【作者】 刘森；

【导师】 汤洁；

【作者基本信息】 吉林大学 ， 环境科学， 2012， 硕士

【摘要】 草地生态系统是受人类活动影响最为敏感的陆地生态系统之一，同时其对全球变化的响应也是极为显著的。作为陆地生态系统的重要组成部分，草地生态系统在全球碳循环过程中发挥了重要作用。随着全球变暖形势的日趋严峻，对陆地生态系统这个巨大碳库的研究也引起了越来越多研究者的重视。近二十年来，位于吉林省西部的草地格局发生了巨大变化，从草地面积锐减到生态恢复草地重建，处于半干旱区碱性土壤生境的草地经历了怎样的碳汇集和碳释放过程值得关注。本文针对吉林省西部草地分布典型区域——大安市的草地碳储量开展了研究，以1996、2000、2004和2008年四个草地格局变化较为突出的年份为研究时段。结合遥感影像解译结果，运用DNDC模型，在ArcGIS10平台下绘制出了大安市四个研究年份的草地碳密度分布图；并采用面积加权法估算了研究区四个年份的草地碳储量，针对草地碳储量变化情况进行深入分析；以大安市2008年的草地碳储量为基准，采用控制变量法对气候因子以及大气中CO2浓度进行情景假设，定量分析了不同因子对大安市草地碳储量的影响强度。结合研究区的土地利用现状、以往研究成果和课题组的相关实验数据，分析了土地利用变化、放牧、围栏封育、人工种草和退耕还草对草地土壤碳库的动态影响。研究结果表明，1996、2000、2004和2008年四个研究年份大安市草地碳储量分别为：4.5049TgC、3.9067TgC、3.1453TgC和5.0389TgC，总体呈现先减后增的趋势。其中，2008年大安市草地生态系统由碳流失转变为固碳量增加，草地恢复重建的效果可见一斑。大安市草地碳储量的变化主要源于草地碳密度的改变，以及草地面积的变化。四个研究年份中，大安市草地面积经历了连续两次锐减而后增加的变化，一方面受到土地利用等人为因素的影响，另一方面也受到研究时段内气候因子的限制。通过对草地碳密度垂向分布特征的初步探索可知，单位面积草地土壤碳储量均占据了草地碳储量90%以上；处于研究区内的草地地下生物量碳储量要高于地上部分。以2008年为基准的气候因子和CO2浓度变化假设结果显示，研究区内的草地碳储量对降水因子的变化最为敏感，其中，草地植被碳储量对降水的响应变化较土壤碳储量更为显著。在CO2浓度增加一倍的情况下，大安市草地土壤碳储量和植被碳储量都有所增长，从一定程度上反映了大安市草地生态系统作为碳汇的潜力。针对人为因素对草地碳储量影响的分析结果显示，土地利用变化是对草地碳储量影响最为深远的，人工种草和退耕还草对草地碳储量的恢复都较为有效，但结合研究区的实际情况而言，人工种草更为可行。本研究揭示了1996、2000、2004和2008年四个年份大安市草地碳储量的变化情况，并预测了未来该区可能的碳储量变化状况。研究结果为以后土壤盐碱化对草地碳循环影响的研究提供了基础数据，对合理规划和开发利用草地具有借鉴意义。更多还原

【Abstract】 Grassland ecological system is not only one of terrestrial ecological system whichis most sensitive to human activities, but also has an extremely significant response toglobal change. As one of the important component for terrestrial ecological system,grassland ecological system has played an important role in the process of the globalcarbon cycle. With the situation of global warming is getting worse, more and moreresearchers are paying attention to the study of the huge carbon storge, terrestrialecological system. In the past twenty years, the grass pattern located in the west of Jilinprovince has changed a lot.How carbon collection or release of the grassland located insemiarid areas and alkaline soil environment is worth to pay close attention to theprocess, during which the areas of the grassland had experienced by reduced toreconstruction.The research content of this thesis is to estimate grassland carbon stock in Da’ancity, where the grassland pattern had changed a lot in1996,2000,2004and2008. Da’ancity is a typical region of grass distribution. By using DNDC model, distribution figuresof the grass carbon density in Da’an city for the four years are drew by ArcGIS10software with the remote sensing interpreter results. The grassland carbon storge for thefour years are estimated by the area weighting method and a deep analysis of the changefor this time is made. Base on the carbon stock condition in2008, hypothesizes aboutclimate factors and atmospheric CO2concentration are proposed by control variablemethod for a quantitative analysis of the strength about the different factors on theinfluence of the grassland carbon stock in Da’an city. Combined with the present landuse situation, past research results and the related experimental data, this thesis analyzesthe dynamic effects on the soil carbon stock of the grassland caused by land use change,herding, fences, grow grass artificially and so on.The results of the study show that, the grassland carbon stock in Da’an city is4.5049TgC,3.9067TgC,3.1453TgC and5.0389TgC in1996,2000,2004and2008respectively. Among them, the grassland ecological system turned from carbon loss tocarbon growth in2008. This result is due to the grassland reconstruction project. Thegrassland carbon stock change is mainly due to the change of grassland carbon densityand the change of area. On the one hand, land use,etc artificial factors lead to thechanges in the four year of the study, on the other hand the changes are also limited bythe climate factors during the research time. The preliminary exploration on allocationproportion of the grassland carbon stock in unit area among the soil, underground andon the ground shows that the part in the soil occupied more than90%, and theproportion underground is more than that on the ground. The study of hypothesizesbased on the grassland carbon stock in2008shows that, the grassland carbon stock ismost sensitive to the change of the precipitation in the research area. What’s more, thevegetation carbon stock is more marked in response to the precipitation changes. Thegrassland carbon stock grows with the increasing of CO2concentration. Thus it reflectsthe potential of the grassland ecological system in Da’an city to be a carbon sink in a certain extent. The analysis on how the human factors influence the grassland carbonstock shows that, the change of land use is the most influential human factor, andartificial planting and grain for green are both effective measures to recover thegrassland carbon stock. But considering the actual situation in the research area,artificial planting is a better choice. This study reveals the grassland carbon stockchanges rule in1996,2000,2004and2008in Da’an city, and forecast the possibilitychange in the future. The research result provides the basic data for the further researchon how soil salinity influence on the grassland carbon cycle. It also has the significanceof reference for planning and developing grassland reasonablely.更多还原