对全球环境变化产生一定的影响,是近年来较活跃的研究领域。土壤腐殖质因在土壤有机质中不易被微生物分解或具有微生物抗性而成为稳定有机碳,这与其自身的化学组成和微结构密不可分。目前,对土壤腐殖质组成和结构的研究主要集中于森林生态系统以及不同生态系统之间的更替转换,相对而言,农田生态系统,尤其是长期免耕、轮作和秸秆覆盖还田等农业措施下稻田生态系统的碳素循环研究得到的规律性认识还较少。这样,深入了解典型稻田生态系统有机质的累积效应和稳定机制已成为全球变化研究的重要内容。因此,本文以四川盆地紫色水稻土垄作免耕长期定位试验为主要对象(涉及8个处理:常规平作（中稻-冬水）、冬水免耕（中稻-冬水）、油菜免耕（中稻-油菜）、厢作免耕（中稻-油菜）、绿肥免耕（中稻-绿肥）、油菜翻耕（中稻-油菜）、厢作翻耕（中稻-油菜）和水旱轮作（中稻-油菜）,辅助室内稻草腐解培养实验,在全面了解长期保护性耕作下四川盆地紫色水稻土腐殖质特性的基础上,运用元素分析、同位素¹³C天然丰度法、傅立叶变换红外光谱（FTIR）、固体核磁共振(solid-stateCP/MAS ¹³C-NMR)等现代分析技术和方法表征了紫色水稻土胡敏酸和富里酸的化学组成,同时分析短期培养实验中稻草腐解对紫色土壤胡敏酸和富里酸组成和结构的影响。讨论紫色水稻土团聚体组成、稳定性及其与有机碳关系,估算了不同耕作方式下紫色水稻土的碳储量,主要结果如下:1)、耕作方式显著影响紫色水稻土耕作层和犁底层土壤胡敏酸和富里酸的数量和光学性质（E₄/E₆、色调系数（⊿log K）和相对色度（RF））。耕作层用NaOH+Na₄P₂O₇可提取的土壤腐殖酸碳含量占土壤有机碳含量的37%-40%。与常规平作比较,垄作免耕和厢作免耕土壤腐殖酸碳含量分别增加39.29%和8.70%,水旱轮作降低23.52%。垄作免耕和厢作免耕犁底层土壤腐殖酸碳含量分别比常规平作高54.97%和66.38%,说明保护性耕作有利于紫色水稻土耕作层和犁底层腐殖酸碳含量的增加。土壤胡敏酸碳含量为腐殖酸和土壤有机质碳含量的38%-65%和12%-29%,16年垄作免耕和厢作免耕耕作层土壤胡敏酸碳含量分别增加41.62%和10.52%。除厢作免耕增加外,垄作免耕和水旱轮作犁底层土壤胡敏酸碳含量分别为1990年的81.91%和70.82%,垄作免耕和厢作免耕与常规平作差异显著。紫色水稻土耕作层和犁底层土壤富里酸碳含量分别为土壤碳含量12%-22%和11%-25%,垄作免耕和厢作免耕耕作层土壤富里酸碳含量比1990年分别增加23.08%和77.69%,比同期常规平作高25.49%和20.45%,与常规平作和水旱轮作差异不显著。垄作免耕和厢作免耕犁底层土壤富里酸碳含量比1990年分别增加61.00%和10.91%,分别比常规平作增加43.79%和50.69%,因此,保护性耕作有利于增加紫色水稻土耕作层和犁底层富里酸碳含量。紫色水稻土胡敏酸的E₄/E₆比值介于4.65-5.89之间,长期种植水稻使得紫色水稻土胡敏酸的E₄/E₆值增加。同时,土壤胡敏酸的E₄值变化说明免耕、轮作和秸秆覆盖表层土壤胡敏酸的分子结构趋于简单化,其犁底层土壤胡敏酸的芳构化程度增强,而传统耕作土壤胡敏酸的变化正好相反。用NaOH+Na₄P₂O₇提取的耕作层土壤胡敏酸的色调系数为0.75-0.80,低于NaOH提取相应土壤胡敏酸的⊿log K（0.94-1.02）。与常规平作比较,垄作免耕、厢作免耕和水旱轮作耕作层用NaOH+Na₄P₂O₇提取的土壤胡敏酸的⊿log K降低,RF增加,其土壤胡敏酸中与金属和粘土矿物络合的有机化合物中羧基、羰基和酚羟基的含量增加,而甲氧基和醇羟基的含量降低,土壤胡敏酸的氧化程度和芳构化程度增强。常规平作和垄作免耕犁底层土壤胡敏酸的⊿logK降低相对色度（RF）增加,土壤胡敏酸的氧化程度和芳构化程度增强。厢作免耕和水旱轮作土壤胡敏酸的⊿log K增加,RF降低,则其氧化程度和芳构化程度降低。与土壤胡敏酸比较,土壤富里酸的⊿log K增加,RF降低,用0.1 mol L^-1NaOH提取耕作层土壤富里酸的⊿log K为1.05-1.27,RF为14-24。用0.1 mol L^-1NaOH+Na₄P₂O₇提取耕作层和犁底层土壤富里酸的RF分别大于用0.1 mol L^-1NaOH提取的相应土壤富里酸的RF（40-43和39-59）,垄作免耕、厢作免耕和水旱轮作耕作层土壤富里酸的RF依次增加,其氧化程度和芳构化程度增加。垄作免耕和厢作免耕犁底层土壤富里酸的⊿log K降低,RF明显高于常规平作。因此,随着深度的增加,免耕有利于土壤富里酸中羧基、羰基和酚羟基的含量增加,而甲氧基和醇羟基的含量降低,土壤富里酸的氧化程度和芳构化程度增强。长期水稻种植有利于增加土壤有机碳含量,同时耕作方式显著影响有机碳、氮、C/N比率和有机质碳δ¹³C值在耕作层和犁底层中的分布格局。土壤有机碳含量顺序为:厢作免耕＞垄作免耕＞水旱轮作,不同土层有机碳含量降低幅度不同。土壤有机质的δ¹³C值介于-27.85‰～-25.56‰,其中厢作免耕和垄作免耕土壤有机质δ¹³C值在-27‰左右,水旱轮作土壤有机质的碳同位素δ¹³C值随着深度的增加而增加,20-40 cm和0-5 cm土壤有机质δ¹³C值之差达到1.92‰。不同耕作方式下土壤有机质δ¹³C值均高于油菜和水稻的秸秆和根系的δ¹³C值。土壤胡敏酸δ¹³C值介于-28‰～-30‰之间,低于土壤有机质的δ¹³C值1‰～2‰,而更接近于油菜和水稻秸秆和根系的δ¹³C值,因此,胡敏酸中含有较多的脂类。除常规平作土壤胡敏酸的δ¹³C值随着深度的增加而略有降低外,垄作免耕、厢作免耕和水旱轮作土壤胡敏酸的δ¹³C值均随着深度的增加而略有增加。不同耕作方式下有机组分的δ¹³C值顺序为:土壤富里酸＞土壤有机质＞土壤胡敏酸。土壤富里酸与土壤有机质δ¹³C值之差为2‰左右,而与土壤胡敏酸之差约为4‰左右,均显著高于油菜和水稻秸秆与根系的δ¹³C值,土壤富里酸中含有较多的碳水化合物,而胡敏酸中可能含有较多的木质素和脂类。随着深度的增加,常规平作和厢作免耕土壤富里酸δ¹³C值降低,而水旱轮作和垄作免耕土壤富里酸δ¹³C值分别增加1‰。耕作层和犁底层土壤胡敏素碳同位素δ¹³C值分别介于-23.68‰～-24.85‰和-22.59‰～-24.21‰。随着深度的增加,常规平作、垄作免耕、厢作免耕和水旱轮作分别增加1.86‰、0.14‰、0.64‰和1.51‰。各组分δ¹³C值递减顺序为:胡敏素＞富里酸＞土壤有机质＞稻草（油菜）残体＞胡敏酸。植被类型、土层深度、土壤颗粒组成和保护性耕作是影响紫色水稻土有机质和腐殖质组分碳同位素δ¹³C值的主要因素。2)、采用元素自动分析仪、FTIR和固体-CPMAS ¹³C-NMR和有机化学结构分析方法剖析了长期免耕、轮作和秸秆覆盖下紫色水稻土腐殖质的化学组成。紫色水稻土胡敏酸的元素重量百分比以C为主（50%-53%）,其次为O（30%-36%）,H为5%-6%,S为4%-7%,N为4%-6%。与1990年比较,垄作免耕土壤胡敏酸的总酸度、羧基和酚羟基含量降低,羰基含量约增加1倍。与常规平作耕作层土壤胡敏酸比较,厢作免耕土壤胡敏酸的总酸度、羰基和酚羟基含量增加,羧基含量降低。水早轮作土壤胡敏酸的总酸度、羧基和酚羟基含量降低,而羰基含量显著增加。犁底层常规平作土壤胡敏酸的含氧官能团均增加,水旱轮作土壤胡敏酸的总酸度和酚羟基降低,羧基和羰基含量增加。