Biodiversity and ecological network of epiphytic bryophytes and their host trees in the forests of the southeastern Qinghai-Tibet Plateau

Abstract

The Qinghai-Tibet Plateau (QTP), the highest and largest plateau in the world, plays a vital role in maintaining the balance of the global ecosystem and China's ecological barriers. The QTP ecosystems are facing serious challenges under the scenario of global climate change. Epiphytic plant diversity is one of the most significant contributors to forest diversity. Epiphytic bryophytes play an important role in forest ecosystem functioning. However, previous studies of epiphytic bryophyte diversity have rarely considered both phorophyte diversity and their ecological networks, factors that are crucial for revealing the ecological processes of community assembly and the mechanisms of biodiversity maintenance and ecosystem stability. We investigated the diversity of epiphytic bryophytes and their host trees in 18 forest sites in the southeastern QTP and analyzed the characteristics of their ecological network. A total of 57 epiphytic bryophyte species in 35 genera and 24 families and 72 individuals of host trees belonging to 14 genera and 10 families were recorded. Epiphytic bryophyte species on Picea, Abies, and Sorbus accounted for 77% of all species. The ecological network structure of epiphytic bryophytes-phorophytes exhibited low connectance and nestedness and a low degree of specialization. The cover of epiphytic bryophytes was significant positively correlated with host tree size (diameter at breast height) and not significantly correlated with bark roughness. Both tree size and bark roughness were weakly positively correlated with epiphytic bryophyte richness. The study results showed that increasing tree diversity is essential for the maintenance of the epiphytic bryophyte diversity in forests of the QTP. Biodiversity conservation of epiphytic bryophytes is consistent with conservation of their host trees.