2. Material and methods

Studied site

The studied site is located in Nyingchi City, Tibet Autonomous Region, China (E94°45’25”, N29°58’10”), which has a warm and semi-humid plateau climate with annual precipitation and temperature of 650 mm and 8.7℃, respectively. This region belongs to the upper reaches of the Yarlung Zangbo River high mountain gorge area, and the average elevation is 2940 m. The typical soil types are mountain brown soil, -yellow-brown soil and sandy loam deposited in river flats, which are generally in coarse textures and possess various gravel contents (Gao et al.,2021). The main native herbage plants include Kobresia myosuroides , Stipa capillata , Carex hirta, Potentilla chinensis, Elymus dahuricus .