| Hulunbuir forest-steppe ecotone, which belongs to the large-meso scale ecotone and isthe key area where the relation between China’s famous Da Hinggan Mountains forest regionand the Hulunbuir steppe is inter-dependent, is one of the important ecological barriers ofNorth China, and has an important strategic significance to maintain the ecological safety ofNortheast China and even North China. However, with the impact of the global climatechange and human activities disturbance, regional ecological environment has undergonegreat changes, which has become the important ecological problem to restrict regionalresources environment and soc-economic sustainable development. Therefore, takingModis/Terra images from2000to2010as data sources, combined with the meteorologicaldata and social statistical data, this thesis analyzed the dynamic change of vegetationproductivity pattern driven by the fluctuation of temperature and precipitation in Hulunbuirforest-steppe ecotone, and provided the theory foundation to enhance the ability that theanimal husbandry adapts to climate change, adjust land use policy and expand the radiationeffect of the ecosystem service function.First of all, taking Xinbaerhu Right Banner, Erguna and Boketu as the typical area ofgrassland ecosystem, forest-steppe ecotone and forest ecosystem respectively, this thesisanalyzed their water-heat distribution changes based on yearly and monthly scales from1961to2010. The results showed that:(1) The temporal and spatial distribution of temperature and precipitation in Hulunbuirwas uneven and regional differences.(2) In the past50years, the temperature and precipitation in Hulunbuir had a fluctuationchange, which overall showed temperatures increase, precipitation decrease and climate“warming and drying” trends. The degree of warming and drying was higher from2000to2010than from1961to2010in the study areas.(3) The water-heat distribution in Hulunbuir had obvious seasonal characteristics. Theannual temperature showed characteristic of cold winter and warm summer, and temperaturedifference was larger. The precipitation almost concentrated on the vegetation growth periodwhile the temperature is higher.Secondly, in terms of landscape index and the vegetation net primary productivity, taking into account both regional difference and the impact of human activities disturbance,this thesis chose three study sites in the forest-steppe ecotone of Erguna, Chenbaerhu Bannerand Evenk Autonomous Banner to analyze the dynamic change of the productivity patternfrom2000to2010, respectively. The results were as follows:(1) Landscape index dynamic analysis: from the viewpoint of landscape scale, during thestudy period the degree of landscape fragmentation in forest-steppe ecotone increased, thedistribution discrete degree of the same patche class changed constantly and was bigger from2008to2010than entire period; from the viewpoint of class level, there were greatdifferences in patch number and area for patches of different productivity levels, the patchesthat NPP level was between200g/m~2and400g/m~2constructed the main parts of Hulunbuirforest-steppe ecotone. The trend and degree of changes in patch number and area also weredifferent.(2) Regional productivity dynamic analysis: taking2006as a change point, vegetationnet primary productivity (NPP) in Hulunbuir forest-steppe ecotone had a fluctuation changetrend in the study period.Finally, taking the forest-steppe ecotone in Erguna as an example, this thesis analyzedthe influence of temperature and precipitation on vegetation net primary productivity from2000to2010. It was found out that both of temperature and precipitation were no obviouslylinearly related to the vegetation net primary productivity, and that the correlation of climatesingle factor with vegetation NPP was obvious but not remarkable in three time scales ofmonth, the critical period and year. The productivity estimation model built by precipitationand temperature in July, annual precipitation, mean temperature of the critical period andvegetation NPP, could better reflect the relationship between the climate factors andvegetation NPP.Overall, it was a comprehensive process that the fluctuations of temperature andprecipitation influenced on the grassland NPP in the study area. To be specific, the impact ofair temperature on vegetation NPP is negative effect, while the increase of precipitation isbeneficial to the accumulation of NPP. |
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