Auteur(s)

Giai Petit¹, Georg von Arx^2,3, Natasa Kiorapostolou^1,4, Silvia Lechthaler¹, Angela Luisa Prendin¹, Tommaso Anfodillo¹, Maria C. Caldeira⁵, Hervé Cochard⁶, Paul Copini^4,7, Alan Crivellaro¹, Sylvain Delzon⁸, Roman Gebauer⁹, Jozica Gricar¹⁰, Leila Gronholm¹¹, Teemu Holtta¹¹, Tuula Jyske¹², Martina Lavric¹⁰, Anna Lintunen¹¹, Raquel Lobo-do-Vale⁵, Mikko Peltoniemi¹², Richard L. Peters², Elisabeth M. R. Robert¹³, Sılvia Roig Juan¹², Martin Senfeldr⁹, Kathy Steppe¹⁴, Josef Urban^9,15, Janne Van Camp¹⁴, Frank Sterck⁴

Résumé

Trees scale leaf (AL) and xylem (AX) areas to couple leaf transpiration and carbon gain with xylem water transport. Some species are known to acclimate in AL : AX balance in response to climate conditions, but whether trees of different species acclimate in AL : AX in similar ways over their entire (continental) distributions is unknown. We analyzed the species and climate effects on the scaling of AL vs AX in branches of conifers (Pinus sylvestris, Picea abies) and broadleaved (Betula pendula, Populus tremula) sampled across a continental wide transect in Europe. Along the branch axis, AL and AX change in equal proportion (isometric scaling: b ~ 1) as for trees. Branches of similar length converged in the scaling of AL vs AX with an exponent of b = 0.58 across European climates irrespective of species. Branches of slow-growing trees from Northern and Southern regions preferentially allocated into new leaf rather than xylem area, with older xylem rings contributing to maintaining total xylem conductivity. In conclusion, trees in contrasting climates adjust their functional balance between water transport and leaf transpiration by maintaining biomass allocation to leaves, and adjusting their growth rate and xylem production to maintain xylem conductance.

Mots clés

allocation, climate change, functional balance, leaf area, plant architecture, sapwood, structural balance, xylem.