uning

One way to reconstruction of climatic variables, especially temperature, is dendroclimatogy or the use of trre-ring width chronology. There is no tree-ring based reconstruction of long term temperature in Caspian Ecosystem. In this research, temperature was reconstructed using Fagus Orientalis tree-ring chronology collected from high elevated regions of Koliak (Nowshahr). To this target, a correlation between annual tree ring width with meteorological variables in local and global scales was considered. Correlation analysis showed that the reduction of maximum temperature is a limiting factor of tree growth, particularly in the period March-September. So, the average of March-September maximum temperature based on data measured at Nowshahr’s station was reconstructed. The results of temperature reconstruction showed that this region has experienced very cold years more than very warm ones in two past centuries. Also 1900th, 1950-1970 and 1830th, 1930-1950 were the warmest and coldest periods, respectively. Besides, the significant effect of negative NAO on temperature rising in the early months of growth period was revealed. Reconstructed temperatures of this research like the results of other researchers in Eastern Mediterranean didn’t show the warming trend in recent years.

The beginning and the ending of radial growth in trees depend on genetics and climatic factors and its intensity varies during a growing season. Studying wood formation dynamics in a growing season will increase our knowledge about xylogenesis of important species and the influencing parameters. For this reason and in order to have a better understanding of a radial growth in oak, four Quercus castaneifolia individual treeswere selected in the research forest of University of Tehran located in the Hyrcanian forest. In 2012, micro-core samples were extracted from trees by Tropher in monthly intervals. Cambial cell divisions and radial growth started approximately on mid-April and terminated at the end of September. The highest number of cambium cell (15-17) and the maximum daily growth rates of all trees were achieved around Mid-June. The results of this research showed that the majority of radial growth in oak occurs from May to mid- July and this fact should be considered in dendroclimatological studies.

Gole of this study was to analyze relationships between the annual variability of the Quercus cataneifolia and Quercus macranthera tree-ring chronologies and the variability of the main climatic parameters in Caspian forests. The study areas represented by a forestry ecosystem located from west to east of Caspian forests in north of Iran. 6 sites were slected from Gilan (cool and moist)، Mazandaran (moist with moderate winters) and Golestan (warm and arid) provinences. The measurements of the cores were made with the LINTAB device and TSAP program. The Principal Component Analysis (PCA) was applied to the time-series of the treerings indices as well as to the residual time-series of the monthly precipitation and temperature derived from 6 meteorological stations located near to the study regions. The results of ring width variation (111 years of data) showed that 30. 2% of the total variance of tree-rings chronologies could be attributed to the common variability of the climatic parameters: Finally، results have shown that 30. 2% of variance has a significant and positive correlation with June precipitation in both species and in all sites. Precipitation in spring is an important factor to all physiological activities of tree، like cambium activation. Results have shown that this area has a good potential to reconstruct past climate.