【作者】 李娜；

【导师】 汤洁；

【作者基本信息】 吉林大学 ， 环境科学， 2012， 博士

【摘要】 在全球变化研究中，诸多学者一直重视陆地生态系统碳循环及其他温室气体的变化研究，取得了大量的研究成果。但是，已有的研究成果多注重植物生长期土壤有机碳的动态变化，较少考虑冻融作用下的土壤有机碳变化；已有的冻融研究成果其研究区也多限于三江平原湿地、松嫩平原黑土、西北地区不同覆盖条件下的耕地，以及高原山区冻土带，北方盐碱土区土壤有机碳的研究鲜见报道；研究方法多以室内模拟实验为主，界定冻融温度和冻融循环次数有所限制，且冻融期土壤有机碳的影响机理研究方面涉及较少，只有将冻融期土壤有机碳储量纳入到全年土壤有机碳储量研究中，其结果才能更全面、更准确。本研究主要以遥感技术、环境模拟、空间分析、实验室测试和数据分析为主要技术支持，选择吉林西部典型的水田、旱田、草地和盐碱地，开展了冻融模拟实验，系统分析了冻融期土壤有机碳、全氮、土壤酶活性的动态变化规律，探讨土壤有机碳、全氮对土壤酶活性的响应机制，为我国北方地区冻融期土壤有机碳循环和全氮的研究提供了技术参考。本文研究了-5~5℃FTC（冻融循环作用，Freezing-thawing-cycles）、-25~5℃FTC、-5~5℃FT（长期冻融作用，Freezing-thawing）和-25~5℃FT不同冻融作用下土壤有机碳、全氮的动态变化。无论是在FTC还是FT过程中，各地类有机碳、全氮含量均随土壤深度的增加而降低，且二者之间具有较强的相关性；冻融作用影响了土壤有机碳和全氮含量，但其影响程度不一致。一般情况下，表层土壤（0~10cm、10~20cm和20~30cm）理化性质变化趋势一致，而30~40cm、40~50cm的变化趋势相同。除在-25~5℃FTC下，盐碱地土壤有机碳呈现出下降趋势外，土壤有机碳含量均在10次FTC结束后呈现出不同程度的增加。方差分析表明，FTC下，冻融次数是引起土壤有机碳变化的主要影响因素，而冻结温度则为次要因素。但在FT中，土壤有机碳的波动幅度较小，受冻结温度和冻结次数影响较少。在FTC作用下，水田和旱田土壤全氮量在冻融循环结束后，均呈现出增加的趋势，而草地和盐碱地土壤全氮量趋势相反；FT过程中，土壤全氮量均呈现出不同程度的降低。方差分析表明，FTC作用下，冻结温度和冻结次数均为土壤全氮量变化的主要影响因素，而在FT中，冻结温度对土壤全氮量的影响不显著。对冻融期土壤酶活性进行监测得到，冻融结束后，除草地脱氢酶活性有所降低外，其余地类土壤脱氢酶活性均呈现出不同程度的升高趋势；土壤多酚氧化酶均呈现出降低的趋势；各地类土壤过氧化氢酶活性均有小幅度波动，但变化不显著；土壤脲酶均呈现出增加的趋势。季节性冻融作用对土壤酶活性具有显著的影响，且不同的土壤酶类以及不同土壤层次的土壤酶对季节性冻融的影响也有着一定的差异。利用SPSS法对土壤酶活性与土壤有机碳、全氮含量进行相关性分析得到，二者之间的相关性较强；除盐碱地土壤有机碳、全氮与不同酶之间均呈正相关且回归系数相差不大外，其余土壤酶活性对土壤有机碳、全氮的影响作用大小均为土壤脲酶最大，而土壤过氧化氢酶最小，该结果与利用SIMCA-P软件得到的多元回归结果相似。土壤酶对土壤系统中有机物质的分解起到重要作用，催化土壤微生物活性，稳定土壤结构，分解有机物残体，参与营养元素循环。土壤酶经历不断的合成、积累、抑制或分解过程，对农业土壤营养物质循环具有重要作用。在冻融作用下，随着土壤温度以及土壤中自由水形态的变化，土壤酶经历了多次好氧和厌氧过程的反复，酶活性随之改变，从而影响土壤有机质和全氮。虽然，冻融期绝大部分土壤有机碳和全氮量呈现出不同程度的升高趋势，但从冻融期不同地类土壤碳密度计算结果可以看出，在冻融期土壤碳密度变化幅度较小，计算得到冻融作用下不同地类之间土壤有机碳储量增加，储量大小为水田<盐碱地<草地<旱田。利用DNDC模型的模拟结果，结合遥感解译得到的大安市水田、旱田、草地和盐碱地的面积，得到大安市地类2009年的温室气体排放情况，并利用IPCC净变暖潜势模型，估算不同冻融作用下大安市不同地类变暖潜势值，判断冻融期土壤碳截存过程，旱田土壤均表现为碳汇；而水田在-5~5℃FTC和-25~5℃FTC中，表现为碳源，而在-5~5℃FT和-25~5℃FT中为弱碳汇；草地土壤在-25~5℃FTC下表现为碳汇，其余作用下为碳源；盐碱地分别在-5~5℃FTC和-25~5℃FT作用下，表现为碳汇；进而推广到研究区，得到大安市冻融期净增温潜势呈现出西北地区较低，而中部较高的分布特点。以往土壤有机碳研究的重点多放在植物生长季，本研究利用实验模拟技术探讨冻融作用对吉林西部水田、旱田、草地和盐碱地不同地类土壤有机碳、全氮和土壤酶活性的波动和影响机制，可弥补研究区内尚未开展冻融期盐碱地、草地、耕地（旱田和水田）有机碳的系统研究的空白，为东北盐碱土分布区冻融期碳循环研究提供范例。更多还原

