【作者】 展茗；

【导师】 曹凑贵；

【作者基本信息】 华中农业大学 ， 生态学， 2009， 博士

【摘要】 本研究以稻鸭复合种养（RD）、间歇灌溉（RW）、常规淹水灌溉（CK）3种不同的稻田生态系统为研究对象,于2007年和2008年通过大田试验和室内分析,系统研究了三种稻田生态系统植株碳固定、土壤碳排放、土壤有机碳库组分的动态特征,及其相互关系,明确了不同稻作模式下稻田碳过程的变化机制,初步认识了短时间尺度内土壤有机碳组分变化与水稻产量的关系,为认识和评价我国稻作模式的变化对碳循环造成的影响提供了依据,并为我国高产稻田的土壤碳管理积累了研究资料。主要研究结果如下:（1）不同稻作模式下水稻植株的碳固定2007年和2008年两年内CK、RD、RW地上部分净固碳量平均分别达到776.6g.m^-2、778.9 g.m^-2、705.5 g.m^-2,RW分别比CK和RD显著低9.2%和9.4%;CK和RD间差异不显著。（2）不同稻作模式稻田CH₄排放2007年和2008年两年内RD的平均CH₄排放通量13.65 mg.m^-2.h^-1,累积排放量为34.15 g.m^-2,分别比CK减少了19.15%、21.4%（P＜0.01）。其甲烷减排效应主要发生在稻鸭共作期间。2007年和2008年两年内RW的平均CH₄排放通量为10.03 mg.m^-2.h^-1,累积排放量为25.49 g.m^-2,分别比CK减少了36.9%、36.8%（P＜0.01）。其甲烷减排效应可发生在水稻的各个生育阶段。与CH₄排放呈正相关的因素有TOC、DOC、MBC、土壤温度、过氧化氢酶活性、水稻植株固碳量的变化量、土壤pH:有负相关作用的因子有HA、FA、土壤NH₄⁺。土壤DOC是影响甲烷排放的最主要的土壤有机碳组分。（3）不同稻作模式稻田CO₂排放2007年和2008年两年内RW的平均CO₂排放通量159.4 mg.m^-2.h^-1,累积排放量为385.4g.m^-2,分别比CK和RD增加了29.4%、22.0%（P＜0.01）。RD的CO₂排放通量和排放量与CK差异不显著。与CO₂排放呈正相关的因素有TOC、ROC、水稻植株固碳量;有负相关作用的因子有DOC、MBC、HA、FA、土壤pH、纤维素酶活性。（4）不同稻作模式稻田土壤有机碳组分数量特征和动态2007年和2008年两年内CK的平均TOC为11.64 g.kg^-1,ROC、DOC、MBC、HA、FA含量分别为2.21 g.kg^-1、0.57 g.kg^-1、0.29 g.kg^-1、0.34 g.kg^-1、2.09 g.kg^-1,其在TOC中的比例分别为22.31%、4.46%、2.38%、3.81%、19.88%。2007年和2008年两年内RD的平均TOC为11.05 g.kg^-1,ROC、DOC、MBC、HA、FA含量分别为2.62 g.kg^-1、0.51 g.kg^-1、0.27 g.kg^-1、0.46 g.kg^-1、2.08 g.kg^-1,其在TOC中的比例分别为24.14%、4.60%、2.46%、4.18%、19.02%。2007年和2008年两年内RW的平均TOC为10.79 g.kg^-1,ROC、DOC、MBC、HA、FA含量分别为2.58 g.kg^-1、0.44 g.kg^-1、0.25 g.kg^-1、0.40 g.kg^-1、2.13 g.kg^-1,其在TOC中的比例分别为24.27%、3.99%、2.24%、3.76%、20.16%。与CK相比,RD提高了土壤ROC、HA及其在TOC中的比例;RW减慢了土壤有机碳的积累速度,提高了ROC及其有效率,降低了DOC及其有效率,同时提高了FA在有机碳中的比例。（5）土壤有机碳组分的相关性和变化的敏感性ROC的绝对量及其ECRI与微生物量商有显著的正相关性,ROC的绝对量与其它有机碳组分间没有相关性,但其ECRI与DOC、DOC/TOC,与HA及其有效率有显著的负相关性。DOC、DOC/TOC的绝对量和ECRI与MBC、MBC/TOC、FA有正相关关系;与HA、HA/TOC、HA/FA间有显著的负相关关系。不同的稻作模式对有机碳组分之间的关系有影响。利用ECRI对土壤有机碳组分关系作分析与用绝对量作分析具有不同的作用。因为ECRI表征的是土壤有机碳的变化量,具有动态性,能显示出土壤有机碳组分之间变化的因果关系。在短时间尺度内,利用有机碳指标的ECRI和绝对量结合起来进行相关分析能比较全面地反应有机碳组分之间的关系。有机碳组分有效响应指数（ECRI）和有效变异系数法可有效分析土壤有机碳组分变化的敏感性。反应敏感性的大小为MBC、MBC/TOC、DOC/TOC、DOC、HA、FA、ROC、ROC/TOC、TOC、HA/TOC、FA/TOC、HA/FA。（6）稻田植株碳固定、土壤碳排放及有机碳组分之间的相关性稻田植株碳固定、土壤碳排放及土壤有机碳组分变化三个过程之间相互联系、相互影响。水稻植株的累积固碳量与土壤中变化较慢TOC、HA、HA/TOC、FA、FA/TOC等组分有显著的相关性,而与土壤中变化较快的活性碳部分没有显著的相关性。固碳量的变化量则与土壤中变化较快的ROC、MBC、MBC/TOC组分表现出极显著的正相关关系,说明了土壤中新鲜有机碳输入量的变化会引起土壤活性有机碳的敏感性变化。CH₄排放通量与水稻植株固碳量的变化呈极显著的正相关关系,而与累积固碳量没有显著关系。而CO₂排放通量与水稻植株的累积固碳量与固碳量的变化都有显著或极显著的相关关系。对于CK而言,CO₂排放通量与土壤TOC极显著正相关,而与DOC及其有效率、MBC及微生物量商呈显著或极显著的负相关性。对于RD而言,CO₂排放通量与土壤ROC与显著正相关,而与DOC及其有效率、HA呈显著负相关。对于RW而言,TOC含量越多、HA含量越低能明显促进CO2的排放。三处理中活性较高和活性较低的有机碳组分均与CH₄排放通量间有显著的相关性。其中DOC、DOC/TOC、MBC、MBC/TOC在三处理中均表现出与CH₄排放通量间显著或极显著的正相关关系。而HA、HA/TOC在三处理中表现出与CH₄排放通量间极显著的负相关性。对于RD、RW而言FA、FA/TOC也表现出与CH₄排放通量间的显著负相关性。对于CK和RD而言,土壤TOC与CH₄排放通量间有显著的正相关关系。可见在稻田土壤中,丰富的碳源是CH₄产生的前提条件,但CH₄排放量的多少则直接与MBC和DOC的多少有关。（7）土壤有机碳组分与水稻产量的关系水稻产量与TOC、DOC、DOC/TOC、MBC的绝对量有显著或极显著的正相关关系,与HA/TOC、FA/TOC、HA/FA、ROC/TOC的绝对量有显著或极显著的负相关关系。同时,DOC/TOC、MBC、MBC/TOC、ROC、ROC/TOC、FA/TOC的ECRI及CSI均与水稻产量有显著或极显著的负相关关系,HA、HA/TOC、TOC的ECRI与水稻产量有显著或极显著的正相关关系。说明要获得较高的水稻产量,稻田土壤要维持较高的总有机碳、可溶性有机碳和微生物量碳,同时要求ROC、DOC、MBC变化速度较慢,要有较快的有机碳的积累速率,较快的HA的变化速率。研究表明,与常规淹水稻田相比,稻田养鸭和间歇灌溉没有降低水稻产量。更多还原

