Variations of density-dependent seedling survival in a temperate forest

Abstract

Seedling dynamics are driven by various biotic factors (for example, neighborhood interactions) and abiotic conditions (for example, light availability, topography, and soil nutrients). Therefore, quantifying the drivers of seedling survival is critical for understanding seedling dynamics within plant communities. However, how the importance of certain biotic and abiotic factors changes over growth stages is still relatively unknown. In the present study, the importance of density and distance dependence were examined, as well as the effects of abiotic factors, in regard to the survival of both newly germinated and established seedlings and saplings (<1 cm DBH; taller than 30 cm in height; and at least 2 years of age). A total of 1305 seedlings belonging to 21 species of a temperate forest in northeastern China were monitored. It was found there were significant conspecific negative density dependence (CNDD) effects impacting the survival of the established seedlings. In addition, the newly germinated seedlings were found to be less affected by the CNDD. The abiotic effects on seedling survival were not found to be significant. These results suggested that at the community level, the density dependence effects may be stronger during the seedling stage when compared with the abiotic factors. The distance dependence was observed to be mainly effective within a radius of approximately 5 m for both the newly germinated and established seedling communities. The directions and magnitudes of the aforementioned factors were affected by different life-history strategies. The seedlings which were wind-dispersed and the shade-tolerant species tended to suffer less from the CNDD. Therefore, based on an unusually large set of observations in a temperate forest, this study identified and analyzed the factors affecting seedling survival for different life-history strategies. The obtained results will potentially provide new perspectives for deepening the understanding of the dynamics of temperate forests.