The Reconstruction of the Annual Rainfall of over a Century through from Quercus Persica Tree Rings in Zagros Forests (Case Study of Dena Region)

Knowledge of past climate needs long-term and accurate climatic data for future planning and predicting. In this study, we reconstructed the average maximum temperature in spring and minimum temperatures in fall and winter by applying the width of annual ringsofQuercusPersica through multiple- regression. With this goal in mind, two growth heights were selected in Dena Forests and 40 growth samples from 20 bases in two geographical directions of southwest and northeast were extracted at breast height and measured with AutoCAD software with an accuracy of 3 microns. After cross dating stage, to eliminate non-climate effects, all climatic parameters and tree rings time series were standardized. The calculated Residual Chronology (RES) was calibrated with climatic variations of the period 1881-2011 and positive and significant correlation with the width of growth rings was confirmed. Based on the relations and correlation between the calculated chronology and joint statistical climatic data the reconstruction of annual rainfall was performed and it was found that the average rainfall of the last three decades had a 4 percent increase in comparison to the average rainfall of the last century.