厢作免耕土壤胡敏酸的总酸度和羧基含量与常规平作相近,而羰基含量显著增加。红外光谱分析结果说明,紫色水稻土胡敏酸的含氧官能团主要有羧基、羟基和羰基,只是不同耕作方式下含氧官能团的数量有所不同而已。紫色水稻土胡敏酸以脂肪族（烷基碳和烷氧碳）为主,为50%-86%,其次为羰基碳（18%-31%）,芳香碳最低（9%-24%）,芳香度为8%-33%。脂肪族以烷氧碳为主（27%-43%）,烷基碳为20%-29%。耕作层土壤胡敏酸脂族性以常规平作（70.91%）、厢作免耕（60.21%）和水旱轮作（52.80%）顺序递减,犁底层土壤胡敏酸以厢作免耕（50.80%）、常规平作（59.13%）和水旱轮作（85.75%）顺序递增。随着深度增加,常规平作和厢作免耕胡敏酸脂族性降低,芳香性增强;水旱轮作为脂族性增强,芳香性急剧减弱。不同耕作方式下胡敏酸碳类型差异主要来源于含氧官能团含量在深度上的变化,说明垄（厢）作免耕、轮作和秸秆覆盖还田结合影响了土壤胡敏酸的化学组成。不同耕作方式下紫色水稻土富里酸的元素重量百分比以O含量最高,为71%-81%,其次为S和C,分别为6%-10%和7%-18%,H和N含量分别为2%左右和1%左右。与土壤胡敏酸的红外光谱比较,土壤富里酸的红外光谱出现的吸收峰少,主要含氧官能团包括羧基、羰基和羟基,不同耕作方式下功能团含量存在一定差异。土壤富里酸以脂肪族（烷基碳和烷氧碳）为主,为50%-68%,其次为羧基碳（19%-50%）,芳香碳最低（7%-28%）,芳香度为12%-35%。脂肪族以烷氧碳为主（25%-43%）,烷基碳为24%-31%。耕作层土壤富里酸的脂族特性以下列顺序递增:常规平作（49.34%）、厢作免耕（52.57%）、垄作免耕（59.37%）和水旱轮作（67.27%）。水旱轮作、厢作免耕、垄作免耕和常规平作犁底层土壤富里酸的脂肪族比例分别为52.45%、61.22%、66.31%和67.52%。因此,土壤富里酸化学组成中碳水化合物和糖类对深度的变化最敏感,变化最大,芳香度随着深度的增加而降低（水旱轮作除外）。3)、通过短期室内培养实验,采用元素自动分析仪、FTIR和固体-CPMAS ¹³C-NMR和有机化学结构分析法研究了稻草腐解进程中土壤胡敏酸和富里酸化学组成的变化。添加稻草显著提高土壤有机碳含量,45 d、90 d和135 d土壤有机碳含量分别比相应对照增加64.00%、55.59%和31.38%。70℃和100℃时0.1 mol L^-1NaOH+Na₄P₂O₇提取添加稻草土壤腐殖酸碳含量分别为土壤有机碳含量的24%-32%和47%-53%,土壤胡敏酸碳含量在土壤腐殖酸碳含量中所占的比例（PQ）分别为57%-67%和46%-52%。70℃和100℃时0.1 mol L^-1NaOH提取添加稻草土壤腐殖酸碳含量分别为土壤有机碳含量的22%-26%和40%左右,PQ分别为22%-26%和50%-54%。添加稻草进而显著影响土壤胡敏酸的⊿logK和RF,土壤胡敏酸的类型以Rp型为主。添加稻草和对照土壤胡敏酸的元素重量百分比均以C为主（52%左右）,其次O含量27%-31%,H和S含量相近,N含量最低为4.0%-4.5%。同期添加稻草和对照土壤HA的元素含量没有显著差异。随着培养时间的延长,对照土壤胡敏酸的总酸度和酚羟基增加,羧基和羰基保持稳定。添加稻草对土壤胡敏酸的总酸度、酚羟基和羰基含量增加,羧基含量在90 d时达到最大,随后降低。添加稻草土壤胡敏酸的主要含氧官能团有羧基、羟基和羰基。土壤胡敏酸的有机组分以脂肪族化合物为主,为57%-60%（其中70%左右为碳水化合物或多聚糖）,芳香碳21%-24%,羰基碳含量最低,为18%-19%,芳香度30%-33%,添加稻草后土壤胡敏酸的脂族特性增强。土壤富里酸的元素组成以O和S含量为主（83.32%-93.078%）。用0.1 mol L^-1NaOH在70℃提取添加稻草土壤富里酸的⊿log K随着培养时间增加而降低,RF变化趋势正好相反。用0.1 mol L^-1NaOH在100℃提取的土壤富里酸的⊿log K低于在70℃时的同期水平,RF高于70℃时同期水平,但均在90 d时出现一个转折点。用0.1 mol L^-1NaOH+Na₄P₂O₇在100℃时提取添加稻草土壤富里酸的⊿log K随着培养时间增加而增加,RF则是降低,但其绝对数值高于用0.1 mol L^-1NaOH提取的土壤富里酸的数值,分异程度不如同期土壤胡敏酸的变化。土壤富里酸含有羟基、烷基、羧基和苯环。添加稻草和对照土壤富里酸的化学组成以脂肪族化合物为主,分别为42%-53%和58%-72%。对照土壤富里酸烷氧碳含量最高,添加稻草土壤富里酸羧基碳最高,对照和添加稻草土壤富里酸的芳香度分别为8%-17%和15%-21%。4)、运用国际通用分级方法分析水稻土微团聚体组成及其有机碳分配,继而探讨水稻土大团聚体组成和稳定性及其与有机碳的关系,结合定位试验长期田间观测数据估算了紫色水稻土碳储量,阐明团聚体对有机碳的物理保护作用。油菜免耕、厢作免耕、绿肥免耕、垄作翻耕和厢作翻耕0-10 cm大团聚体分别比对照（12%）增加23%、69%、9%、36%和28%,而10-20 cm大团聚体比对照低9%-38%。冬水免耕、油菜免耕和绿肥免耕0-10 cm大团聚体中有机碳含量分别比对照增加13%、31%和32%,而10-20 cm各处理有机碳浓度低于对照28%-54%,10-20 cm大团聚体和微团聚体中碳浓度差异低于0-10 cm。不同耕作方式下0-10 cm土壤总有机碳储量比对照增加8%-28%,而10-20 cm有机碳储量低于对照4%-22%。传统耕作转变为保护性耕作13年后0-10 cm和10-20 cm土壤有机碳固定率分别为53 gm^-2y^-1和25 gm^-2y^-1,传统耕作有机碳固定率分别为26 gm^-2y^-1和33 gm^-2y^-1。保护性耕作有利于紫色水稻土表层大团聚体形成和土壤总有机碳储量提高。长期保护性耕作后稻田有机碳含量增加,可能提高土壤团聚体稳定性,进而增强有机碳的物理保护能力。糊化作用和湿润作用后紫色水稻土团聚体稳定性差异不明显,而保护性耕作显著影响团聚体的稳定性。糊化作用后团聚体水稳性强弱顺序为:垄作免耕＞厢作免耕＞冬水免耕＞水旱轮作,湿润作用后团聚体水稳性强弱顺序为:厢作免耕＞垄作免耕＞冬水免耕＞水旱轮作。糊化作用下团聚体稳定性与有机碳含量相关性不显著（r=0.432）,湿润作用下团聚体稳定性与有机碳含量呈极显著正相关(r=0.626^**)。因此,保护性耕作显著影响耕层团聚体组成,提高了大团聚体有机碳含量,增强了大团聚体的稳定性,进而提高土壤有机碳储量。因此,四川盆地紫色水稻土有机碳主要以胡敏素的形式得以稳定存在,其次是胡敏酸。土壤胡敏酸和富里酸均以脂肪族化合物为主,其中烷基碳基本保持稳定,烷氧碳、芳香碳和羧基碳深受耕作方式的影响。长期保护性耕作增加大团聚体有机碳含量,增强其稳定性,进而提高大团聚体的比例,提高土壤有机碳储量。本文从土壤和团聚体尺度研究四川盆地紫色水稻土腐殖质特征及其物理保护机制,获得了比较详实的基础信息,能够为区域稻田生态系统物质循环和能量流动规律的认识提供一手资料。今后应进一步从团聚体层面深入研究土壤腐殖质在土壤碳库稳定、积累和转化过程中的重要作用。更多还原

