High resilience of temperate oak populations to climate change in Europe: A mixed model analysis of a large multisite provenance tests
Sessile oak Quercus petreae is one of the most important tree species of deciduous European forest, from Spain to Norway, Ukraine and Georgia, providing habitat to a wide biodiversity of plants, animals, insects and fungus species. Responses of oak dominated forests to climate change are of major concerns for the sustainability of European temperate and Mediterranean terrestrial ecosystems. Herein we present results of a long term continental wide scale common garden experiment, of one of the two widest natural distributed European oak: Quercus petraea. 116 populations were reshuffled in Europe by transplantation of more than 155,000 sessile oak seedlings across 23 field test sites on six countries and thus submitted to different climates as compared to their origin. Mixed model analysis was conducted, focusing on the effect of the climatic transfer distance: difference between climate of the test site minus climate of the provenance.
We found limited responses across a large climatic transfer distance range, with low population specific response patterns. However, a severe decline of survival and growth occur after a climatic transfer threshold is exceeded (if transfer distance > 0.02 of an annual aridity index or > 0.06 of a growing season aridity index, respectively; both indices are the ratio of degree days to mean annual precipitation). Climatic change impacts would be very different depending of the European region. It would reduce height growth up to 30 % and survival by 13 %, in regions undergoing reduced precipitation (e.g. Turkey); predicted changes are limited in northern Europe (e.g. Denmark) (- 2 % and – 3 %, respectively), at least under intermediate (A1B) future scenarios (about + 2.8 °C by year 2100).