Research On Urban Ecological Security Pattern Based On Self-purification Service Value

Human welfare relies on ecosystem services directly or indirectly.How to maintain and promote ecosystem services value is an essential precondition for coordinating with ecological influence and economic development.Also,it is an important foundation for maintaining regional ecological security and building an ecological security pattern.Ecosystem self-purification service is one of the important functions of ecosystem services.A reasonable assessment of self-purification value of ecosystem directly affects the level of regional sustainable development.At the meantime,it can provide a reference and basis for the restoration of urban ecosystems and national spatial planning.Based on self-purification mechanism of ecological land and non-ecological land,this thesis takes Xuzhou planning area as an example.The evaluation models of self-purification value are constructs with the revision of temporal value.Another research work is constructing the ecological security pattern of the study area,which is based on the evaluation of the ecosystem self-purification services.At last,a simulation for the future land use pattern is carried out under the scenarios of protection and non-ecological protection respectively.Finally,this thesis analyze the urban expansion trend in the target year.The thesis reached the following conclusions:(1)In the study area,the total value of self-purification services showed a gradual decline from 1998 to 2018.The decline rates in Xuzhou urban planning area and central urban area were 13.62%and 136.84%,respectively,and the rate of change has been rapid in the past 10 years.In the past 20 years,the value of self-purification services in the urban planning area has shown a downward trend in space.The low-value areas have gradually expanded from the central urban area to the surrounding area,and the range has gradually spread.(2)The ecological security pattern of the study area was constructed based on the evaluation results of the ecosystem self-purification services in different years.In 1998,2008 and 2018,the ecological source area of the study area was 533.74km~2,414.83km~2,1006.87km~2,respectively,a total of 78,70,76,accounting for 17.43%,13.55%,32.87%of the total area.The ecological source area is mainly cultivated land,mainly distributed in the periphery of the planned area of Xuzhou City.The ecological source area is larger in Tongshan District and Yunlong District.102,103,and 63 ecological corridors were constructed,with a total length of 356.84km,293.29km,and 179.00km,respectively.The distribution pattern was continuous,compact,and scattered in the middle.There were 49,37 and 35 ecological nodes were identified in each research year respectively.Most of them were located in the periphery of the central urban area.(3)Based on the correspondence between the value of ecosystem self-purification services and the trend of urban expansion,the simulation scenarios of urban expansion with and without ecological security patterns were conducted.Comparing ecological security pattern protection scenario with non-ecological protection scenario,the ecological land is protected.The urban expansion trend in 2028 is almost same in the two simulated scenarios.From the city center to the periphery,the cumulative value of the self-purification service value shows an S-shaped change,which experiences a gradual change,then a rapid increase and a gradual change at last.But the expansion rate is increasing.