【Abstract】 The close relationship betwween the stability,enhancement or release of soil organic carbon pool and the concentration of CO₂ in atmosphere has become one of hotspot in international science.Whether SOC pool continued to increase or stability subjected to the important theoretic baisis that terristral ecosystem was a sink for absortion and sequestration CO₂ in atomsphere,Which has been one of the key issue of the study on the soil and global change.Since the last 1980s’,the increase of SOC storage in paddy soil of China indicated that paddy soil may be a sink for CO₂ in atomsphere.However,it was uncertain about the capacity of SOC sequestration and its stability mechanisms among different soil types.The dynamics of the stable fractions of soil organic matter（SOM）,the humus substances,has been rarely studied in purple paddy soil of Sichuan basin.It is imperative to determine the characteristic of humus substances and the organic carbon protection mechanism in aggregates in paddy soil.In this paper,we evaluated extraction yields,elemental composition,isotopicδ¹³C abundance,Fourier transform infrared spectroscopy （FTIR）and solid-stae cross-polarization magic angle spinning technique（CPMAS）¹³C nuclear magnetic resonance（NMR）spectra of humic substances isolated from purple paddy soil in Sichuan basin in order to asses the influence of conservation tillage such as no-tillage,crop rotation and rice stalk mulch on the composition of soil humic acids（HA）and flumic acids（FA）and the physical protection mechanisms of SOM in aggregates under a long-term field experiment,including conventional tillage（rice（Oryza sativa L.）-fallow）（CT）,no tillage and ridge culture（rice-fallow）（NT-R）,no tillage and ridge culture （rice-rape）（NT-RR）,no tillage and plain culture（NP-RR）,no tillage and ridge culture（rice-rape/green manure）（NT-RR）conventional tillage and ridge culture（rice-rape）（CT-RR）,convention tillage and plain culture（rice-rape）（CT-PR）and water-upland rotation（rice-rape）（PU-RR）,which located in Southwest university experimental farm.1)The significant differences of organic carbon and humic acid carbon were observed between conservation tillage and conventional tillage.Conservation tillage made the extractable humus carbon increased in plow layer and plow pan.Extractable humus carbon accounted for 37%-40%of soil organic carbon in cultivated layer.Compared with the CT,it was reduced about 23.52%under PU-RR and increased about 39.29%and 8.70%under NR-RR and NP-RR,respectively.In soil of plow pan,the extractable humus carbon under NR-RR and NP-RR increased about 54.97%and 66.38%compared with those under CT,respectively.Humic acid carbon content accounted for the content of hurhic acid and organic carbon about 38%-65%and 12%-29%,respectively.The humic acid carbon content in plow layer of purple paddy soil increased under long-term conservation tillage.Compared with the original soil（in 1990 yr）,it had increased 41.62%and 10.52%under NR-RR and NP-RR,respectively.In 20-40 cm soil layer,the humic acid carbon content only increased under NP-RR and about 81.91%and 70.82%of original