Evaluation of Juniper trees (Juniperus polycarpos C. Koch) radial growth in three sites of Iran by using dendrochronology

By comparing the pattern of narrow and width rings among the trees in one area, the exact year of each rings could be determine. This is the base of Dendrochronology. In this study, according to the important role of Juniper (Juniperus polycarpos) trees, an investigation have been done on variation of tree rings in three sites of Iran; Lain (Khorasan), Firouzkouh (Tehran) and Zanjan. 15 trees have been cored in each sites and ring width of each core was measured. After crossdating and standardization, 3 ring width chronologies were prepared and compared with climate data. Lain's trees were older than the others and Zanjan was the worst site. In many cases, the chronologies had similarities, especially between Lain and Zanjan and in extreme years like 1902, 1917, 1961 and 1975. There were significant correlations between tree ring width and temperature and precipitation in the study areas. Some of the most important ones were the positive effect of precipitation during autumn and winter period before and during the current growing season. The temperature had mostly negative effect on juniper trees but the temperature during September had mostly positive effect concerning the improvement of latewood cell’s expansion. The results showed that the Juniper trees are appropriate trees in Iran for studying dendroclimatology.