Study On Eco-environmental Effect And Optimization Regulation Of Taihang Mountain Greening Area

Taihang Mountain is located in the transition zone of the second and third steps of geomorphology in China,and is the watershed between the Loess Plateau and the North China Plain.It is an important ecological barrier in The Beijing-Tianjin-Hebei region and a key node in the construction of national ecological security strategy.For a long time,this area has been undertaking ecological construction tasks such as Taihang Mountain greening project and Beijing-Tianjin area sandstorm source control,and has high requirements for environmental protection.At the same time,Taihang Mountain is also a poverty-stricken area and an ecologically fragile overlapping area in the Beijing-Tianjin-Hebei urban agglomeration.In the context of rapid urbanization and industrialization,the phenomenon of turning to the mountain to meet the development needs of human production and life is increasingly intensified,resulting in prominent contradictions between economic development,food security and ecological security.Therefore,to clarify the eco-environmental effects of Taihang Mountains greening project and explore optimal management strategies is not only an urgent need to scientifically understand the effects of Taihang Mountain greening project construction,but also an important prerequisite for rational territorial space development and ecological system protection and restoration.Based on this,this paper takes the Taihang Mountain greening project area as the case study area,combines the three periods of land use and digital elevation data from 2000 to 2020,and uses the methods of land use vertical gradient index,topographic position index and transfer matrix to illustrate the evolution process of land use and topographic gradient effect in the greening process of Taihang Mountain.With the help of remote sensing products,In VEST3.2 model and Arc GIS10.2 software,Sen slope estimation,Hurst index and Mann-Kendall test were used to reveal the response rules of key ecosystem services such as ecosystem production services and water conservation services in Taihang Mountain.This paper analyzed the influence degree of land use on key ecosystem services,and based on this,put forward the optimal control strategy of land use,providing scientific basis for ecological benefit evaluation and ecological protection and restoration of Taihang Mountain greening project.The main conclusions are as follows:（1）From 2000 to 2020,the land use of Taihang Mountain was mainly farmland and forest,accounting for 75.52%to 78.46%of the total area,and construction land only accounted for 5.31%.However,from 2010 to 2020,the construction land increased rapidly,and the undynamic type reached 6.27%.In Taihang Mountain,the land use transfer pattern was obvious.The farmland area decreased continuously on 0～1500 m elevation,0～15°slope and 0～1.5 terrain,while the forest area increased on 1000～2000m elevation,8～35°slope and 1.0～2.5 terrain due to the gradual decrease of grassland.Local scale,the Taihang Mountain in 2010-2020,90%and 74%of the counties newly-increased farmland and construction land transfer to the high altitude,97%and92%of the counties newly-increased farmland and construction land expansion to steep slope region,but newly-increased forest tends to low elevation and gentle slope area extension,the contradiction of national spatial development and utilization and ecological civilization construction.（2）From 2000 to 2020,the annual mean of net primary productivity of Taihang Mountain ranged from 251.46 to 427.80 g C·m^-2·a^-1,and showed an overall trend of fluctuation and significant increase.The future trend of NPP was more persistent than anti-persistent,and the future trend of NPP increased significantly.In terms of spatial distribution,the mean value of NPP was high in the middle and low in the periphery.The high value was mainly distributed in the central and southern regions,while the low value was mainly concentrated in the southeastern plain region.The overall situation of NPP of vegetation was stable,and the proportion of NPP in the stable area was 44.08%,and the proportion of NPP in the stable area was 80.88%and 17.06%,respectively.Land use change promoted the increase of NPP,and the total increase of NPP from 2010to 2020 was significantly greater than that from 2000 to 2010.（3）From 2000 to 2020,the total water conservation services in Taihang Mountain was 128.2～228.19×10⁸ m³,showing a trend of increasing first and then decreasing.The spatial difference of water conservation services was obvious,with the characteristics of"high in the south and low in the north".The total amount of water conservation services increased first and then decreased with the elevation increasing,and fluctuated less with the slope increasing,and concentrated in the altitude of 500～1000 m and the slope of 8～15°.The total amount of water conservation service of cultivated land was larger than that of forest land and grassland,and distributed in the area with altitude of500～1000 m and slope<15°,accounting for 37.54%of the total amount of water conservation service of the whole region.With the greening construction,the total amount of water conservation service increased,but the increase rate was less than that of forest land.（4）From the perspective of ecosystem services,five areas of land use optimization and regulation in Taihang Mountain were proposed:Key restoration areas,basic protection areas,vegetation net primary productivity improvement areas,water conservation services improvement and improvement areas and comprehensive improvement areas to clarify land use optimization measures,such as comprehensive management of key restoration areas,priority of natural restoration of basic protection areas,to provide a basis for the continuous promotion of greening construction.