**2. Materials and Methods**

#### *2.1. Study Area*

This research is conducted over the Southern part of China, which in Chinese is simply referred to as "the South". The study area comprises of eight provinces (Anhui, Hunan, Hubei, Jiangxi, Jiangsu, Zhejiang, Fujian, and Guangdong) and one municipality (Shanghai) (Figure 2a). It is approximately the mega-region within China separated by the Qingling-Huaihe Line, which is a reference line used by geographers to distinguish between the Northern and the Southern China, corresponding roughly to 33rd parallel [52]. From Qingling-Huaihe, "Qingling" refers to the Qingling Mountain, and "Huaihe" refers to the Huai River, running from the Qingling Mountain in the West to the Huai River in the East. It divides Eastern China into the North and the South regions, which differ from each other in climate, demography and terrain. All major rivers of China flow across this region, e.g., the Yangtze River,

the Huai River, the Han River, the Qu River, the Qiangtang River, the Ou River, the Gan River, the Min River, the Xiang River, the Zi River, the Yuan River and the Lishui River. In addition, some major lakes such as the Dongting Lake, the Tai Lake and the Chaozhou Lake are also located in this region. Moreover, regions laying in the South of the line tend to be tropical and subtropical. Some major mountainous series such as the Huangshan, the Dabie, the She, the Mufu, the Jiuling, the Luoxiao, the Huaiyu, the Wuyi, the Jiulian, the Dayu, the Nong are also located in this region. The Southern part is hotter and wetter than the Northern part. Normally, the weather conditions are with short, cool, damp winters, and very hot, humid summers. The average temperature in winter and summer remains between 3 °C to 9 °C and 27 °C to 30 °C, respectively. The average annual precipitation is between 1200 to 1900 mm, much of it falling in the form of heavy rains occurring in late spring and summer. In addition, half of the most developed tier 1 cities of China are located in the South.
