Research On Spatial-Temporal Characteristics Of Cultivated Land Use Change In Bayan

The study on the characteristics of cultivated land use change plays a very important role in protection, consolidation and utilization of cultivated land. Bayan as a typical agricultural county in Black Soil Region of Songnen High Plain is one of the important commodity grain base in China. However, as the economy continues to develop the cultivated land use occurred great changes there.A comprehensive analysis of spatial-temporal characteristics of cultivated land quantity, cultivated land landscape pattern, cultivated land quality and cultivated land ecological security of the study area will directly impact on the regional food security and human socio-economic development.This paper selected the typical area of Black Soil Region of Songnen High Plain—Bayan County in Heilongjiang Province as the study area and divided cultivated land use zoning, and then analyzed the characteristics of changing amplitude and speed, roll-in and roll-out, changing spatial distribution, and landscape distribution of cultivated land. In this paper, cultivated land quality evaluation units were obtained by laying over the cultivated land use map, soil map, slope map and administrative division map. On this basis, the evaluation index attribute data that could reflect the characteristics of cultivated land quality was extracted by means of3S technologies. Meanwhile, the comprehensive score of1991and2009was calculated by using the multi-factor synthetic evaluation model and divided rank on the score. Then we further analyzed the spatial and temporal changes of cultivated land quality in Bayan from1991to2009. Finally, in order to make a comprehensive analysis of spatial-temporal characteristics of cultivated land quantity, cultivated land landscape pattern, cultivated land quality and cultivated land ecological security, nine factors that directly or indirectly had impact on cultivated land ecological security were selected to analyze the changes of cultivated land ecological security in Bayan, and single-factor pollution index and comprehensive pollution index method were used to evaluate the cultivated land pollution status of the area in2009.The results show that,(1) The total area of cultivated land kept increasing, but the net annual average speed declined during the three time points. Unutilized land, forest land and construction land were always the main land use types transformed into cultivated land. Cultivated land was mainly transformed into forest land, unutilized land, grassland and construction land. Spatial differences of cultivated land change were remarkable in Bayan County. Newly increased cultivated land was mainly from the reclaimed floodplain along the Songhua River, the deforestation of northeast hilly areas and the construction land change in northwest.(2) The number and density of cultivated land plaque were on the rise, human interference degree increased and the fragmentation was growing. Landscape shape index and fractal dimension was decreasing, and the shape of cultivated landscape plaque was becoming simpler and more regular. High cultivated land landscape connectivity indicated that the spatial distribution of cultivated landscape had a high degree of aggregation.(3) Cultivated land quality grade by and large showed cross-distribution among plain area, hilly and mountain, and it had a close relationship with geomorphic type, soil type and altitude, showing significant regional differentiation regularity. There was a greater difference in cultivated land quality grade among towns, and this could directly influence the types of economic activity and the development of agricultural production. The geographical difference of cultivated land quality grade in the area was remarkable from1991to2009. Increased grade region was concentrated in Hongguang Township of cultivated land area in northwestern plains and Huashan Township of gentle slope cultivated land area in central hilly plains. Reduced grade region was focused on Longmiao Township and Tianzeng Township of gentle slope cultivated land area in central hilly plains. The region its grade remain the same was concentrated in Bayan Township of cultivated land area in the southern plains and Dexiang Township of gentle slope cultivated land area in central hilly plains.(4) Ecological security of cultivated land in the area had shown a downward trend from1991to2009. Land degradation and soil erosion were severe of steep slope cultivated land area in eastern hilly region. Region with severe heavy metal pollution of soil mercury, cadmium and lead levels exceeded the standard of natural background limits was concentrated in Region IV, Region II and Region III in2009. Cultivated land pollution was in the warning level status among nearly89%of the sampling points, and such sampling point cross located in various districts. Cultivated land environment was safe and clean among less than10%of the sampling points. The rest of the sampling points mainly located in Bayan Township of Region IV and Hongguang Township of Region I were in the state of various degrees of pollution.