Study of Climate Change on the Structure and Decline of Persian Oak (Quercus brantii Lindl.) in Zagros Ecosystems (Case study: Forests of Gilan-e-Gharb County)

Extended Abstract Introduction and Objective: For about two decades, the Zagros forests have been facing a declining issue, and the effects of this crisis are visible in various regions. Material and Methods: In the current study, the effect of climate change on the decline of Persian oak in the Zagros forest stands is probed using meteorological data and sample plots over time. To conduct this research, in order to collect field data, a regular random sampling model with fixed sample plots with two sampling periods in 1998 and 2018 was used. Furthermore, the trend of four climatic elements of precipitation, temperature, frost, and relative humidity in Gilan-e-Gharb station from 1988 to 2018 was studied. Results: The results showed that the frequency and stock of Persian oak species in the second period compared to the first period was decreased. The cross-sectional per hectare of Iranian oak was decreased from 5.2 in the first stage sampling to 4.4 in the second sampling. The results of comparing the quality and health conditions in two samples showed that in the first period, 11.9% of Persian oak trees were decayed and dried, while in the second period it was 71.55%. The oak decline rate in the second-period sampling was higher in health and quality grades 2 and 1 (41.9% and 28.5%, respectively) and was decreased in grades 4 and 5 (8.2% and 3/1%, respectively). However, the deterioration in higher degrees leads to the death of Persian oak trees. The Mann-Kendall analysis results of climatic elements showed that during the study period, the trend of precipitation, frost, and relative humidity was decreasing and the temperature was increasing. In the first decade and to some extent in the second decade, noticeable stability was observed in the studied indices, but in the third decade, there were many fluctuations. Conclusion: According to the obtained results, it can be said that climate change and the occurrence of severe drought stresses cause oak trees to suffer from physiological weakness. By creating physiological weakness in the trees, the conditions for the invasion of pests and various diseases are provided to them and the oak tree goes to dryness and decay.