Phytosociological and palynological studies of alpine steppe communities on the northern Tibetan Plateau, Qinghai Province, China

摘要

The dry cold climate in the highland of the eastern Kunlun Mountains in Qinghai Province,north-western part of China supports the establishment of alpine grassland, consisting ofPoaceae and Cyperaceae species and dwarf shrub communities dominated by Potentillaand Krascheninnikovia shrubs. The phytosociological vegetation studies carried out aroundLake Heihai (36°00′N/93°26′E, 4446 m a.s.l.) reveals a complex pattern of high moun-tainous vegetation, including three major vegetation communities. APolygonum sibiricumcommunity occupies wet and slightly saline sites close to the Heihai lake shoreline andKobresia robusta and Poa pachyantha communities are characteristic for the drier slopes.These communities differ in ecological conditions, exposureand several characteristicspecies that form local subunits. Main ecological factors influencing plant growth are mois-ture coming from glacial melt water and the composition and texture of the surface sedi-ments. The atmospheric circulation (i.e. monsoonal wind system) and the different amountof insolation of the southern and northern slopes are of minor importance for the estab-lishment of the different communities. The reflection of the vegetation composition in themodern pollen rain is generally poor, since the pollen spectrum is highly influenced by thelocal appearance of taxa. Though the vegetation unit of a alpine steppe can be detected.