Sub-annual growth responses of Persian oak (Quercus brantii Lindl.) to climate in the Zagros Mountains, western Iran: regional climate imprint is stronger than the influences of microclimate and elevation

Mountain ecosystems are dynamic and highly sensitive to the negative impacts of climate change. Within this study, we conducted the first comprehensive dendrochronological, multi-site and multi-elevational study of Persian oak (Quercus brantii Lindl.) across the Zagros Mountains in Western Iran. Besides total ring-width (TRW), we separately measured earlywood width (EWW) and latewood width (LWW) to analyze climate impact on oak growth with sub-annual resolution. We found strong correlations between TRW, EWW, and LWW, as well as between the individual site chronologies. Several negative extreme events and long-term growth patterns were captured by all site chronologies, revealing an increase in the frequency of negative extreme events during recent decades (1930–2022). The standard chronologies exhibited strong climate signals representative for larger areas in West Asia and the Mediterranean region. Climate-growth response analyses indicated that winter precipitation is the most important growth-limiting factor, having a strong positive effect on the growth of the native oak species. Conversely, we found negative correlations between Tmax and Tmean and TRW, EWW, and LWW of Persian oak during the previous and current growth years. Correlations with various drought indices confirmed the strong negative impacts of dry periods on oak forests, particularly for the central and southern parts of the Zagros Mts. The very homogenous growth response across elevation and different microsite conditions emphasizes the dominant role of macroclimate on oak growth. Correlation analysis between annual and sub-annual ring-width parameters of Q. brantii and climate indices highlights the strong effect of large-scale teleconnection patterns on the Zagros oak forests. Our findings highlight the pivotal role of sufficient winter precipitation supply. Therefore, watershed management that promotes soil moisture conservation under current and expected future climate change is recommended to ensure long-term resilience of Persian oak forests.