Abstract: Six tree species were tested for their dormancy depth of seedlings by transfering them periodically from yard into growth chamber and recording the time span from trasfering to budbreaking. Fraxinus mandshurica needed >180 days and Tilia amurensis needed 296 days for breaking the deep dormancy in early October. However, the dormancy was reduced to 15—20 days in the next January. Similar patterns of change in dormancy depth are also reported for other tree species having less dormancy depth such as Magnolia parviflora and Kalopanax septemlobum. The implications of the results are discussed.

Key words: Contaminated environment, Microorganism, Pollutant-degrading gene, Molecular ecology