Study location

The Qinling and Bashan mountain ranges in central and south-western China (30˚5'–34˚59'N, 102˚54'–112˚4'E, about 222 300 km²) are characterized by complex topography and distinct environmental conditions between the northern and southern regions (Wang et al. 2017). The highest peaks in the Qinling and Bashan Mountains are at 3767 and 3105 meters above sea level (m asl), respectively. The mountains serve as natural barriers between the southern subtropical and the northern warm temperate regions of central China, and also as a boundary between the Palearctic and Oriental Regions in eastern Asia. In the Qinling Mountains, areas lower than 1000 m asl on south-facing slopes are dominated by a subtropical climate while the areas above 1000 m asl on south-facing slopes and all elevations on north-facing slopes are more temperate. The Bashan Mountains are approximately 50 km south of the Qinling Mountains, extend from east to west in parallel with them (Zhan et al. 2009), and are dominated by a subtropical climate. In the Qinling Mountains, the average annual temperature is 11–13 °C and the average annual precipitation is between 590 and 764 mm (Zhao et al. 2014). The average annual temperature in the Bashan Mountains ranges from 14.5 to 16.5 °C, and average annual precipitation is between 800 and 1400 mm (Li et al. 1990).