Sumitra Dewan, Pieter De Frenne, Sebastian Kepfer-Rojas, Safaa Wasof, Kristine Vander Mijnsbrugge, Kris Verheyen

Background and aims
Clinal variation in bud phenology and growth has repeatedly been reported in common garden experiments for many tree species. The response of the seedlings generated from such translocated trees has not been studied yet, despite its relevance regarding the role of transgenerational plasticity in the adaptation of long-living trees in the face of climate change. Here, we aim to understand the effects of warming on bud burst, germination success and growth performance of tree seedlings of different origins (provenances) but that shared their maternal environment.
Methods
We collected seeds from a mature provenance trial of five different provenances of oak (Quercus robur, Fagaceae) and seeds were grown in two common gardens at two different latitudes representing a mean annual temperature difference of nearly 2°C in Belgium and Denmark. We assessed seed germination, bud burst time and biomass of seedlings in two common gardens.
Results
We observed an interaction between provenances and common gardens in seedlings’ bud burst time indicating the prevalence of an environmental effect at the site of origin (provenance), which depends on the seedlings’ growing environment (across the two common gardens). The germination success and shoot biomass were reduced across all provenances in the southern common garden.
Conclusions
Our results indicate that the environment of origin influences the bud phenology of seedlings and this provenance effect is dependent on the seedlings’ growing environment. In addition, our results suggest that the effect of warming might differ between provenances and that the environmental history of the previous generations is likely to influence the response of tree seedlings as well.