Landscape Pattern Changes And Ecological Risk Assessment In Coal Mining Subsided Area

As a country with coal-based energy consumption,coal production plays an important role in the development of national economy and social progress.The rapid development of coal industry promotes the development of regional economy,but also it brings great damage to the ecological environment of mining area.As a result,the contradiction among population,resources and environment in mining area has become increasingly prominent,which directly affects the stability of regional economy and society.Therefore,a thorough and systematic study on landscape pattern evolution characteristics and land use ecological risk assessment in subsided area can provide technical support for dynamic monitoring and early warning of coal-mining subsided area.And it also provides a scientific basis for spatial-temporal optimal allocation of land use,and ultimately promotes the sustainable development of population,resources and environment in mining area.Jining City is one of the most important coal production bases in our China,and it is also a serious coal-mining subsided area.Based on the theories of geography,landscape ecology,spatial statistics and geostatistics,using remote sensing and geographic information system,and taking Weishan mining area in southwestern Jining as an example,this study firstly analyzed the quantity,direction and spatial change of land use in the study area.Based on the scale effect theory of landscape ecology,the landscape pattern and the gradient along longitudinal sampling belt under optimum scale were analyzed.Then the scenaris simulation of land use landscape pattern evolution was carried out.On this basis,assessment and spatial-temporal heterogeneity of land use ecological risk in mining area were studied.The main results are as follows:(1)Analysis of land use change characteristics.Conclusions were as followings:(1)The quantitative and direction change characteristics of land use types were as follows: Cultivated land area showed a fluctuating decreasing trend in the past 17 years.From 2000 to 2005,the area of urban and rural construction land and subsided seeper area increased rapidly,and then increased slowly.From 2010 to 2016,the area of construction land and subsided seeper area were decreasing.(2)The gravity center change characteristics of land use types were as follows: The deviation direction and distance of water area and cultivated land gravity center were larger.The gravity center of water area shifted to the southeast,and cultivated land shifted to the northwest.Secondly,the gravity center deviation distance of intertidal zone and marsh and subsided seeper area was also larger.The gravity center of intertidal zone and marsh shifted to the northeast,and subsided seeper area shifted to the southeast and lake area,but the deviation direction was not large.The gravity center of other agricultural land shifted to northwest,and the deviation direction and distance were not large.The gravity center deviation distance of urban and rural construction land was the smallest,and the gravity center shifted to the northeast as a whole.(2)Landscape pattern evolution characteristics and gradient analysis under optimum grain and extent.Conclusions were as followings: 50 m and 250 m were the optimum spatial analysis scale.The results of landscape level showed that,before 2005,landscape pattern showed low fragmentation,the dominant landscape was obvious,and the natural connectivity was high.After 2005,driven by rapid economic development and urbanization,landscape pattern tended to be complicated and diverse,the fragmentation was high and the connectivity was reduced.After 2010,due to land consolidation and renovation of subsided area,landscape pattern tended to be regular.The results of class level showed that,cultivated land area decreased dramatically from 2000 to 2005,then increased slowly and centralized from 2005 to 2010.Urban and rural construction land area gradually increased and was high aggregation and centralized after 2000.Subsided land area increased as a whole,and it was scattered and low connected.After 2005,subsided land became more regular after renovation.Landscape pattern gradient analysis along longitudinal sampling belt showed that,at the intersection of land-water area and the serious subsided area,around residential area and lakeshore,the landscape pattern was diverse,complex and more and more fragmented,while dominance,aggregation and connectivity were decreased.(3)Scenario simulation of land use landscape pattern evolution.Firstly,the spatial distribution of land use in 2016 was predicted based on 2005 land use data.The accuracy of predicted result was tested.On this basis,the spatial distribution of land use in 2025 was simulated under natural development scenario,ecological protection scenario and cultivated land protection scenario.Conclusions were as followings: The Kappa index of 2016 simulation result and 2016 actual interpretation data was 0.829,which showed that CLUE-S model had a good simulation effect.Under the three scenarios,the area of other agricultural land and water area showed an increasing trend,while the area of cultivated land,urban and rural construction land,subsided seeper area and intertidal zone and marsh showed a decreasing trend.And the area of urban and rural construction land and intertidal zone and marsh decreased fastest.Under ecological protection scenario,the area of cultivated land decreased faster than the other two scenarios,which was mainly transferred to ecological land such as garden land and water area.(4)Spatial-temporal change and spatial heterogeneity of land use ecological risk analysis under appropriate scale.Conclusions were as followings: A 1km × 1km regular grid was the best research scale.Under this scale,the spatial distribution of land use ecological risk in the research area was concentrated and had strong positive spatial correlation.The random variation on a small scale of land use ecological risk index was gradually replaced by spatial structural variation on a larger scale between 2000 and 2005.The total spatial variability of ecological risk in 2005 was high.Between 2005 and 2016,the degree of spatial variability caused by random factors was increased.In the past 17 years,land use ecological risk was characterized by the transition from medium-high and high ecological risk to medium and medium-low ecological risk.Ecological risk stable and improved area accounted for 79.21% of the total area,land use ecological risk has been greatly reduced.Ecological risk deteriorated and obviously deteriorated area were mainly distributed around the eastern mining area,along the roads,where human activities were frequent and subsidence was serious.