2.1 | Study site
This study was conducted in a semiarid grassland on the Inner Mongolia Plateau (41°46′43.6″ N, 111°53′41.7″ E; elevation 1456 m). This area has a temperate continental grassland climate, with annual mean temperature and precipitation of 3.6 °C and 214 mm, respectively (Wang et al., 2014). About 80% of precipitation occurs during the growing season (May to September). The vegetation in the experiment site was dominated byStipa breviflora and Cleistogenes songorica . The soil is a Kastanozem soil (FAO soil classification) with a sandy loam texture. This area is traditionally used as pastures for free grazing and 90 % of them have been degraded due to overgrazing (Kemp et al., 2013).