Study On Ecological Security Evaluation And Ecological Pattern Optimization In Gansu Section Of The Taolai River Basin

The optimization of ecological security pattern is an important approach to achieve regional ecological security and maintain regional sustainable development.The Taolai River basin is a typical arid inland river basin with fragile and sensitive ecological background and prominent ecological problems.It is urgent to evaluate the ecological security situation and optimize the ecological security pattern based on the evaluation results.This study takes the Taolai River Basin in Gansu Section as an example.According to the ecological environment situation of the study area,the evaluation framework of ecosystem services and ecosystem health was selected to assess the ecological security of the basin in 2000 and 2015.On this basis,ecological sources were identified.With the help of Linkage Mapper tool,the least cost corridors were extracted.Suboptimal corridors were constructed based on the Circuitscape software.In addition,barriers were identified by using Barrier Mapper tool.In order to provide references for the development and construction of arid areas and ecological protection,the optimization strategies of ecological security pattern in the basin were put forward.The results showed that:(1)On the whole,the ecological security of the basin was not optimistic.In terms of area,in 2000 and 2015,the low security area of the Taolai River Basin in Gansu section accounted for 63.68% and 61.25% of the total area of the study area,respectively,while the high level security areas and higher level security areas accounted for only 13.93% and 15.80%.From the perspective of spatial distribution,there were significant differences in the ecological security of the Taolai River Basin in Gansu Section.The south and the central regions were higher than the north region.In 2000,the high security area was mainly located in the Qilian Mountain areas in the south of the basin,where the forest land and grassland were widely distributed,and the condition of ecosystem health and service were good.The higher security area was mainly located in the central irrigation agricultural area.However,due to the overdevelopment,the ecological security level of Jinta County,Jiayuguan City and Suzhou District of Jiuquan City is relatively low.Low-security areas are dominated by land use types that threaten ecological security,such as bare rock,bare soil,and sandy land.In 2015,the newly increased cultivated land from unused land in the basin was of moderate ecological security level.The area of the lower ecological security zone in Jiayuguan City and Suzhou District increased with the expansion of the city.(2)Construct and optimize the ecological security pattern based on the identification results of the ecological source,the least cost corridor,the suboptimal corridor,and the barrier.Ecological sources were mainly distributed in the mountain of Sunan Yugur Autonomous County in the south of the basin and the agricultural areas of Jinta County,Jiayuguan City and Suzhou District in the middle areas of the basin.The vegetation coverage of the northern Gobi and desert areas was low;therefore,there was no ecological source.Southern ecological sources contributed the most to the landscape connectivity of the basin.A total of 1122 least cost paths with a total length of 3468.150 km were generated among ecological sources.There were 242 corridors distributed among the relatively far away source areas with higher resistance,which separated by higher resistance,such as bare rock and bare land.There were 386 medium-resistance corridors,most of which distributed among ecological sources in the Qilian Mountains areas.There were 494 lower resistance corridors,mainly distributed among farmland patches in the middle of the basin.Distribution of the suboptimal corridors was consistent with that of the optimal corridors,which were mainly concentrated among the patches of cultivated land,grassland and woodland in the middle and south of the basin.However,there is almost no corridor in the north bare rock and bare land area.The barriers affecting the distribution of corridors and sources were mainly distributed in the cultivated land in the middle of the basin and the bare rock,bare land,and sparse grass land among patches in the Qilian Mountains area in the south.(3)The optimization of ecological security pattern in the Taolai River Basin should adhere to the principle of ‘adaptation to local conditions' and combine with the land-use types to improve ecological environment condition.Based on the above analysis,the study area was divided into three parts.(1)Ecological Stability Area,where the land use types are all unused land such as bare rock and bare land,with harsh environment and sparse population.In the region,the ecological environment should be maintained stable to prevent further desertification from spreading.(2)Ecological Development Area,which is mainly located in the middle of farming area,has a high population density and a large demand of water and soil resources,It should strictly follow the principle of protecting cultivated land and basic farmland,improve the utilization of water and land resources based on environmental carrying capacity,and seek coordinated development of ecological protection and improvement of livelihood.(3)Key Ecological Protection Area,which mainly consisted of grassland and woodland in the Qilian Mountains,and some interphase distributed sparse grassland,bare rock,and bare land,has fragile ecological environment.In order to improve the service function of water conservation and biodiversity protection,in this region,the government should strengthen the management of degraded grasslands,the protection of natural forests,and the prevention and control of soil erosion.