Abstract: As indispensable biological resource, myxomycetes play an important role in the forest ecosystem. In order to explore the diversity of myxomycetes and the factors affecting the species composition and diversity in the forests of Northwest China, continuously two years' investigations were carried out in Qilian Mountain National Nature Reserve of Gansu province. Totally 826 specimens were collected and identified as 4 orders, 5 families, 22 genera, and 71 species by morphological characters, and 30 species were new records in Gansu province. According to species similarity analysis, 9 species including Ceratiomyxa fruticulosa were widely distributed in the natural reserve. The total number of myxomycetes (58 species) and endemic myxomycetes (38 species) in coniferous forest were higher than those in broad-leaved forest (33 species and 13 species). There was not found any obvious effect of altitude on diversity. The principal component analysis showed that the species diversity occurring on the rotten wood substrate is the most abundant, and the myxomycetes species occurring on the woody and herbaceous substrates were significantly different. This results suggests that the vegetation type and substrate type of the mountain forest are important factors affecting the species composition and diversity of myxomycetes in Qilian Mountain Natural Reserve of Gansu province.

Key words: Myxomycetes, taxonomy, species diversity, forest ecosystem, distribution characteristics