soil（1990 yr）under NR-RR and PU-RR,respectively.It was found that the difference between NR-RR/NP-RR and CT was very significant.Soil FA carbon content was about 12%-22%and 11%-25%of soil organic carbon content in plow layer and plow pan of purple paddy soil,respectively.Compared the original soil（1990 yr）,it increased 23.08% and 77.69%in surface layer under NR-RR and NP-RR,which was 25.49%and 20.45%higher than that in CT,respectively.There was no significant difference between CT and PU-RR.Compared with the original soil（in 1990 yr）,the FA carbon content increased 61.00%and 10.91%in plow pan of under NR-RR and NP-RR,which was 43.79%and 50.69%higher than CT,respectively.It indicated that the conservation tillage contributed to increasing FA carbon content of purple paddy soil.The ratio of E₄/E₆ of HA was increased under long-term paddy planting with the value range from 4.65 to 5.89.The change of E4 of HA indicated that the molecular structure of HA tended to be more simplified whereas the aromatization degree of HA in plow pan was reinforced under conservation tillage.Thus the change of E₄ of HA maybe can better reflect the complicated degree of humic acid in purple paddy soil. The⊿log K of the NaOH+Na₄P₂O₇-extractable HA was at the range from 0.75 to 0.80 which was lower than that by NaOH（0.94-1.02）and the RF was at the range from 164 to 205 which was higher than that by NaOH（52-93）.Compared with CT,⊿log K of HA was decreased and RF was increased under NR-RR.The contents of Carboxyl content,carbonyl content and phenol-hydroxy content of HA in cultivated horizon were increased whereas the contents of methoy and alcoholic hydroxyl reduced.The oxidation degree and aromatic components reinforced.The RF of soil FA(extracted by 0.1 mol L^-1NaOH+Na₄P₂O₇)was higher than that by 0.1 mol L^-1 NaOH in plow layer and plowpan（in the range of 40-43 and 39-59,respectively）.The increasing order sorting of The RF,oxidation degree and aromatization degree of FA in cultivated horizon were NR-RR, NP-RR and PU-RR.In cultivated layer under NR-RR and NP-RR,the⊿log K of FA was decreased and the RF of FA was significantly higher than the control treatment（CT）.Therefore with the increase of soil depths, the content of carboxyl,carbonyl and phenol-hydroxy of FA increased,and the contents of methys and alcoholic hydroxylof FA reduced.The oxidation degree and aromaticity of FA were more significant.The distribution of SOM under long-term conservation tillage was studied by isotopesδ¹³C abundance.The results showed that soil organic carbon content increased after long-term paddy planting, and organic carbon content,nitrogen content,ratio of C/N andδ¹³C values were all significantly affected by tillage systems in plow layer and plow pan.The decreasing order soring of organic carbon contents in different tillage systems was NP-RR＞NR-RR＞PU-RR and the reduced range was not the same for different soil layer.Theδ¹³C values of whole soil organic matter were between - 27.85‰and - 25.56‰, and theδ¹³C values under NP-RR and NR-RR were about - 27‰.The increase of stable carbon isotope