Research On Ecological Source Extraction And Ecological Security Pattern Construction In Weiyuan County

Ecological security pattern refers to the regional spatial pattern that can protect and restore biodiversity,maintain ecosystem health,and effectively control regional ecological and environmental problems on the basis of eliminating disturbances.The optimization of ecological security pattern is an important way to ensure regional ecological security,maintain ecosystem stability and improve ecosystem service capacity.Weiyuan County is located at the source of the Wei River,the largest tributary of the Yellow River,and is an important water conservation area of the Wei River,and the construction of its ecological security pattern is of great value to the entire Wei River Basin.Taking Weiyuan County,Dingxi City,Gansu Province as the research area,based on land use data,remote sensing image data and other data in Weiyuan County,and on the basis of ecosystem structure analysis,landscape pattern analysis and ecological security analysis in Weiyuan County,this paper evaluated the spatial morphology,ecological quality,service function and ecological sensitivity of the ecosystem in the study area by using a variety of remote sensing indexes,principal component analysis methods and spatial analysis methods.The ecological source areas were extracted from four perspectives,and the final ecological source scheme was determined after comparison and synthesis.Combined with the Minimum Cumulative Resistance(MCR)model and circuit theory,ecological corridors,radiation corridors and ecological strategic nodes were extracted by using ecological sources and comprehensive resistance surfaces,and the ecological security pattern of Weiyuan County was constructed.The main conclusions of this paper are as follows:(1)On the whole,Weiyuan County has an uneven distribution structure and rich landscape variety,but some areas have problems such as high degree of patch fragmentation and high degree of dispersion,and the ecosystem is relatively fragile.From the perspective of ecosystem type composition,the distribution of farmland ecosystem and woodland ecosystem in the study area was the mainstay,accounting for49.24% and 30.34% of the total area of the study area,respectively,and the distribution was relatively concentrated.Due to the relatively homogeneous structure of ecosystems,it is difficult to self-restore when ecosystems are destroyed.The farmland ecosystem with the largest proportion is the type of ecosystem with the strongest human activities,and the superposition of these two factors leads to the fragile ecological environment in the study area.From the perspective of landscape index,the number of patches in the study area was large(reaching 88953),and most ecosystem types were less clustered and fragmented.Except for cultivated land and forest land,there are almost no concentrated contiguous homogeneous patches,and this landscape pattern distribution has a great impact on the exertion of ecosystem service functions in the study area.(2)From the perspective of ecological security,the ecological risk of Weiyuan County is mainly "high level",and the proportion of other grades is relatively small,showing a pattern of high south and low north.The area of the "higher level" grade area accounts for 48.72% of the total area,mainly distributed in the central part of Weiyuan County;The area of the "medium level" grade area accounts for 24.36% of the total area,mainly distributed in the central and northern parts of Weiyuan County;The "lowlevel" area accounts for 15.94% of the area,mainly distributed in the southern part of Weiyuan County.Among the four levels of ecological risk,the proportion of "highlevel" areas is the smallest,only 10.98%,mainly distributed in densely populated settlements such as Luyuan Town,Qingyuan Town and Huichuan Town,mainly because these areas are construction land and are greatly affected by human activities.In addition to these areas,the ecological risk level of Beizhai Town and Xinzhai Town in the north is also relatively high,mainly due to the large number of geological hazard points in these areas.Based on these different reasons for the low level of ecological security,the study believes that targeted treatment should be carried out.(3)The four methods of ecological source extraction have their own advantages,and the comprehensive application can complement each other.In this study,ecological sources were extracted based on four methods: Morphological Spatial Pattern Analysis(MSPA),sensitivity evaluation,remote sensing ecological index evaluation and ecosystem service function evaluation,and the extraction results were comparatively analyzed.The results show that the MSPA method can screen for landscape connectivity,but it cannot quantitatively reflect the environmental quality of the source area.The remote sensing ecological index model can promote the area with better ecological environment as ecological source,but it is not easy to distinguish between natural vegetation and crops.The sensitivity evaluation method can exclude areas with serious soil erosion or frequent geological disasters,but there are many evaluation factors,which need to be selected and assigned,so it is greatly affected by subjective factors.The assessment method based on ecosystem service function better reflects the difference of ecological service function,but the selection of ecological function is subjective judgment and it is difficult to obtain high-precision data.Based on this,the ecological source areas obtained by the four methods were synthesized,that is,the four ecological sources were superimposed to remove the parts located in the high ecological sensitivity area and the low ecological security level area,and the final ecological source area was obtained after area screening and connectivity screening.In this study,the advantages of each method are concentrated and have the effect of complementing each other.(4)The constructed ecological security pattern improves the overall unity and connectivity of the landscape pattern,and can maximize the ecological function.Based on the extraction results of ecological sources,this study constructed the ecological security pattern of Weiyuan County by using the MCR model.The ecological trend area was mainly medium-level trend area,accounting for 33.54% of the total area of the study area.A total of 20 ecological corridors were identified using the two tools Arc GIS and Linkage Mapper,mainly located in the southern part of the study area;There are22 radiation corridors extracted by the catchment principle,spread throughout the study area;Based on the spatial distribution results of ecological corridors and radiation corridors,48 ecological strategy nodes were extracted.These components together constitute an ecological security pattern,which can maximize the advantages of the landscape pattern and provide an ecological foundation for regional sustainable development.The results of this study can provide a reference for Weiyuan County to carry out land and spatial planning scientifically.