Dynamic evolution of cultivated land fragmentation in coal mining subsidence area of the Lower Yellow River Basin:A case study of Jining city,Shandong Province

The coal mining areas in the Lower Yellow River Basin are mostly high water table mining areas.Coal mining leads to surface subsidence and serious water accumulation.At the same time,there are problems such as the continuous decline of a cultivated land area and ecological imbalance,which seriously affect the sustainable utilization of resources,and social and economic construction.In the key period of ecological protection and food security,it is urgent to reveal the dynamic change law of cultivated land resources and solve the problem of land resources utilization and protection in coal mining subsidence areas.In this study,Jining mining area in the “coal grain” composite area in the Lower Yellow River Basin is taken as the research object.Based on the probability integral method,the subsidence land expansion and land resource damage in Jining mining area from 2019 to 2030 are predicted.Combined with the morphological spatial pattern analysis (MSPA),1 pixel and 2 pixel width thresholds were selected,the patch importance index (IdPC) was used to extract the large and concentrated core areas of cultivated land in the study area under different thresholds.Finally,the dynamic evolutionary process of cultivated land fragmentation caused by collapse damage in the core area of cultivated land from 2018 to 2030 was quantitatively analyzed by the integral index of connectivity (IIIC).The results show that:① the coal mining subsidence area in Jining City will continue to expand from 2018 to 2030.By 2030,the coal mining subsidence area is predicted to be 50 613.52 hm2,and the cultivated land area of damaged land is 32 603.65 hm2,and Dongtan coal mine is the most seriously damaged cultivated land.② In MSPA analysis,the threshold setting of edge width will lead to significant changes in the number of patches and internal connectivity,and the fragmentation of small cultivated land caused by collapse is obvious at 1 pixel threshold.③ In the next 10 years,the coal mining sub-sidence in Jining city will cause the continuous decrease of cultivated land area,and the important core area of cultivated land will gradually fade away.The cultivated land in the mining area will be fragmented and scattered,and the small-scale change of cultivated land area in the coal mining area will lead to the decrease of cultivated land connectivity in large areas around.④ Different coal mining areas have different resource occurrence,production and utilization status,which leads to obvious differences in the fragmentation characteristics of cultivated land in different coal mines.The average IIIC value of cultivated land in Daizhuang Shengjian coal mine and Beixulou coal mine decreases by 0.65 and 0.64 respectively.The average IIIC value of Gaozhuang coal mine,Henghe coal mine,Jining No.2 coal mine,Sanhekou coal mine and Yangzhuang coal mine decreases by 0.58,0.55,0.55,0.51 and 0.51 respectively,which indicate that the cultivated land connectivity in the mining area decreases significantly and the degree of fragmentation increases in the next 10 years.In general,the reduction of cultivated land in the subsidence areas has reduced the connectivity of cultivated land in the city to a certain extent.Therefore,in the future land reclamation work,the coal mining areas need to strengthen the intensity of cultivated land reclamation to reduce the negative impact on agricultural production.