2.1 Study area and sites
Location of 223 sample sites and main vegetation types were described in Qinghai Plateau including alpine desert, alpine steppe, alpine meadow and without vegetation (Fig. 1). This study was conducted in alpine desert ecosystem with a plateau continental climate. Average air temperature and precipitation were −3.68 oC and 92.94 mm. Altitude ranged from 2600 to 3200 m. Soil types mainly included grey-brown desert soil, aeolian sandy soil, and saline alkali soil.
Alpine deserts were dominated by Kalidium foliatum (Pall.) Moq., Sympegma regelii Bunge, Nitraria tangutorum Bobr., Salsolacollina Pall., Artemisia sphaerocephala Krasch., Tamarix chinensis Lour., Ceratoides latens, Ephedra przewalskii Stapf, Haloxylon ammodendron Bunge, Reaumuria kaschgarica Rupr., Reaumuria songarica, Peganum harmala, Lyciumchinense Miller.