Interannual seedling dynamic and influencing factors on seedling survival of tree species in a broadleaved Korean pine (Pinus koraiensis) mixed forest in Changbai Mountains, northeastern China.

This paper is to understand the interannual dynamic and influencing factors on seedling survival in a broadleaved Korean pine (Pinus koraiensis) mixed forest in northeastern China. 100 seedling monitoring (1 m×1 m) quadrats were set at Changbai Mountains, of which DBH1 cm seedlings in quadrats were tagged, measured and identified to the species. Based on seven censuses from 2006 to 2014, we analyzed the species composition and interannual dynamic of all seedlings, especially for seedling recruitment and death. We examined the relative importance of biotic neighborhood and habitat heterogeneity on seedling survival by using generalized mixed linear model. A total of 13 tree seedling species were identified and recorded. Results showed that: 1) there were a little difference of the species composition from 2006 to 2014, and we monitored 9 common seedling species each year. 2) There were great temporal fluctuation in seedling density, of which the highest was 38.9 seedlings per m2 and the lowest was 3.8 seedlings per m2. 3) Tree seedlings had a large number of regeneration and death every year. On the age structure of arbor seedlings in the community, 1-year-old seedlings had most individuals in most cases, some years had a little difference. With the increase of seedling age, seedling numbers decreased gradually. The dynamic change of total seedling numbers agreed with that of regenerated seedling numbers. The seedling death peak was 1 year time delay than the seedling total peak. We found that both biotic neighbors and habitat heterogeneity had significant effects on the seedling survival at community level. 4) The basal area at breast height of conspecific adult and canopy openness had significant positive effect on seedling survival, while heterospecific seedling neighbors showed negative effect. Our results suggested that the majority of tree species in Changbai Mountains were recruitment-limited, which might have important consequences for species coexistence. High temporal variability in seedling density emphasized the importance of long term studies to understanding of forest dynamics. Nearly a decade of seedling monitoring can make us understand the community regeneration process more accurately.