Studies On Seasonal Dynamics Of Tree Seedlings And Its Influencing Factors In A Secondary Forest In Montane Region Of Eastern Liaoning Province,China

Natural regeneration is one of the important contents of forest ecosystem dynamics research.To explore the seasonal dynamics of tree seedlings and its influencing factors in a montane secondary temperate forest of eastern liaoning province,and also the species coexistence mechanisms and ecological processes,based on the 4 hm~2 dynamic forest plot,this study analyzed species composition and seasonal dynamics of tree seedlings,the spatial patterns and interspecific associations of tree species in seedling stage relative to other developmental stages and factors affecting seasonal survival of tree seedlings,using data of adult monitoring in 2017,tree seedling surveys from 2018 to 2019,and habitat factors.1.Species composition and seasonal dynamics of tree seedlings showed that a total of 24 species of tree seedlings were recorded.The species composition of tree seedlings did not vary significantly among seasons,but varied greatly among quadrats.The number of tree seedlings varied greatly among different tree species and seasons,and showed a decreasing trend.There were significant inter-species and inter-season differences in seedling recruits and death,the recruits of tree seedlings in July were more than that in September.The recruitment rates showed significant differences among tree species and seasons.The mortality rates of most species in July were higher than that in September,and the mortality rate of recruit seedlingss were much higher than that of existing seedlings.2.The spatial patterns and interspecific associations of tree species in seedling stage relative to other developmental stages showed that under the null model of complete spatial randomness most species showed aggregated pattern at seedling,sapling and adult stages,and the aggregated distributed proportion of species almost showed a decreasing trend under the scales of 0-50 m.After eliminating the effect of habitat heterogeneity,the regular or random distribution at seedling,sapling and adult stage became the dominant pattern under the null model of heterogeneous poisson process.Under the null model of complete spatial randomness,the percentages of species pairs with positive correlation would decrease with increasing of life stages.After eliminating the effect of habitat heterogeneity,under the null model of heterogeneous poisson process,the negative correlated and uncorrelated patterns became the dominant patterns at the three stages.3.The seasonal survival of tree seedlings and its influencing factors showed that the survival of tree seedlings was mainly affected by biological factors on community level.Seedling survival was negatively correlated with conspecific adult neighbors in both periods,and was positively correlated with conspecific seedling neighbors from July to September.The seedling survival of wind-dispersal tree species was mainly affected by their heights.The seedling survival of gravity-dispersal tree species was affected by both biological factors and habitat factors.The seedling survival of gravity-dispersal tree species was negatively correlated with conspecific adult neighbors,and positively correlated with conspecificseedling neighbors and elevation.On species level,seedling survival of most species was significantly positively correlated with their heights,and seedling survival of Ulmus laciniata was negatively correlated with the slope due to the influence of slope on soil thickness,soil moisture and nutrients.