2.1. Study area
The LP covers 62.4×104 km2 (34–45°5’N, 101–114°33’N)
and is located in the upper and middle reaches of the Yellow River in
the central-northern part of China. The LP is surrounded by complicated
mountain conditions, with the Yin Mountain in the north, the Qinling
Mountain in the south, the Riyue Mountain in the west and the Taihang
Mountain in the east. The terrain over the LP gradually declines from
northwest to southeast, with a unique topography composed of abysses,
ridges, gullies and hills. The LP lies in the continental monsoon
climate zone, spanning 750 km from north to south and 1000 km from east
to west, so the LP exhibits various climate characteristics (Zhang, Wu
et al. 2014, Liu, Wang et al. 2016, Zhao, Zhai et al. 2017). The LP
covers a wide temperature gradient decreasing from south to north and a
large precipitation gradient decreasing from southeast to northwest.
2.2. Data