The adaptive potential of Douglas-fir to drought: twenty years of collaborative investigation

ROZENBERG P; CHAUVIN T; RUIZ-DIAZ M; DALLA SALDA G; SERGENT AS; MARTINEZ-MEIER A; SEGURA V; FERNÁNDEZ ME; COCHARD H

Bariloche

Conferencia; International Conference: Adapting forest ecosystems and wood products to biotic and abiotic stress; 2019

LIA Forestia - INTA (Argentina) e INRA (Francia)

During the last 50 years, Douglas-fir became a key coniferspecies in France for forest Managers and the wood industry. The FrenchDouglas-fir forest comes from seed orchards composed of trees from the mosttemperate and humid coastal parts of the natural range. Global warmingincreases their vulnerability to drought stress. During the last 30 years,these stands have suffered diebacks associated to drought and heat waves.During the last 20 years, we developed genetic, dendroecological andecophysiological studies of the Douglas-fir adaptation potential to drought. Wefound that wood density, wood anatomy and resistance to cavitation play a majorrole. Cavitation process seems to start in the latewood and to finish in thetransition part between earlywood and latewood. We showed that intra-ringdensity variables were significantly related with survival to drought and withresistance to cavitation in different parts of the tree and at various geneticlevels. We established with common garden experiments that variable climaticselection pressures in the natural area have shaped local adaptation atdifferent geographical scales, with provenances from the warmer and dryer partsshowing increased wood density and resistance to cavitation and more efficientxylem cell wall pits. However, these global trends does not obscure strongwithin-provenance variation, contrasting genetic determinism of ring densityvariables and complex relationships between the variables involved at differentspatial, geographical and time scales. Nevertheless, the observed adaptationstrategies suggest that the French plantations may cross their Adaptive limitshortly after the global warming exceeds 2°C. We were able to reveal that besidethe consistent statistical and explanatory trends of Douglas-fir resistance todrought, there was a multifaceted network of relationships revealing the forceand the complexity of the Douglas-fir evolutionary potential of adaptation todrought.