ObjectiveElucidating the maintenance of diversity in plant communities has long been a challenge for ecologists and a key goal of community ecology. Reports on the effects of distance and density dependence on seedling growth in temperate forests are currently lacking. We explore whether there is a distance or density dependence in temperate forests. If so, whether soil pathogens are the driving factors for distance or density dependence.

MethodBased on the greenhouse experiment, we selected three tree species in a broadleaved Korean pine forest in Jiaohe in Jilin Province of northeastern China to monitor the seedling growth for 4 months. We analyzed the effects of the seedling density, distance to adult tree (parental distances) and soil sterilization on seedling height growth and seedling biomass.

ResultThe results showed that the height growth of Pinus koraiensis, Fraxinus mandschurica and Phellodendron amurense seedlings at low seedling density was significantly higher than that of high seedling density, indicating that there was significantly negative density dependence in our temperate forest. However, soil sterilization can only significantly increase the height growth of F. mandschurica seedlings. Although the height growth of F. mandschurica and P. amurense seedlings was significantly affected by the parental distances, it didn’t show the trend that the seedling height grew well with increasing distance from the adult tree. Thus, our results didn’t meet the phenomenon of distance dependence growth. We found that the root, stem, leaf and total biomass of F. mandschurica and P. amurense seedlings were only significantly correlated with seedling density. The root, stem, leaf and total biomass at low seedling density were significantly higher than that of high seedling density, indicating that biomass accumulation was also affected by density dependence growth. The parental distances and soil sterilization, however, had no significant effect on seedling root, stem, leaf and total biomass.

ConclusionThe results show that there is obvious negative density dependence growth in the temperate forest, but there is no distance dependence growth. This study suggests that the factor that causes the negative density dependence growth maybe the strong intraspecific competition, while the role of soil pathogens is very limited. Our results do not support the distance dependence growth. Second, the lack of evidence of distance dependence growth indicates that the soil pathogens in our temperate forest do not have intense host specificity. The generalist soil pathogens may play a role in negative density dependence growth. In the future, it is necessary to further explore the relative importance of the intra- and inter-specific competition and generalist soil pathogens in driving the seedling growth.