# Urbanization and Grain Production Pattern of China: Dynamic Effect and Mediating Mechanism
## 5 Discussion  
The GPP in China has changed profoundly. Its COG has transferred gradually to the northeast, showing a spatial distribution pattern from the northeast to the southwest. The SDE of grain production covered most of the major grain-producing areas in eastern, central, and western China, and the coverage of the northern provinces is gradually expanding. A spatial clustering and distribution pattern of grain production transfer and expansion to the north, especially to the northeast, was formed. This is in general agreement with the findings of existing studies [11]. The northward transfer of the COG is mainly attributed to a relatively large increase in the distance shifted northward in the north-south direction and a smaller increase in the distance shifted in the east-west direction. From the perspective of production, the COG transfer is mainly manifested in the rising grain production in the northeast and northwest regions. In the northeast region, grain production plays an increasingly important role in ensuring national food security, while it is gradually declining in the economically developed southern region, especially the southeast coastal region. Changes in China's GPP are affected by a variety of natural and socioeconomic factors, which are accompanied by significant spatial and path dependencies. The presence of spatial spillover effects suggested that a region's GPCI was also affected by the positive spillover from neighboring regions; that is, grain production in one region has a strong demonstration and transmission effect on the grain production in neighboring regions. The presence of path dependency implied that the GPP values in the current period were positively affected by the GPP of the previous period. The time lag coefficient is significantly larger than the spatial lag coefficient, indicating that the cumulative effect resulting from the path dependency of changes in the GPP is more prominent. However, the changes are still a relatively slow process. Since the focus of urbanization is still transitioning from scale expansion to quality improvement, population movement and land scale are still the main human-land conflicts facing grain production [53]. The progress of urbanization promoted population agglomeration, infrastructure improvement, and non-agricultural industry development, which have brought about the outward expansion demand of urban land space from urban outskirts. As a result, the regional grain supply was affected by the non-agriculturalization and encroachment of cropland, and the GPCI decreased. Despite China having implemented the requisition-compensation balance of cropland policy in the expansion of urbanization [54], the quality of cropland is often reduced due to insufficient or neglected compensation for occupied cropland, which affects regional grain production. Changes in factor input intensity and the consumption-demand structure, the spread of new technologies, and other factors triggered by the reduction of cropland have overlapping effects on grain production. Among the three significant transmission paths by which urbanization affects the GPP, cropland utilization, planting structure, and agricultural