Study On Dynamic Change Of Vegetation Coverage And Response To Climate Change In The Three-north Shelter Forest Program

Under the background of the global warming, the climate in the Shelter ForestSystem Program in Three-North Region of China (the Three-North Shelter ForestProgram, TNSFP)has changed a lot. It is very important and significant for theecological environmental and economic development to study the theory of surficialprocess under the background.Vegetation dynamic is the important research contentof land resources and environmental changes. The ecological environment hasbecome the foundation of human survival and development, but also is the foundationof the social and economic development. Using the RS with the data sources with theall-weather and multi-temporal, it is efficient to integrate the spatial analysis technicalof GIS and analyze the temporal and spatial characteristics of NDVI in TNSFP tounderstand the basic facts and the features of the variation of NDVI, while thecoupling analysis with NDVI and regional climate is to take a step forward to exploreunder the background of the climate change in TNSFP.The Shelter Forest System Program in Three-North Region of China is thelargest ecological reforestation program in the world, and has made greatachievements since it was initiated in1978. It covered13provinces and551countiesof China, with longitude of73°26’ E~127°50’ E and latitude of33°30’ N~50°12’ N,total area of406.9×104km~2, accounting for42.4%of the national territory. It isconstructed from November1978to December2050, lasting73years, divided intothree phases and eight stages project of construction. The total planned afforestation isaccumulated to be35.1×104km~2. TNSFP vegetation research not only has importantecological environment meaning, but also attaches profound social and economicsignificance. In this paper, GIMMS AVHRR NDVI (Normalized DifferenceVegetation Index) datasets, a globe dataset with8-km spatial resolution (square pixels)were developed by the Global Inventory Monitoring and Modeling Studies (GIMMS)group was selected as the data source. The spatio-temporal variation of the vegetationcoverage of the Three-North Regions of China was dynamically studied by adoptingNDVI average method, retrieval of vegetation cover and linear regression trendanalysis methods during the period from1982to2006.This paper explored thespatio-temporal variation of the vegetation coverage and its relationship with major climatic factors (temperature and precipitation), analysis of vegetation cover andtemperature, precipitation variation the changes of hysteresis, and the Hurst indexacross TNSFP was examined by using NDVI dataset and climatic data during theperiod from1982to2006. General trends in vegetation cover change and its spatialvariation in the future was predicted. And on this basis, through the use of residualanalysis, investigates the influence of human activities on vegetation cover spatialpattern.The results show that:(1) In the past25years, NDVI vegetation of the study area has an entirely risingtrend, with the growth rate of0.007/10a. The growth of Sandy Area and Northeast andNorth China Plain was obvious, but Northwest Desert Area showed a subtle decliningtendency. The increase of Vegetation variation is slightly higher than the reduction inamplitude.(2) The vegetation coverage of four construction regions has been improved indifferent degrees. Moreover, the vegetation coverage in Gully Region of LoessPlateau rises fastest, with the vegetation coverage improved by9.66%.In the threeperiods of1982-1991,1992-2001and2002-2006, vegetation coverage area of thestudy has been increased by472994km~2,451032km~2and435196km~2,but reduced byabout197717km~2,270192km~2and182690km~2respectively. The regions ofimproved vegetation coverage mainly appeared in the central and southern part of theDa Hinggan Mts., the central part of the Xiao Hinggan Mts., the northeast part of theChangbai Mts., Yan Mts., Liao Xi hilly region, Altay Mts., Tianshan Mts., east part ofthe Qilian Mts., eastern part of the northwest desert and southern part of the GullyRegion of Loess Plateau, etc. the regions of decling Vegetation coverage were mainlydistributed in the both sides of the Da Hinggan Mts., the western part of theHulunBuir Tableland,the northern part of Sanjiang plain, southern part of KerqinDesert, southern part of the northwest desert and northern part of the Gully Region ofLoess Plateau, etc.(3) The annual average temperature rised overall in the Three-North Regions andits four construction regions. Temperature tendency rate was0.61℃/10a, whileoverall years accumulative precipitation appeared to decline, which reduced 13mm/10a in the study area. Vegetation coverage, temperature and precipitationoverall were positively correlated on the study area.17.74%of the regions and thetemperature were negatively correlated, but6.84%of the regions were a positivecorrelation.10.60%of the regions and the precipitation were negatively correlatedwhile19.53%of the regions were a positive correlation. The precipitation ofvegetation is more significant than the temperature of the area, and it is also the key tofactor of vegetation’s growth on the study area. In different time, correlation with thedifference is obvious in temperature, precipitation and NDVI. The vegetation hasobvious seasonal variation characteristics. And NDVI in vegetation growth along withtemperature, precipitation change had the hysteresis phenomenon.(4) The Hurst index of NDVI time series in TNSFP over the past10years wasgenerally higher, and was significantly different in space. Sustainable strength aresequentially arranged for I> II> III> IV. Inter-annual residuals of vegetationvariation showed a significant positive correlation ratio of7.70%which was greaterthan that in the area of a significant negative correlation area ratio7.17%, and thepower of human construction on vegetation is stronger than the destructive one.Therefore, the positive ecological impact of TNSFP construction is appearing.Vegetation residuals significantly increases concentrating on the north part ofTianshan Mts., Tarim Basin, Hexi Corridor, Hetao plain,the east part of Erdos Plateau,the southern part of Wulanchabu plateau, Chifeng, the southeastern part of Tongliao,the western part of HulunBuir Tableland, the central and southern part of the DaHinggan Mts., Songnen Plain and Liaohe Plainand and so on. However, significantdeclining areas focus on Taklamakan Desert surrounding area, Alashan plateau,Qaidam Basin,the east part of Qinghai, the east part of Gansu, the central part ofShanxi, Bayannaoer plateau, Horqin sandy land andthe central part of ChangbaiMts.and so on.