values with depths was was about 1.92‰under PU-RR and the dispersion between 20-40 cm and 0-5 cm soil layers.Theδ¹³C values of soil under different tillage systems were higher than those of stalks and roots of rape and paddy.Theδ¹³C values of HA were at range from -28‰to -30‰,which were lower than those of SOM（about 1‰-2‰）but closer to these of stalks and roots of rape and paddy.It indicated that more fatty matters could be stored in HA.Except that under CT,theδ¹³C values of soil HA were a bit increased with the increasing of soil depth under the other treatments.The decreasing order sorting of theδ¹³C values was FA＞SOM＞HA.The margin value of theδ¹³C values was about 2‰between soil HAs and SOM,and about 4‰difference between soil HAs and humin.It indicated that there were more carbohydrate components of soil HAs.With the increase of soil depths,theδ¹³C values of soil HAs were decreasing under CT and NP-RR and about 1‰increased under PU-RR and NR-RR.Theδ¹³C values of soil humin in plowlayer and plowpan were at the range of - 23.68‰～24.85‰and - 22.59‰～24.21‰,respectively.With the increase of soil depths,theδ¹³C values of soil humic acid increasing 1.86‰,0.14‰,0.64‰and 1.51‰under CT,NR-RR,NP-RR and PU-RR,respectively.The decreasing order of theδ¹³C values in each fraction was humin＞FAs＞SOM＞rice（rape）residues＞HAs.The main factors that affected theδ¹³C values of SOM and humus substance were vegetable types,soil depths,patrticulate composition,and conservation tillage.2)The carbon was the main contents（50%-53%）,followed by oxygen（30%-36%）,hydrogen（5%-6%）, sulfur（4%-7%）and nitrogen（4%-6%）of the soil HAs in purple paddy soil.Compared with the original soil（1990yr）,the total acidity,carboxyl and phenolic hydroxyl content of the soil HAs decreased and the carbonyl content increased about 1 times under NR-RR.Compared with the HA in plow layer under CT, the total acidity,carbonyl and phenol-hydroxyl contents increased and the carboxyl groups reduced under NP-RR,and the total acidity,carboxyl and phenolic-hydroxyl content of the soil HAs decreased and the carbonyls content increased under PU-RR.The total acidity and carboxyl groups content of the soil HAs were nearly same between NP-RR and CT.The carbonyls content was significantly increased under NP-RR. By means of infrared spectrum analysis,it was found that the major oxygen-containing functional groups of the soil HAs in purple paddy soil were carboxyl groups,hydroxyls and carbonyls,and their contents were different under each tillage system.The carbon of aliphatic components（including alkyl-C and carbohydrate-C）accounted for the largest part（50%-86%）of humic acids in purple paddy soil,followed by carbonyl C（18%-31%）and aroma carbon （9%-24%）.Carbohydrate components were the major part in aliphatic components,and then was the alkyl-C.In plow layer the decreasing order sorting of aliphatic components of HA was CT（70.91%）＞NP-RR（60.21%）＞PU-RR（52.80%）and in plough pan,the increasing order sorting of the aliphatic characteristics of HA was（50.80%）＞CT（59.13%）＞PU-RR（85.75%）.The aliphatic characteristics of the soil