# Spatiotemporal Analysis of Urban Expansion in Beijing, China
## 3 Results  
### Quantitative Characteristics of Urban Expansion in Beijing  
According to Figure 2, the urban construction land area in the urban area of Beijing (the red areas in the study area) expanded by 0.53 times from 1995 to 2020 (Figure 3, Appendix A). Among these areas, the construction land area decreased by a factor of 0.02 from 1995 to 2000, expanded by a factor of 0.08 from 2000 to 2005, expanded by a factor of 0.29 from 2005 to 2010, expanded by a factor of 0.08 from 2010 to 2015, and expanded by a factor of 0.03 from 2015 to 2020. The urban expansion of Beijing from 1995 to 2020 showed the characteristic of \"contraction slow medium slow\" (Figure 4). According to the study by [PERSON] et al. (2020), the expansion intensity in Beijing was slow from 2000 to 2005, moderate from 2005 to 2010, and slow from 2010 to the present. The expansion speed and intensity in Beijing are gradually slowing, and urban construction land is showing a stable trend.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Classified** & **Index** \\ \hline Research methods for determining the & Urban expansion speed index \\ quantitative characteristics of urban expansion & Urban expansion intensity index \\ \hline Research methods on the spatial characteristics & Fractal dimension of urban space \\ of urban expansion & Transfer of the urban spatial center of gravity \\  & Elastic coefficient of urban expansion \\ \hline \hline \end{tabular}
\end{table}
Table 1: Urban expansion technology system.  
Figure 2: Quantitative characteristics of urban expansion from 1995 to 2020.  
As shown in Figure 5, there are differences in the expansion of different urban areas. Xicheng District, Dongcheng District, and Shijingshan District did not expand between 1995 and 2020, and the urban construction land area remained basically unchanged. The area and expansion speed of urban construction land in other districts are as follows: Daxing > Shunyi > Fangshan > Tongzhou > Changping > Chaoyang > Haidian > Mentougou > Fengtai > Shijingshan > Xicheng > Dongcheng. Compared with the urban construction land area in 1995, Daxing, Shunyi, Fangshan, Tongzhou, Changping, Chaoyang, Haidian, Mentougou, and Fengtai had expanded by factors of 1.22, 0.74, 0.61, 0.65, 0.6, 0.37, 0.22, 0.35, and 0.2, respectively. The expansion intensity was as follows: Mentougou > Daxing > D  
\(>\) Shunyi \(>\) Tongzhou \(>\) Fangshan \(>\) Changping \(>\) Chaoyang \(>\) Haidian \(>\) Fengtai \(>\) Shijingshan \(>\) Xicheng \(>\) Dongcheng. Construction land resources in the central urban area of Beijing are scarce, and the land utilization rate is high. The land resources in peripheral urban areas are abundant, and the expansion cost is lower, increasing the suitability for expansion. The results also reveal that the expansion area, expansion speed, and expansion intensity of peripheral urban areas are greater than those of central urban areas. Overall, the expansion type of Beijing is the extensional type.  
According to Table 1, from 1995 to 2000, except for Shijingshan, Xicheng, and Dongcheng, the urban construction land area in other districts showed a decreasing trend. During the three periods of 2000-2005, 2005-2010, and 2015-2020, the expansion speed of Daxing District was the fastest, and the expansion intensity of Mentougou was the highest. From 2010 to 2015, Fangshan District had the fastest expansion, and Tongzhou had the highest expansion intensity. From 1995 to 2020, the expansion speed and intensity of Mentougou in Daxing District were particularly prominent. The overall expansion of Beijing is characterized by the central urban area remaining basically unchanged, while the peripheral areas are rapidly expanding, showing a phenomenon of rapid growth first and then stabilizing, and the urban layout is basically stable.