Linking seed size and number to trait syndromes in trees
Authors: Bogdziewicz Michal , Acuña Marie‐Claire Aravena , Andrus Robert , Ascoli Davide , Bergeron Yves , Brveiller Daniel , Boivin Thomas , Bonal Raul , Caignard Thomas , Cailleret Maxime , Calama Rafael , Calderon Sergio Donoso , Camarero J. Julio , Chang‐Yang Chia‐Hao , Chave Jerome , Chianucci Francesco , Cleavitt Natalie L. , Courbaud Benoit , Cutini Andrea , Curt Thomas , Das Adrian J. , Davi Hendrik , Delpierre Nicolas , Delzon Sylvain , Dietze Michael , Dormont Laurent , Farfan‐Rios William , Gehring Catherine A. , Gilbert Gregory S. , Gratzer Georg , Greenberg Cathryn H. , Guignabert Arthur , Guo Qinfeng , Hacket‐Pain Andrew , Hampe Arndt , Han Qingmin , Hoshizaki Kazuhiko , Ibanez Ines , Johnstone Jill F. , Journé Valentin , Kitzberger Thomas , Knops Johannes M. H. , Kunstler Georges , Kobe Richard , Lageard Jonathan G. A. , LaMontagne Jalene M. , Ledwon Mateusz , Leininger Theodor , Limousin Jean‐Marc , Lutz James A. , Macias Diana , Marell Anders , McIntire Eliot J. B. , Moran Emily , Motta Renzo , Myers Jonathan A. , Nagel Thomas A. , Naoe Shoji , Noguchi Mahoko , Oguro Michio , Kurokawa Hiroko , Ourcival Jean‐Marc , Parmenter Robert , Perez‐Ramos Ignacio M. , Piechnik Lukasz , Podgórski Tomasz , Poulsen John , Qiu Tong , Redmond Miranda D. , Reid Chantal D. , Rodman Kyle C. , Šamonil Pavel , Holik Jan , Scher C. Lane , Van Marle Harald Schmidt , Seget Barbara , Shibata Mitsue , Sharma Shubhi , Silman Miles , Steele Michael A. , Straub Jacob N. , Sun I‐Fang , Sutton Samantha , Swenson Jennifer J. , Thomas Peter A. , Uriarte Maria , Vacchiano Giorgio , Veblen Thomas T. , Wright Boyd , Wright S. Joseph , Whitham Thomas G. , Zhu Kai , Zimmerman Jess K. , Zywiec Magdalna , Clark James S. 
Published: March 2023

Aim

Our understanding of the mechanisms that maintain forest diversity under changing climate can benefit from knowledge about traits that are closely linked to fitness. We tested whether the link between traits and seed number and seed size is consistent with two hypotheses, termed the leaf economics spectrum and the plant size syndrome, or whether reproduction represents an independent dimension related to a seed size–seed number trade‐off.

Location

Most of the data come from Europe, North and Central America and East Asia. A minority of the data come from South America, Africa and Australia.

Time period

1960–2022.

Major taxa studied

Trees.

Methods

We gathered 12 million observations of the number of seeds produced in 784 tree species. We estimated the number of seeds produced by individual trees and scaled it up to the species level. Next, we used principal components analysis and generalized joint attribute modelling (GJAM) to map seed number and size on the tree traits spectrum.

Results

Incorporating seed size and number into trait analysis while controlling for environment and phylogeny with GJAM exposes relationships in trees that might otherwise remain hidden. Production of the large total biomass of seeds [product of seed number and seed size; hereafter, species seed productivity (SSP)] is associated with high leaf area, low foliar nitrogen, low specific leaf area (SLA) and dense wood. Production of high seed numbers is associated with small seeds produced by nutrient‐demanding species with softwood, small leaves and high SLA. Trait covariation is consistent with opposing strategies: one fast‐growing, early successional, with high dispersal, and the other slow‐growing, stress‐tolerant, that recruit in shaded conditions.

Main conclusions

Earth system models currently assume that reproductive allocation is indifferent among plant functional types. Easily measurable seed size is a strong predictor of the seed number and species seed productivity. The connection of SSP with the functional traits can form the first basis of improved fecundity prediction across global forests.