HAs decreased and the aromaticity of HA increased under CT and NP-RR.The aliphatic characteristics of HA increased and the aromaticity of HA decreased rapidly under PU-RR.The differences of soil HAs carbon types among treatments mainly resulted from the changes of oxygen-containing functional groups with soil depths.It indicated that the chemical compositions of soil HA were affected by agriculture management practices such as no-tillage,crop rotation and stalk mulch.The oxygen was the largest composition（71%-81%）in FA constitution of purple paddy soil,followed by sulfur（6%-10%）,carbon（7%-18%）,hydrogen（about 2%）and nitrogen（about 1%）.Compared with the infrared spectra characteristics of HA,the absorption peaks in infrared spectra characteristics of soil FAs were not so many.The major oxygen-containing functional groups included carboxyl,carbonyl and hydroxyl groups.Differences among these different functional groups were found.The aliphatics carbon was the largest composition of FA（50%-68%）,followed by carboxyl carbon（19%-50%）,and the aroma carbon was the lowest part.The aliphatics carbon was composed of carbohydrate-C（25%-43%）,alkyl-C （24%-31%）and some others.In cultivated layer,the aliphatic characteristics of FA could be ranked as CT （49.34%）＜NP-RR（52.57%）＜NR-RR（59.37%）＜PU-RR（67.27%）and among tillage systems the decreasing order was CT（67.52%）＞NR-RR（66.31%）＞NP-RR（61.22%）＞PU-RR（52.45%）.So,the carbohydrate and saccharide were more sensitive to the soil depths change and the aromaativity was decreased with the increasing soil of depths（except under PU-RR）.3)Reclaiming of the straw mulch has been taken as an important method to improve soil in many areas of China.In order to evaulate the mechanism of straw mulch improving soil,the effects of straw mulch on the soil humus substances（humic acids and fluvic acids）were studied by elemental composition,FTIR and solid-stae CP/MAS ¹³C NMR spectra in purple paddy soil with incubation experiment.SOC contents were significantly increased in the application of rice stalk.Compared weith those of CK,the SOC contents of the application of rice stalk were about 1.64,1.56 and 1.31 times in the incubation time of 45d,90d and 135d,respectively.The HS under the application of rice stalk extracted by 0.1 mol L^-1NaOH+Na₄P₂O₇ at 70℃and 100℃was about 24%-32%and 47%-53%of soil carbon content and the PQ was about 57%-67%and 46%-52%,while about 22%-26%and 40%of soil carbon content and,the PQ was about 22-26%and 50%-54%by 0.1 mol L^-1NaOH at 70℃and 100℃,respectively,Which would significantly affected⊿log K and RF of HA whatever adding rice stalks or not.The Rp type was the main sort of the extracted HA.For both the application of rice stalks and CK,the carbon was the largest composition（about 52%）in HA constitution,followed by oxygen（27%-31%）,hydrogen and sulfur,and nitrogen was the smallest part （about 4%-6%）.No obvious differences were found between the application of rice stalks and CK.With incubation time increase,the total acid and phenolhydroxyl content of soil HA increased and the carboxyl and carbonyl content of soil HA