Research On Ecological Risk Assessment Of Land Use In Hefei City Based On Geographical National Data

The statistical analysis of geographical conditions is an important part of the survey of geographical conditions and is also a key process for the application of the results of the survey of geographical conditions.Statistical analysis of geo-national census data can reflect the interactions between socio-economic,resource,ecological,environmental and other factors and their own characteristics from different dimensions,provide data support for social development and economic construction,and thus exert geographical national conditions.The potential and value of census data applications enable its results to be fully absorbed and applied to serve the country.Based on the results of Hefei High Score Image and National Database in 2015 and 201 7,this paper takes into account other results data.The four jurisdictions of Hefei City are used as research areas,using Arc GIS,Fragstats and Excel software,combined with mathematical modeling.,3S technology,spatial analysis and other technical means to analyze the basic characteristics of surface cover elements in Hefei City;the last case study,according to Hefei City's geographical conditions data classification of its land use types,from ecological multi-risk sources,multi-risk receptors and more The three levels of risk effects are used to construct the ecological risk assessment model of land use in Hefei City by using analytic hierarchy process,membership function method and comprehensive index method.The ecological risk assessment results of land use in Hefei City are analyzed.Finally,the ecological environment status and actual development of Hefei City are combined.Need to put forward the corresponding land use ecological risk management and control recommendations and countermeasures.The main conclusions are as follows:(1)Statistical analysis of the geographical factors of Hefei City:The elevation value of Hefei City is between-81m and 265m,and the slope value is between 0°-60°.The surface cover factors of Hefei City are mainly forest and grass cover,planting land and house building(district),accounting for 21.352%,20.1 76%and 17.625%respectively.The proportion of other elements is as follows:water area(14.776%)>Artificial excavation(9.337%)>Railways and roads(9.183%)>Structures(7.547%)>Desert and bare ground(0.004%).According to the results of statistical analysis of surface cover factor transfer,the order of transfer area from large to small is:artificial excavation>forest cover>planting land>house building(district)>structure>water area>railway and road>desert and Bare land;the area to be transferred from large to small is sorted into artificial excavation>house building(district)>forest and grass cover>structure>railway and road>planting land>water area>desert and bare land.Hefei's housing construction types are mainly multi-storey and above housing construction areas and low-rise housing construction areas,followed by low-rise independent housing construction,multi-storey and above independent housing construction and abandoned housing construction areas.The total length of urban roads in Hefei is 1930.15km,the total length of rural roads is 603.01km,the total length of highways is 570.25km,and the density of road lines is between 0-831.77km/km2.The total length of the linear water system in Hefei City is 897.7794km;the total area of the planar water system is 163.9938km2.(2)Analysis of land use change in Hefei City:?The land use type of Hefei City is mainly construction land.By 2017,the land area of each type of Hefei City will be:construction land>water area>garden land>grassland>forest land>Cultivated land>unused land.From the perspective of land use dynamics,the largest annual change rate is cultivated land,with a change rate of 10.20%;followed by grassland and construction land;the change of garden,water and forest area is small,and the unused land has not changed.?From the results of the transfer matrix,the largest reserved area in each type of land is construction land,followed by waters;the largest transfer area is grassland and cultivated land,and the most transferred area is construction land.This shows that the mutual transformation between grassland,cultivated land and construction land is more obvious.?From the perspective of land use degree,the comprehensive index of land use degree in Hefei City is higher,from 301.79 in 2015 to 306.80 in 2017.The land use degree in Hefei City is gradually strengthened and is in the development period.?From the perspective of landscape pattern,between 2015 and 2017,the difference in plaque type in the study area becomes smaller,the plaque connectivity becomes higher and higher,the plaque gathers more and more closely,the landscape fragmentation decreases,and the largest plaque is affected by humans.The disturbance of activities is strengthened;the construction land is the main landscape of the study area,the distribution is relatively concentrated,the degree of aggregation is getting higher and higher,and human activities are frequent.(3)Results of land ecological risk assessment in Hefei City:?On the whole,the ecological risk level of Hefei City in 2015 is at a higher ecological risk level,but the increase is not particularly obvious.?From the four jurisdictions of Hefei City,the ecological risk value distribution ranges of Hefei City in 2015 and 2017 were between 0.4440-0.5152 and 0.4481-0.5199 respectively,and Laoshan District,Yuyang District and Yaohai District were all in a high ecological risk state.Baohe District is in a state of medium ecological risk,and the ecological risk values of the four jurisdictions are increasing,indicating that the ecological environment is deteriorating,but the deterioration is not serious.?From the spatial distribution of the overall land use ecological risk value in the study area,the ecological risk value range of land use in Hefei City in 2017 is between 0.1262-0.5625.