【Abstract】 This study selected three different paddy farming systems which are typical in southern regions of China,including rice-duck integrated farming system（RD）, intermittent irrigation system（RW）,and conventional flooded irrigation system（CK）.In 2007 and 2008,dynamics of carbon sequestration by rice plants,soil carbon emissions, soil organic carbon components of three kind of paddy farming systems and their mutual relations were studied through field experiments and laboratory analysis.Mechanism of the three carbon cycle process were understood in different paddy farming systems,and the relationship between soil organic carbon components and rice yield was preliminarily affirmed during the short term scale of rice growth stage.Those studies would benefit to evaluate the impact of the changes of paddy farming systems on carbon cycling in the paddy ecosystem,and accumulate the data for soil carbon management in high-yielding rice fields in China.The main results are summarized as follows.（1）Carbon fixation by rice plant of different farming systemIn the two years of 2007 and 2008,average net carbon fixation by rice plants above ground of CK,RD and RW reached 776.6 g.m^-2、778.9 g.m^-2、705.5 g.m^-2 respectively. Net carbon fixation of RW was significantly lower by 9.2%and 9.4%than that of CK and RD.There was no significant difference between CK and RD.（2） CH₄ emissions from paddy of different farming systemsIn the two years of 2007 and 2008,the average CH₄ emission flux of RD was 13.65 mg.m^-2.h^-1,Cumulative amount of CH₄ emissions reached 34.15 g.m^-2,lower than that of CK by 19.15%and 21.4%（P＜0.01） respectively.Compared with CK,RD primarily mitigated CH₄ emission during the period of coexisting of rice and duck.In the two years of 2007 and 2008,the average CH₄ emission flux of RW was 10.03 mg.m^-2.h^-1,Cumulative amount of CH₄ emissions reached 25.49 g.m^-2,lower than that of CK by 36.9%and36.8%（P＜0.01） respectively.Compared with CK,RW could reduce CH₄ emission during the whole growth stage of rice.Factors of soil TOC,DOC,MBC,soil temperature,catalase activity,the changing amount of carbon fixation,soil pH positively correlated with CH₄ emission,while soil HA,FA and NH₄⁺ negatively correlated with CH₄ emission.The one of important reasons for mitigating CH₄ emission of RW was that RW could effectively reduce soil DOC.