University of Guilan Caspian Journal of Environmental Sciences 1735-3033 2026 02 22 Do extreme climate events impact oak decline phenomenon in the Zagros Region, Western Iran? 1 14 9465 10.22124/cjes.2026.9465 EN Mahdieh Garoosiha Department of Forestry and Forest Economics, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Pedram Attarod Department of Forestry and Forest Economics, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Samira Beiranvand Department of Forestry and Forest Economics, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Shahram Khalighi Sigaroodi Department of Reclamation of Arid and Mountainous Regions, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Mohammad Javad Mehdikhani Department of Forestry and Forest Economics, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Javad Bazrafshan Department of Irrigation and Reclamation Engineering, Faculty of Agricultural Engineering and Technology, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Journal Article 2026 02 22 Assessments of forest vulnerability to climate change often emphasize average meteorological conditions, overlooking the role of extreme events in shaping forest dynamics. This study quantifies the influence of climate extremes on the decline of Zagros forests in western Iran. Using RClimDex, we analyzed minimum and maximum temperatures and precipitation records from 19 synoptic stations over 33 years (1987–2019). Stations were grouped into three climate types, semi-dry, Mediterranean, and very humid, and divided into two temporal phases: pre-decline (1987-2000) and post-decline (2001-2019). Trends in 14 extreme climate indices, including temperature extremes, precipitation intensity, spell durations, growing season length, and annual wet-day totals, were evaluated for each region and period. Of 266 trends analyzed, 21% were statistically significant in both pre- and post-decline phases. In the very humid region, the proportion of significant trends fell from 28.5% to 21.4% after the decline, while in the semi-dry region, significance remained stable (~19%). The Mediterranean region showed a slight increase from 19.5% to 23%. Over the full study period, 52.2% of trends were significant, with the highest proportion (69%) in the very humid region, followed by semi-dry (48.8%) and Mediterranean (50%). These results highlight marked spatial and temporal variability in extreme climate events, underscoring their importance in accelerating forest decline. This work provides a quantitative basis for incorporating extreme climate indices into adaptive forest management and climate resilience strategies. https://cjes.guilan.ac.ir/article_9465_3d2f9431b18801de4612b02c35526ec1.pdf