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

Drought and Pathogen Effects on Survival, Leaf Physiology, Oxidative Damage, and Defense in Two Middle Eastern Oak Species

The charcoal disease agents, Biscogniauxia mediterranea and Obolarina persica are two latent, ascomycetous oak pathogens in the Middle Eastern Zagros forests, where they have devastating effects, particularly during drought. Under greenhouse conditions, we investigated the effects of the two charcoal disease agents individually and in combination with drought on survival, growth, foliar gas-exchange, pigment content, oxidative stress and the antioxidant response of Quercus infectoria and Q. libani, two of the dominant tree species in this region. Commonly, the strongest negative effects emerged in the drought–pathogen interaction treatments. Q. infectoria showed less severe lesions, higher survival, more growth, and less leaf loss than Q. libani under combined biotic and abiotic stress. In both oak species, the combination of pathogen infection and drought resulted in more than 50% reduction in foliar gas-exchange parameters with partial recovery over time in Q. infectoria suggesting a superior defense system. Indeed, enhanced foliar anthocyanin, total soluble protein and glutathione concentrations imply an upregulation of the antioxidant defense system in Q. infectoria under stress while none of these parameters showed a significant treatment response in Q. libani. Consequently, Q. infectoria foliage showed no significant increase in superoxide, lower lipoxygenase activity, and less electrolyte leakage compared to the highly elevated levels seen in Q. libani indicating oxidative damage. Our findings indicate greater drought tolerance and pathogen resilience in Q. infectoria compared to Q. libani. Under future climate scenarios, we therefore expect changes in forest community structure driven by a decline in Q. libani and closely associated organisms