Global patterns and environmental drivers of forest functional composition
Authors: Bouchard Elise , Searle Eric B. , Drapeau Pierre , Liang Jingjing , Gamarra Javier G. P. , Abegg Meinrad , Alberti Giorgio , Zambrano Angelica Almeyda , Alvarez‐Davila Esteban , Alves Luciana F. , Avitabile Valerio , Aymard Gerardo , Bastin Jean‐François , Birnbaum Philippe , Bongers Frans , Bouriaud Olivier , Brancalion Pedro , Broadbent Eben , Bussotti Filippo , Gatti Roberto Cazzolla , Češljar Goran , Chisholm Chelsea , Cienciala Emil , Clark Connie J. , Corral‐Rivas José Javier , Crowther Thomas W. , Dayanandan Selvadurai , Decuyper Mathieu , de Gasper André L. , de‐Miguel Sergio , Derroire Géraldine , DeVries Ben , Djordjević Ilija , Van Do Tran , Dolezal Jiri , Fayle Tom M. , Fridman Jonas , Frizzera Lorenzo , Gianelle Damiano , Hemp Andreas , Hérault Bruno , Herold Martin , Imai Nobuo , Jagodziński Andrzej M. , Jaroszewicz Bogdan , Jucker Tommaso , Kepfer‐Rojas Sebastian , Keppel Gunnar , Khan Mohammed Latif , Kim Hyun Seok , Korjus Henn , Kraxner Florian , Laarmann Diana , Lewis Simon , Lu Huicui , Maitner Brian S. , Marcon Eric , Marshall Andrew R. , Mukul Sharif A. , Nabuurs Gert‐Jan , Nava‐Miranda María Guadalupe , Parfenova Elena I. , Park Minjee , Peri Pablo L. , Pfautsch Sebastian , Phillips Oliver L. , Piedade Maria Teresa F. , Piotto Daniel , Poulsen John R. , Poulsen Axel Dalberg , Pretzsch Hans , Reich Peter B. , Rodeghiero Mirco , Rolim Samir , Rovero Francesco , Saikia Purabi , Salas‐Eljatib Christian , Schall Peter , Schepaschenko Dmitry , Schöngart Jochen , Šebeň Vladimír , Sist Plinio , Slik Ferry , Souza Alexandre F. , Stereńczak Krzysztof , Svoboda Miroslav , Tchebakova Nadezhda M. , ter Steege Hans , Tikhonova Elena V. , Usoltsev Vladimir A. , Valladares Fernando , Viana Helder , Vibrans Alexander C. , Wang Hua‐Feng , Westerlund Bertil , Wiser Susan K. , Wittmann Florian , Wortel Verginia , Zawiła‐Niedźwiecki Tomasz , Zhou Mo , Zhu Zhi‐Xin , Zo‐Bi Irié C. , Paquette Alain 
Published: December 2023

Aim

To determine the relationships between the functional trait composition of forest communities and environmental gradients across scales and biomes and the role of species relative abundances in these relationships.

Location

Global.

Time period

Recent.

Major taxa studied

Trees.

Methods

We integrated species abundance records from worldwide forest inventories and associated functional traits (wood density, specific leaf area and seed mass) to obtain a data set of 99,953 to 149,285 plots (depending on the trait) spanning all forested continents. We computed community‐weighted and unweighted means of trait values for each plot and related them to three broad environmental gradients and their interactions (energy availability, precipitation and soil properties) at two scales (global and biomes).

Results

Our models explained up to 60% of the variance in trait distribution. At global scale, the energy gradient had the strongest influence on traits. However, within‐biome models revealed different relationships among biomes. Notably, the functional composition of tropical forests was more influenced by precipitation and soil properties than energy availability, whereas temperate forests showed the opposite pattern. Depending on the trait studied, response to gradients was more variable and proportionally weaker in boreal forests. Community unweighted means were better predicted than weighted means for almost all models.

Main conclusions

Worldwide, trees require a large amount of energy (following latitude) to produce dense wood and seeds, while leaves with large surface to weight ratios are concentrated in temperate forests. However, patterns of functional composition within‐biome differ from global patterns due to biome specificities such as the presence of conifers or unique combinations of climatic and soil properties. We recommend assessing the sensitivity of tree functional traits to environmental changes in their geographic context. Furthermore, at a given site, the distribution of tree functional traits appears to be driven more by species presence than species abundance.