Urbanization Induced Land Use Change And Ecological Risk In The Karst Mountainous Region Of Jinan

In recent years,due to the strong influence of human activities and the acceleration of urbanization process,the land use pattern of Jinan karst mountainous region has changed greatly,which has caused many environmental problems in urban karst region and brought great ecological hazards to the sustainable development of the city.This paper takes the southern mountainous area of Jinan in the typical karst area of the north as the research area,this paper interprets the remote sensing images of the study areas in 1987,1995,2000,2009 and 2016.The land use change status of Jinan karst mountainous region is analyzed concretely by using the single land use change dynamic degree and the comprehensive land use change dynamic degree,and combining the land use transfer matrix.At the same time,based on the data of land use change,the ecological risk index model of the study area was constructed,and analyzed the ecological risk situation of Jinan karst mountainous region.Combining with the elasticity theory of microeconomics,the response elasticity coefficient of the study area was put forward,and the response characteristics of the ecological risk change of each township in the study area were analyzed concretely.The main conclusions of this paper are as follows:(1)In the karst mountain region of Jinan,cultivated land and forest land account for the largest proportion,accounting for more than 60% of the total area of the study area,followed by grassland and construction land,and the proportion of water and unused land is small.(2)The land use of the Jinan karst mountainous region has changed greatly from 1987 to 2016,the land use structure changed continuously,and the dynamics of comprehensive land use change showed an increasing trend.The land use change speed in the karst mountain region of Jinan continued to accelerate,and the dynamics of single land use change is unstable.Affected by urbanization,the change of construction land and cultivated land in Jinan Karst Mountains was the most dramatic during 1987-2016.The area of construction land increased the most and continued to grow,accounting for about 10% of the total area of the study area,of which the fastest growth was in 2000-2009.The area of cultivated land decreased the most,accounting for about 10% of the total area of the study area.The water area is relatively stable,and the overall area has little change.Unused land grew rapidly from 2000 to 2009,and its annual dynamic degree reached 310.199%.This was mainly due to the large amount of land degradation and the increase of wasteland area during the process of urbanization.(3)From 1987 to 2016,the area of cultivated land transfer was the largest,and the construction land was transferred to the largest area.The cultivated land is mainly converted into construction land,grassland and woodland.The forest area is mainly converted from cultivated land and grassland.In addition to the greater contribution of cultivated land,the increase in grassland area has also resulted in more land transfer and construction land.The unused land was mainly converted from cultivated land,woodland and grassland.It changed little from 1987 to 2000,and the growth area was more in 2000-2009.The water area has not changed much.(4)The process of urbanization leads to changes in the land use situation in the study area,which in turn causes changes in the ecological risk of the study area.Based on the constructed ecological risk index,according to the autocorrelation analysis,the Moran's I index of ecological risk in the study area from 1987 to 2016 is positive,and all of them pass the significance test of P=0.05 level,which has strong positive spatial correlation characteristics.It shows that the ecological risk based on land use change in Jinan karst mountains region is concentrated in space,and the spatial correlation of the adjacent ecological risk values is significant.From 1987 to 2016,the distribution of "low-low" areas was relatively stable,mainly distributed in the forestland and grassland areas of Xiying Town,Liubu and Wande Subdistrict in the eastern part of the study area;the "high-high" areas were mainly distributed in the steep ditches,Qixian,Guyunhu,Dangjiazhuang,Shiliulihe and Xinglong Subdistrict in the northwestern part of the study area,mainly because of the rapid urbanization speed of these townships and the growth of urban construction land area.A large number of forestland,grassland and cropland have been transformed,which has a great impact on the natural environment of the region.Its vulnerability is relatively high,and the ecological risk is increasing.(5)Based on the research on the elastic coefficient of response of land use change to land use,the ecological risk of the study area increased rapidly from 2000 to 2009,and the response elasticity of all towns and villages was positive.The land use change caused the substantial growth of ecological risk in the study region.In other periods,the ecological risks caused by changes in land use in towns and villages have risen and fallen.Land use changes in Dougou,Qixian,Shiliulihe,Wande,Guyunhu,Xinglong Subdistrict and Xiying Town have been causing ecological risk growth in all streets.Most of these towns are close to the urban area.Under the background of urbanization,the continuous development of the urban area has promoted the development of its surrounding areas.The towns close to the urban areas have changed their land use types rapidly,and the urban construction land area continues to grow,making the cultivated land,the forest land and so on are decreasing.The construction of a large area of the city has caused the destruction of the original ecological environment,coupled with some unreasonable development and utilization,resulting in the growth of local ecological risks.Other township ecological risks have risen and fallen with changes in land use.The main reason is that the conversion between land use types is more frequent.When the construction land is converted to grassland or forest land,the ecological risk will decline.On the other hand,if grassland,woodland or other places are converted to construction land,the ecological risk of the area will increase.