| 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. |
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