Study On Tree Seedling Regeneration Dynamics In Different Succession Stages Of Broad-leaved Korean Pine Mixed Forest In Changbai Mountains

The broad-leaved Korean pine forest in the areas of Changbai Mountains has been seriously destroyed since the 20 th century,which resulting in a large area of secondary forest community.Based on seedling censuses in three succession stages of broad-leaved Korean pine mixed forest including secondary poplar-birch forests,secondary conifer and broad-leaved mixed forests and broad-leaved Korean pine forests in Changbai Mountains from 2018 to 2019,we analyzed species composition and quantitative dynamics of tree seedlings in different communities.To explore the effect of understory herb layer on the growth of seedlings in the early life stage and the relationship between the herbaceous plants and seedling survival,a control experiment of herb removal was conducted.The result showed that a total of 19 tree seedling species belonging 11 families and 14 genera were found in three plots during the investigation,the species composition of tree seedlings in forests at different succession stages is different and the species richness of tree seedlings in secondary conifer and broad-leaved mixed forests was the highest.The species composition changed a little in different forest types,but there was great fluctuation in number of seedlings and varied significantly between species.Understory herb layer significantly affect the seedling growth.In secondary poplar-birch forests,the herbs promote the height growth of tree seedling,while in late succession stages of forests has opposite effects.The effect of herbs on height growth of tree seedlings also varied with life stage and species.Herbs are significantly related to seedling survival.The species richness of herbs was positively correlated with the tree seedlings survival in late succession stages of forests,while the relationship between herbs abundance and tree seedling survival varied in different forest types,and there is no relationship between herb cover and seedling survival in three forests.This study revealed that the growth and survival of generated tree seedlings was affected by herbs,but the effects were influenced by different forest types,seedling life stages and seedling species.