Increasing Drought Sensitivity and Decline of Atlas Cedar (Cedrus atlantica) in the Moroccan Middle Atlas Forests

background

Since the 1980s, severe droughts have influenced Atlas cedar mortality in Morocco. This study looked at relative contributions of tree characteristics and stand structure on the increment-growth and decline of Atlas cedar trees (Cedrus atlantica) in stands affected by past logging and heavy grazing.

Research Goals & Methods

The researchers hypothesized that logged and overgrazed stands would have stronger Atlas cedar declines in response to drought stress. The region’s climate was analyzed by studying climate records. Trees were cored and competition estimated, to understand the effects of tree density and age on growth. The study’s analyses indicate long-term declines and changes in seasonality of precipitation. Age and mean BAI (basal area increment) strongly correlate to Atlas cedar decline in the 20th century, with old, slow-growing trees having the maximum likelihood of decline.

Conclusions & Takeaways

Results show that Atlas cedar decline is mostly due to climate change, with tree age and growth rates predisposing older trees to mortality. Logging increases likelihood that holm oak (Quercus rotundifolia) and prickly juniper (Juniperus oxycedrus) will replace Atlas cedar stands. Holm oak has reproductive advantages in heavily logged, moisture-stressed environments (coppicing, more efficient hydraulic system).