【Abstract】Thymus mongolicus steppe was a vegetation formation dominated by typical dwarf semi-shrub of Lamiaceae. Based on the previous literature and primary plot data sampled during the growing seasons from 2015 to 2017, the distribution, ecological features, community characteristics, and classification of T. mongolicus steppe were summarized. (1) T. mongolicus steppe was mainly distributed on the loess hills of Xar Moron River Watershed, Bashang region in the northwest of Hebei Province, the hills surrounding the Yinshan Mountains, the east part of Erdos Plateau and the northern Loess Plateau. This formation occurred mainly on the stony slopes or loess hills with severe soil erosion. (2) In total, 167 seed plant species belonging to 101 genera of 34 families were recorded in the 91 sample sites, and families of Compositae, Leguminosae and Gramineae played crucial roles in the species composition. Eight of these families were semi-shrub and dwarf semi-shrub species, and 112 were perennial forb species. The typical xerophytes (58 species) and Meso-xerophytes (45 species) accounted for more than half part of all species. Eight geographic elements were involved. East Palaearctic (70 species) and East Asia (46 species) were the two major floristic elements. (3) Based on the life form and dominance of species in the community, the formation was classified into six association groups (T. mongolicus, semi-shrubs/dwarf semi-shurbs association group; T. mongolicus association group; T. mongolicus, bunchgrasses association group; T. mongolicus, rhizomatous grasses association group; T. mongolicus, Carex association group; T. mongolicus, forbs association group), consisting of 28 associations.

【Keywords】 Thymus mongolicus; dwarf semi-shrubby steppe; life form; floristic geographic elements; community classification;

【DOI】

【Funds】 National Basic Research Program of China (2014CB-138800) Key Program of National Fundamental Scientific Research (2015FY210200)