（3） CO₂ emission from paddy soil of different farming systemIn the two years of 2007 and 2008,the average CO₂ emission flux of RW was 159.4 mg.m^-2.h^-1,Cumulative amount of CH₄ emissions reached 385.4 g.m^-2,more than that of CK by 29.4%and 22.0%（P＜0.01） respectively,while there was no significant difference between CK and RD.Factors of soil TOC,ROC,the changing amount of carbon fixation positively correlated with CO₂ emission,while soil HA,FA,DOC,MBC and soil pH negatively correlated with CH₄ emission.（4）Dynamics of soil organic carbon components in paddy of different farming systemsIn the two years of 2007 and 2008,the average soil TOC content of CK was 11.64 g.kg^-1,and the content of soil ROC、DOC、MBC、HA、FA was 2.21 g.kg^-1、0.57 g.kg^-1、0.29 g.kg^-1、0.34 g.kg^-1、2.09 g.kg^-1 respectively,while which proportion of TOC was 22.31%、4.46%、2.38%、3.81%、19.88%respectively.In the two years of 2007 and 2008,the average soil TOC content of RD was 11.05 g.kg^-1,and the content of soil ROC、DOC、MBC、HA、FA was 2.62 g.kg^-1、0.51 g.kg^-1、0.27 g.kg^-1、0.46 g.kg^-1、2.08 g.kg^-1 respectively,while which proportion of TOC was 24.14%、4.60%、2.46%、4.18%、19.02%respectively.In the two years of 2007 and 2008,the average soil TOC content of RD was 10.79g.kg^-1,and the content of soil ROC、DOC、MBC、HA、FA was 2.58 g.kg^-1、0.44 g.kg^-1、0.25 g.kg^-1、0.40 g.kg^-1、2.13 g.kg^-1 respectively,while which proportion of TOC was 24.27%、3.99%、2.24%、3.76%、20.16%respectively.Compared with CK,RD increased soil ROC,HA and its proportion in the TOC;RW slowed down the accumulation speed of soil organic carbon,improved ROC and its proportion in the TOC,and decreased DOC and its proportion in the TOC,also increased the proportion of FA in the TOC.（5） Relativity and sensitivity of soil organic carbon componentsThe absolute amount of ROC had no correlations with other SOC components except positively with MBC/TOC,but its effective carbon response index（ECRI） showed significant positive correlation with DOC and DOC/TOC,while negative correlation with HA.DOC and its proportion in TOC had significant positive correlation with MBC, MBC/TOC,FA,while negatively correlated with HA,HA/TOC,HA/FA.Different farming systems of rice had different influence on the relationship among SOC components.ECRI of SOC components had different roles of their absolute amount for analysis of correlations between SOC components,because ECRI represented changing amount of SOC components,could dynamically reveal the causal relationship among SOC components.Combined use of ECRI and absolute amount of SOC components in correlation analysis could comprehensively reflect the relationship among SOC components at the short-term scale.ECRI of SOC components and their effective coefficient of variation（ECV） could be used to effectively analyze the changing sensitivity of SOC components.The sensitivity of MBC,MBC/TOC, DOC/TOC,DOC,HA,FA,ROC,ROC / TOC,TOC,HA/TOC,FA/TOC,HA/FA descended from strong to weak.