Abstract: Based on the tree-ring width chronologies of Fraxinus mandshurica in Changbai Mountains area, the relationships between tree-ring width and climatic factors were analyzed, and the temporal variations of precipitation in this area since 1765 were reconstructed. The results showed that over past 240 years, the precipitation in Changbai Mountains area fluctuated evidently. The amplitude of the fluctuation was comparatively great before 1850, and relatively stable from 1850 to 1900, with a low level of precipitation. After 1900, the amplitude of the fluctuation increased significantly, and the durations of wetness and drought were extended. Especially after 1920, the precipitation fluctuated acutely, and several wet and drought periods could be clearly identified. The driest period with an evident decrease of precipitation appeared in 1816-1820, and the wettest period was in 1975-1979. The drought periods which appeared from 1925 to 1936 and from 1947 to 1957 were particularly notable for their durations. There were significant periodical variations of precipitation in the Changbai Mountains area, and the periodicities were 2.64-3.03 years, 5.28-6.96 years, and 12.13-22.63 years, respectively.

Key words: Cluster analysis, Ecotype of drought resistance, Wheat