Abstract: Poplar is one of the major tree species in the Loess Plateau. According to the analysis of degree of correlation between increment data of analytic Poplar stem measured under different site conditions and the climatic data in the same period, 8 climatic factors whose degrees of correlation are higher were selected as the cluster factors, and then the weight of each factor was obtained based on the value of degree of correlation. The climatic data were collected from 68 meteorological stations in the western part of the Loess Plateau (1951-1980). After these data were standardised and by using dynamic cluster analysis, western Loess Plateau were divided into different forest climate zones.

Key words: dynamic cluster analysis, Loess Plateau, forest climate, degree of correlation, weight