Study On Tree Seedling Regeneration Dynamics In A Secondary Mixed Conifer And Broad-leaved Forest In Jiaohe,Jilin,China

Based on three seedling censuses conducted from 2016 and 2018 of 451 tree seedling census stations belong to three successional stages including a half mature forest(HF),a mature forest(MF)and an old-growth forest(OF)in the secondary mixed conifer and broad-leaved forest,Jiaohe,Jilin,the author analyzed species composition and quantitative dynamics of tree seedlings.And taking the mature forest as an example,generalized mixed linear models were used to test the relative importance of biotic neighborhood and habitat heterogeneity on density pattern and individual survival of tree seedlings,and seedlings growth and biomass distribution pattern were explored under four density treatments through control experiments.The results showed that 22 species of tree seedlings belonging to 11 families and 15 genera were found in all seedling cencus stations during the three censuses from 2016 and 2018,and the number of new-bom and dead seedlings varied significantly between species and cencus years.The density pattern and individual survival of tree seedlings were affected by dispersal limitation,density dependence and habitat filtering,but their relative importance varied with age classes and species characteristics.The effects of dispersal limitation and density dependence were verified in this study,and habitat factors connected by soil nutrient conditions had a significant impact on seedling regeneration.Compared with annual seedlings,habitat filtering had a more significant impact on perennial seedling regeneration.Density restricted seedling growth and biomass allocation of Korean pine.seedling basal diameter growth,root,leaf dry weight and total dry weight per plant all increased with density.Sterilization treatment had no significant effect on the growth and biomass allocation of Korean pine seedlings.This study revealed the relationship between seedling regeneration and dispersal limitation,density dependence and habitat filtering,and provided theoretical basis and data support for the maintenance mechanism of species diversity in temperate forests.