Which oak provenances for the 22nd century in Western Europe?Dendroclimatology in common gardens.

Didier Bert,Brigitte Musch,Stéphane Ponton,Alexis Ducousso,François Lebourgeois,Sergio Rossi

doi:10.1371/journal.pone.0234583

Abstract

The current distribution area of the two sympatric oaks Quercus petraea and Q. robur covers most of temperate Western Europe. Depending on their geographic location, populations of these trees are exposed to different climate constraints, to which they are adapted. Comparing the performances of trees from contrasting populations provides the insight into their expected resilience to future climate change required for forest management. In this study, the descendants of 24 Q. petraea and two Q. robur provenances selected from sites throughout Europe were grown for 20 years in three common gardens with contrasting climates. The 2420 sampled trees allowed the assessments of the relationship between radial growth and climate. An analysis of 15-year chronologies of ring widths, with different combinations of climate variables, revealed different response patterns between provenances and between common gardens. As expected, provenances originating from sites with wet summers displayed the strongest responses to summer drought, particularly in the driest common garden. All provenances displayed positive significant relationships between the temperature of the previous winter and radial growth when grown in the common garden experiencing the mildest winter temperatures. Only eastern provenances from continental cold climates also clearly expressed this limitation of growth by cold winter temperatures in the other two common gardens. However, ecological distance, calculated on the basis of differences in climate between the site of origin and the common garden, was not clearly related to the radial growth responses of the provenances. This suggests that the gradient of genetic variability among the selected provenances was not strictly structured according to climate gradients. Based on these results, we provide guidelines for forest managers for the assisted migration of Quercus petraea and Q. robur provenances.

Highlights

Genetic adaptation, phenotypic plasticity and migration are the three mechanisms by which populations face environmental variations, such as global warming [1,2,3]
The objectives of this study were (1) to analyze the tree growth-climate relationships of 24 Q. petraea and 2 Q. robur provenances selected throughout Europe and planted at three French sites with contrasting climate conditions, (2) to assess the effect of ecodistance on the growth response to climate, (3) to provide guidelines for choosing suitable provenances adapted to future climate conditions
This study was based on three common gardens of Quercus petraea and Q. robur established in the northern half of France at the start of the 1990s

Summary

Introduction

Phenotypic plasticity and migration are the three mechanisms by which populations face environmental variations, such as global warming [1,2,3]. Which oak provenances for the 22nd century in Western Europe?. The concept of “local adaptation” of populations as a population having a greater average fitness in its environment of origin than it would have in another environment. Environmental changes can, alter the hierarchy of population growth potentials. The time scale of climate change is a key issue, as adaptation and migration are very slow in trees, due to their longevity and sessile lifestyle. The persistence of trees under rapid climate change is dependent principally on the phenotypic plasticity of individuals, and assisted migration in managed forests [5]

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Conclusion