Tree functional diversity can increase forest productivity by enhancing species interactions and providing greater growth stability. However, very few studies have examined the influence of tree community trait structure on survivor growth, recruitment and mortality simultaneously, which are the main drivers of forest population dynamics. Here, we explore the interactions among functional diversity, productivity and climate to investigate the role of the trait structure of communities on forest productivity and to determine under what circumstances functional diversity should be promoted to ensure forest adaptive capacity under future climate. Using random-forest modelling and a network of permanent sample plots covering a broad gradient of climatic conditions, we isolated the effects of functional diversity-described as the distribution of trait values in a community-and climate variables on net forest productivity (NFP), survivor growth, recruitment and mortality. Based on our findings, community-level trait structure affects forest productivity in different ways. NFP was influenced by three traits from three different plant strategy dimensions, whereas survivor growth and recruitment were strongly correlated with leaf and resource acquisition traits, and tree mortality with a mix of traits reflecting various plant strategies. We also observed climate interactions with the functional trait structure of tree communities. For instance, we observed an interaction between drought tolerance and mean annual temperature: At low temperatures, NFP biomass accumulation increased with the value of the drought tolerance trait; however, at higher temperatures, the opposite pattern was observed. However, we found contrasting patterns of population response to climate variability, depending on their functional diversity. Greater functional diversity does not necessarily increase biomass accumulation under different climatic conditions. Synthesis. As all components of forest productivity contribute to NFP, studies on forest productivity should consider not only survivor growth but also recruitment and mortality. Each component responds differently in terms of biomass changes in climatic variation, according to the trait structure of tree communities. This study provides a framework to identify the trait structure that should be targeted under different climate scenarios to anticipate change and help strengthen forest response capacity to climate change. La diversit & eacute; fonctionnelle des arbres peut accro & icirc;tre la productivit & eacute; des for & ecirc;ts en am & eacute;liorant les interactions entre les esp & egrave;ces, en plus d'assurer une plus grande stabilit & eacute; pour la croissance. Cependant, tr & egrave;s peu d'& eacute;tudes ont examin & eacute; l'influence de la diversit & eacute; fonctionnelle des arbres sur, & agrave; la fois, la croissance, le recrutement et la mortalit & eacute;. Cette & eacute;tude explore les interactions diversit & eacute;-productivit & eacute;-climat afin d'& eacute;tudier le r & ocirc;le des traits pour la productivit & eacute; foresti & egrave;re et d & eacute;terminer dans quelles circonstances ils doivent & ecirc;tre promus pour garantir la capacit & eacute; d'adaptation des for & ecirc;ts dans le contexte du climat futur. En utilisant des mod & egrave;les random-forest et un r & eacute;seau de placettes & eacute;chantillons permanentes couvrant une vari & eacute;t & eacute; de conditions climatiques, les effets des traits et des variables climatiques sur la productivit & eacute; foresti & egrave;re nette (PFN), la croissance, le recrutement et la mortalit & eacute; ont & eacute;t & eacute; isol & eacute;s. Selon nos r & eacute;sultats, la structure des traits affecte diff & eacute;remment la productivit & eacute;. La PFN est influenc & eacute;e par des traits appartenant & agrave; trois strat & eacute;gies v & eacute;g & eacute;tales. La croissance et le recrutement ont & eacute;t & eacute; li & eacute;s aux traits foliaires et & agrave; l'acquisition des ressources, tandis que la mortalit & eacute; a & eacute;t & eacute; li & eacute;e & agrave; un m & eacute;lange de traits refl & eacute;tant diverses strat & eacute;gies. Les communaut & eacute;s d'arbres ont g & eacute;n & eacute;ralement r & eacute;agi de mani & egrave;re positive & agrave; l'augmentation des temp & eacute;ratures et pr & eacute;cipitations. Par exemple, une interaction entre la tol & eacute;rance & agrave; la s & eacute;cheresse et la temp & eacute;rature a & eacute;t & eacute; observ & eacute;e: & agrave; basse temp & eacute;rature, la biomasse li & eacute;e & agrave; la PFN augmentait avec la valeur de ce trait, alors qu'& agrave; des temp & eacute;ratures & eacute;lev & eacute;es, l'inverse & eacute;tait observ & eacute;. Cependant, selon les traits, les communaut & eacute;s d'arbres ont montr & eacute; des r & eacute;ponses contrast & eacute;es aux variations climatiques. Synth & egrave;se. Toutes les composantes de la productivit & eacute; foresti & egrave;re contribuent & agrave; la PFN, il est alors imp & eacute;ratif de non seulement consid & eacute;rer la croissance, mais & eacute;galement le recrutement et la mortalit & eacute;. En fonction des traits, chaque composante de la PFN a r & eacute;agi diff & eacute;remment en termes d'accumulation de biomasse face aux variations climatiques. Cette & eacute;tude fournit un cadre utile pour identifier la structure de trait qui devrait & ecirc;tre privil & eacute;gi & eacute;e en fonction du climat afin d'anticiper les changements et de contribuer & agrave; renforcer la capacit & eacute; d'adaptation des for & ecirc;ts. As all components of forest productivity contribute to net forest productivity, studies on forest productivity should consider not only survivor growth but also recruitment and mortality. Each component responds differently in terms of biomass changes in climatic variation, according to the trait structure of tree communities. This study provides a framework to identify the trait structure that should be targeted under different climate scenarios to anticipate change and help strengthen forest response capacity to climate change.image
