2.1. Study site
The study area is in Hongyuan County, Aba Tibetan and Qiang Autonomous
Prefecture, northwest of Sichuan, China, on the southeastern edge of the
Tibetan Plateau, and is the largest plateau peat swamp wetland area in
the world, whose special ecological geographic location makes it an
important regulator of the global ecological environment. The study was
carried out in Wache Township, Hongyuan County (33°10′N, 102°37′E), a
typical demonstration area for sandy control in Sichuan Province. The
sample area is flat, with a relatively uniform topography and slope. The
topography slopes from southeast to northwest, and the landscape is
typical of the transition from mountain plain to hilly plateau, with an
altitude of 3600 m above sea level. The climate is continental plateau
cold temperate monsoon climate. The mean annual precipitation is 791.95
mm and temperature is 1.5℃. The plants are dominated by sea buckthorn,
Salix cupularis and medicinal plants, include Rhodiola rosea, Qianglong,
Songbei, Astragalus, Cordyceps, Kobresia setchwanensis, Leymus
secalinus, and Anaphalis flavescens. The area is fenced off from grazing
and the experiment was conducted in an ecological restoration area of
Salix cupularis.