Effects Of Thinning Interference On Seedling Regeneration Dynamics In A Mixed Conifer And Broad-Leaved Forest In Jiaohe,Jilin,China

Based on two seedling censuses conducted from 2018 and 2019 of 100 seedling plots belong to 4 hm~2different thinning intensity(control,20%thinning,40%thinning and 60%thinning)in the mixed conifer and broad-leaved forest in Jiaohe,Jilin.This study compared the species composition and seedling survival state under different thinning intensity.By calculating the biomass and functional traits of the 4dominant species,we compared the change rules of seedling biomass distribution and functional traits and analyzed the correlation among the indexes.We also analyzed the effects of biological and abiotic factors on seedling survival and abundance by linear regression.The results showed that:(1)The main seedling species are Fraxinus mandschurica,Acer mandshuricum,Acer mono,Ulmus japonica and so on.Thinning affected the species composition and quantity dynamics of seedlings,the number in the 20%thinning sample plot was higher than the others.After thinning,the mortality rate of seedlings reduced and it was the lowest under 60%thinning intensity.The supplementation rate increased and it was the highest under 20%thinning intensity.(2)Thinning affected the biomass allocation and functional characteristics.With the increased of thinning intensity,the proportion of underground biomass and the specific stems length increased,the specific leaf area decreased.There was a correlation among different indexes.(3)Seedling regeneration was influenced mainly by conspecific neighborhood,seedling height,herbage,light and soil.The factors existed differences under different thinning intensity.Annual seedlings were mainly affected by biological factors,while perennial were abiotic factors.There were interspecific differences in the factors under different thinning intensities.The results showed that thinning was beneficial to the seedling regeneration,and the seedling regeneration status was better under 20%thinning intensity and 60%thinning intensity.It provided theoretical basis for formulating reasonable thinning measures and realizing sustainable forest management.