Quel avenir pour le sapin blanc en Suisse sous les effets des changements climatiques?

Abstract

Foresters in many countries are currently seeking for the most suitable forest species or provenances for facing the future climate, which will be much warmer than today with more extreme summer droughts. While it is clear that some tree species will increasingly suffer from climate warming, the fate of silver fir (Abies alba Mill.) remains very uncertain because contradictory results have been published about the suitability of this species to cope with climate warming. On the one hand, species distribution models predict a strong decline of its climatic niche in the future. On the other hand, paleoecological studies reveal that this species was widely distributed under much warmer and probably drier climate, suggesting a high potential to face future climate warming. This literature survey shows that this species could actually grow under warmer conditions provided that precipitation remains sufficient, which seems to be the case for most regions of Switzerland according to climatic model predictions for the end of the century. In addition, dendroecological studies have shown a higher resistance and resilience of silver fir to drought compared to Norway spruce, suggesting that silver fir could be promoted by foresters. Nowadays, the greatest threat to silver fir is undoubtedly the browsing pressure by ungulates which can jeopardize its regeneration and must therefore be properly regulated to increase the proportion of silver fir in Swiss mixed forests.