Abstract: A key to solve the problems about coniferous plantation degradation in montane regions of eastern Liaoning Province is to convert pure coniferous plantations into mixed coniferbroadleaf forests or promote the natural regeneration of broadleaved tree species in coniferous plantations. Seedling growth, a period of tree regeneration sensitive to environmental changes, is a crucial process to determine either the success or failure of plant regeneration. Moreover, soil nutrient is a dominant factor to ensure seedling growth. We took the seedlings of three dominant tree species including Juglans mandshurica, Fraxinus rhynchophylla and Quercus mongolica as the research objects to explore: (1) the effect of soil (from larch plantation, Korean pine plantation and secondary forest) on seedling growth, and (2) the relationship between seedling growth and soil nutrients. The results showed that the differences of soil nutrient in the three forest types had no obvious effect on seedling biomass for J. mandshurica and Q. mongolica, and there were no significant correlations between nutrient contents in seedlings and soil nutrients (P>0.05). In contrast, there were positive correlations between soil nutrient and seedling biomass allocation and nutrient contents in root, stem and leaf for Q. mongolica and F. rhynchophylla (P<0.05). Based on the N/P ratios in the leaves of seedlings, the growth of J. mandshurica seedling was likely to be restricted by the N content in the soil of secondary forest (N/P=10.7) and pine plantation (N/P=11.6). However, the growth of F. rhynchophylla seedling was possibly restricted by the P content in the soil of secondary forest (N/P=25.0) and larch plantation (N/P=19.4), and the growth of Q. mongolica seedling was not restricted by N or P in the three studied forest soils. All of these results indicated that the seedling growth of Q. mongolica and F. rhynchophylla was more sensitive to the dynamics of soil N and P contents than that of J. mandshurica grown in the soil of coniferous plantations. In future, more attention should be paid to other factors such as light and temperature, which may affect the seedling growth of broadleaved tree species in the coniferous plantations.

Key words: field experiment, cross-talk, jasmonates, resistance elicitor, plant growth-defense trade-offs, induced plant anti-herbivore defensive reaction, induction method