1.1 Study area
The study sites were located in the Qilian mountain nature reserve in
Gansu province, China (94°10′-103°04′E, 35°50′-39°19′N). In the
horizontal distribution, the vegetation gradually deteriorates from
southeast to northwest, which results in the formation of four
vegetation zones in an order of forest, shrub, grassland and desert.
Vegetation at the vertical belt spectrum, from low altitude to high
altitude, was grassland belt, forest belt and alpine meadow grassland
belt. The main types of soil were mountain gray cinnamon soil, subalpine
meadow soil, alpine meadow soil, alpine cold desert soil. The annual
precipitation varied from 100 to 500mm, mostly from June to September,
the average annual temperature was -0.6-2.0°C, the average annual
relative humidity was 20%-70%, the average annual evaporation was
about 1200-1400 mm, the frost-free period was 90-120 days.