Analysis Of Bryophyte Diversity And Pedigree Structure Based On Forest Dynamic Monitoring Plots

Bryophytes are small in size and simple in structure.They are considered to be higher plant groups in the transition from aquatic plants to terrestrial plants.Because pseudo roots of bryophytes do not have an absorption function,bryophytes directly absorb nutrients through the plant body,making them very sensitive to environmental changes.Because of its unique biological characteristics,bryophytes have become the ideal model organisms for detecting the distribution of species,and have an irreplaceable role in the study of the maintenance mechanisms of higher plant species.Therefore,in order to understand the formation and maintenance mechanism of forest biodiversity,more and more studies on bryophyte species diversity have been made in recent years.In this study,25 hectares of large-scale fixed monitoring sample plots in Baotianman National Nature Reserve,Henan Province,located in the transition zone between subtropical and warm temperate zones of China,were used as the platform to study the bryophytes in the 11 plot with the highest species richness in the center of other plots.A comprehensive survey of bryophytes and habitat factors was conducted from June to September 2016.Based on the survey data,the species composition and community structure of bryophytes in the sample plot were studied.The correlation between environmental factors and bryophyte community was analyzed by RDA sequencing.Bayesian evolutionary trees of bryophyte community in Baotianman sample plot were constructed using four DNA barcodes,rps4,trn L-F,rbc L and psba,and calculated separately.The net lineage relationship index(NRI)and the nearest lineage relationship index(NTI)of four bryophyte communities on different scales of 5m * 5m,10 m * 10 m and 20 m * 20 m were studied to explore the process of bryophyte community construction and the mechanism of affecting community construction.The main results are as follows:1.There are 137 species of bryophytes belonging to 73 genera and 35 families in the study plot,of which 13 species fall within 12 genera and 12 families of bryophytes and 124 species belong to 61 genera and 23 families of bryophytes.Among them,the species richness of lithophytic bryophytes is the highest,followed by epiphytic bryophytes of trees and soil bryophytes,saprophytic bryophytes get the least number of species.In terms of floristic distribution,temperate and East Asian elements accounted for a higher proportion,indicating that the floristic composition of bryophytes in the sample area was still dominated by north temperate elements,and was greatly influenced by East China flora.In addition,the area also contains a small amount of tropical elements,reflecting to a certain extent the characteristics of the North-South transition of bryophyte floristic elements in this area.2.In this experiment,RDA constrained ordination was utilized to rank species distribution in sample plots.The climate factors explained the distribution of epiphytic bryophytes of trees at 24.47% and topographic factors explained the distribution of soil and stone bryophytes at 18.68% and 40.44%.Therefore,the epiphytic bryophytes of trees are strongly affected by climatic factors,while the distribution of soil bryophytes and stone bryophytes is greatly affected by topographic factors.However,the explanations for the distribution of saprophytic bryophytes by both climatic and topographic factors are low,indicating that the effects of both factors on the community structure of saprophytic bryophytes are weak.3.Through analysis of NIR and NTI of bryophyte communities on different substrates,it was found that there were more divergent patches of epiphytic bryophyte communities on four substrates,but the percentage of clustered patches to total patches increased with the increase of scale.It is concluded that the negative density restriction is an important factor for maintaining species diversity on a small scale,and the effect of habitat filtration on community structure increases with the increase in research scale.Tree,soil and stone bryophyte communities exhibit lineage divergence at all scales,which indicate that the competition among bryophytes on these three substrates is fierce,and under the influence of negative density constraints,the species richness and lineage divergence of bryophyte communities are enhanced.Saprophytic bryophytes show strong pedigree aggregation at medium and high scales,which indicate that habitat filtration is the main factor to maintain the diversity of saprophytic bryophyte communities.