Inferring phenotypic plasticity and population responses to climate across tree species ranges using forest inventory data
Résumé
Aim To test whether intraspecific trait responses to climate among populations across species distribution ranges can be untangled using field observations, under the rationale that, in natural forest tree populations, long-term climate shapes population responses while recent climate change drives phenotypic plasticity. Location Europe. Time period 1901-2014. Taxa Silver fir (Abies alba Mill.) and sessile oak [Quercus petraea (Matt.) Liebl.]. Methods We estimated the variation of individual tree height as a function of long-term and short-term climates to tease apart provenance effects (variation among populations of different geographical origin), plasticity and their interaction, using mixed-effect models calibrated with national forest inventory data (in-situ models). To validate our approach, we tested the ability of in-situ models to predict independently tree height observations in common gardens experiments where provenance and plastic effects can be measured and separated. In-situ model predictions of tree height variation among provenances and among planting sites were compared to observations in common gardens and to predictions from a similar model calibrated using common garden data (ex-situ model). Results In Q. petraea, we found high correlations between in-situ and ex-situ model predictions of provenance and plasticity effects and their interaction for tree height (r > .80). We showed that the in-situ models significantly predicted tree height variation among provenances and sites for A. alba and Q. petraea. Spatial predictions of phenotypic plasticity across species distribution ranges indicate decreasing tree height in populations of warmer climates in response to recent anthropogenic climate warming. Main conclusions Our modelling approach using national forest inventory observations provides a new perspective for understanding patterns of intraspecific trait variation across species ranges. Its application is particularly interesting for species for which common garden experiments do not exist or do not cover the entire climatic range of the species.