Temporal-spatial Change Of Cultivated Land Quality In The Typical Black Soil Region Of Northeast China

Good cultivated land quality is the key to ensure food production security and social stability.Black soil is the most precious soil resource of cultivated land resources.It is recognized as the most fertile soil in the world with the characteristics of loose texture,high fertility and strong fertility supplying capacity.However,due to the long-term destruction of natural and human factors,the quality of black soil in China has gradually deteriorated,resulting in the productivity of black soil gradually declined.Since the 18 th National Congress of the Communist Party of China,the protection of black land attached great importance by government,increasing investment and governance,and issuing a series of policies for the protection of cultivated land.Nowadays,after several years of management,what is the status of the black land in Northeast China? how has it changed compared to the past?how is the effect of governance?and how to manage and protect it in the future?These are necessary to research deeply during the new evaluation of cultivated land quality in Northeast China.In this study,the evaluation of cultivated land quality in the typical black soil area of Northeast China were explored with 16 evaluation indices by means of the Delphi method,with weights determined by an analytic hierarchy process based on the national standard of cultivated land quality grade(GB/T 33469—2016).Arc GIS software was used to evaluate the quality of cultivated land in the region using the same evaluation system and grading standard between 2008 and 2018,in order to investigate the temporal-spatial changes of cultivated land quality in the study area.Furthermore,this study introduced the function of obstacle degree to diagnose the indices of cultivated land quality to get the main obstacle factors.According to the primary and secondary order of obstacle degree,the obstacle types of cultivated land quality were divided,and then the measures for improving cultivated land quality were pointed out.The main results were showed as follows:(1)The quality of cultivated land in the study region was dominated by medium-and low-level land in 2008,with an average cultivated land quality grade of 5.14.In 2018,the quality of cultivated land was mainly in medium-and high-level land,with an average cultivated land quality grade of 3.92.Over the past 10 years,the integrated cultivated land quality increased by 1.22.The area of first-to fourth-grade cultivated land had increased,and the area of fifth-to tenth-grade land had decreased.The plot with one grade of quality improvement accounted for the largest proportion in the study area in the 10 years.The quality grade of most plots fluctuated between-4 and 2(increased by four grades to decreased by two grades).The total area of cultivated land increasing grade was 3.5 times than those decreasing.(2)In 2008,the typical black soil areas in northeast China were mainly distributed in the south and northeast,while the low-grade lands were mainly distributed in the central and northwestern regions.In the 10 years,the quality of cultivated land in the central,western and northwestern parts of the typical black soil region of Northeast China had increased significantly,while it in the southern and northeastern regions had decreased.The grade variation showed the strengthened variation from south and north to central.In the past 10 years,the quality of typical black soil cultivated land in Heilongjiang and Jilin provinces had improved,while it in Liaoning Province had declined.(3)The main obstacles to arable land quality in 2008 in typical black soil areas of Northeast China were irrigation capacity,effective soil layer thickness,drainage capacity,organic matter content,and farmland forest network rate.In 2018,the main obstacles were irrigation capacity,organic matter,drainage capacity,and farmland forest network.In the 10 years,irrigation capacity,effective soil layer thickness,drainage capacity,and available potassium have obvious effects on improving the quality of cultivated land and irrigation capacity was always the most restrictive of cultivated land quality in the study area.Based on the changes in the types of cultivated land quality obstacle zone over the past 10 years,the irrigation capacity obstacle zone was identified as long-term key improvement zone.In the future,the efficiency of agricultural irrigation water needs to be improved.The obstacle zone of farmland forest network was identified as short-term key protection zone.In the future,it is necessary to strengthen the construction of farmland forest nets and focus on improving the ecological environment of farmland.