maitained stable under CK.The total acid,phenolhydroxyl and carbonyl content increased during the incubation time and the peak of the carboxyl content changes appeared at the 90th day under application of rice stalks.The results of FTIR Showed that the aliphatic characteristics of the soil HAs increased and the mainly oxygen-containing functional groups were carboxyl,hydroxyl and carbonyl in the application of rice stalks.The alphiatic components,about 70%of which was carbohydrate or saccharide,was the main part of the soil HAs（57%-60%）,and then the aromatic components （21%-24%）,the carbonyl carbon content was the lowest（18%-19%）.Except the O and S content of soil FA among treatments were much higher than those of main soil types of China,other elements are all lower than those of China.⊿log K of FA extracted by 0.1 mol L^-1NaOH at 70℃decreased with the incubation time,and the trend of RF was the on the opposite.At the same incubation time,the⊿log K of FA extracted at 100℃was lower than that extracted at 70℃,and one turning point was observed at 90 d.the⊿log K of FA under the application of rice stalks extracted by 0.1 mol L^-1NaOH+Na₄P₂O₇ at 100℃was increased and the RF decreased with the incubation time,and their values were higher than those extracted by 0.1 mol L^-1NaOH.The change degree of FA was not as severe as that of HA at the same incubation time.The results of FTIR showed that soil FA contained these functional groups such as hydroxyl,alkyl and carbonyl and benzene.With the incubation time increasing, the aliphatic compounds was the main part of soil FA chemical composition in both treatments with and without rice stalks addition,which was about 42%-53%and 58%-72%,respectively.The aromaticity was about 8%-17%and 15%-21%in CK and the application of rice stalks,respectively.The main component of FA was alkyl-C in CK and carboxyl-C was the major part in the application of rice stalks.4)A 13 years long-term experiment in purple paddy soil of Sichuan Basin was used to evaluate effects of conservational tillage systems on aggregates composition and carbon storages.The results showed that aggregates composition and soil carbon storages were significantly controlled by conservational tillage systems.In the 0-10 cm layer,the amount of macroaggregates under conservational tillage systems: no-tillage and ridge culture（rice-rape）（NT-RR）,no-tillage and plain culture（rice-rape）（NP-RR）,no-tillage and ridge culture（rice-green manure）（NT-RGM）,tillage and ridge culture（rice-rape）（TR-RR）,tillage and plain culture（rice-rape）（TP-RR）were 23%,69%,9%,36%and 28%higher compared with conventional tillage（CT）（12%）,respectively.In the 10-20 cm layer,the macroaggregates proportion was 9%-38%lower than that of CT.The organic carbon concentration in macroaggregates at 0-10 cm depths under no-tillage and ridge culture（rice-fallow）（NR-RF）,NR-RR and NR-RGM were 13%,31%and 32%higher than that of CT,while 28%-54%lower at 10-20 cm depths,respectively.The differences of organic carbon concentration between macroaggregates and microaggregates in the 10-20 cm layer were lower