2.1 Study field
This study was conducted in Inner Mongolia steppe in China (43°33′N,
116°40′E). The mean elevation of the location is 1225 m (range: 1200
m–1250 m). This location is characterized by mild humid summer and dry
clod winter, which is temperate semi-arid continental monsoon climate.
Annual mean temperature is around -1.1 °C–0.2 °C. There is a large
temperature difference within a year (-21.4 °C in the coldest month in
January, while 18.5 °C in the warmest month in July). The frost-free
period is around 100 days in a year. The annual mean precipitation
between 1980 and 2000 is 350 mm, where the precipitation mainly occurs
in June and August, and the amount of rainfall during this period is
around 80% of the amount of rainfall in the whole year. The site is
dominated by dark chestnut soil (Jia et al., 2005; Lisetskii and
Rodionova 2015). The dominant species are Dauri-Mongolian species such
as L. chinensis , S. grandis , A. frigida andP. acaulis (Li and Li 2002).