Is there tree senescence? The fecundity evidence.
Tong QiuMarie-Claire Aravena AcuñaRobert A AndrusDavide AscoliYves BergeronRoberta BerrettiMichał BogdziewiczThomas BoivinRaul BonalThomas CaignardRafael CalamaJ Julio CamareroConnie J ClarkBenoit CourbaudSylvain DelzonSergio Donoso CalderónWilliam Farfan-RiosCatherine A GehringGregory S GilbertCathryn H GreenbergQinfeng GuoJanneke Hille Ris LambersKazuhiko HoshizakiInés IbáñezValentin JournéChristopher L KilnerRichard K KobeWalter D KoenigGeorges KunstlerJalene M LaMontagneMateusz LedwońJames A LutzRenzo MottaJonathan A MyersThomas A NagelChase L NuñezIan S PearseŁukasz PiechnikJohn R PoulsenRenata Poulton-KamakuraMiranda D RedmondChantal D ReidKyle C RodmanC Lane ScherHarald Schmidt Van MarleBarbara SegetShubhi SharmaMiles SilmanJennifer J SwensonMargaret SwiftMaria UriarteGiorgio VacchianoThomas T VeblenAmy V WhippleThomas G WhithamAndreas P WionS Joseph WrightKai ZhuJess K ZimmermanMagdalena ZywiecJames S ClarkPublished in: Proceedings of the National Academy of Sciences of the United States of America (2021)
Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current estimates are dominated by overrepresentation of small trees in regression models. We combined global fecundity data, including a substantial representation of large trees. We compared size-fecundity relationships against traditional allometric scaling with diameter and two models based on crown architecture. All allometric models fail to describe the declining rate of increase in fecundity with diameter found for 80% of 597 species in our analysis. The strong evidence of declining fecundity, beyond what can be explained by crown architectural change, is consistent with physiological decline. A downward revision of projected fecundity of large trees can improve the next generation of forest dynamic models.