Land Cover Change And Ecological Network Security Of The China’s Three-North Shelterbelt

The Three-North Shelterbelt Project is currently one of the greatest ecological projects in the history of the game between mankind and nature.The"Green Great Wall"has been built for 73 years as a national ecological security barrier.The second phase of the project has ended,and it will enter the third phase of the final decisive victory in 2021.A comprehensive and in-depth assessment of the ecological security pattern is of great significance.With the degradation of ecosystems caused by humans,the loss of biodiversity,and the intensification of climate change,the United Nations has launched the 10-year ecosystem restoration initiative.my country has taken ecological civilization as a long-term strategic plan for building a harmonious,sustainable and eco-friendly society.Based on this,the construction of China’s Three-North Shelterbelt Project needs new thinking in the new domestic and international context.This article combines remote sensing observations,land cover changes and ecological networks to explore standardized methods for territorial and spatial planning.The scientific theory of"man-land collaboration"provides technical practice.For the first time,the Remote Sensing Ecological Index(RSEI)was cited as the adjustment coefficient to construct the ecological resistance surface,and the multi-zone ecological planning and the multi-process minimum cumulative resistance model(MCR)were combined to construct a global multi-scale ecological network.The efficiency of ecological network,the importance of ecological nodes,and the level of ecological corridors are evaluated through complex network analysis methods and spatial syntax.Research indicates:(1)In the past 40 years of project construction,the total amount of grassland has decreased,but the leaf area index(LAI)has shown a significant increase.The woodland has increased by7,600 km~2,mainly in northern and eastern China,but the risk of ecological degradation remains severe.In the past 40 years,the grassland has been reduced by 102,400 km~2,mainly in the Yellow River Basin,North China and Northeast China.The grassland adjacent to the desert has changed frequently,indicating that China’s Three North Shelterbelt Project has made a huge contribution to the front line of ecological restoration.Combining the temporal and spatial trends of LAI for 40 years,it is found that woodland and grassland show a significant increase,especially woodland.Meanwhile,the areas where the grassland growth trend declines mainly occur in the Inner Mongolia Plateau.This place should be the center of gravity of the third stage of China’s Three North Shelterbelt Project.(2)The Three-North Shelterbelt in China spans 5 temperature zones,and its greenness,humidity,heat,dryness and RSEI show significant spatial differences.The overall greenness is high and the regional differences are significant;the heat has high spatial heterogeneity,the regional differences are significant,the overall is higher,but the greenness is lower;the regional difference in humidity is not big,the overall is low;the dryness area The difference is large,and the overall humidity is relatively high.RSEI collected four indicators to assess the ecological status of China’s Three North Shelterbelts,indicating significant regional ecological differences,and positioning key ecological regions,such as the eastern mountains of Northeast China,the Alxa and Hexi Corridor,and the Tarim and Turpan Basins.(3)China’s Three-North Shelterbelt has established an efficient ecological network in the eastern region,and a preliminary ecological network has been formed in the western region,and natural reserves have been planned at important ecological nodes.Research has found that key protection areas have been formed around Beijing,the southern Qilian Mountains,northern Shaanxi,and the Hunshandake sandy land in Inner Mongolia have become fragile protected areas that need to be strengthened.This is the focus of China’s Three North Shelterbelt Project in the next 30 years of nature reserve planning.Based on the evaluation of the protection degree of the ecological network of the Three Norths region through data mining,a picture of the ecological planning of China’s Three Norths Shelterbelt Project is proposed to clarify China’s green Great Wall,ecological beacon towers and regional ecological networks of different levels.