| Since the 20th century,the level of industrialization and urbanization has been continuously improved with the development of productivity,the resulting high-intensity land development has increasingly intensified the contradiction between people and natural ecological environment,soil erosion,soil pollution,land desertification,grassland,forest degradation and a series of ecological problems gradually highlights,directly or indirectly influences the regional ecological security and sustainable development.And it is of great significance to construct and strengthen ecological security pattern in semi-arid areas and identify important ecological components to maintain regional ecological security and stability and curb the trend of ecological environment degradation,it’s also effectively to resolve the conflict between ecological protection and economic development,thus ensuring ecological security and sustainable development in semi-arid regions.This paper took Lintao County,Dingxi City,Gansu Province,a county-level administrative unit in the inland semi-arid area of Northwest China,as the research area.As a regional ecological security pattern according to its first demonstration area construction and ecological civilization construction goal request,the clear ecological system on the basis of composition and spatial distribution,12 landscape pattern indices were selected from the patch type and landscape level to systematically analyze the characteristics of the landscape pattern in the study area,and quantitatively evaluated the ecological environment quality,ecosystem service function,and ecological sensitivity of the study area.The ecological source area was identified based on the MCR model and each ecological component was identified,and the ecological security pattern of the study area was constructed,in order to provide reference for the construction of the ecological security pattern at the county scale in semi-arid areas.The main conclusions are as follows:（1）There were significant differences in landscape characteristics among different types of land use in Lintao County,and there were significant differences in landscape characteristics among different types of land use in Lintao County.The ecosystem in the study area is mainly farmland and grassland,accounting for nearly 80%of the county area.The ecosystem is relatively single and greatly affected by human activities,so the ecosystem is very fragile.In terms of landscape characteristics,the fragmentation degree of each patch in the study area is large and the number of patches is large,but each patch has neither central tendency nor dispersed tendency,and is in a relatively balanced state.Among them,the construction land had the largest number of patches（47,974）and the largest patch density（up to 16.80）,while the cultivated land had the largest patch area（141333.9 hm~2）and the largest patch area（the maximum patch area ratio was 25.3716）,and the edge density reached 110.1161.The sprawl index was the highest in Lanzhou Military Racecourse,which was 74.5007.Longmen Town has the largest landscape shape index,which is 59.775.The highest diversity index and evenness index were found in Taoyang Town.The highest aggregation index is Lanzhou Junmachang,as high as 94.672.（2）The results of ecological quality assessment showed that there were significant spatial heterogeneity in all ecological indexes of Lintao County,and the ecological sources of Lintao County were mainly distributed in the valley and the southern part of the study area.The high values of greenness index in the study area are distributed in the northeast of Lanzhou Military Horse Farm,Xindian Town,Shangying town and Nanping town.The high values of humidity index were distributed in the valley along Taohe River,the valley of Maxian Mountain and the forest area in the south of Nanping Town.The low values of dryness index were distributed in the south of Nanping Town,Taohe River valley and Lanzhou Junmachang of Maxian Mountain.The heat values in the southern towns of the whole study area are low,and the low temperature values in Lanzhou Junmachang,the northeast of Xindian Town and the northeast of Shangying Township are also obvious.The regions with excellent ecological environmental quality evaluation were extracted as the ecological sources,which were mainly distributed along the Taohe River Valley,the southern towns of the whole study area,especially the southern part of Nanping Town,and the northeastern part of Shangying township,Lanzhou Junmachang,and Xindian Town,with a total area of 543.74 km~2,accounting for 19.04%of the total area of the county.These areas are the best ecological environment quality of the county,high vegetation coverage,soil conditions are relatively good.