Abstract: Based on the field investigations about the seed bank, seed germination, seedling emergence, and seedling survival and growth in the Larix olgensis plantations with different thinning intensities and various ground preparations in the montane regions of eastern Liaoning Province, the main factors affecting the natural regeneration of L. olgensis were analyzed in this paper. The results showed that in the seed rain of 40 years old L. olgensis lantation, 30% of the seeds had viability, which could meet the needs of natural regeneration. The seeds in soil seed bank mainly distributed in litter layer, and the seedlings younger than one-year old emerged in April and reached the peak in June. The accumulative emergence rate of the seedlings had no significant correlation with thinning intensities, but was affected by ground preparations. The average survival rate of appeared seedlings increased with increasing thinning intensities, but the seedling growth was generally slow in the plantation stands, e.g., the seedling height was less than 6 cm, and most of the seedlings disappeared in September. In the plantation stands, it was difficult to find the L. olgensis seedlings elder than one-year; but in the clearcut area with enough light and less ground cover, more seedlings could survive and grew well. Based on the above mentioned results, it was concluded that the main obstacles for the natural regeneration of L. olgensis plantations in montane regions of eastern Liaoning Province could be light intensity and ground cover.

Key words: freeze-thaw cycle, aggregates stability, black soil, Le Bissonnais method, aggregate porosity