Abstract: Using the spectral analysis method, this paper studied the young Quercus variabilis population that had obvious increase characteristics, and analyzed the population's stability under disturbance. The result shows that Q.variabilis population has 20-47 year periodic fluctuations under the basic one, which is related to its regeneration and therefore can maintain its stability itself. But the internal periodic length of the basic one cannot be distinguished because the tree's age is not old enough. The results also shows that human disturbance have affected the population's fluctuation.

Key words: winter wheat, elevated CO_2, elevated O₃, DIMBOA, allelochemicals.