Mechanism of cultivated land system change in black soil areas of Northeast China

Abstract: Black soil region in northeast China is one of the four largest black soil areas in the world, serving as an important grain production base with a commodity rate of more than 70%. Production capacity depends directly on the cultivated land system. Taking Keshan County in northeast China as the research area, geo-detector models were used to identify the key influencing factors of cultivated land system changes in 1986, 2010, and 2018. Mechanism of cultivated land system change was also clarified using GIS, RS, and Matlab programming, including the weight and interaction of key influencing factors. The results showed that: 1) A cultivated land system was a three-dimensional organic space with a length, width, and height, where the comprehensive action of all elements was within a certain range. The length and width were determined by the scale of cultivated land, while the height was determined by the types of crops and the thickness of the cultivated layer. Each element of the cultivated land system had an irreplaceable position and function. A micro-ecological environment also dominated the surrounding vertical and horizontal factors. 2) A total of five, eight and six key factors were found to have important influence on the changes of cultivated land systems in 1986, 2010, and 2018, respectively. All cultivated land system changes were affected by the internal factors of the system from 1986 to 2018. The influence of horizontal factors on the cultivated land system changes strengthened year by year, whereas, the influence of vertical factors weakened as time went by. The key factors were dominated from natural factors to the dual influence of natural and human activities in recent years. The influence of other factors was relatively weak. 3) There was the greatest impact of the interaction between the internal influencing factors of the cultivated land system and others in the vertical and horizontal directions on the cultivated land system change from 1986 to 2018. There was also different significance in the interaction between the horizontal and vertical directions. The interaction between factors had significantly higher spatial differentiation of cultivated land system changes in the study area than the single factors, indicating a double-factor or nonlinear enhancement. There was a relatively significant influence of single and interactive partial factors on the cultivated land system change. Combining with two parts of the factors, some single factors had no significant impact on the cultivated land system change, but the interaction effect was significant. The sensitivity of internal and external factors can also be objectively revealed via the single and interactive factors in the spatial differentiation of cultivated land system change. The finding can provide a scientific basis to protect cultivated land for food security.