【Abstract】 Among global climate change studies, carbon cycle of terrestrial ecosystem and the changesof other greenhouse gases are continuously import to scholars all around the world. However,most existing results focus on the trend of soil organic carbon (SOC) during the plant growingseason, without consideration of SOC change during freezing-thawing period. In addition, theexisting studies in freezing-thawing period are mostly limited in Sanjiang plain, Songnen plain,arable land under different mulch in northwestern of China, as well as the tundra of plateau. TheSOC research of saline-alkali soil paddy field in northern areais rarely reported. Researchmethods mainly adopt indoor simulation experiments withthe limits of freezing-thawingtemperature and cycling time. And impact mechanism of SOC is little during freezing-thawingperiod. It will get more comprehensive and accurate results if the SOC storage offreezing-thawing period is added into the annualstudy.Several technical methods are chosen to finish this study, such asremote sensing,environmental modeling, spatial analysis, laboratory testing and data analysis. Typical paddyfields, dry fields, meadows and saline-alkali soil are selected to study the dynamic change of soilorganic carbon, total nitrogen, soil enzyme activity during freezing-thawing period. The resultscan provide technical reference for the freezing-thawing study in northern area of our country.The temperature of-25℃,-5℃,5℃is chosen to carry out the experiments. Fourmechanisms are designed as following:-5~5℃FTC (12h-Freezing-12h-thawing-cycles),-25~5℃FTC,-5~5℃FT(120h-Freezing-120h-thawing) and-25~5℃FT. SOC and TN decreased as thesoil depth increased in all soil types and the correlation of the both indexes are high. But the twoindexes changes are different during the freezing and thawing period. Generally speaking, SOCchange trend is similar in surface soil (0-10cm,10-20cm and20-30cm) while the one in the flatis the same. The SOC is certain increasing duiring-25~5℃FTC except the SOC of saline-alkalisoil. The times of freezing-thawing is the main impact factor compares the temperature. The TNof paddy and dry fields is increased at the end of freezing-thawing-cycles and the situation isopposite in the grassland and saline-alkali soil. The temperature and times of freezing-thawingare also the main factors to impact TN changes. But the temperature unaffected TN at FT.The soil dehydrogenase increased after freezing-thawing except the one in grassland. Thepolyphenol oxidase decreased by the affect of freezing-thawing. The change of catalase is little in four typical soils. The urease has the increasing trend. The freezing-thawing effect obviouslyaffect the soil enzymes and certain difference exist in various soil.It is easy to get the high correlation between SOC, TN and soil enzymes by SPSS. Thecorelation indexes between the three ones of saline-alkali soil are similar. The correlation ofurease is the highest while the one of catalase is the lowest. The result is similar to the calculatinthrough SIMCA-P. The enzyme play an important role in decomposing SOC, catalyticingmicromass activity, stabilizing soil structure, affecting elements cycles. The soil enzymes is veryimportant to soil elements cycles by synthesizing、accumulating、restraining and decomposing.The soil environment is alternately change between anaerobic and aerobic circumstance as thechange of soil temperature and water. Soil enzyme changes and affect SOC and TN.Althugh SOC and TN increased under freezing-thawing effect, the change of SOCD (soilorganic carbon density) and TND (total nitrogen density) is little. The SOC storage increased infour soil and the storage sequence is paddy fields<saline-alkali<meadows <dry fields. The TNstorage is1.5×104~259×104t with different decrease under freezing-thawing.On the basis of the establishment of the underlying database of soil, vegetation and climatein western Jilin Province the annual greenhouse gas emissions (CO2, CH4, and N2O) aresimulated to assess the global warming potential of four land use types by using DNDC model.The GWP of IPCC is also selected to evaluate the GWP of four typical soils under differentfreezing-thawing to judge soil organic carbon sequestration. The dry fileds is carbon source. Thepaddy fields (-5~5℃FTC and-25~5℃FTC) is carbon source and the one (-5~5℃FT and-25~5℃FT) is carbon sink. The meadows(-25~5℃FTC) is carbon sink and the one in other conditionis carbon source. The saline-alkali soil (-5~5℃FTC and-25~5℃FT) is carbon sink. The GWP islow in northwest and high in the center of the studying area.The previous study of soil organic carbon is focus on the plant growing season. In this study,the experimental simulation techniques is used to study the mechanisms of soil organic carbon/total nitrogen/soil enzyme of different land use types under freezing-thawing effect in westernJilin Province. The results can be provides an example for studying soil organic carbon storage infreezing-thawing period.更多还原