Modeling rings width of Alder, Walnut and Brutian Pine and some climatical variables (case study: Darabkola Forest)

In this study effect of several environmental factors on growth rings width of three planted species, including: Alnus subcordata (22 year old), Juglans regia (21 year old) and Pinus brutia (15 year old) was investigated. In chronology studies, at first accordance among samples (15 samples for each species) was obtained then Average Species Sensitivity (ASS), Trees Correlation (TC), Expressed Population Signal (EPS), Signal-to-Noise Ratio (SNR)MS values were calculated. The purpose of this research was to develop a regression model in relation to effects of temperature, precipitation, actual evapotranspiration, Torentveit heat index, relative humidity (by month, season and growth period) on annual ring growth width in Educational and Experimental Forest of Sari Natural Resources Faculty. Overall, 162 independent climatical variables (temperature, precipitation, evapotranspiration, etc.) and 45 dependent variables (growth ring width) were analyzed. Results of variance analysis showed that there is a significant relationship between the three species in respect to their uniform growth ring width. Using filtration methods in multiple regression analysis, variables with lowest coefficient variation and highest coefficient indication were selected step by step. Results showed that growth rings width is positively correlated with summer maximum humidity in J. regia, but is negatively correlated with December maximum temperature and February evapotranspiration and is positively correlated with summer maximum humidity in A. subcordata whereas is negatively correlated with February humidity in P. brutia. These correlations are accordance with the ecological restrictions of the species. Finally, a multiple regression model was developed for each species and its accuracy was confirmed, based on model calibration results.