Ecological Security Assessment And Pattern Optimization Of Main Grain-producing Areas In The Loess Plateau

In recent years,under the influence of population growth and urban expansion,a large number of ecological land in the alluvial plain area of the Loess Plateau has been occupied,and regional ecological environmental problems have become increasingly prominent,which have threatened the sustainable development of the Loess Plateau.It is of great significance to evaluate the characteristics of regional ecological security and construct ecological security corridor for the protection of regional ecological environment and the sustainable development of regional economy.Based on Landsat remote sensing data from2000 to 2018,this paper constructed and analyzed the remote sensing ecological index(RSEI)and its temporal and spatial changes of the main grain-producing areas on the Loess Plateau,and quantitatively analyzed the regional ecological security pattern using the minimum cumulative resistance(MCR)based on nine factors.The main conclusions are as follows:(1)The fraction vegetation coverage(FVC)in the study area changed greatly.Since 2000,the fraction vegetation coverage of Yinchuan Plain has been decreasing,and the vegetation coverage has been destroyed.The fraction vegetation coverage increased year by year and the vegetation was restored in the Former Hetao area.The fraction vegetation coverage in the Latter Hetao area showed an upward trend.The fraction vegetation coverage in the Fen River Valley increased first and then decreased,showing an overall upward trend,and the vegetation coverage recovered to a certain extent.The vegetation coverage of Wei River Plain showed a downward trend,and the vegetation coverage was seriously damaged.(2)From 2000 to 2018,the RSEI of Yinchuan Plain increased first and then decreased,showing a general trend of decline,and the ecological environment significantly deteriorated.The RSEI of Hetao Plain showed a downward trend,decreasing by 0.01,and the ecological environment was relatively stable.The RSEI of Fen River Valley first increased from 0.49 to 0.52,and then decreased to 0.50.However,the remote sensing ecological index showed an upward trend on the whole,and the ecological environment was slightly improved.Because the spatial fluctuation of the ecological environment was large,the north-south change was obvious.Among the four plains,the RSEI of Wei River Plain was not the lowest,but it had the most significant degradation with a RSEI decrease of 0.07.(3)The change of ecological environment in Yinchuan Plain was mainly caused by the change of land use.Since 2000,the area of cultivated land and woodland has been decreasing.Besides,the area of water and unused land has also been decreasing,while the area of construction has increased significantly.The unused land area of the Forrer Hetao Plain has decreased,the building land has increased,and the area of farmland has expanded due to the increase of population.In the Latter Hetao Plain,the unused land types have decreased,the vegetation area has decreased,and the building area has increased first and then has decreased.The change of land use/cover(LUCC)of Fen River Valley was mainly reflected in the expansion of floor area.From 2000 to 2018,the urban development speed was fast and the floor area expanded.Vegetation reduction and construction area expansion in the Wei River Plain mainly manifested in the urban agglomeration near Xi ’an City.Besides,narrow river channels and fast land use transfer speed had negative impacts on the environment.(4)Based on the quantitative analysis results of ecological security pattern,we can see that the regions with low comprehensive ecological resistance value had higher ecological security level and their ecological environment were good,while the regions with high ecological resistance value had lower ecological security level and their ecological environment were poor.Among them,the resistance value of river channels and areas with high FVC was low,while the resistance value of the areas with concentrated towns and large building area was high.The existing corridors in the study area are mostly distributed along rivers and main roads.The construction of overland corridors and strong auxiliary corridors should be added to improve the connection of ecological sources.River is an important support for ecological security pattern.During the construction process,attention should be paid to protecting the Yellow River and strengthening node construction.In the future,the construction of ecological source areas should be strengthened and the urban layout should be reasonably planned.