عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this study, the simultaneous effect of short and long-term water resources was investigated on growth of Quercus Infectoria trees in Kermanshah by using multivariate standard precipitation index (MSPI), which is based on modified standardized precipitation index (SPImod). The index is based on principal component analysis technique (PCA). Results of correlation between MSPI and tree rings width during 1968-2008 showed that the overall status of water resources in January to September had the greatest impact on growth of oak trees and also the highest MSPI correlation with tree ring width was in July. Then based on linear relationship between tree ring width and MSPI of July, This index was reconstructed over the 1818-2008 periods. According to the results of this research, Droughts average duration were 2 years, nevertheless severe droughts duration were 3 and 4 years. The most severe droughts during the past two centuries have occurred in the 1960-1963, 1827-1830 and 1999-2001 periods, respectively. Results have a good agreement with Iran’s historical famines and droughts records and also with neighbor countries research results, far east (China) and western countries (Turkey and the Mediterranean zone), especially in the case of severe drought. But the results of this research are most consistent with the results of research conducted in countries on the path of the Mediterranean air masses (south of Mediterranean Sea and Middle East region). It seems that the results of this research can be used for investigation of Middle East past climate, confidently.