（6） Correlations among rice carbon fixation,soil carbon emissions and organic carbon componentsThe process of rice carbon fixation mutually interrelated to the process of soil carbon emission and the change of organic carbon components.Accumulative amount of carbon fixation by rice plants positively correlated with soil TOC、HA、HA/TOC、FA、FA/TOC which transformed rather slowly in the soil,while had no significant correlations with the active soil organic carbon which transformed faster in the soil.Contrarily,the changing amount of carbon fixation positively correlated with soil ROC、MBC、MBC/TOC,which proved that input of fresh organic carbon into the soil could cause the change of soil active organic carbon sensitively. CH₄ emission flux had significant positive correlation with the changing weight of carbon fixation,but no significant relationship with the accumulative of carbon fixation. While both of the two factors positively correlated with CO₂ emission flux.For CK,soil TOC was significantly positively correlated with CO₂ emission flux, while DOC,DOC/TOC,MBC and MBC/TOC showed significant negative correlations with it.In terms of RD,CO₂ emission flux positively correlated with soil ROC,while negatively correlated with DOC,DOC/TOC and HA.For RW,more TOC and less HA content in the soils would promote CO₂ emission.Both higher active and less active soil organic carbon components had significant correlations with CH4 emission flux for the three treatments.Among the indicators of soil organic carbon,DOC,DOC / TOC,MBC and MBC / TOC showed significant positive correlations with CH4 emission flux,while HA and HA / TOC significantly negatively correlated with it.FA and FA / TOC also showed negative correlations with CH4 emission flux for RD and RW.For CK and RD,there was a significant positive correlation between soil TOC and CH4 emission flux.In a word,the rich carbon source is the prerequisite for CH4 formation,but the amount of CH4 emissions are directly related to the amount of MBC and DOC in paddy soil.（7） Relationship of SOC components and rice grain yieldIn the terms of absolute amount of SOC components,soil TOC,DOC,DOC/TOC, MBC had significant positive correlations with rice yield,while HA/TOC,FA/TOC, HA/FA,ROC/TOC negatively correlated with the yield.In the terms of ECRI,DOC/TOC, MBC,MBC/TO,ROC,ROC/TOC,FA/TOC had significant negative correlations with rice yield,while HA,HA/TOC,TOC positively correlated with the rice yield.The results revealed higher content of soil TOC,DOC and MBC,slower changing rate of ROC,DOC and MBC,faster accumulative rate of TOC,and faster transferring rate of HA are the important conditions to gain higher rice yield.The results showed RD and RW did not decrease the rice grain yield compared with CK.更多还原