2. Materials and methods
2.1. Experimental design
The study site is located in a semiarid grassland (42020
N,
116170
E and 1324 m a.s.l) in Duolun County, Inner Mongolia, China.
Long-term (1953e2007) mean annual temperature and precipitation
are 2.1 C and 383.5 mm, respectively. The soil is Haplic Calcisols
(FAO classification) with mean bulk density of 1.31 g cm3
and pH of 6.84. The vegetation is typical steppe dominated by
perennial herbs, including Stipa krylovii Roshev., Artimesia frigida
Willd., Potentilla acaulis L., Cleistogenes squarrosa (Trin.) Keng.,
Allium bidentatum Fisch. Ex Prokh., and Agropyron cristatum (L.)
Gaertn.
S