Bryophyte Diversity And Its Influencing Factors In Temperate Deciduous Broad-leaved Forest In Funiu Mountain

Bryophytes are the second largest group of higher plants after angiosperms and they are widely distributed in terrestrial ecosystems.The study of bryophyte biodiversity and community coexistence mechanism is very important to strengthen the protection of bryophyte diversity,and different habitats,different scales and different functional traits will have a great impact on the diversity and community coexistence mechanism of bryophyte.In this study,we investigated the effects of different environmental factors on bryophyte diversity in funiu Mountain temperate broad-leaved forest plot,such as topography,light and bark physical and chemical properties.The coexistence mechanisms and influencing factors of tree epiphytic bryophytes specialized and non-specialized species at different scales were compared.The effect of spore size on the coexistence mechanism of tree epiphytic bryophytes community was analyzed.The specific research conclusions are as follows:(1)Through field investigation and specimen identification,a total of 35851 bryophytes in Funiu Mountain were analyzed,belonging to 182 species,96 genera and 36 families.In order to study the effect of different growth substrates on the phylogenetic diversity of bryophytes,the phylogenetic diversity index of bryophytes under different substrates was calculated by constructing phylogenetic tree.The effects of different substrates on the diversity of bryophytes were studied by Mantel test.The results were as follows : the phylogenetic diversity of soil bryophytes was the largest,while that of tree epiphytic bryophyte was the smallest;the phylogenetic diversity of saprophytic bryophytes was significantly correlated with topography and light;the diversity of soil bryophyte flora was significantly correlated with light;the diversity of lithophytic bryophyte flora was only significantly correlated with topography;there was no significant correlation between the diversity of bryophytes and topography or light.(2)In order to study the effects of topography,light and bark physical and chemical properties on tree epiphytic bryophyte diversity,canonical correspondence analysis,Mantel test and linear regression were used to study the effects of topography,light and bark physical and chemical properties on tree epiphytic bryophyte species diversity,functional diversity and pedigree diversity index.In this paper,variance decomposition and structural equation model(SEM)were used to study the direct and indirect relationship between environmental factors and the variation of species,function and pedigree diversity of tree epiphytic bryophytes.The results showed that light was the main driving factor for the changes of tree epiphytic bryophyte biodiversity,which drove the changes of tree epiphytic bryophyte species diversity,functional diversity and pedigree diversity.The physicochemical properties of bark mainly affect the functional diversity of tree epiphytic bryophytes,but have little effect on the species diversity and pedigree diversity of tree epiphytic bryophytes.(3)In order to understand the effects of different scales on the assembly mechanism of tree epiphytic bryophyte communities,we divided the tree epiphytic bryophyte communities at 5 m×5 m,10 m× 10 m,20 m× 20 m and 50 m× 50 m by niche width index.The habitats of tree epiphytic bryophytes were divided by multiple regression trees.Normalized stochastic model and C-Score checkerboard method were used to quantify the effects of randomness and certainty on the coexistence mechanism of tree epiphytic bryophytes generalized species,neutral taxa species and specialized species in at four scales.The effects of topography and spatial structure on the assembly mechanism of tree epiphytic bryophytes at four scales were quantified by variance decomposition.The results showed that deterministic processes dominated the community assembly mechanism of generalized species at 5 m×5 m,10 m× 10 m,20m× 20 m and 50 m× 50 m scales.Random processes dominated the assembly mechanism of neutral taxa species at all four scales.At the small scale(5 m×5 m,10m×10 m),random processes dominated,while at the large scale(20 m×20 m,50m×50 m),deterministic processes dominated.With the increase of scale,the amount of environmental variables explaining the assembly mechanism of tree epiphytic bryophyte community increased.The spatial structure has a higher explanatory rate for neutral taxa and specialized species than for generalized species.Topography has less influence on the assembly mechanism of bryophyte communities than spatial variables.(4)In order to understand the influence of different spore size on coexistence of tree epiphytic bryophytes community,the species of tree epiphytic bryophytes were divided by spore diameter.The effects of randomness and certainty on community assembly of bryophyte species with different spore diameters were quantified by normalized random ratio and C-score chessboard method.The results are as follows :The community structure of bryophytes with different spore sizes is different.The community assmbly of bryophytes with smaller spore diameter is mainly dominated by the random process,while the community assembly of bryophytes with larger spore diameter is dominated by the deterministic process.In summary,based on the sample plots of deciduous broad-leaved forest in the temperate zone of Funiu Mountain,the effects of different substrates,different environmental factors,different scales and different spore diameters on bryophyte biodiversity and community coexistence were studied in this study.The results of this study are helpful for the protection of bryophyte biodiversity,community coexistence, narrow-range distribution specialization species and microspore species in this region,and help to better understand the structure,function and dynamics of bryophyte community,which provides a scientific basis for the protection of bryophyte diversity in temperate forests and the maintenance of forest ecosystem stability.