Effect of climatic factors on distribution of forest types using multivariate statistical methods

In order to determine the effect of climatic factors on the distribution of forest types in one of the western provinces of Iran, Charmahal, among 71 climatic elements effective in ecological conditions of forest species, 3 factors were selected using factor analysis method.The factors covering 91.82 percent of total variance included thermal temperature, rainfall and radiation. Finally, the effect of each factor as well as the primary climatic varieties on distribution of these species and the mean elevation of the plant types in each distribution class was determined. The results of factor analysis indicate that thermal temperature and rainfall are the most important factors in relation to distribution of forest species. Moreover it can be concluded that semi humid and moderate climatic zones are the best habitats for distribution of Quercus brantii and its associated species, which are the dominant forest types in Charmahal province. This study also suggests that the distribution of Quercus brantii and the appearance of Lonicera nummularrifolia and Amygdalus spp. have been controlled by increasing altitude and decreasing temperature. On the other hand, these two types are found in cold and dry mountainous regions. In conclusion, the selection of climatic variables related to ecological condition of species is important in determining the effects of climatic factors on the distribution of forest types in Charmahal province.