Effects of environmental factors and heavy metals on the vertical distribution of bryophytes in a sinkhole environment

A sinkhole ecosystem, as a refuge for plant diversity, has been subjected to intensive exploitation, leading to ecosystem destruction of sinkholes in China. Understanding the responses of bryophyte distribution to destruction of the sinkhole environment are crucial to implementing protection measures for bryophyte diversity. Haolong sinkhole in Guangxi Zhuang Autonomous Region of China, the third largest sinkhole in the world, was selected as the study area. The Wilson Shmida index was used to analyse bryophyte species diversity; a Generalized Linear Model (GLM) was used to reveal species vertical distribution of bryophytes, the Single and Multiple Species Distribution Models (SSDM, MSDM) were used for analysis of the relationship between bryophyte species distribution, environmental factors and heavy metals. A total of 183 species from 74 genera in 36 families of bryophytes were collected from Haolong sinkhole, of which 26 species are endemic to China. Bryophyte species diversity was ranked in the order: agricultural section < forest section < grassland. In the vertical direction, bryophyte distribution was divided into point, disjunctive and continuous distributions using the GLM. The SSMA and MSDM indicated that bryophyte species of each of these three distributions can be divided into a temperature-slope zone, light-depth-pH-humidity zone, Pb (B)-Hg (B) zone and mixed heavy metals zone according to the effect of environmental factors and heavy metals such as As. Environmental factors or heavy metals, such as As, in Haolong sinkhole effectively cooperate in bryophyte distribution. An effective way to protect bryophyte diversity, in particular species endemic to China in the sinkhole environment, is through education and involvement of the local villagers to minimize further damage to the sinkhole environment.