Study on community characteristics of bryophytes in dolomite cave twilight zones:An example of the Shuidong Cave in Suiyang county, Guizhou Province

Dolomite caves are one of unique habitats in karst mountainous areas, where some special bryophyte communities live in dolomite cave twilight zones. A study of species composition, ecological types and distribution of bryophyte communities was conducted in the Shuidong Cave at Suiyang county, Guizhou Province, China. From April to September in 2015, sixty bryophyte samples were collected in this cave, and 47 typical bryophyte communities were recorded. Research shows that species composition in this cave is extremely rich. The cave flora is made up of 55 taxa in 34 genera of 17 families, representing the largest species diversity of bryophytes in known in China so far. The life-forms of bryophytes are simple in the cave, only four types, which are Wefts(47.27%), Short turfs (34.55%), Mats (9.09%) and Tall turfs(9.09%). According to the growth substrates, the bryophyte communities could be divided into four ecological types, which are bryophyte communities on calcareous soil, bryophyte communities on the dolomite, bryophyte communities on travertine and aquatic bryophyte communities. Travertine deposition associated with bryophyte communities is weak. From 0 m to 37 m within the cave entrance, with the increasingly weak of light, the distribution of bryophyte communities exhibits regular changes. For example, the number of bryophyte species has a sharp decline from 21 to 1 and species composition of bryophyte communities changes from multi-species communities to single-species communities.