than those in the 0-10 cm layer.The organic carbon storages among conservational tillage systems in the 0-10 cm layer were 8%-28%higher than that of CT,while lower 4%-22%in the 0-10 cm layer.The ratio of mean organic carbon sequestration on the conversion from CT to conservational tillage at 0-10 cm and 10-20 cm depths since 1990,were 53 g m^-2y^-1and 25g m^-2,y^-1,while under CT were 26 g m^-2y^-1and 33 g m^-2y^-1, respectively.The conservational tillage systems favorably led to the formation of macroaggregates and the enhancement of soil organic carbon storages.Long-term conservation tillage is an effective agricultural management to improve soil structure in severely destroyed paddy soil by increase of soil organic carbon （SOC）,more work is still needed to understand the impacts of conservation tillage on the mechanisms of aggregates stability.Soil samples in 0-20 cm layer were adopted from the long-term experiment:（1）, paddy-upland rotation and plain culture（rice-rape）（PU-RR）,（2）no-tillage and ridge culture （rice-fallow）（NT-RF）,（3）no-tillage and ridge culture（rice-rape）（NT-RR）and（4）no-tillage and plain culture （rice-rape）（NT-PR）.Different pretreatment,such as slaking in fast wetting,wetting and subsequent slaking, were applied to simulate the breakdown mechanisms of aggregate in paddy soil.The results showed that there was no significant difference of aggregate stability between slaking in fast wetting and wetting,but significant difference of aggregate stability exited between conservation tillage and conventional tillage. The aggregate stability in slaking pretreatment ranked in the order of NT-RR＞NT-PR＞NT-RF＞PU-RR. The aggregate stability order under wetting was NT-PR＞NT-RR＞NT-RF＞PU-RR.The organic carbon content in aggregates was significantly positive related to the aggregate stability under wetting（r=0.626^* *）,while low correlation under slaking treatment（r=0.432）.The results suggest that long-term conservation tillage favorably led to the increase of SOC in aggregates,and the enhancement of aggregates.As above all,the main SOC was observed in soil humin,followed by soil humic acids and soil fluvic acids in purple paddy soil of the Sichuan basin.The humic acids and fluvic acids mainly comprise of alphiatic components,and alkyl-c maitained stability,land use practices have greatly effects on the multitude of carbohydrate-C,aromatic C and carboxyl-C.The evnidences surggested that conservation tillage favorably led to the increase of OC content in mcroaggregate,enhancement of mcroaggregates stability,increase of the mcroaggregates propertion and SOC storage.In this paper,characteristics of humus substances and organic carbon physical protection mechanisms in aggregates were investgated,and achieved basis information about HS composition,which could surpported the firstly reference for the study on the recognization of substances cycle and energy transformation in paddy field system.In the future,more ephersis should be played on the important role of humus substances in the processes of SOC pool stability,acumulation,and its transformation.更多还原