Atlas cedar response to climate-driven disturbances at its southern range edge

Abstract

The Atlas cedar (Cedrus atlantica), a relict species endemic to the mountains of North Africa, is increasingly threatened by climate change-in particular by the increasing frequency and intensity of droughts-and anthropogenic pressure, especially on its southern edge (the Saharan Atlas). While previous studies have documented historical disturbances in Atlas cedar forests of the Sahara Atlas, critical gaps remain in understanding their spatial extent and the forests' ability for recovery. This study leverages Landsat time series and the Anomalous Vegetation Change Detection (AVCD) method to analyse three decades of disturbance and regeneration dynamics in Saharan Atlas cedar forests. The main results show that frequent disturbances have occurred over the last three decades, peaking during the severe drought of 2001-2002, with cedar stands at lower elevations (≤ 1500 m) disproportionately affected. The recovery of the cedars demonstrated considerable variation. A total of 27% of the disturbed areas did not recover, 32% (mainly at altitudes ≤ 1500 m) were converted into holm oaks (Quercus ilex) and 35% (mainly at altitudes ≥ 1750 m) regenerated into cedar forests. Cedar disturbance was positively correlated with long droughts, while cedar regrowth was positively correlated with winter precipitation and snow periods. These findings on the resilience of cedars in dry-warm environments are crucial for the development of climate-adapted conservation strategies.

Keywords: Anthropogenic fire; Drought; Endangered species; Forest change monitoring; Resilience.