2.1 Study area
The present study was conducted in the northeast of Eurasian steppes, Xilinhot City, China. The area experiences continental precipitation with an average of 350 mm (200-500 mm) over 30 years, with 60 to 70% falling between July and August. The average monthly temperature varies from -21.6℃ in January to 19.0℃ in July, annual mean temperature of 0.3℃. Approximately 150 to 180 days per year are considered favorable for plant growth (Bai et al., 2010). The most prevalent plant species in the area are Stipa grandis P.A. Smirn., and Leymus chinensis (Trin.) Tsvel. (Li et al., 2015).