Divergence of epiphytic lichen diversity of native and introduced tree species in the secondary forests of Shennongjia Mountain.
Objective: Epiphytic lichens play an important role in maintaining biodiversity, nutrient and water cycle, also in indicating environmental quality in forest ecosystem. This paper investigated the divergence of epiphytic lichen diversity of introduced and native tree species in the secondary forests of Shennongjia Mountain. Method: Three introduced tree species (Pinus armandii, Pinus massoniana and Larix kaempferi) and seven dominant native trees species (Salix fargesii, Salix wallichiana, Quercus aliena var. acuteserrata, Cerasus pusilliflora, Pteroceltis tatarinowii, Bothrocaryum controversum, Abies fargesii) were surveyed, then we estimated their expected lichen species richness with the software package EstimateS 9.1.0. Lichen species and their growth form on each tree species were listed to analyze the difference of community composition among tree species. Shannon-Wiener (H), Simpson (D) and Evenness (E) were calculated to evaluate lichen community diversity at tree species level, as well at native group vs introduced group level. Finally, lichen community of 10 tree species were clustered with SPSS 10.0 to demonstrate their similarity. Result: Expected lichen species richness was significantly different among 10 tree species, and the expected species richness of introduced tree group was a little higher than that of the native tree group. Practical lichen species richness of 10 tree species varied moderately, there were no difference between native group and introduced group. Furthermore, the dominant lichen species of the introduced tree species differed significantly from those of the native tree species. Usnea luridorufa, Stereocaulon japonicum, Lecanora thysanophora, and Heterodermia diademata were dominant in the native tree species. In contrast, Ramalina minuscula, and Petrelia olivetorum were dominant in the introduced species. In addition, some lichen species such as Ramalina americana, Ramalina minuscula and Ramalina hossei were found only in introduced tree species, suggesting that some lichens prefer to certain tree species. Lichen community diversity index varied among 10 tree species. In the native tree group, Quercus aliena var. acuteserrata displayed the highest diversity, but Salix fargesii displayed the lowest diversity, while the introduced tree group displayed an order of Pinus armandii > Pinus massoniana > Larix kaempferi. Lichen community of ten tree species were clustered into three subgroups, all the introduced tree species were clustered into one subgroup. Conclusion: We concluded that the secondary forests of Shnenongjia Mountain possessed a higher epiphytic lichen species richness, and epiphytic lichen diversity varied widely among tree species, so tree species diversity should be of special importance in maintaining diversity of epiphytic lichens in this area. Impacts of the introduced exotic tree species on lichen diversity of the secondary forests of Shennongjia Mountain, should be deeply studied in the future.