2.1 Study site
The study was performed in a desert grassland located in Inner Mongolia, China (41°46 ’43.6 ”N, 111°53’ 41.7” E; 1456 m a.s.l.). The climate is a typical mid-temperate continental monsoon climate with a dry and windy spring, hot summer and cold winter. The average annual precipitation (2004-2022) is about 232 mm (Figure S1), of which about 85% occurs during the growing season from May to September. The average annual temperature during the study period was 3.8℃ (Figure S1), with a mean diurnal temperature difference of 13-14 ℃. The soil at the study site has a sandy loam texture and is classified as Kastanozem according to the Food and Agriculture Organization classification system (FAO, 1993). The soil (0–10 cm depth) has a soil bulk density of 1.3 g cm-3, a total N of 1.7 g kg-1, a total carbon of 16.9 g kg-1 and pH of 8.0. Plant communities at the study site are dominated by two perennial grasses,Stipa breviflora and Cleistogenes songorica , and one perennial semi-shrub, Artemisia frigida . Other common species included Kochia prostrata , Convolvulus ammannii and Allium tenuissimum .