Réponse à la sécheresse de conifères indigènes et exotiques: Une étude dendroécologique

Abstract

The sensitivity to drought of five conifers was studied along a climatic gradient covering the northern flank of the Swiss Alps, the Swiss Plateau, the Jura foothills and the central Alps. Three native species, i.e., Norway spruce, Scots pine and European larch, and two non-native species, i.e., Douglas fir and black pine, were analyzed. A total of 770 trees on 14 sites were sampled. To assess the sensitivity of conifers to drought, dendroecological analyses were performed for the period 1941-2006. On dry sites in the central Alps, spring water deficits sharply reduce growth, while on mesic sites located on the Swiss Plateau and the Jura foothills summer droughts significantly restrict growth. Spruce, larch and Scots pine are, depending on the site conditions, the most vulnerable species to extreme droughts, which implies that their long-term performance and survival may be compromised if the climate becomes warmer and drier. Conversely, black pine and Douglas fir were less drought-sensitive and grew faster than native species along the gradient. Selecting species with different but complementary strategies regarding drought could secure the productivity and efficiency of water use of forest stands and increase their resistance to climate change.