The Influence of Rural Urbanization on the Change in Soil Organic Matter of Farmland in Northeast China

Studying the impact of urbanization on changes in the soil organic matter (SOM) content of farmland plays an important role in determining the influence mechanism of urbanization regarding regional environmental change. Taking the farmland in Yushu City, northeast China, as the research area, in May 2019, 68,393 sample plots (each plot: 60 m × 60 m) were set up in farmland and sampled to measure the SOM content of each plot while combining image data from the same period in the study area (resolution: 60 m). This investigation was based on 17 levels divided by the size of areas occupied by residences, using residential areas as the center and a radius of 60 m. Through a gradually buffered extrapolation method combined with mathematical functions, the influence of rural urbanization on the changes in SOM content was revealed. These results showed that the slope of the linear function between the SOM content and the residential area level was greater than zero and that with the continuous advancement of urbanization, the SOM content had an increasing trend. When urbanization advanced to the stage of larger cities, large-scale mechanized production led to land degradation. When urbanization advanced to the stage of towns, intensive cultivation was beneficial for land restoration. The findings of this study provide a reference basis for future studies of the relationship between rural urbanization and agricultural mechanization around the world.