Composition and temporal dynamics of tree seedlings at different successional stages of conifer and broad-leaved mixed forests in Jiaohe, Jilin Province, China

Abstract

Aims Our objective was to explore the composition and temporal dynamics of woody plant seedlings and the ecological processes that affect the amount of seedlings in Jiaohe, Jilin Province, China. Methods We established a total of 415 seed-seedling census stations in three large permanent field plots belong- ing to three successional stages in the conifer and broad-leaved mixed forests. Based on three seedling censuses from 2012 to 2014, we analyzed species composition, quantitative character, height-classes structure and their inter-annual dynamics. Multiple linear regression was used to test the relationship between the abundance of seed- lings for five major species and the forest types, the sum of the basal area of conspecific adult within 20 m away from a seed trap, as well as canopy openness. Important findings Our results show that: (1) The species composition of seedlings slightly varied among dif- ferent successional stages, and was similar with that of trees in the plots. The rank of important values for seedling species among different years and successional stages varied slightly. (2) The number of seedlings and seedling species distributed mainly between 5-20 cm height classes, and decreased with the increasing height class. The number of seedlings decreased faster than that of seedling species, indicating that compared with interspecific competition, intraspecific competition was the main driver that led to seedling death. It confirmed the role of the negative density dependence in affecting seedling regeneration. (3) The amount of seedlings for all of the five major species was significantly positively related to the sum of the basal area of conspecific adults, which indicated that the quantity and distribution of seedlings were affected by dispersal limitation as well as niche