（3）There were significant differences in the distribution patterns of different types of ecosystem services in Lintao County.The ecological source areas of Lintao County accounted for 1/5 of the total area of Lintao County,which were mainly distributed in Junmachang,Yaxia Ji town and Nanping Town.The important areas of biodiversity protection were mainly distributed in the south of Lintao County.In addition to Nanping Mountain,there were obvious aggregations in Maxian Mountain and the northern part of Hongqi Township.The areas with extremely important water conservation function are mainly distributed in the water source area of northeast Maxian Mountain,with high altitude,relatively few human activities and large vegetation coverage.The high values of carbon sequestration and oxygen release were mainly distributed in the southern towns of the study area.The ecological source area extracted based on the assessment of ecosystem service function is 520.05 km~2,accounting for 18.21%of the total area of the county,which is concentrated in Lanzhou Junmachang,Yaxia Market town and Nanping Town,while there is almost no ecological source area in the northern towns.（4）The ecological source areas of Lintao County were distributed in Junmachang and Nanping town,and the area of ecological source areas was the smallest.The ecological source areas of Lintao County were distributed in Junmachang and Nanping town.The insensitive areas of soil erosion in the study area were mainly distributed in Taohe River Valley,Lanzhou Junmachang and Nanping Town.The insensitive areas also appeared along highways,national roads and provincial roads.The insensitive areas of geological disasters are obviously distributed,which indicates that geological disasters are relatively developed in the whole study area.The area that was not sensitive to the comprehensive evaluation of ecological sensitivity was selected as the ecological source,covering an area of 498.54 km~2,accounting for 17.46%of the total area of the county.It was concentrated in Lanzhou Junmachang and Nanping Town,taohe Wetland Park of Taishi Town and Taohe Wetland Park of Taishi Town,and scattered in other towns.On the whole,the distribution of ecological sources is fragmented,and the ecological sources in the southern towns are more than those in the northern towns.（5）The results showed that the ecological sources were mainly distributed in the southern towns of Lintao County（Nanpingshan,Maxian Mountain,Lanzhou Junmachang and valley agricultural area）,and the ecological sources were mainly distributed in Lintao county,expressway,national road and Zhongpu industrial park.Based on the evaluation results of ecological environment quality,ecosystem service function and ecological sensitivity and superposition of national and provincial nature reserve information,the final identification result of ecological source area of the study area is 138.91 km~2,accounting for 4.87%of the total area of the county.Mainly distributed in Nanping Mountain forest,Maxian Mountain,Lanzhou Junmachang and river valley along Taohe agricultural area.On the whole,a large number of ecological sources are distributed in the southern towns of the study area.In addition,considering the land use and economic conditions,the area of urban source areas in the study area is 58.16 km~2,accounting for 2.04%of the total area of the county,and they are concentrated in Lintao County seat,highway,national road and Zhongpu industrial park.（6）The results of MCR model showed that the ecological security pattern of Lintao County was mainly high（about 50%）,and different measures should be taken for different types of ecological security zones.Ecological corridors,radiation channels and ecological strategic nodes were important components of ecological security pattern.Ecological security pattern of Lintao County was established based on MCR model.Among them,the area of high-level ecological safety zone is 583.78 km~2,accounting for 20.45%of the total area of the county;The area of the higher level ecological safety zone is 1321.29 km~2,accounting for 46.27%of the total area of the county.The area of the mid-level ecological safety zone is 764.14 km~2,accounting for26.76%of the total area of the county.The area of the low-level ecological safety zone is 186.67 km~2,accounting for 6.54%of the total area of the county.Different types of ecological safety areas should take different measures to ensure the ecological safety of Lintao County,and strive to achieve a new pattern of blue sky,green mountains,clean water,clean soil and beautiful scenery.Ecological corridors,radiation channels and ecological strategic nodes are indispensable components of ecological security pattern.In this paper,56 ecological corridors with a total length of 538.86 km,96 radiation channels with a total length of 243.23 km and 81 ecological strategic nodes were identified.The results showed that there was a significant difference in the ecological security pattern of Lintao County,and the ecological security pattern of Lintao County could be used to determine the ecological security of lintao County. |
