ASSESSING THE CLIMATE-GROWTH RELATIONSHIP OF CEDRUS ATLANTICA IN MOROCCO.

Atlas cedar (Cedrus atlantica) is a climate-sensitive confier species endemic to the mountainous regions of Northern Africa. The species is increasingly threatened by intensified drought conditions associated with climate change. Understanding how this species responds to climate variability, particularly drought at different temporal scales, is crucial for assessing its resilience and informing conservation strategies. This study investigates the relationship between radial growth of Cedrus atlantica and climate variables at two sites in Morocco, Boulzane and Col du Zad, using dendrochronological techniques. Tree-ring width chronologies were developed from increment cores and crossdated and standardised to isolate climate-driven growth signals. The resulting chronologies span 594 years (1429-2022) for Boulzane and 1112 years (911-2022) for Col du Zad. Crossdating accuracy was verified using the COFECHA program and standardised using ARSTAN. Dendrochronological statistics, including means sensitivity, interseries correlation (Rbar), and the Expressed population signals (EPS), were calculated to evaluate year-to-year growth variability, the strength of the common growth signal among trees, and the reliability of the site chronologies. The chronology developed for this study was compared with previously published chronologies. This helps to validate developed chronology in regional context and assess their consistency with existing records. Growth-climate relationships were assessed using monthly average temperature and precipitation, the Palmer Drought Severity Index (PDSI) and the Standardised Precipitation Evapotranspiration Index (SPEI) calculated at 1- ,3-, and 6- month temporal scale. Results shows that radial growth is primarily controlled by moisture availability rather than temperature and precipitation alone. Weak and inconsistent correlation were observed with short-term drought conditions, whereas stronger and more coherent positive correlation was observed with longer accumulated period. Spring and summer moisture availability was identified as a key driver of growth variability. Overall, this study highlights the strong sensitivity of Cedrus atlantica growth to prolonged drought stress and underscores the vulnerability of Atlas cedar forests under ongoing climate warming and drying trends.