Comparing the impact of climate variables on healthy and declined masses of oak (Quercus brantti Lindl) in the “Khorram Abad” city

In this study, using dendroclimatology (a branch of the science of dendrochronology), the impact of climate variables on normal masses and declined oak in the city “Khorram Abad” was studied. After the selection of 12 samples from healthy trees and 12 trees from declined ones, breast height (1.30 m) discs were prepared. Then, the samples were scanned and ring width was measured using Corel Draw software. Using TSAP and ARSTAN softwares, cross dating between samples were done and chronology was prepared respectively. From the nearest meteorological station, rainfall and temperature data obtained and their effects on growth rings of trees was investigated using Pearson's correlation coefficient. The results of this study showed that both chronologies were equally affected by climatic factors. The temperature during the growing season and before it has a similar effect on both chronologies. Until 2010, the growth of trees is almost the same, but from this year onwards, curve of declined trees identified a drop in growth, probably due to the impact of pests and the deterioration in the trees. From this year onwards, despite the significant increase in precipitation, compared with previous years, increasing growth of the declined trees was not found and this means that due to the factors causing deterioration and thus reduce the activity of cambium, the trees have lost their re-growth and even with the improvement of environmental conditions, there was no possibility of resuming growth.