## 3 Results
### Transferring Characteristics of PLES from 1980 to 2018  
PLES is an important expression of the man-land relationship. As the man-land relationship is influenced by people's cognitive evolution, technological updates and resource awareness, PLES shows phased characteristics in a long time series. This leads to changes in the functional demand pattern of the territory. Thus, it changes the distribution pattern of the PLES pattern. 1980 was defined as the base year, and the total amount of PLES changed by 2018 was 28,458.3 km\({}^{2}\), accounting for only 13.9% of the study area (Figure 8). The largest transferring type scale was PS-ES. The transferring area was more than 20,000 km\({}^{2}\), accounting for 77.81% of all types of the transferring area (Table 3). This is because the normal production space could not satisfy the huge demand for agricultural products before the reform and opening up, a lot of unsuitable land was reclaimed into arable land. After 1990, the supply and demand of agricultural products tended to be stable, and the BTH region suffered from serious dust weather. The government issued the policy of returning farmland to forest, which restored a large amount of agricultural space to ES, and reconstructed the pattern of rural PLES.  
The spatial distribution of PLES types in 1980 and 2018 was overlayed to obtain the spatial pattern of the PLES shifting type. According to the naturalness of PLES types, the transferring process can be divided into two orientations: the process of increasing nature and the process of decreasing nature. The decreasing nature process includes the transfer of PS to LS, ES to PS and ES to LS. The other three transfer types were included in the process of increasing nature. The result of the standard deviation ellipse is shown in Figure 9a,b. It was shown that the distribution of different transfer directions and types of space in the study area is different. Significantly, in the process of decreasing nature, which used to be ES, the patches forming PS are widely distributed and mainly located in the central area, while the patches forming LS are mostly distributed in the periphery of Beijing and Tianjin, extending to the south of the North China Plain. The patches from PS to LS are mainly distributed in the North China Plain. In the process of increasing nature, the production space patches, which were LS, are distributed on the north and south sides of Beijing and Tianjin, while the ES patches are gathered around Beijing and Tianjin. The PS patches from ES are distributed in the Taihang Mountain area. In the study area, the three transferring types of decreasing nature are highly overlapped, which are centered in the urban areas of Beijing and Tianjin and extended to the north of the North China Plain. It can be seen that the expansion of high-level urban areas led to the transformation of territorial space to decreasing nature in a certain range around the area. In contrast, the distribution of increasing nature types presents a pattern of parallel movement from the northwest to the southeast. The overlap occurs only in part of the transition zone, from the shallow mountainous area to the North China Plain in the northwest of Beijing. With the process of parallel movement, the difficulty of transferring gradually increased. The LS-ES ellipse is almost distributed on the North China Plain. The huge difference in the distribution  
\begin{table}
\begin{tabular}{c c c c} \hline  & **PS2018** & **LS2018** & **ES2018** \\  & **(km\({}^{2}\))** & **(km\({}^{2}\))** & **(km\({}^{2}\))** \\ \hline PS1980 & 98,807.90 & 4196.57 & 22,144.28 \\ LS1980 & 335.50 & 15,203.01 & 81.31 \\ ES1980 & 1516.29 & 184.34 & 62,196.70 \\ \hline \end{tabular}
\end{table}
Table 3: PLES transfer matrix from 1980 to 2018.  
of transferring types shows the re-optimization of regional endowment on the choice of spatial functions. It was necessary to analyze its internal mechanism by type.